Nuclear Parton Distribution Functions
I. Schienbein, J.Y. Yu, C. Keppel, J.G. Morfin, F. Olness, J.F. Owens
2009-06-01
We study nuclear effects of charged current deep inelastic neutrino-iron scattering in the framework of a {chi}{sup 2} analysis of parton distribution functions (PDFs). We extract a set of iron PDFs which are used to compute x{sub Bj}-dependent and Q{sup 2}-dependent nuclear correction factors for iron structure functions which are required in global analyses of free nucleon PDFs. We compare our results with nuclear correction factors from neutrino-nucleus scattering models and correction factors for charged-lepton--iron scattering. We find that, except for very high x{sub Bj}, our correction factors differ in both shape and magnitude from the correction factors of the models and charged-lepton scattering.
NUCLEAR MODIFICATION TO PARTON DISTRIBUTION FUNCTIONS AND PARTON SATURATION.
QIU, J.-W.
2006-11-14
We introduce a generalized definition of parton distribution functions (PDFs) for a more consistent all-order treatment of power corrections. We present a new set of modified DGLAP evolution equations for nuclear PDFs, and show that the resummed {alpha}{sub s}A{sup 1/3}/Q{sup 2}-type of leading nuclear size enhanced power corrections significantly slow down the growth of gluon density at small-x. We discuss the relation between the calculated power corrections and the saturation phenomena.
Global analysis of nuclear parton distributions
NASA Astrophysics Data System (ADS)
de Florian, Daniel; Sassot, Rodolfo; Zurita, Pia; Stratmann, Marco
2012-04-01
We present a new global QCD analysis of nuclear parton distribution functions and their uncertainties. In addition to the most commonly analyzed data sets for the deep-inelastic scattering of charged leptons off nuclei and Drell-Yan dilepton production, we include also measurements for neutrino-nucleus scattering and inclusive pion production in deuteron-gold collisions. The analysis is performed at next-to-leading order accuracy in perturbative QCD in a general mass variable flavor number scheme, adopting a current set of free nucleon parton distribution functions, defined accordingly, as reference. The emerging picture is one of consistency, where universal nuclear modification factors for each parton flavor reproduce the main features of all data without any significant tension among the different sets. We use the Hessian method to estimate the uncertainties of the obtained nuclear modification factors and examine critically their range of validity in view of the sparse kinematic coverage of the present data. We briefly present several applications of our nuclear parton densities in hard nuclear reactions at BNL-RHIC, CERN-LHC, and a future electron-ion collider.
Nuclear modifications of Parton Distribution Functions
NASA Astrophysics Data System (ADS)
Adeluyi, Adeola Adeleke
This dissertation addresses a central question of modern nuclear physics: how does the behavior of fundamental degrees of freedom (quarks and gluons) change in the nuclear environment? This is an important aspect of experimental studies at current facilities such as the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory and the Continuous Electron Beam Accelerator Facility (CEBAF) at the Thomas Jefferson National Laboratory (JLAB). It is also highly relevant to planned experimental efforts at the Large Hadron Collider (LHC) and the future Electron Ion Collider (EIC). All these facilities probe matter via collisions involving nuclei; thus complications arise due to the presence of the attendant nuclear medium. Theoretical efforts to understand and interpret experimental results from such collisions are therefore largely dependent on the resolution of this question. The development of nuclear physics demonstrates that theoretical description is most efficient in terms of the effective degrees of freedom relevant to the scale (energy) being probed. Thus at low energies, nuclei are described as bound states of protons and neutrons (nucleons). At higher energies, the nucleons are no longer elementary, but are revealed to possess an underlying substructure: they are made up of quarks and gluons, collectively termed partons. The mometum distributions of these partons in the nucleon are referred to as Parton Distribution Functions (PDFs). Parton distributions can be determined from experimental measurements of structure functions. The ratio of nuclear structure functions to nucleon structure functions (generically referred to as nuclear ratio) is a measure of the nuclear modifications of the free nucleon PDFs. Thus a study of the nuclear ratio suffices to gain an understanding of nuclear modifications. In this dissertation we aim to describe theoretically nuclear modifications in a restricted region where the nuclear ratio is less than unity, the so
Recent progress on nuclear parton distribution functions
NASA Astrophysics Data System (ADS)
Hirai, M.; Kumano, S.; Saito, K.
2011-09-01
We report current status of global analyses on nuclear parton distribution functions (NPDFs). The optimum NPDFs are determined by analyzing high-energy nuclear reaction data. Due to limited experimental measurements, antiquark modifications have large uncertainties at x > 0.2 and gluon modifications cannot be determined. A nuclear modification difference between u and d quark distributions could be an origin of the long-standing NuTeV sin2θw anomaly. There is also an issue of nuclear modification differences between the structure functions of charged-lepton and neutrino reactions. Next, nuclear clustering effects are discussed in structure functions F2A as a possible explanation for an anomalous result in the 9Be nucleus at the Thomas Jefferson National Accelerator Facility (JLab). Last, tensor-polarized quark and antiquark distribution functions are extracted from HERMES data on the polarized structure function b1 of the deuteron, and they could be used for testing theoretical models and for proposing future experiments, for example, the one at JLab. Such measurements could open a new field of spin physics in spin-one hadrons.
Nuclear Parton Distributions with the LHeC
NASA Astrophysics Data System (ADS)
Klein, Max
2016-03-01
Nuclear parton distributions are far from being known today because of an infant experimental base. Based on design studies of the LHeC and using new simulations, of the inclusive neutral and charged current cross section measurements and of the strange, charm and beauty densities in nuclei, it is demonstrated how that energy frontier electron-ion collider would unfold the complete set of nuclear PDFs in a hugely extended kinematic range of deep inelastic scattering, extending in Bjorken x down to values near to 10-6 in the perturbative domain. Together with a very precise and complete set of proton PDFs, the LHeC nPDFs will thoroughly change the theoretical understanding of parton dynamics and structure inside hadrons.
Guzey, Vadim; Goeke, Klaus; Siddikov, Marat
2009-01-01
We generalize the leading twist theory of nuclear shadowing and calculate quark and gluon generalized parton distributions (GPDs) of spinless nuclei. We predict very large nuclear shadowing for nuclear GPDs. In the limit of the purely transverse momentum transfer, our nuclear GPDs become impact parameter dependent nuclear parton distributions (PDFs). Nuclear shadowing induces non-trivial correlations between the impact parameter $b$ and the light-cone fraction $x$. We make predictions for the deeply virtual Compton scattering (DVCS) amplitude and the DVCS cross section on $^{208}$Pb at high energies. We calculate the cross section of the Bethe-Heitler (BH) process and address the issue of the extraction of the DVCS signal from the $e A \\to e \\gamma A$ cross section. We find that the $e A \\to e \\gamma A$ differential cross section is dominated by DVCS at the momentum transfer $t$ near the minima of the nuclear form factor. We also find that nuclear shadowing leads
Global NLO Analysis of Nuclear Parton Distribution Functions
Hirai, M.; Kumano, S.; Nagai, T.-H.
2008-02-21
Nuclear parton distribution functions (NPDFs) are determined by a global analysis of experimental measurements on structure-function ratios F{sub 2}{sup A}/F{sub 2}{sup A{sup '}} and Drell-Yan cross section ratios {sigma}{sub DY}{sup A}/{sigma}{sub DY}{sup A{sup '}}, and their uncertainties are estimated by the Hessian method. The NPDFs are obtained in both leading order (LO) and next-to-leading order (NLO) of {alpha}{sub s}. As a result, valence-quark distributions are relatively well determined, whereas antiquark distributions at x>0.2 and gluon distributions in the whole x region have large uncertainties. The NLO uncertainties are slightly smaller than the LO ones; however, such a NLO improvement is not as significant as the nucleonic case.
A global reanalysis of nuclear parton distribution functions
NASA Astrophysics Data System (ADS)
Eskola, Kari J.; Kolhinen, Vesa J.; Paukkunen, Hannu; Salgado, Carlos A.
2007-05-01
We determine the nuclear modifications of parton distribution functions of bound protons at scales Q2 >= 1.69 GeV2 and momentum fractions 10-5 <= x <= 1 in a global analysis which utilizes nuclear hard process data, sum rules and leading-order DGLAP scale evolution. The main improvements over our earlier work EKS98 are the automated χ2 minimization, simplified and better controllable fit functions, and most importantly, the possibility for error estimates. The resulting 16-parameter fit to the N = 514 datapoints is good, χ2/d.o.f = 0.82. Within the error estimates obtained, the old EKS98 parametrization is found to be fully consistent with the present analysis, with no essential difference in terms of χ2 either. We also determine separate uncertainty bands for the nuclear gluon and sea quark modifications in the large-x region where they are not stringently constrained by the available data. Comparison with other global analyses is shown and uncertainties demonstrated. Finally, we show that RHIC-BRAHMS data for inclusive hadron production in d+Au collisions lend support for a stronger gluon shadowing at x < 0.01 and also that fairly large changes in the gluon modifications do not rapidly deteriorate the goodness of the overall fits, as long as the initial gluon modifications in the region x ~ 0.02-0.04 remain small.
nCTEQ15 - Global analysis of nuclear parton distributions with uncertainties
Kusina, A.; Jezo, T.; Clark, D. B.; Keppel, Cynthia; Lyonnet, F.; Morfin, Jorge; Olness, F. I.; Owens, Jeff; Schienbein, I.
2015-09-01
We present the first official release of the nCTEQ nuclear parton distribution functions with errors. The main addition to the previous nCTEQ PDFs is the introduction of PDF uncertainties based on the Hessian method. Another important addition is the inclusion of pion production data from RHIC that give us a handle on constraining the gluon PDF. This contribution summarizes our results from arXiv:1509.00792 and concentrates on the comparison with other groups providing nuclear parton distributions.
Generalized parton distributions in nuclei
Vadim Guzey
2009-12-01
Generalized parton distributions (GPDs) of nuclei describe the distribution of quarks and gluons in nuclei probed in hard exclusive reactions, such as e.g. deeply virtual Compton scattering (DVCS). Nuclear GPDs and nuclear DVCS allow us to study new aspects of many traditional nuclear effects (nuclear shadowing, EMC effect, medium modifications of the bound nucleons) as well as to access novel nuclear effects. In my talk, I review recent theoretical progress in the area of nuclear GPDs.
Structure functions and parton distributions
Olness, F.; Tung, Wu-Ki
1991-04-01
Activities of the structure functions and parton distributions group is summarized. The impact of scheme-dependence of parton distributions (especially sea-quarks and gluons) on the quantitative formulation of the QCD parton model is highlighted. Recent progress on the global analysis of parton distributions is summarized. Issues on the proper use of the next-to-leading parton distributions are stressed.
Global parton distributions with nuclear and finite-Q^2 corrections
Owens, J. F.; Accardi, Alberto; Melnitchouk, Wally
2013-05-01
We present three new sets of parton distribution functions (PDFs) determined by global fits to a wide variety of data for hard scattering processes. The analysis includes target mass and higher twist corrections needed for the description of deep inelastic scattering data at large x and low Q^2, and nuclear corrections for deuterium targets. The PDF sets correspond to three different models for the nuclear effects, and provide a more realistic uncertainty range for the d quark PDF, in particular, compared with previous fits. We describe the PDF error sets for each choice of the nuclear corrections, and provide a user interface for utilizing the distributions.
Parton Distributions Working Group
de Barbaro, L.; Keller, S. A.; Kuhlmann, S.; Schellman, H.; Tung, W.-K.
2000-07-20
This report summarizes the activities of the Parton Distributions Working Group of the QCD and Weak Boson Physics workshop held in preparation for Run II at the Fermilab Tevatron. The main focus of this working group was to investigate the different issues associated with the development of quantitative tools to estimate parton distribution functions uncertainties. In the conclusion, the authors introduce a Manifesto that describes an optimal method for reporting data.
Impact of hadronic and nuclear corrections on global analysis of spin-dependent parton distributions
Jimenez-Delgado, Pedro; Accardi, Alberto; Melnitchouk, Wally
2014-02-01
We present the first results of a new global next-to-leading order analysis of spin-dependent parton distribution functions from the most recent world data on inclusive polarized deep-inelastic scattering, focusing in particular on the large-x and low-Q^2 regions. By directly fitting polarization asymmetries we eliminate biases introduced by using polarized structure function data extracted under nonuniform assumptions for the unpolarized structure functions. For analysis of the large-x data we implement nuclear smearing corrections for deuterium and 3He nuclei, and systematically include target mass and higher twist corrections to the g_1 and g_2 structure functions at low Q^2. We also explore the effects of Q^2 and W^2 cuts in the data sets, and the potential impact of future data on the behavior of the spin-dependent parton distributions at large x.
Hadron production in deuteron-gold collisions and nuclear parton distributions
Adeluyi, Adeola; Fai, George
2007-11-15
We calculate nuclear modification factors R{sub dAu}, central-to-peripheral ratios, R{sub CP}, and pseudorapidity asymmetries Y{sub Asym} in deuteron-gold collisions at {radical}(s)=200 GeV in the framework of leading-order (LO) perturbative quantum chromodynamics. We use the Eskola-Kolhinen-Salgado (EKS), the Frankfurt-Guzey-Strikman (FGS), and the Hirai-Kumano-Nagai (HKN) nuclear parton distribution functions and the Albino-Kramer-Kniehl (AKK) fragmentation functions in our calculations. Results are compared to experimental data from the BRAHMS and STAR collaborations.
Hadron production in deuteron-gold collisions and nuclear parton distributions
NASA Astrophysics Data System (ADS)
Adeluyi, Adeola; Fai, George
2007-11-01
We calculate nuclear modification factors RdAu, central-to-peripheral ratios, RCP, and pseudorapidity asymmetries YAsym in deuteron-gold collisions at s=200 GeV in the framework of leading-order (LO) perturbative quantum chromodynamics. We use the Eskola-Kolhinen-Salgado (EKS), the Frankfurt-Guzey-Strikman (FGS), and the Hirai-Kumano-Nagai (HKN) nuclear parton distribution functions and the Albino-Kramer-Kniehl (AKK) fragmentation functions in our calculations. Results are compared to experimental data from the BRAHMS and STAR collaborations.
Medium Effects in Parton Distributions
William Detmold, Huey-Wen Lin
2011-12-01
A defining experiment of high-energy physics in the 1980s was that of the EMC collaboration where it was first observed that parton distributions in nuclei are non-trivially related to those in the proton. This result implies that the presence of the nuclear medium plays an important role and an understanding of this from QCD has been an important goal ever since Here we investigate analogous, but technically simpler, effects in QCD and examine how the lowest moment of the pion parton distribution is modified by the presence of a Bose-condensed gas of pions or kaons.
nCTEQ15: Global analysis of nuclear parton distributions with uncertainties in the CTEQ framework
NASA Astrophysics Data System (ADS)
Kovařík, K.; Kusina, A.; Ježo, T.; Clark, D. B.; Keppel, C.; Lyonnet, F.; Morfín, J. G.; Olness, F. I.; Owens, J. F.; Schienbein, I.; Yu, J. Y.
2016-04-01
We present the new nCTEQ15 set of nuclear parton distribution functions (PDFs) with uncertainties. This fit extends the CTEQ proton PDFs to include the nuclear dependence using data on nuclei all the way up to 208Pb. The uncertainties are determined using the Hessian method with an optimal rescaling of the eigenvectors to accurately represent the uncertainties for the chosen tolerance criteria. In addition to the deep inelastic scattering and Drell-Yan processes, we also include inclusive pion production data from the Relativistic Heavy Ion Collider to help constrain the nuclear gluon PDF. Furthermore, we investigate the correlation of the data sets with specific nuclear PDF flavor components and asses the impact of individual experiments. We also provide comparisons of the nCTEQ15 set with recent fits from other groups.
nCTEQ15 - Global analysis of nuclear parton distributions with uncertainties in the CTEQ framework
Kovarik, K.; Kusina, A.; Jezo, T.; Clark, D. B.; Keppel, C.; Lyonnet, F.; Morfin, J. G.; Olness, F. I.; Owens, J. F.; Schienbein, I.; et al
2016-04-28
We present the new nCTEQ15 set of nuclear parton distribution functions with uncertainties. This fit extends the CTEQ proton PDFs to include the nuclear dependence using data on nuclei all the way up to 208Pb. The uncertainties are determined using the Hessian method with an optimal rescaling of the eigenvectors to accurately represent the uncertainties for the chosen tolerance criteria. In addition to the Deep Inelastic Scattering (DIS) and Drell-Yan (DY) processes, we also include inclusive pion production data from RHIC to help constrain the nuclear gluon PDF. Here, we investigate the correlation of the data sets with specific nPDFmore » flavor components, and asses the impact of individual experiments. We also provide comparisons of the nCTEQ15 set with recent fits from other groups.« less
Partonic Transverse Momentum Distributions
Rossi, Patrizia
2010-08-04
In recent years parton distributions have been generalized to account also for transverse degrees of freedom and new sets of more general distributions, Transverse Momentum Dependent (TMD) parton distributions and fragmentation functions were introduced. Different experiments worldwide (HERMES, COMPASS, CLAS, JLab-Hall A) have measurements of TMDs in semi-inclusive DIS processes as one of their main focuses of research. TMD studies are also an important part of the present and future Drell-Yan experiments at RICH and JPARC and GSI, respectively, Studies of TMDs are also one of the main driving forces of the Jefferson Lab (JLab) 12 GeV upgrade project. Progress in phenomenology and theory is flourishing as well. In this talk an overview of the latest developments in studies of TMDs will be given and newly released results, ongoing activities, as well as planned near term and future measurements will be discussed.
Hirai, M.; Kumano, S.; Nagai, T.-H.
2007-12-15
Nuclear parton distribution functions (NPDFs) are determined by global analyses of experimental data on structure-function ratios F{sub 2}{sup A}/F{sub 2}{sup A'} and Drell-Yan cross-section ratios {sigma}{sub DY}{sup A}/{sigma}{sub DY}{sup A'}. The analyses are done in the leading order (LO) and next-to-leading order (NLO) of running coupling constant {alpha}{sub s}. Uncertainties of the NPDFs are estimated in both LO and NLO for finding possible NLO improvement. Valence-quark distributions are well determined, and antiquark distributions are also determined at x<0.1. However, the antiquark distributions have large uncertainties at x>0.2. Gluon modifications cannot be fixed at this stage. Although the advantage of the NLO analysis, in comparison with the LO one, is generally the sensitivity to the gluon distributions, gluon uncertainties are almost the same in the LO and NLO. It is because current scaling-violation data are not accurate enough to determine precise nuclear gluon distributions. Modifications of the PDFs in the deuteron are also discussed by including data on the proton-deuteron ratio F{sub 2}{sup D}/F{sub 2}{sup p} in the analysis. A code is provided for calculating the NPDFs and their uncertainties at given x and Q{sup 2} in the LO and NLO.
Accardi, Alberto; Owens, Jeff F.
2013-07-01
Three new sets of next-to-leading order parton distribution functions (PDFs) are presented, determined by global fits to a wide variety of data for hard scattering processes. The analysis includes target mass and higher twist corrections needed for the description of deep-inelastic scattering data at large x and low Q^2, and nuclear corrections for deuterium targets. The PDF sets correspond to three different models for the nuclear effects, and provide a more realistic uncertainty range for the d quark PDF compared with previous fits. Applications to weak boson production at colliders are also discussed.
An improved global analysis of nuclear parton distribution functions including RHIC data
NASA Astrophysics Data System (ADS)
Eskola, Kari J.; Paukkunen, Hannu; Salgado, Carlos A.
2008-07-01
We present an improved leading-order global DGLAP analysis of nuclear parton distribution functions (nPDFs), supplementing the traditionally used data from deep inelastic lepton-nucleus scattering and Drell-Yan dilepton production in proton-nucleus collisions, with inclusive high-pT hadron production data measured at RHIC in d+Au collisions. With the help of an extended definition of the χ2 function, we now can more efficiently exploit the constraints the different data sets offer, for gluon shadowing in particular, and account for the overall data normalization uncertainties during the automated χ2 minimization. The very good simultaneous fit to the nuclear hard process data used demonstrates the feasibility of a universal set of nPDFs, but also limitations become visible. The high-pT forward-rapidity hadron data of BRAHMS add a new crucial constraint into the analysis by offering a direct probe for the nuclear gluon distributions—a sector in the nPDFs which has traditionally been very badly constrained. We obtain a strikingly stronger gluon shadowing than what has been estimated in previous global analyses. The obtained nPDFs are released as a parametrization called EPS08.
Off-forward parton distribution
Ji, X.
1998-12-01
Recent developments in studying off-forward parton distributions are discussed. In this talk, the author discusses the recent developments in studying the off-forward parton distributions (OFPD`s). He has written a topical review article on the subject, which will soon be published in Journal of Physics G. The interested audience can consult that article for details. His talk consists of three parts: definition of the new distributions, their physical significance, and experimental measurements.
Extractions of polarized and unpolarized parton distribution functions
Jimenez-Delgado, Pedro
2014-01-01
An overview of our ongoing extractions of parton distribution functions of the nucleon is given. First JAM results on the determination of spin-dependent parton distribution functions from world data on polarized deep-inelastic scattering are presented first, and followed by a short report on the status of the JR unpolarized parton distributions. Different aspects of PDF analysis are briefly discussed, including effects of the nuclear structure of targets, target-mass corrections and higher twist contributions to the structure functions.
Structure functions and parton distributions
Martin, A.D.; Stirling, W.J.; Roberts, R.G.
1995-07-01
The MRS parton distribution analysis is described. The latest sets are shown to give an excellent description of a wide range of deep-inelastic and other hard scattering data. Two important theoretical issues-the behavior of the distributions at small x and the flavor structure of the quark sea-are discussed in detail. A comparison with the new structure function data from HERA is made, and the outlook for the future is discussed.
Modeling Nucleon Generalized Parton Distributions
Radyushkin, Anatoly V.
2013-05-01
We discuss building models for nucleon generalized parton distributions (GPDs) H and E that are based on the formalism of double distributions (DDs). We find that the usual "DD+D-term'' construction should be amended by an extra term, generated by GPD E(x,\\xi). Unlike the $D$-term, this function has support in the whole -1 < x< 1 region, and in general does not vanish at the border points|x|=\\xi.
Parton distributions with threshold resummation
NASA Astrophysics Data System (ADS)
Bonvini, Marco; Marzani, Simone; Rojo, Juan; Rottoli, Luca; Ubiali, Maria; Ball, Richard D.; Bertone, Valerio; Carrazza, Stefano; Hartland, Nathan P.
2015-09-01
We construct a set of parton distribution functions (PDFs) in which fixed-order NLO and NNLO calculations are supplemented with soft-gluon (threshold) resummation up to NLL and NNLL accuracy respectively, suitable for use in conjunction with any QCD calculation in which threshold resummation is included at the level of partonic cross sections. These resummed PDF sets, based on the NNPDF3.0 analysis, are extracted from deep-inelastic scattering, Drell-Yan, and top quark pair production data, for which resummed calculations can be consistently used. We find that, close to threshold, the inclusion of resummed PDFs can partially compensate the enhancement in resummed matrix elements, leading to resummed hadronic cross-sections closer to the fixed-order calculations. On the other hand, far from threshold, resummed PDFs reduce to their fixed-order counterparts. Our results demonstrate the need for a consistent use of resummed PDFs in resummed calculations.
Modeling Nucleon Generalized Parton Distributions
Radyushkin, Anatoly V.
2013-05-01
We discuss building models for nucleon generalized parton distributions (GPDs) H and E that are based on the formalism of double distributions (DDs). We found that the usual "DD+D-term" construction should be amended by an extra term, xiE^1_+ (x,xi) built from the alpha/Beta moment of the DD e(Beta,alpha) that generates GPD E(x,xi). Unlike the D-term, this function has support in the whole -1< x<1 region, and in general does not vanish at the border points |x|=xi.
Jet correlations from unintegrated parton distributions
Hautmann, F.; Jung, H.
2008-10-13
Transverse-momentum dependent parton distributions can be introduced gauge-invariantly in QCD from high-energy factorization. We discuss Monte Carlo applications of these distributions to parton showers and jet physics, with a view to the implications for the Monte Carlo description of complex hadronic final states with multiple hard scales at the LHC.
Unraveling hadron structure with generalized parton distributions
Andrei Belitsky; Anatoly Radyushkin
2004-10-01
The recently introduced generalized parton distributions have emerged as a universal tool to describe hadrons in terms of quark and gluonic degrees of freedom. They combine the features of form factors, parton densities and distribution amplitudes - the functions used for a long time in studies of hadronic structure. Generalized parton distributions are analogous to the phase-space Wigner quasi-probability function of non-relativistic quantum mechanics which encodes full information on a quantum-mechanical system. We give an extensive review of main achievements in the development of this formalism. We discuss physical interpretation and basic properties of generalized parton distributions, their modeling and QCD evolution in the leading and next-to-leading orders. We describe how these functions enter a wide class of exclusive reactions, such as electro- and photo-production of photons, lepton pairs, or mesons.
Generalized parton distributions at CLAS
Silvia Pisano
2010-11-01
The understanding of the hadron structure in terms of QCD degrees of freedom is one of the main challenges of hadron physics. Indeed, despite the large amount of theoretical and experimental activity devoted to the subject in the last years, a full comprehension of mesons and baryons in terms of quark and gluon fields is still lacking. In order to operate a more detailed investigation of the hadron structure, new quantities have been introduced ten years ago, the Generalized Parton Distributions (GPDs), defined as bilocal, off-forward matrix elements of quark and gluon operators. From an experimental point of view, GPDs are accessible through two main processes: Deeply Virtual Compton Scattering (DVCS) and Deeply Virtual Meson Electroproduction (DVMP). Depending on the polarization degrees of freedom acting in the process (like, for example, the simultaneous presence of a polarization in the beam and in the target, or the usage of a polarized beam with an unpolarized target), various combinations of GPDs can be accessed. In the case of DVCS, for example, the measurement of the Single Spin Asymmetry of processes like View the MathML source – realized by using a longitudinally polarized target - gives access to a combination of the GDPs H and H̃. The CEBAF Large Acceptance Spectrometer (CLAS) installed in the Hall-B at JLab, is particularly suited for the extraction of these quantities. Its large acceptance implies a good capability in the reconstruction of exclusive final states, allowing the investigation of the aforementioned processes in a wide range of kinematics. In this presentation, an overview of the main GPD measurements performed by CLAS will be given. In particular, the first DVCS measurements realized both with unpolarized and polarized target, together with the measurements of some exclusive meson electroproduction processes, will be described.
Transverse-momentum-dependent parton distributions (TMDs)
NASA Astrophysics Data System (ADS)
Bacchetta, Alessandro
2011-10-01
Transverse-momentum-dependent parton distributions (TMDs) provide three-dimensional images of the partonic structure of the nucleon in momentum space. We made impressive progress in understanding TMDs, both from the theoretical and experimental point of view. This brief overview on TMDs is divided in two parts: in the first, an essential list of achievements is presented. In the second, a selection of open questions is discussed.
Generalized parton distributions of the pion
Broniowski, Wojciech; Arriola, Enrique Ruiz; Golec-Biernat, Krzysztof
2008-08-31
Generalized Parton Distributions of the pion are evaluated in chiral quark models with the help of double distributions. As a result the polynomiality conditions are automatically satisfied. In addition, positivity constraints, proper normalization and support, sum rules, and soft pion theorems are fulfilled. We obtain explicit expressions holding at the low-energy quark-model scale, which exhibit no factorization in the t-dependence. The crucial QCD evolution of the quark-model distributions is carried out up to experimental or lattice scales. The obtained results for the Parton Distribution Function and the Parton Distribution Amplitude describe the available experimental and lattice data, confirming that the quark-model scale is low, around 320 MeV.
PARTON SATURATION, PRODUCTION, AND EQUILIBRATION IN HIGH ENERGY NUCLEAR COLLISIONS
VENUGOPALAN,R.
1999-03-20
Deeply inelastic scattering of electrons off nuclei can determine whether parton distributions saturate at HERA energies. If so, this phenomenon will also tell us a great deal about how particles are produced, and whether they equilibrate, in high energy nuclear collisions.
Constraints on parton distribution from CDF
Bodek, A.; CDF Collaboration
1995-10-01
The asymmetry in W{sup -} - W{sup +} production in p{bar p} collisions and Drell-Yan data place tight constraints on parton distributions functions. The W asymmetry data constrain the slope of the quark distribution ratio d(x)/u(x) in the x range 0.007-0.27. The published W asymmetry results from the CDF 1992.3 data ({approx} 20 pb{sup -1}) greatly reduce the systematic error originating from the choice of PDF`s in the W mass measurement at CDF. These published results have also been included in the CTEQ3, MRSA, and GRV94 parton distribution fits. These modern parton distribution functions axe still in good agreement with the new 1993-94 CDF data({approx} 108 pb{sup -1} combined). Preliminary results from CDF for the Drell-Yan cross section in the mass range 11-350 GeV/c{sup 2} are discussed.
Studies of Transverse Momentum Distributions of Partons
NASA Astrophysics Data System (ADS)
Avagyan, Harut
2014-03-01
The detailed understanding of the orbital structure of partonic distributions, encoded in Transverse Momentum Dependent (TMD) parton distributions, has been widely recognized as key objective of the JLab 12 GeV upgrade, the polarised pp program at RHIC, and a driving force behind the construction of the Electron Ion Collider. Several proposals have been already approved by the JLab PAC to study TMDs using different spin-azimuthal asymmetries at JLab12 and were awarded the highest physics rating. Although the interest in TMDs has grown enormously we are still in need of fresh theoretical and phenomenological ideas. One of the main challenges still remaining is the extraction of actual 3D parton distribution functions from hard scattering processes in nucleons and nuclei. In this talk, we present an overview of the latest developments and future studies of the TMDs.
The parton distribution function library
Plothow-Besch, H.
1995-07-01
This article describes an integrated package of Parton Density Functions called PDFLIB which has been added to the CERN Program Library Pool W999 and is labelled as W5051. In this package all the different sets of parton density functions of the Nucleon, Pion and the Photon which are available today have been put together. All these sets have been combined in a consistent way such that they all have similar calling sequences and no external data files have to be read in anymore. A default set has been prepared, although those preferring their own set or wanting to test a new one may do so within the package. The package also offers a program to calculate the strong coupling constant {alpha}, to first or second order. The correct {Lambda}{sub QCD} associated to the selected set of structure functions and the number of allowed flavours with respect to the given Q{sup 2} is automatically used in the calculation. The selection of sets, the program parameters as well as the possibilities to modify the defaults and to control errors occurred during execution are described.
Progress in the dynamical parton distributions
Jimenez-Delgado, Pedro
2012-06-01
The present status of the (JR) dynamical parton distribution functions is reported. Different theoretical improvements, including the determination of the strange sea input distribution, the treatment of correlated errors and the inclusion of alternative data sets, are discussed. Highlights in the ongoing developments as well as (very) preliminary results in the determination of the strong coupling constant are presented.
Evolution and models for skewed parton distribution
Musatov, I.C.; Radyushkin, A.V.
1999-05-17
The authors discuss the structure of the ''forward visible'' (FW) parts of double and skewed distributions related to usual distributions through reduction relations. They use factorized models for double distributions (DDs) {tilde f}(x,{alpha}) in which one factor coincides with the usual (forward) parton distribution and another specifies the profile characterizing the spread of the longitudinal momentum transfer. The model DDs are used to construct skewed parton distributions (SPDs). For small skewedness, the FW parts of SPDs H ({tilde x},{xi}) can be obtained by averaging forward parton densities f({tilde x}-{xi}{alpha}) with the weight {rho}({alpha}) coinciding with the profile function of the double distribution {tilde f}(x, {alpha}) at small x. They show that if the x{sup n} moments {tilde f}{sub n}({alpha}) of DDs have the asymptotic (1-{alpha}{sup 2}){sup n+1} profile, then the {alpha}-profile of {tilde f}(x,{alpha}) for small x is completely determined by small-x behavior of the usual parton distribution. They demonstrate that, for small {xi}, the model with asymptotic profiles for {tilde f}{sub n}({alpha}) is equivalent to that proposed recently by Shuvaev et al., in which the Gegenbauer moments of SPDs do not depend on {xi}. They perform a numerical investigation of the evolution patterns of SPDs and give interpretation of the results of these studies within the formalism of double distributions.
Parton Distributions and Spin-Orbital Correlations
Yuan, Feng
2007-09-24
In this talk, I summarize a recent study showing that the large-x parton distributions contain important information on the quark orbital angular momentum of nucleon. This contribution could explain the conflict between the experimental data and the theory predictions for the polarized quark distributions. Future experiments at JLab shall provide further test for our predictions.
PARTON DISTRIBUTIONS AND SPIN-ORBITAL CORRELATIONS.
FENG,Y.
2007-05-21
In this talk, the author summarizes a recent study showing that the large-x parton distributions contain important information on the quark orbital angular momentum of nucleon. This contribution could explain the conflict between the experimental data and the theory predictions for the polarized quark distributions. Future experiments at JLAB shall provide further test for our predictions.
Uncertainties in determining parton distributions at large x
Alberto Accardi, Wolodymyr Melnitchouk, Jeff Owens, Michael Christy, Cynthia Keppel, Lingyan Zhu, Jorge Morfin
2011-07-01
We critically examine uncertainties in parton distribution functions (PDFs) at large x arising from nuclear effects in deuterium F2 structure function data. Within a global PDF analysis, we assess the impact on the PDFs from uncertainties in the deuteron wave function at short distances and nucleon off-shell effects, the use of relativistic kinematics, as well as the use of less a restrictive parametrization of the d/u ratio. We find that in particular the d-quark and gluon PDFs vary significantly with the choice of nuclear model. We highlight the impact of these uncertainties on the determination of the neutron structure function, and on W boson production and parton luminosity at the Tevatron and the LHC. Finally, we discuss prospects for new measurements sensitive to the d-quark and gluon distributions but insensitive to nuclear corrections.
Delineating parton distributions and the strong coupling
Jimenez-Delgado, P.; Reya, E.
2014-04-29
In this study, global fits for precision determinations of parton distributions, together with the highly correlated strong coupling α_{s}, are presented up to next-to-next-to- leading order (NNLO) of QCD utilizing most world data (charm and jet production data are used where theoretically possible), except Tevatron gauge boson production data and LHC data which are left for genuine predictions. This is done within the 'dynamical' (valencelike input at Q_{0}^{2} = 0.8 GeV^{2} ) and 'standard' (input at Q_{0}^{2} = 2 GeV^{2}) approach. The stability and reliability of the results are ensured by including nonperturbative higher-twist terms, nuclear corrections as well as target mass corrections, and by applying various (Q^{2}, W^{2}) cuts on available data. In addition, the Q_{0}^{2} dependence of the results is studied in detail. Predictions are given, in particular for LHC, on gauge and Higgs boson as well as for top-quark pair production. At NNLO the dynamical approach results in α_{s}(M_{Z}^{2}) = 0.1136 ± 0.0004, whereas the somewhat less constrained standard fit gives α_{s}(M_{Z}^{2}) = 0.1162 ± 0.0006.
Delineating parton distributions and the strong coupling
Jimenez-Delgado, P.; Reya, E.
2014-04-29
In this study, global fits for precision determinations of parton distributions, together with the highly correlated strong coupling αs, are presented up to next-to-next-to- leading order (NNLO) of QCD utilizing most world data (charm and jet production data are used where theoretically possible), except Tevatron gauge boson production data and LHC data which are left for genuine predictions. This is done within the 'dynamical' (valencelike input at Q02 = 0.8 GeV2 ) and 'standard' (input at Q02 = 2 GeV2) approach. The stability and reliability of the results are ensured by including nonperturbative higher-twist terms, nuclear corrections as well asmore » target mass corrections, and by applying various (Q2, W2) cuts on available data. In addition, the Q02 dependence of the results is studied in detail. Predictions are given, in particular for LHC, on gauge and Higgs boson as well as for top-quark pair production. At NNLO the dynamical approach results in αs(MZ2) = 0.1136 ± 0.0004, whereas the somewhat less constrained standard fit gives αs(MZ2) = 0.1162 ± 0.0006.« less
Modeling the Pion Generalized Parton Distribution
NASA Astrophysics Data System (ADS)
Mezrag, C.
2016-02-01
We compute the pion Generalized Parton Distribution (GPD) in a valence dressed quarks approach. We model the Mellin moments of the GPD using Ansätze for Green functions inspired by the numerical solutions of the Dyson-Schwinger Equations (DSE) and the Bethe-Salpeter Equation (BSE). Then, the GPD is reconstructed from its Mellin moment using the Double Distribution (DD) formalism. The agreement with available experimental data is very good.
Evolution and models for skewed parton distributions
Musatov, I. V.; Radyushkin, A. V.
2000-04-01
We discuss the structure of the ''forward visible'' (FV) parts of double and skewed distributions related to the usual distributions through reduction relations. We use factorized models for double distributions (DD's) f(tilde sign)(x,{alpha}) in which one factor coincides with the usual (forward) parton distribution and another specifies the profile characterizing the spread of the longitudinal momentum transfer. The model DD's are used to construct skewed parton distributions (SPD's). For small skewedness, the FV parts of SPD's H(x(tilde sign),{xi}) can be obtained by averaging forward parton densities f(x(tilde sign)-{xi}{alpha}) with the weight {rho}({alpha}) coinciding with the profile function of the double distribution f(tilde sign)(x,{alpha}) at small x. We show that if the x{sup n} moments f(tilde sign){sub n}({alpha}) of DD's have the asymptotic (1-{alpha}{sup 2}){sup n+1} profile, then the {alpha} profile of f(tilde sign)(x,{alpha}) for small x is completely determined by the small-x behavior of the usual parton distribution. We demonstrate that, for small {xi}, the model with asymptotic profiles for f(tilde sign){sub n}({alpha}) is equivalent to that proposed recently by Shuvaev et al., in which the Gegenbauer moments of SPD's do not depend on {xi}. We perform a numerical investigation of the evolution patterns of SPD's and give an interpretation of the results of these studies within the formalism of double distributions. (c) 2000 The American Physical Society.
Generalized parton distributions and exclusive processes
Guzey, Vadim
2013-10-01
In last fifteen years, GPDs have emerged as a powerful tool to reveal such aspects of the QCD structure of the nucleon as: - 3D parton correlations and distributions; - spin content of the nucleon. Further advances in the field of GPDs and hard exclusive processes rely on: - developments in theory and new methods in phenomenology such as new flexible parameterizations, neural networks, global QCD fits - new high-precision data covering unexplored kinematics: JLab at 6 and 12 GeV, Hermes with recoil detector, Compass, EIC. This slide-show presents: Nucleon structure in QCD, particularly hard processes, factorization and parton distributions; and a brief overview of GPD phenomenology, including basic properties of GPDs, GPDs and QCD structure of the nucleon, and constraining GPDs from experiments.
Parton Distributions in the Impact Parameter Space
Matthias Burkardt
2009-08-01
Parton distributions in impact parameter space, which are obtained by Fourier transforming GPDs, exhibit a significant deviation from axial symmetry when the target and/or quark is transversely polarized. In combination with the final state interactions, this transverse deformation provides a natural mechanism for naive-T odd transverse single-spin asymmetries in semi-inclusive DIS. The deformation can also be related to the transverse force acting on the active quark in polarized DIS at higher twist.
Access to generalized parton distributions at COMPASS
Nowak, Wolf-Dieter
2015-04-10
A brief experimentalist's introduction to Generalized Parton Distributions (GPDs) is given. Recent COMPASS results are shown on transverse target-spin asymmetries in hard exclusive ρ{sup 0} production and their interpretation in terms of a phenomenological model as indication for chiral-odd, transverse GPDs is discussed. For deeply virtual Compton scattering, it is briefly outlined how to access GPDs and projections are shown for future COMPASS measurements.
Generalized Parton Distributions and their Singularities
Anatoly Radyushkin
2011-04-01
A new approach to building models of generalized parton distributions (GPDs) is discussed that is based on the factorized DD (double distribution) Ansatz within the single-DD formalism. The latter was not used before, because reconstructing GPDs from the forward limit one should start in this case with a very singular function $f(\\beta)/\\beta$ rather than with the usual parton density $f(\\beta)$. This results in a non-integrable singularity at $\\beta=0$ exaggerated by the fact that $f(\\beta)$'s, on their own, have a singular $\\beta^{-a}$ Regge behavior for small $\\beta$. It is shown that the singularity is regulated within the GPD model of Szczepaniak et al., in which the Regge behavior is implanted through a subtracted dispersion relation for the hadron-parton scattering amplitude. It is demonstrated that using proper softening of the quark-hadron vertices in the regions of large parton virtualities results in model GPDs $H(x,\\xi)$ that are finite and continuous at the "border point'' $x=\\xi$. Using a simple input forward distribution, we illustrate the implementation of the new approach for explicit construction of model GPDs. As a further development, a more general method of regulating the $\\beta=0$ singularities is proposed that is based on the separation of the initial single DD $f(\\beta, \\alpha)$ into the "plus'' part $[f(\\beta,\\alpha)]_{+}$ and the $D$-term. It is demonstrated that the "DD+D'' separation method allows to (re)derive GPD sum rules that relate the difference between the forward distribution $f(x)=H(x,0)$ and the border function $H(x,x)$ with the $D$-term function $D(\\alpha)$.
Generalized parton distributions and their singularities
Radyushkin, A. V.
2011-04-01
A new approach to building models of generalized parton distributions (GPDs) is discussed that is based on the factorized DD (double distribution) ansatz within the single-DD formalism. The latter was not used before, because reconstructing GPDs from the forward limit one should start in this case with a very singular function f({beta})/{beta} rather than with the usual parton density f({beta}). This results in a nonintegrable singularity at {beta}=0 exaggerated by the fact that f({beta})'s, on their own, have a singular {beta}{sup -a} Regge behavior for small {beta}. It is shown that the singularity is regulated within the GPD model of Szczepaniak et al., in which the Regge behavior is implanted through a subtracted dispersion relation for the hadron-parton scattering amplitude. It is demonstrated that using proper softening of the quark-hadron vertices in the regions of large parton virtualities results in model GPDs H(x,{xi}) that are finite and continuous at the 'border point' x={xi}. Using a simple input forward distribution, we illustrate implementation of the new approach for explicit construction of model GPDs. As a further development, a more general method of regulating the {beta}=0 singularities is proposed that is based on the separation of the initial single DD f({beta},{alpha}) into the 'plus' part [f({beta},{alpha})]{sub +} and the D term. It is demonstrated that the ''DD+D'' separation method allows one to (re)derive GPD sum rules that relate the difference between the forward distribution f(x)=H(x,0) and the border function H(x,x) with the D-term function D({alpha}).
Nondiagonal parton distributions at small x
NASA Astrophysics Data System (ADS)
Frankfurt, L. L.; Freund, A.; Guzey, V.; Strikman, M.
1997-04-01
In this paper we make predictions for nondiagonal parton distributions in a proton in the LLA. We calculate the DGLAP-type evolution kernels in the LLA, solve the nondiagonal GLAP evolution equations with a modified version of the CTEQ-package and comment on the range of applicability of the LLA in the asymmetric regime. We show that the nondiagonal gluon distribution x2G(x1,x2,Q2) can be well approximated at small x by the conventional gluon density xG(x,Q2) and explain that the cross sections of hard diffractive processes are determined by x2G(x1,x2).
First moments of nucleon generalized parton distributions
Wang, P.; Thomas, A. W.
2010-06-01
We extrapolate the first moments of the generalized parton distributions using heavy baryon chiral perturbation theory. The calculation is based on the one loop level with the finite range regularization. The description of the lattice data is satisfactory, and the extrapolated moments at physical pion mass are consistent with the results obtained with dimensional regularization, although the extrapolation in the momentum transfer to t=0 does show sensitivity to form factor effects, which lie outside the realm of chiral perturbation theory. We discuss the significance of the results in the light of modern experiments as well as QCD inspired models.
Evolution of minimum-bias parton fragmentation in nuclear collisions
Trainor, Thomas A.
2009-10-15
Minimum-bias fragment distributions (FDs) are calculated by folding a power-law parton energy spectrum with parametrized fragmentation functions (FFs) derived from e{sup +}-e{sup -} and p-p collisions. Substantial differences between measured e{sup +}-e{sup -} and p-p FFs suggest that FF 'universality' may not be a valid assumption. The common parton spectrum is constrained by comparison with a p-p p{sub t} spectrum hard component. Changes in FFs due to parton 'energy loss' or 'medium modification' are modeled by altering FF parametrizations consistent with rescaling QCD splitting functions. In-vacuum and in-medium FDs are compared with spectrum hard components from 200-GeV Au-Au collisions for several centralities. The reference for all nuclear collisions is the FD derived from in-vacuum e{sup +}-e{sup -} FFs. The hard component for p-p and peripheral Au-Au collisions is found to be strongly suppressed for smaller fragment momenta, consistent with the FD derived from in-vacuum p-p FFs. At a particular centrality the Au-Au hard component transitions to enhancement at smaller momenta and suppression at larger momenta, consistent with FDs derived from in-medium e{sup +}-e{sup -} FFs. Fragmentation systematics suggest that QCD color connections change dramatically in more-central A-A collisions. Observed parton and hadron spectrum systematics are inconsistent with saturation-scale arguments used to support assumptions of parton thermalization.
Self-Organizing Maps and Parton Distribution Functions
K. Holcomb, Simonetta Liuti, D. Z. Perry
2011-05-01
We present a new method to extract parton distribution functions from high energy experimental data based on a specific type of neural networks, the Self-Organizing Maps. We illustrate the features of our new procedure that are particularly useful for an anaysis directed at extracting generalized parton distributions from data. We show quantitative results of our initial analysis of the parton distribution functions from inclusive deep inelastic scattering.
Parton and valon distributions in the nucleon
Hwa, R.C.; Sajjad Zahir, M.
1981-06-01
Structure functions of the nucleon are analyzed in the valon model in which a nucleon is assumed to be a bound state of three valence quark clusters (valons). At high Q/sup 2/ the structure of the valons is described by leading-order results in the perturbative quantum chromodynamics. From the experimental data on deep-inelastic scattering off protons and neutrons, the flavor-dependent valon distributions in the nucleon are determined. Predictions for the parton distributions are then made for high Q/sup 2/ without guesses concerning the quark and gluon distributions at low Q/sup 2/. The sea-quark and gluon distributions are found to have a sharp peak at very small x. Convenient parametrization is provided which interpolates between different numbers of flavors.
A.V. Efremov, P. Schweitzer, O.V. Teryaev, P. Zavada
2011-03-01
We derive relations between transverse momentum dependent distribution functions (TMDs) and the usual parton distribution functions (PDFs) in the 3D covariant parton model, which follow from Lorentz invariance and the assumption of a rotationally symmetric distribution of parton momenta in the nucleon rest frame. Using the known PDFs f_1(x) and g_1(x) as input we predict the x- and pT-dependence of all twist-2 T-even TMDs.
Experimental studies of Generalized Parton Distributions
NASA Astrophysics Data System (ADS)
Niccolai, Silvia
2015-12-01
Generalized Parton Distributions (GPDs) are nowadays the object of an intense effort of research, in the perspective of understanding nucleon structure. They describe the correlations between the longitudinal momentum and the transverse spatial position of the partons inside the nucleon and they can give access to the contribution of the orbital momentum of the quarks to the nucleon spin. Deeply Virtual Compton scattering (DVCS), the electroproduction on the nucleon, at the quark level, of a real photon, is the process more directly interpretable in terms of GPDs of the nucleon. Depending on the target nucleon (proton or neutron) and on the DVCS observable extracted (cross-sections, target- or beam-spin asymmetries, etc.), different sensitivity to the various GPDs for each quark flavor can be exploited. This article is focused on recent promising results, obtained at Jefferson Lab, on cross-sections and asymmetries for DVCS, and their link to GPDs. These data open the way to a “tomographic” representation of the structure of the nucleon, allowing the extraction of transverse-space densities of the quarks at fixed longitudinal momentum. The extensive experimental program to measure GPDs at Jefferson Lab with the 12 GeV-upgraded electron accelerator and the complementary detectors that will be housed in three experimental Halls (A, B and C), will also be presented.
New model for nucleon generalized parton distributions
Radyushkin, Anatoly V.
2014-01-01
We describe a new type of models for nucleon generalized parton distributions (GPDs) H and E. They are heavily based on the fact nucleon GPDs require to use two forms of double distribution (DD) representations. The outcome of the new treatment is that the usual DD+D-term construction should be amended by an extra term, {xi} E{sub +}{sup 1} (x,{xi}) which has the DD structure {alpha}/{beta} e({beta},{alpha}, with e({beta},{alpha}) being the DD that generates GPD E(x,{xi}). We found that this function, unlike the D-term, has support in the whole -1 <= x <= 1 region. Furthermore, it does not vanish at the border points |x|={xi}.
Nucleon Generalized Parton Distributions from Full Lattice QCD
Robert Edwards; Philipp Haegler; David Richards; John Negele; Konstantinos Orginos; Wolfram Schroers; Jonathan Bratt; Andrew Pochinsky; Michael Engelhardt; George Fleming; Bernhard Musch; Dru Renner
2007-07-03
We present a comprehensive study of the lowest moments of nucleon generalized parton distributions in N_f=2+1 lattice QCD using domain wall valence quarks and improved staggered sea quarks. Our investigation includes helicity dependent and independent generalized parton distributions for pion masses as low as 350 MeV and volumes as large as (3.5 fm)^3.
Pion valence-quark parton distribution function
NASA Astrophysics Data System (ADS)
Chang, Lei; Thomas, Anthony W.
2015-10-01
Within the Dyson-Schwinger equation formulation of QCD, a rainbow ladder truncation is used to calculate the pion valence-quark distribution function (PDF). The gap equation is renormalized at a typical hadronic scale, of order 0.5 GeV, which is also set as the default initial scale for the pion PDF. We implement a corrected leading-order expression for the PDF which ensures that the valence-quarks carry all of the pion's light-front momentum at the initial scale. The scaling behavior of the pion PDF at a typical partonic scale of order 5.2 GeV is found to be (1 - x) ν, with ν ≃ 1.6, as x approaches one.
Generalized parton distributions: Status and perspectives
Weiss, Christian
2009-01-01
We summarize recent developments in understanding the concept of generalized parton distributions (GPDs), its relation to nucleon structure, and its application to high-Q^2 electroproduction processes. Following a brief review of QCD factorization and transverse nucleon structure, we discuss (a) new theoretical methods for the analysis of deeply-virtual Compton scattering (t-channel-based GPD parametrizations, dispersion relations); (b) the phenomenology of hard exclusive meson production (experimental tests of dominance of small-size configurations, model-independent comparative studies); (c) the role of GPDs in small-x physics and pp scattering (QCD dipole model, central exclusive diffraction). We emphasize the usefulness of the transverse spatial (or impact parameter) representation for both understanding the reaction mechanism in hard exclusive processes and visualizing the physical content of the GPDs.
First JAM results on the determination of polarized parton distributions
Accardi, Alberto; Jimenez-Delgado, Pedro; Melnitchouk, Wally
2014-01-01
The Jefferson Lab Angular Momentum (JAM) Collaboration is a new initiative to study the angular momentum dependent structure of the nucleon. First results on the determination of spin-dependent parton distribution functions at intermediate and large x from world data on polarized deep-inelastic scattering are presented. Different aspects of global QCD analysis are discussed, including the effects of nuclear structure of deuterium and {sup 3}He targets, target mass corrections and higher twist contributions to the g{sub 1} and g{sub 2} structure functions.
First JAM results on the determination of polarized parton distributions
Jimenez-Delgado, Pedro
2013-04-01
The Jefferson Lab Angular Momentum (JAM) collaboration is a new initiative aimed to the study of the angular-momentum-dependent structure of the nucleon. First results on the determination of spin-dependent parton distribution functions from world data on polarized deep-inelastic scattering will be presented and compared with previous determinations from other groups. Different aspects of global QCD analysis will be discussed, including effects due to nuclear structure, higher twist, and target-mass corrections, as well as the impact of different data selections.
Parton distributions from SMC and SLAC data
Ramsey, G.P. |; Goshtasbpour, M. |
1996-01-04
We have extracted spin-weighted parton distributions in a proton from recent data at CERN and SLAC. The valence, sea quark and Antiquark spin-weighted distributions are determined separately. The data are all consistent with a small to moderate polarized gluon distribution, so that the anomaly term is not significant in the determination of the constituent contributions to the spin of the proton. We have analyzed the consistency of the results obtained from various sets of data and the Biorken sum rule. Although all data are consistent with the sum rule, the polarized distributions from different experiments vary, even with higher order QCD corrections taken into account. Results split into two models, one set implying a large polarized strange sea which violates the positivity bound, and the other set yielding a smaller polarized strange sea. Only further experiments which extract information about the polarized sea will reconcile these differences. We suggest specific experiments which can be performed to determine the size of the polarized sea and gluons.
Prospects For Measurements Of Generalized Parton Distributions At COMPASS
Neyret, Damien
2007-06-13
The concept of Generalized Parton Distributions extends classical parton distributions by giving a '3-dimensional' view of the nucleons, allowing to study correlations between the parton longitudinal momentum and its transverse position in the nucleon. Measurements of such generalized distributions can be done with the COMPASS experiment, in particular using Deeply Virtual Compton Scattering events. They require to modify the set-up of COMPASS by introducing a recoil proton detector, an additional electromagnetic calorimeter and a new liquid hydrogen target. These upgrades are presently under study, and the first data taking could take place in 2010.
Nonperturbative parton distributions and the proton spin problem
NASA Astrophysics Data System (ADS)
Simonov, Yu. A.
2016-05-01
The Lorentz contracted form of the static wave functions is used to calculate the valence parton distributions for mesons and baryons, boosting the rest frame solutions of the path integral Hamiltonian. It is argued that nonperturbative parton densities are due to excitedmultigluon baryon states. A simplemodel is proposed for these states ensuring realistic behavior of valence and sea quarks and gluon parton densities at Q 2 = 10 (GeV/ c)2. Applying the same model to the proton spin problem one obtains Σ3 = 0.18 for the same Q 2.
J.W. Negele; R.C. Brower; P. Dreher; R. Edwards; G. Fleming; Ph. Hagler; U.M. Heller; Th. Lippert; A.V.Pochinsky; D.B. Renner; D. Richards; K. Schilling; W. Schroers
2004-04-01
This talk presents recent calculations in full QCD of the lowest three moments of generalized parton distributions and the insight they provide into the behavior of nucleon electromagnetic form factors, the origin of the nucleon spin, and the transverse structure of the nucleon. In addition, new exploratory calculations in the chiral regime of full QCD are discussed.
The role of the input scale in parton distribution analyses
Pedro Jimenez-Delgado
2012-08-01
A first systematic study of the effects of the choice of the input scale in global determinations of parton distributions and QCD parameters is presented. It is shown that, although in principle the results should not depend on these choices, in practice a relevant dependence develops as a consequence of what is called procedural bias. This uncertainty should be considered in addition to other theoretical and experimental errors, and a practical procedure for its estimation is proposed. Possible sources of mistakes in the determination of QCD parameter from parton distribution analysis are pointed out.
Selected topics on parton distribution functions
Hirai, M.; Saito, K.; Kawamura, H.; Kumano, S.
2011-12-14
We report recent studies on structure functions of the nucleon and nuclei. First, clustering effects are investigated in the structure function F{sub 2} of {sup 9}Be for explaining an unusual nuclear correction found in a JLab experiment. We propose that high densities created by formation of clustering structure like 2{alpha}+neutron in {sup 9}Be is the origin of the unexpected JLab result by using the antisymmetrized molecular dynamics (AMD). There is an approved proposal at JLab to investigate the structure functions of light nuclei including the cluster structure, so that much details will become clear in a few years. Second, tensor-polarized quark and antiquark distributions are obtained by analyzing HERMES measurements on the structure function b{sub 1} for the deuteron. The result suggests a finite tensor polarization for antiquark distributions, which is an interesting topic for further theoretical and experimental investigations. An experimental proposal exists at JLab for measuring b{sub 1} of the deuteron as a new tensor-structure study in 2010's. Furthermore, the antiquark tensor polarization could be measured by polarized deuteron Drell-Yan processes at hadron facilities such as J-PARC and GSI-FAIR. Third, the recent CDF dijet anomaly is investigated within the standard model by considering possible modifications of the strange-quark distribution. We find that the shape of a dijet-mass spectrum changes depending on the strange-quark distribution. It indicates that the CDF excess could be partially explained as a PDF effect, particularly by the strangeness in the nucleon, within the standard model if the excess at m{sub jj}{approx_equal}140 GeV is not a sharp peak.
Transverse momentum dependent (TMD) parton distribution functions: Status and prospects*
Angeles-Martinez, R.; Bacchetta, A.; Balitsky, Ian I.; Boer, D.; Boglione, M.; Boussarie, R.; Ceccopieri, F. A.; Cherednikov, I. O.; Connor, P.; Echevarria, M. G.; et al
2015-01-01
In this study, we review transverse momentum dependent (TMD) parton distribution functions, their application to topical issues in high-energy physics phenomenology, and their theoretical connections with QCD resummation, evolution and factorization theorems. We illustrate the use of TMDs via examples of multi-scale problems in hadronic collisions. These include transverse momentum qT spectra of Higgs and vector bosons for low qT, and azimuthal correlations in the production of multiple jets associated with heavy bosons at large jet masses. We discuss computational tools for TMDs, and present the application of a new tool, TMDLIB, to parton density fits and parameterizations.
Recent progress in the statistical approach of parton distributions
Soffer, Jacques
2011-07-15
We recall the physical features of the parton distributions in the quantum statistical approach of the nucleon. Some predictions from a next-to-leading order QCD analysis are compared to recent experimental results. We also consider their extension to include their transverse momentum dependence.
Illuminating the 1/x Moment of Parton Distribution Functions
Brodsky, Stanley J.; Llanes-Estrada, Felipe J.; Szczepaniak, Adam P.; /Indiana U.
2007-10-15
The Weisberger relation, an exact statement of the parton model, elegantly relates a high-energy physics observable, the 1/x moment of parton distribution functions, to a nonperturbative low-energy observable: the dependence of the nucleon mass on the value of the quark mass or its corresponding quark condensate. We show that contemporary fits to nucleon structure functions fail to determine this 1/x moment; however, deeply virtual Compton scattering can be described in terms of a novel F1/x(t) form factor which illuminates this physics. An analysis of exclusive photon-induced processes in terms of the parton-nucleon scattering amplitude with Regge behavior reveals a failure of the high Q2 factorization of exclusive processes at low t in terms of the Generalized Parton-Distribution Functions which has been widely believed to hold in the past. We emphasize the need for more data for the DVCS process at large t in future or upgraded facilities.
New parton distributions from large-x and low-Q^{2} data
Alberto Accardi; Christy, M. Eric; Keppel, Cynthia E.; Melnitchouk, Wally; Monaghan, Peter A.; Morfin, Jorge G.; Owens, Joseph F.
2010-02-11
We report results of a new global next-to-leading order fit of parton distribution functions in which cuts on W and Q are relaxed, thereby including more data at high values of x. Effects of target mass corrections (TMCs), higher twist contributions, and nuclear corrections for deuterium data are significant in the large-x region. The leading twist parton distributions are found to be stable to TMC model variations as long as higher twist contributions are also included. Furthermore, the behavior of the d quark as x → 1 is particularly sensitive to the deuterium corrections, and using realistic nuclear smearing models the d-quark distribution at large x is found to be softer than in previous fits performed with more restrictive cuts.
New parton distributions from large-x and low-Q2 data
Alberto Accardi; Christy, M. Eric; Keppel, Cynthia E.; Melnitchouk, Wally; Monaghan, Peter A.; Morfin, Jorge G.; Owens, Joseph F.
2010-02-11
We report results of a new global next-to-leading order fit of parton distribution functions in which cuts on W and Q are relaxed, thereby including more data at high values of x. Effects of target mass corrections (TMCs), higher twist contributions, and nuclear corrections for deuterium data are significant in the large-x region. The leading twist parton distributions are found to be stable to TMC model variations as long as higher twist contributions are also included. Furthermore, the behavior of the d quark as x → 1 is particularly sensitive to the deuterium corrections, and using realistic nuclear smearing modelsmore » the d-quark distribution at large x is found to be softer than in previous fits performed with more restrictive cuts.« less
Parton transverse momentum and orbital angular momentum distributions
NASA Astrophysics Data System (ADS)
Rajan, Abha; Courtoy, Aurore; Engelhardt, Michael; Liuti, Simonetta
2016-08-01
The quark orbital angular momentum component of proton spin, Lq, can be defined in QCD as the integral of a Wigner phase space distribution weighting the cross product of the quark's transverse position and momentum. It can also be independently defined from the operator product expansion for the off-forward Compton amplitude in terms of a twist-three generalized parton distribution. We provide an explicit link between the two definitions, connecting them through their dependence on partonic intrinsic transverse momentum. Connecting the definitions provides the key for correlating direct experimental determinations of Lq and evaluations through lattice QCD calculations. The direct observation of quark orbital angular momentum does not require transverse spin polarization but can occur using longitudinally polarized targets.
Moments of nucleon spin-dependent generalized parton distributions
Wolfram Schroers; Richard Brower; Patrick Dreher; Robert Edwards; George Fleming; P. Hagler; Urs Heller; Thomas Lippert; John Negele; Andrew Pochinsky; Dru Renner; David Richards; Klaus Schilling
2004-03-01
We present a lattice measurement of the first two moments of the spin-dependent GPD H-tilde(x,xi,t). From these we obtain the axial coupling constant and the second moment of the spin-dependent forward parton distribution. The measurements are done in full QCD using Wilson fermions. In addition, we also present results from a first exploratory study of full QCD using Asqtad sea and domain-wall valence fermions.
Leading Twist Parton Distribution Amplitudes in Heavy Vector Mesons
NASA Astrophysics Data System (ADS)
Gao, Fei; Ding, Minghui; Chang, Lei; Liu, Yu-Xin; Roberts, Craig D.
2016-03-01
We employed QCD's Dyson-Schwinger equations (DSEs) for heavy quarks and obtained the leading twist parton distribution amplitudes (PDAs) in heavy vector mesons J/Ψ and ϒ. We found that all of the amplitudes are narrower than the asymptotic form, while they deviate from δ function. This indicates that the interaction between the two continent quarks are still important in the mesons consisted of charm and bottom quarks.
Deeply Pseudoscalar Meson Electroproduction with CLAS and Generalized Parton Distributions
Guidal, Michel; Kubarovsky, Valery P.
2015-06-01
We discuss the recent data of exclusive $\\pi^0$ (and $\\pi^+$) electroproduction on the proton obtained by the CLAS collaboration at Jefferson Lab. It is observed that the cross sections, which have been decomposed in $\\sigma_T+\\epsilon\\sigma_L$, $\\sigma_{TT}$ and $\\sigma_{LT}$ structure functions, are dominated by transverse amplitude contributions. The data can be interpreted in the Generalized Parton Distribution formalism provided that one includes helicity-flip transversity GPDs.
Studies of Transverse Momentum Dependent Parton Distributions and Bessel Weighting
NASA Astrophysics Data System (ADS)
Gamberg, Leonard
2015-04-01
We present a new technique for analysis of transverse momentum dependent parton distribution functions, based on the Bessel weighting formalism. Advantages of employing Bessel weighting are that transverse momentum weighted asymmetries provide a means to disentangle the convolutions in the cross section in a model independent way. The resulting compact expressions immediately connect to work on evolution equations for transverse momentum dependent parton distribution and fragmentation functions. As a test case, we apply the procedure to studies of the double longitudinal spin asymmetry in SIDIS using a dedicated Monte Carlo generator which includes quark intrinsic transverse momentum within the generalized parton model. Using a fully differential cross section for the process, the effect of four momentum conservation is analyzed using various input models for transverse momentum distributions and fragmentation functions. We observe a few percent systematic offset of the Bessel-weighted asymmetry obtained from Monte Carlo extraction compared to input model calculations. Bessel weighting provides a powerful and reliable tool to study the Fourier transform of TMDs with controlled systematics due to experimental acceptances and resolutions with different TMD model inputs. Work is supported by the U.S. Department of Energy under Contract No. DE-FG02-07ER41460.
Studies of Transverse Momentum Dependent Parton Distributions and Bessel Weighting
NASA Astrophysics Data System (ADS)
Gamberg, Leonard
2015-10-01
We present a new technique for analysis of transverse momentum dependent parton distribution functions, based on the Bessel weighting formalism. Advantages of employing Bessel weighting are that transverse momentum weighted asymmetries provide a means to disentangle the convolutions in the cross section in a model independent way. The resulting compact expressions immediately connect to work on evolution equations for transverse momentum dependent parton distribution and fragmentation functions. As a test case, we apply the procedure to studies of the double longitudinal spin asymmetry in SIDIS using a dedicated Monte Carlo generator which includes quark intrinsic transverse momentum within the generalized parton model. Using a fully differential cross section for the process, the effect of four momentum conservation is analyzed using various input models for transverse momentum distributions and fragmentation functions. We observe a few percent systematic offset of the Bessel-weighted asymmetry obtained from Monte Carlo extraction compared to input model calculations. Bessel weighting provides a powerful and reliable tool to study the Fourier transform of TMDs with controlled systematics due to experimental acceptances and resolutions with different TMD model inputs. Work is supported by the U.S. Department of Energy under Contract No. DE-FG02-07ER41460.
Pion and kaon valence-quark parton distribution functions
Nguyen, Trang; Bashir, Adnan; Roberts, Craig D.; Tandy, Peter C.
2011-06-15
A rainbow-ladder truncation of QCD's Dyson-Schwinger equations, constrained by existing applications to hadron physics, is employed to compute the valence-quark parton distribution functions of the pion and kaon. Comparison is made to {pi}-N Drell-Yan data for the pion's u-quark distribution and to Drell-Yan data for the ratio u{sub K}(x)/u{sub {pi}}(x): the environmental influence of this quantity is a parameter-free prediction, which agrees well with existing data. Our analysis unifies the computation of distribution functions with that of numerous other properties of pseudoscalar mesons.
Pion and kaon valence-quark parton distribution functions.
Nguyen, T.; Bashir, A.; Roberts, C. D.; Tandy, P. C.
2011-06-16
A rainbow-ladder truncation of QCD's Dyson-Schwinger equations, constrained by existing applications to hadron physics, is employed to compute the valence-quark parton distribution functions of the pion and kaon. Comparison is made to {pi}-N Drell-Yan data for the pion's u-quark distribution and to Drell-Yan data for the ratio u{sub K}(x)/u{sub {pi}}(x): the environmental influence of this quantity is a parameter-free prediction, which agrees well with existing data. Our analysis unifies the computation of distribution functions with that of numerous other properties of pseudoscalar mesons.
Pion and kaon valence-quark parton distribution functions
NASA Astrophysics Data System (ADS)
Nguyen, Trang; Bashir, Adnan; Roberts, Craig D.; Tandy, Peter C.
2011-06-01
A rainbow-ladder truncation of QCD’s Dyson-Schwinger equations, constrained by existing applications to hadron physics, is employed to compute the valence-quark parton distribution functions of the pion and kaon. Comparison is made to π-N Drell-Yan data for the pion’s u-quark distribution and to Drell-Yan data for the ratio uK(x)/uπ(x): the environmental influence of this quantity is a parameter-free prediction, which agrees well with existing data. Our analysis unifies the computation of distribution functions with that of numerous other properties of pseudoscalar mesons.
Transverse momentum dependent (TMD) parton distribution functions: Status and prospects*
Angeles-Martinez, R.; Bacchetta, A.; Balitsky, Ian I.; Boer, D.; Boglione, M.; Boussarie, R.; Ceccopieri, F. A.; Cherednikov, I. O.; Connor, P.; Echevarria, M. G.; Ferrera, G.; Grados Luyando, J.; Hautmann, F.; Jung, H.; Kasemets, T.; Kutak, K.; Lansberg, J. P.; Lykasov, G.; Madrigal Martinez, J. D.; Mulders, P. J.; Nocera, E. R.; Petreska, E.; Pisano, C.; Placakyte, R.; Radescu, V.; Radici, M.; Schnell, G.; Signori, A.; Szymanowski, L.; Taheri Monfared, S.; Van der Veken, F. F.; van Haevermaet, H. J.; Van Mechelen, P.; Vladimirov, A. A.; Wallon, S.
2015-01-01
In this study, we review transverse momentum dependent (TMD) parton distribution functions, their application to topical issues in high-energy physics phenomenology, and their theoretical connections with QCD resummation, evolution and factorization theorems. We illustrate the use of TMDs via examples of multi-scale problems in hadronic collisions. These include transverse momentum q_{T} spectra of Higgs and vector bosons for low q_{T}, and azimuthal correlations in the production of multiple jets associated with heavy bosons at large jet masses. We discuss computational tools for TMDs, and present the application of a new tool, TMD_{LIB}, to parton density fits and parameterizations.
Generalized Parton Distributions, Analyticity and Formfactors
Teryaev, O. V
2008-10-13
The QCD factorization for hard exclusive amplitudes is compared with their crossing and analytic properties. The crucial role is played by their mathematical structure described by Radon and Abel transforms, leading to 'holographic' property of GPDs at LO. These transforms are very different in the even- and odd-dimensional spaces, the latter case related to 'creation' GPDs describing, say, the deuteron breakup. The bounds implied by crossing and analyticity for the angular distributions in two-photon processes are obtained. The contributions of different types of QCD factorization and duality between them are considered. The relations of GPDs to (gravitational) formfactors, equivalence principle (EP) and its extension (EEP) are analyzed. EEP is also considered for the case of vector mesons, showing the possible link with AdS/QCD correspondence.
Nondiagonal parton distributions in the leading logarithmic approximation
NASA Astrophysics Data System (ADS)
Frankfurt, L. L.; Freund, A.; Guzey, V.; Strikman, M.
1998-02-01
In this paper we make predictions for nondiagonal parton distributions in a proton in the LLA. We calculate the DGLAP-type evolution kernels in the LLA, solve the nondiagonal GLAP evolution equations with a modified version of the CTEQ-package and comment on the range of applicability of the LLA in the asymmetric regime. We show that the nondiagonal gluon distribution g(x1,x2,t,μ2) can be well approximated at small x by the conventional gluon density xG(x,μ2).
Experimental overview of Generalized Parton Distribution results from HERMES
Zihlmann, B.
2009-08-04
Over the course of more than a decade the HERMES experiment has accumulated a wealth of data with electron and positron beams on various gaseous targets from Hydrogen up to Xenon. In addition, the beams and targets can be polarized. This data set is viewed in the context of Generalized Parton Distributions, a theoretical formalism with an explicit three dimensional view of the structure of the nucleon. It provides a link between experimental observables and the total angular momentum of the quarks in the nucleon.
Generalized Parton distributions with CLAS and CLAS12
S. Niccolai
2012-04-01
Recent promising results obtained with the Jefferson Lab CLAS detector on deeply virtual exclusive processes and their link to the Generalized Parton Distributions, along with the experimental program to study GPDs at the 12-GeV upgraded JLab using the CLAS12 detector, are discussed here. With its wide acceptance, high luminosity, good resolution and particle identification capabilities, as well as large Q2 and xB coverage (1 GeV < Q2 < 10 GeV2, 0.1 < xB < 0.8), CLAS12 will be the ideal facility to pursue the research on the 3-dimensional structure of the nucleon in the valence region.
Generalized parton distributions from deep virtual compton scattering at CLAS
Guidal, M.
2010-04-24
Here, we have analyzed the beam spin asymmetry and the longitudinally polarized target spin asymmetry of the Deep Virtual Compton Scattering process, recently measured by the Jefferson Lab CLAS collaboration. Our aim is to extract information about the Generalized Parton Distributions of the proton. By fitting these data, in a largely model-independent procedure, we are able to extract numerical values for the two Compton Form Factors $H_{Im}$ and $\\tilde{H}_{Im}$ with uncertainties, in average, of the order of 30%.
Generalized parton distributions from deep virtual compton scattering at CLAS
Guidal, M.
2010-04-24
Here, we have analyzed the beam spin asymmetry and the longitudinally polarized target spin asymmetry of the Deep Virtual Compton Scattering process, recently measured by the Jefferson Lab CLAS collaboration. Our aim is to extract information about the Generalized Parton Distributions of the proton. By fitting these data, in a largely model-independent procedure, we are able to extract numerical values for the two Compton Form Factorsmore » $$H_{Im}$$ and $$\\tilde{H}_{Im}$$ with uncertainties, in average, of the order of 30%.« less
Transverse Momentum-Dependent Parton Distributions From Lattice QCD
Michael Engelhardt, Bernhard Musch, Philipp Haegler, Andreas Schaefer
2012-12-01
Starting from a definition of transverse momentum-dependent parton distributions for semi-inclusive deep inelastic scattering and the Drell-Yan process, given in terms of matrix elements of a quark bilocal operator containing a staple-shaped Wilson connection, a scheme to determine such observables in lattice QCD is developed and explored. Parametrizing the aforementioned matrix elements in terms of invariant amplitudes permits a simple transformation of the problem to a Lorentz frame suited for the lattice calculation. Results for the Sivers and Boer-Mulders transverse momentum shifts are presented, focusing in particular on their dependence on the staple extent and the Collins-Soper evolution parameter.
Transverse Momentum-Dependent Parton Distributions from Lattice QCD
NASA Astrophysics Data System (ADS)
Engelhardt, M.; Musch, B.; Hägler, P.; Negele, J.; Schäfer, A.
Starting from a definition of transverse momentum-dependent parton distributions for semi-inclusive deep inelastic scattering and the Drell-Yan process, given in terms of matrix elements of a quark bilocal operator containing a staple-shaped Wilson connection, a scheme to determine such observables in lattice QCD is developed and explored. Parametrizing the aforementioned matrix elements in terms of invariant amplitudes permits a simple transformation of the problem to a Lorentz frame suited for the lattice calculation. Results for the Sivers and Boer-Mulders transverse momentum shifts are presented, focusing in particular on their dependence on the staple extent and the Collins-Soper evolution parameter.
Studies of transverse momentum dependent parton distributions and Bessel weighting
Aghasyan, M.; Avakian, H.; De Sanctis, E.; Gamberg, L.; Mirazita, M.; Musch, B.; Prokudin, A.; Rossi, P.
2015-03-01
In this paper we present a new technique for analysis of transverse momentum dependent parton distribution functions, based on the Bessel weighting formalism. The procedure is applied to studies of the double longitudinal spin asymmetry in semi-inclusive deep inelastic scattering using a new dedicated Monte Carlo generator which includes quark intrinsic transverse momentum within the generalized parton model. Using a fully differential cross section for the process, the effect of four momentum conservation is analyzed using various input models for transverse momentum distributions and fragmentation functions. We observe a few percent systematic offset of the Bessel-weighted asymmetry obtained from Monte Carlo extraction compared to input model calculations, which is due to the limitations imposed by the energy and momentum conservation at the given energy/Q2. We find that the Bessel weighting technique provides a powerful and reliable tool to study the Fourier transform of TMDs with controlled systematics due to experimental acceptances and resolutions with different TMD model inputs.
A meta-analysis of parton distribution functions
NASA Astrophysics Data System (ADS)
Gao, Jun; Nadolsky, Pavel
2014-07-01
A "meta-analysis" is a method for comparison and combination of nonperturbative parton distribution functions (PDFs) in a nucleon obtained with heterogeneous procedures and assumptions. Each input parton distribution set is converted into a "meta-parametrization" based on a common functional form. By analyzing parameters of the meta-parametrizations from all input PDF ensembles, a combined PDF ensemble can be produced that has a smaller total number of PDF member sets than the original ensembles. The meta-parametrizations simplify the computation of the PDF uncertainty in theoretical predictions and provide an alternative to the 2010 PDF4LHC convention for combination of PDF uncertainties. As a practical example, we construct a META ensemble for computation of QCD observables at the Large Hadron Collider using the next-to-next-to-leading order PDF sets from CTEQ, MSTW, and NNPDF groups as the input. The META ensemble includes a central set that reproduces the average of LHC predictions based on the three input PDF ensembles and Hessian eigenvector sets for computing the combined PDF+α s uncertainty at a common QCD coupling strength of 0.118.
Studies of transverse momentum dependent parton distributions and Bessel weighting
Aghasyan, M.; Avakian, H.; De Sanctis, E.; Gamberg, L.; Mirazita, M.; Musch, B.; Prokudin, A.; Rossi, P.
2015-03-01
In this paper we present a new technique for analysis of transverse momentum dependent parton distribution functions, based on the Bessel weighting formalism. The procedure is applied to studies of the double longitudinal spin asymmetry in semi-inclusive deep inelastic scattering using a new dedicated Monte Carlo generator which includes quark intrinsic transverse momentum within the generalized parton model. Using a fully differential cross section for the process, the effect of four momentum conservation is analyzed using various input models for transverse momentum distributions and fragmentation functions. We observe a few percent systematic offset of the Bessel-weighted asymmetry obtained from Montemore » Carlo extraction compared to input model calculations, which is due to the limitations imposed by the energy and momentum conservation at the given energy/Q2. We find that the Bessel weighting technique provides a powerful and reliable tool to study the Fourier transform of TMDs with controlled systematics due to experimental acceptances and resolutions with different TMD model inputs.« less
Studies of transverse momentum dependent parton distributions and Bessel weighting
NASA Astrophysics Data System (ADS)
Aghasyan, M.; Avakian, H.; De Sanctis, E.; Gamberg, L.; Mirazita, M.; Musch, B.; Prokudin, A.; Rossi, P.
2015-03-01
In this paper we present a new technique for analysis of transverse momentum dependent parton distribution functions, based on the Bessel weighting formalism. The procedure is applied to studies of the double longitudinal spin asymmetry in semi-inclusive deep inelastic scattering using a new dedicated Monte Carlo generator which includes quark intrinsic transverse momentum within the generalized parton model. Using a fully differential cross section for the process, the effect of four momentum conservation is analyzed using various input models for transverse momentum distributions and fragmentation functions. We observe a few percent systematic offset of the Bessel-weighted asymmetry obtained from Monte Carlo extraction compared to input model calculations, which is due to the limitations imposed by the energy and momentum conservation at the given energy/ Q 2. We find that the Bessel weighting technique provides a powerful and reliable tool to study the Fourier transform of TMDs with controlled systematics due to experimental acceptances and resolutions with different TMD model inputs.
Transverse momentum-dependent parton distribution functions in lattice QCD
Engelhardt, Michael G.; Musch, Bernhard U.; Haegler, Philipp G.; Negele, John W.; Schaefer, Andreas
2013-08-01
A fundamental structural property of the nucleon is the distribution of quark momenta, both parallel as well as perpendicular to its propagation. Experimentally, this information is accessible via selected processes such as semi-inclusive deep inelastic scattering (SIDIS) and the Drell-Yan process (DY), which can be parametrized in terms of transversemomentum-dependent parton distributions (TMDs). On the other hand, these distribution functions can be extracted from nucleon matrix elements of a certain class of bilocal quark operators in which the quarks are connected by a staple-shaped Wilson line serving to incorporate initial state (DY) or final state (SIDIS) interactions. A scheme for evaluating such matrix elements within lattice QCD is developed. This requires casting the calculation in a particular Lorentz frame, which is facilitated by a parametrization of the matrix elements in terms of invariant amplitudes. Exploratory results are presented for the time-reversal odd Sivers and Boer-Mulders transverse momentum shifts.
How large is the gluon polarization in the statistical parton distributions approach?
Soffer, Jacques; Bourrely, Claude; Buccella, Franco
2015-04-10
We review the theoretical foundations of the quantum statistical approach to parton distributions and we show that by using some recent experimental results from Deep Inelastic Scattering, we are able to improve the description of the data by means of a new determination of the parton distributions. We will see that a large gluon polarization emerges, giving a significant contribution to the proton spin.
Frederico, T.; Pace, E.; Pasquini, B.; Salme, G.
2010-08-05
Longitudinal and transverse parton distributions for pion and nucleon are calculated from hadron vertexes obtained by a study of form factors within relativistic quark models. The relevance of the one-gluon-exchange dominance at short range for the behavior of the form factors at large momentum transfer and of the parton distributions at the end points is stressed.
Nucleon helicity and transversity parton distributions from lattice QCD
NASA Astrophysics Data System (ADS)
Chen, Jiunn-Wei; Cohen, Saul D.; Ji, Xiangdong; Lin, Huey-Wen; Zhang, Jian-Hui
2016-10-01
We present the first lattice-QCD calculation of the isovector polarized parton distribution functions (both helicity and transversity) using the large-momentum effective field theory (LaMET) approach for direct Bjorken-x dependence. We first review the detailed steps of the procedure in the unpolarized case, then generalize to the helicity and transversity cases. We also derive a new mass-correction formulation for all three cases. We then compare the effects of each finite-momentum correction using lattice data calculated at Mπ ≈ 310 MeV. Finally, we discuss the implications of these results for the poorly known antiquark structure and predict the sea-flavor asymmetry in the transversely polarized nucleon.
From Bethe-Salpeter Wave functions to Generalised Parton Distributions
NASA Astrophysics Data System (ADS)
Mezrag, C.; Moutarde, H.; Rodríguez-Quintero, J.
2016-09-01
We review recent works on the modelling of generalised parton distributions within the Dyson-Schwinger formalism. We highlight how covariant computations, using the impulse approximation, allows one to fulfil most of the theoretical constraints of the GPDs. Specific attention is brought to chiral properties and especially the so-called soft pion theorem, and its link with the Axial-Vector Ward-Takahashi identity. The limitation of the impulse approximation are also explained. Beyond impulse approximation computations are reviewed in the forward case. Finally, we stress the advantages of the overlap of lightcone wave functions, and possible ways to construct covariant GPD models within this framework, in a two-body approximation.
Transverse momentum-dependent parton distribution functions from lattice QCD
Michael Engelhardt, Philipp Haegler, Bernhard Musch, John Negele, Andreas Schaefer
2012-12-01
Transverse momentum-dependent parton distributions (TMDs) relevant for semi-inclusive deep inelastic scattering (SIDIS) and the Drell-Yan process can be defined in terms of matrix elements of a quark bilocal operator containing a staple-shaped Wilson connection. Starting from such a definition, a scheme to determine TMDs in lattice QCD is developed and explored. Parametrizing the aforementioned matrix elements in terms of invariant amplitudes permits a simple transformation of the problem to a Lorentz frame suited for the lattice calculation. Results for the Sivers and Boer-Mulders transverse momentum shifts are obtained using ensembles at the pion masses 369MeV and 518MeV, focusing in particular on the dependence of these shifts on the staple extent and a Collins-Soper-type evolution parameter quantifying proximity of the staples to the light cone.
Iterative Monte Carlo analysis of spin-dependent parton distributions
NASA Astrophysics Data System (ADS)
Sato, Nobuo; Melnitchouk, W.; Kuhn, S. E.; Ethier, J. J.; Accardi, A.; Jefferson Lab Angular Momentum Collaboration
2016-04-01
We present a comprehensive new global QCD analysis of polarized inclusive deep-inelastic scattering, including the latest high-precision data on longitudinal and transverse polarization asymmetries from Jefferson Lab and elsewhere. The analysis is performed using a new iterative Monte Carlo fitting technique which generates stable fits to polarized parton distribution functions (PDFs) with statistically rigorous uncertainties. Inclusion of the Jefferson Lab data leads to a reduction in the PDF errors for the valence and sea quarks, as well as in the gluon polarization uncertainty at x ≳0.1 . The study also provides the first determination of the flavor-separated twist-3 PDFs and the d2 moment of the nucleon within a global PDF analysis.
Generalized Parton Distributions And Deeply Virtual Compton Scattering At Clas
De Masi, Rita
2007-09-01
The deeply virtual Compton scattering is the simplest process to access the generalized parton distributions of the nucleon. A dedicated large statistics experiment for the measurement of deeply virtual Compton scattering with a 6 GeV polarized electron beam on a proton target has been performed at the Hall-B of Jefferson Laboratory with the CLAS spectrometer. The experiment covered a wide kinematic range, allowing the study of the beam spin asymmetry as function of the Bjorken variable xB, the Mandelstam variable t, the virtual photon four-momentum squared Q2 and the angle phi between leptonic and hadronic planes. The preliminary results are in agreement with previous measurements and with the predicted twist-2 dominance.
Towards a model of pion generalized parton distributions from Dyson-Schwinger equations
Moutarde, H.
2015-04-10
We compute the pion quark Generalized Parton Distribution H{sup q} and Double Distributions F{sup q} and G{sup q} in a coupled Bethe-Salpeter and Dyson-Schwinger approach. We use simple algebraic expressions inspired by the numerical resolution of Dyson-Schwinger and Bethe-Salpeter equations. We explicitly check the support and polynomiality properties, and the behavior under charge conjugation or time invariance of our model. We derive analytic expressions for the pion Double Distributions and Generalized Parton Distribution at vanishing pion momentum transfer at a low scale. Our model compares very well to experimental pion form factor or parton distribution function data.
Deeply Virtual Exclusive Processes and Generalized Parton Distributions
,
2011-06-01
The goal of the comprehensive program in Deeply Virtual Exclusive Scattering at Jefferson Laboratory is to create transverse spatial images of quarks and gluons as a function of their longitudinal momentum fraction in the proton, the neutron, and in nuclei. These functions are the Generalized Parton Distributions (GPDs) of the target nucleus. Cross section measurements of the Deeply Virtual Compton Scattering (DVCS) reaction ep {yields} ep{gamma} in Hall A support the QCD factorization of the scattering amplitude for Q^2 {>=} 2 GeV^2. Quasi-free neutron-DVCS measurements on the Deuteron indicate sensitivity to the quark angular momentum sum rule. Fully exclusive H(e, e'p{gamma} ) measurements have been made in a wide kinematic range in CLAS with polarized beam, and with both unpolarized and longitudinally polarized targets. Existing models are qualitatively consistent with the JLab data, but there is a clear need for less constrained models. Deeply virtual vector meson production is studied in CLAS. The 12 GeV upgrade will be essential for for these channels. The {rho} and {omega} channels reactions offer the prospect of flavor sensitivity to the quark GPDs, while the {phi}-production channel is dominated by the gluon distribution.
Dynamical next-to-next-to-leading order parton distributions
Jimenez-Delgado, P.; Reya, E.
2009-04-01
Utilizing recent deep inelastic scattering measurements ({sigma}{sub r},F{sub 2,3,L}) and data on hadronic dilepton production we determine at next-to-next-to-leading order (NNLO) (3-loop) of QCD the dynamical parton distributions of the nucleon generated radiatively from valencelike positive input distributions at an optimally chosen low resolution scale (Q{sub 0}{sup 2}<1 GeV{sup 2}). These are compared with 'standard' NNLO distributions generated from positive input distributions at some fixed and higher resolution scale (Q{sub 0}{sup 2}>1 GeV{sup 2}). Although the NNLO corrections imply in both approaches an improved value of {chi}{sup 2}, typically {chi}{sub NNLO}{sup 2}{approx_equal}0.9{chi}{sub NLO}{sup 2}, present deep inelastic scattering data are still not sufficiently accurate to distinguish between NLO results and the minute NNLO effects of a few percent, despite the fact that the dynamical NNLO uncertainties are somewhat smaller than the NLO ones and both are, as expected, smaller than those of their standard counterparts. The dynamical predictions for F{sub L}(x,Q{sup 2}) become perturbatively stable already at Q{sup 2}=2-3 GeV{sup 2} where precision measurements could even delineate NNLO effects in the very small-x region. This is in contrast to the common standard approach but NNLO/NLO differences are here less distinguishable due to the larger 1{sigma} uncertainty bands. Within the dynamical approach we obtain {alpha}{sub s}(M{sub Z}{sup 2})=0.1124{+-}0.0020, whereas the somewhat less constrained standard fit gives {alpha}{sub s}(M{sub Z}{sup 2})=0.1158{+-}0.0035.
Deeply virtual Compton scattering and generalized parton distributions at CLAS
Niccolai, Silvia
2008-11-01
The exclusive electroproduction of real photons and mesons at high momentum transfer allows us to access the Generalized Parton Distributions (GPDs). The formalism of the GPDs provides a unified description of the hadronic structure in terms of quark and gluonic degrees of freedom. In particular, the Deeply Virtual Compton Scattering (DVCS), ep â e2p2Å , is one of the key reactions to determine the GPDs experimentally, as it is the simplest process that can be described in terms of GPDs. A dedicated experiment to study DVCS has been carried out in Hall B at Jefferson Lab. Beam-spin asymmetries, resulting from the interference of the Bethe-Heitler process and DVCS have been extracted over the widest kinematic range ever accessed for this reaction ( 1.2 < Q 2 < 3.7 (GeV/c 2, 0.09 < - t < 1.3 (GeV/c 2, 0.13 < x B < 0.46 . In this paper, the results obtained experimentally are shown and compared to GPD parametrizations.
Generalized parton distributions of the pion in chiral quark models and their QCD evolution
Broniowski, Wojciech; Ruiz Arriola, Enrique; Golec-Biernat, Krzysztof
2008-02-01
We evaluate generalized parton distributions of the pion in two chiral quark models: the spectral quark model and the Nambu-Jona-Lasinio model with a Pauli-Villars regularization. We proceed by the evaluation of double distributions through the use of a manifestly covariant calculation based on the {alpha} representation of propagators. As a result polynomiality is incorporated automatically and calculations become simple. In addition, positivity and normalization constraints, sum rules, and soft-pion theorems are fulfilled. We obtain explicit formulas, holding at the low-energy quark-model scale. The expressions exhibit no factorization in the t-dependence. The QCD evolution of those parton distributions is carried out to experimentally or lattice accessible scales. We argue for the need of evolution by comparing the parton distribution function and the parton distribution amplitude of the pion to the available experimental and lattice data, and confirm that the quark-model scale is low, about 320 MeV.
Accardi, A.; Brady, L. T.; Melnitchouk, W.; Owens, J. F.; Sato, N.
2016-06-20
Here, we present a new set of leading twist parton distribution functions, referred to as "CJ15", which take advantage of developments in the theoretical treatment of nuclear corrections as well as new data. The analysis includes for the first time data on the free neutron structure function from Jefferson Lab, and new high-precision charged lepton and W-boson asymmetry data from Fermilab, which significantly reduce the uncertainty on the d/u ratio at large values of x.
Working Group I: Parton distributions: Summary report for the HERA LHC Workshop Proceedings
Dittmar, M.; Forte, S.; Glazov, A.; Moch, S.; Alekhin, S.; Altarelli, G.; Andersen, Jeppe R.; Ball, R.D.; Blumlein, J.; Bottcher, H.; Carli, T.; Ciafaloni, M.; Colferai, D.; Cooper-Sarkar, A.; Corcella, G.; Del Debbio, L.; Dissertori, G.; Feltesse, J.; Guffanti, A.; Gwenlan, C.; Huston, J.; /Zurich, ETH /DESY, Zeuthen /Serpukhov, IHEP /CERN /Rome III U. /INFN, Rome3 /Cambridge U. /Edinburgh U. /Florence U. /INFN, Florence /Oxford U. /DSM, DAPNIA, Saclay /Michigan State U. /Uppsala U. /Barcelona U., ECM /Podgorica U. /Turin U. /INFN, Turin /Harish-Chandra Res. Inst. /Fermilab /Hamburg U., Inst. Theor. Phys. II
2005-11-01
We provide an assessment of the impact of parton distributions on the determination of LHC processes, and of the accuracy with which parton distributions (PDFs) can be extracted from data, in particular from current and forthcoming HERA experiments. We give an overview of reference LHC processes and their associated PDF uncertainties, and study in detail W and Z production at the LHC.We discuss the precision which may be obtained from the analysis of existing HERA data, tests of consistency of HERA data from different experiments, and the combination of these data. We determine further improvements on PDFs which may be obtained from future HERA data (including measurements of F{sub L}), and from combining present and future HERA data with present and future hadron collider data. We review the current status of knowledge of higher (NNLO) QCD corrections to perturbative evolution and deep-inelastic scattering, and provide reference results for their impact on parton evolution, and we briefly examine non-perturbative models for parton distributions. We discuss the state-of-the art in global parton fits, we assess the impact on them of various kinds of data and of theoretical corrections, by providing benchmarks of Alekhin and MRST parton distributions and a CTEQ analysis of parton fit stability, and we briefly presents proposals for alternative approaches to parton fitting. We summarize the status of large and small x resummation, by providing estimates of the impact of large x resummation on parton fits, and a comparison of different approaches to small x resummation, for which we also discuss numerical techniques.
Generalized parton distributions and Deeply Virtual Compton Scattering on proton at CLAS
R. De Masi
2007-12-01
Two measurements of target and beam spin asymmetries for the reaction ep→epγ were performed with CLAS at Jefferson Laboratory. Polarized 5.7 GeV electrons were impinging on a longitudinally polarized ammonia and liquid hydrogen target respectively. These measurements are sensitive to Generalized Parton Distributions. Sizable sin phi azimuthal angular dependences were observed in both experiments, indicating the dominance of leading twist terms and the possibility of extracting combinations of Generalized Parton Distributions on the nucleon.
Global parton distributions for the LHC Run II
NASA Astrophysics Data System (ADS)
Ball, R. D.
2016-07-01
We review the next generation global PDF sets: NNPDF3.0, MMHT14 and CT14. We describe the global datasets, particularly the new data from LHC Run I, the developments in QCD theory and PDF methodology, recent improvements in their combination and delivery, and future prospects for parton determination at Run II.
Soft factor subtraction and transverse momentum dependent parton distributions on the lattice
NASA Astrophysics Data System (ADS)
Ji, Xiangdong; Sun, Peng; Xiong, Xiaonu; Yuan, Feng
2015-04-01
We study the transverse momentum dependent (TMD) parton distributions in the newly proposed quasiparton distribution function framework in Euclidean space. In this framework, the parton distributions can be extracted from lattice observables in a systematic expansion of 1 /Pz where Pz is the hadron momentum. A soft factor subtraction is found to be essential to make the TMDs calculable on the lattice. We show that the quasi-TMDs with the associated soft factor subtraction can be applied in hard QCD scattering processes such as Drell-Yan lepton pair production in hadronic collisions. This allows future lattice calculations to provide information on the nonperturbative inputs and energy evolutions for the TMDs. Extension to the generalized parton distributions and quantum phase space Wigner distributions will lead to a complete nucleon tomography on the lattice.
Nuclear and partonic dynamics in high energy elastic nucleus-nucleus scattering
NASA Astrophysics Data System (ADS)
Małecki, Andrzej
1991-10-01
A hybrid description of diffraction which combines a geometrical modeling of multiple scattering with many-channel effects resulting from intrinsic dynamics on the nuclear and subnuclear level is presented. The application to 4-4He elastic scattering is satisfactory. Our analysis suggests that, at large momentum transfers, the parton constituents of nucleons immersed in nuclei are deconfined.
Nuclear and partonic dynamics in high energy elastic nucleus-nucleus scattering
Malecki, A. )
1991-10-01
A hybrid description of diffraction which combines a geometrical modeling of multiple scattering with many-channel effects resulting from intrinsic dynamics on the nuclear and subnuclear level is presented. The application to {sup 4}He-{sup 4}He elastic scattering is satisfactory. Our analysis suggests that, at large momentum transfers, the parton constituents of nucleons immersed in nuclei are deconfined.
Pion transverse momentum dependent parton distributions in the Nambu and Jona-Lasinio model
NASA Astrophysics Data System (ADS)
Noguera, Santiago; Scopetta, Sergio
2015-11-01
An explicit evaluation of the two pion transverse momentum dependent parton distributions at leading twist is presented, in the framework of the Nambu-Jona Lasinio model with Pauli-Villars regularization. The transverse momentum dependence of the obtained distributions is generated solely by the dynamics of the model. Using these results, the so called generalized Boer-Mulders shift is studied and compared with recent lattice data. The obtained agreement is very encouraging, in particular because no additional parameter has been introduced. A more conclusive comparison would require a precise knowledge of the QCD evolution of the transverse momentum dependent parton distributions under scrutiny.
Evolution of the helicity and transversity Transverse-Momentum-Dependent parton distributions
Prokudin, Alexei; Bacchetta, Alessandro
2013-07-01
We examine the QCD evolution of the helicity and transversity parton distribution functions when including also their dependence on transverse momentum. Using an appropriate definition of these polarized transverse momentum distributions (TMDs), we describe their dependence on the factorization scale and rapidity cutoff, which is essential for phenomenological applications.
Evolution of the helicity and transversity Transverse-Momentum-Dependent parton distributions
Prokudin, Alexey; Bacchetta, Alessandro
2013-10-01
We examine the QCD evolution of the helicity and transversity parton distribution functions when including also their dependence on transverse momentum. Using an appropriate definition of these polarized transverse momentum distributions (TMDs), we describe their dependence on the factorization scale and rapidity cutoff, which is essential for phenomenological applications.
Transverse-momentum-dependent parton distributions in a spectator diquark model
F Conti, A Bacchetta, M Radici
2009-09-01
Within the framework of a spectator diquark model of the nucleon, involving both scalar and axial-vector diquarks, we calculate all the leading-twist transverse-momentum-dependent parton distribution functions (TMDs). Naive Time-odd densities are generated through a one-gluon-loop rescattering mechanism, simulating the final state interactions required for these functions to exist. Analytic results are obtained for all the TMDs, and a connection with the light-cone wave functions formalism is also established. The model parameters are fixed by reproducing the phenomenological parametrizations of unpolarized and helicity parton distributions at the lowest available scale. Predictions for the other parton densities are given and, whenever possible, compared with available parametrizations.
Constraints on spin-dependent parton distributions at large x from global QCD analysis
NASA Astrophysics Data System (ADS)
Jimenez-Delgado, P.; Avakian, H.; Melnitchouk, W.
2014-11-01
We investigate the behavior of spin-dependent parton distribution functions (PDFs) at large parton momentum fractions x in the context of global QCD analysis. We explore the constraints from existing deep-inelastic scattering data, and from theoretical expectations for the leading x → 1 behavior based on hard gluon exchange in perturbative QCD. Systematic uncertainties from the dependence of the PDFs on the choice of parametrization are studied by considering functional forms motivated by orbital angular momentum arguments. Finally, we quantify the reduction in the PDF uncertainties that may be expected from future high-x data from Jefferson Lab at 12 GeV.
Probing transverse momentum dependent parton distributions in charmonium and bottomonium production
NASA Astrophysics Data System (ADS)
Mukherjee, Asmita; Rajesh, Sangem
2016-03-01
We propose the study of unpolarized transverse momentum dependent gluon parton distributions as well as the effect of linearly polarized gluons on transverse momentum and rapidity distributions of J /ψ and ϒ production within the framework of transverse momentum dependent factorization employing a color evaporation model (CEM) in an unpolarized proton-proton collision. We estimate the transverse momentum and rapidity distributions of J /ψ and ϒ at LHCb, RHIC and AFTER energies using TMD evolution formalism.
CARROLL,J.
1999-09-10
The RIKEN-BNL center workshop on ''Hard parton physics in high energy nuclear collisions'' was held at BNL from March 1st-5th! 1999. The focus of the workshop was on hard probes of nucleus-nucleus collisions that will be measured at RHIC with the PHENIX and STAR detectors. There were about 45 speakers and over 70 registered participants at the workshop, with roughly a quarter of the speakers from overseas. About 60% of the talks were theory talks. A nice overview of theory for RHIC was provided by George Sterman. The theoretical talks were on a wide range of topics in QCD which can be classified under the following: (a) energy loss and the Landau-Pomeranchuk-Migdal effect; (b) minijet production and equilibration; (c) small x physics and initial conditions; (d) nuclear parton distributions and shadowing; (e) spin physics; (f) photon, di-lepton, and charm production; and (g) hadronization, and simulations of high pt physics in event generators. Several of the experimental talks discussed the capabilities of the PHENIX and STAR detectors at RHIC in measuring high pt particles in heavy ion collisions. In general, these talks were included in the relevant theory sessions. A session was set aside to discuss the spin program at RHIC with polarized proton beams. In addition, there were speakers from 08, HERA, the fixed target experiments at Fermilab, and the CERN fixed target Pb+Pb program, who provided additional perspective on a range of issues of relevance to RHIC; from jets at the Tevatron, to saturation of parton distributions at HERA, and recent puzzling data on direct photon production in fixed target experiments, among others.
The parton distributions in nuclei and in polarized nucleons
Close, F.E.
1988-01-01
The emerging information was reviewed on the way quark and anti-quark, and gluon distributions are modified in nuclei relative to free nucleons. Some implications of the recent data on polarized leptoproduction are discussed. 27 refs., 6 figs.
Novel phenomenology of parton distributions from the Drell-Yan process
NASA Astrophysics Data System (ADS)
Peng, Jen-Chieh; Qiu, Jian-Wei
2014-05-01
The Drell-Yan massive lepton-pair production in hadronic collisions provides a unique tool complementary to the Deep-Inelastic Scattering for probing the partonic substructures in hadrons. We review key concepts, approximations, and progress for QCD factorization of the Drell-Yan process in terms of collinear or transverse momentum dependent (TMD) parton distribution functions. We present experimental results from recent fixed-target Drell-Yan as well as W and Z boson production at colliders, focusing on the topics of flavor structure of the nucleon sea as well as the extraction of novel Sivers and Boer-Mulders functions via single transverse spin asymmetries and azimuthal lepton angular distribution of the Drell-Yan process. Prospects for future Drell-Yan experiments are also presented.
Statistical approach of parton distributions: a closer look at the high-xregion
Soffer, Jacques
2011-09-21
We recall the physical features of the parton distributions in the quantum statistical approach of the nucleon, which allows to describe simultaneously, unpolarized and polarized Deep Inelastic Scattering data. Some predictionsfrom a next-to-leading order QCD analysis are compared to recent experimental results and we stress the importance of some tests in the high-x region, to confirm the validity of this approach.
Polarized Parton Distributions and the Polarized Gluon Asymmetry
NASA Astrophysics Data System (ADS)
Ramsey, Gordon P.
The flavor-dependent valence, sea quark and antiquark spin distributions can be determined separately from theoretical assumptions and experimental data. We have determined the valence distributions using the Bjorken sum rule and have extracted polarized sea distributions, assuming that the quarks and anti-quarks for each flavor are symmetric. Other experiments have been proposed which will allow us to completely break the SU(3) symmetry of the sea flavors. To create a physical model for the polarized gluons, we investigate the gluon spin asymmetry in a proton, AG(x, Q2) = (Δ G(x, Q2))/(G(x, Q2)). By assuming that htis is is approximately Q2 invariant, we can completely determine the x-dependence of this asymmetry, which satisfies constituent counting rules and reproduces the basic results of the Bremsstrahlung model originated by Close and Sivers. This asymmetry can be combined with the measured unpolarized gluon density, G(x,Q2) to provide a prediction for Δ G(x,Q2). Existing and proposed experiments can test both the prediction of scale-invariance for AG(x,Q2) and the nature of Δ G itself. These models will be discussed along with suggestions for specific experiments which can be performed at energies typical of HERA, RHIC and LHC to determine the nature of these polarized distributions.
Photon parton distributions in nuclei and the EMC effect
Frankfurt, Leonid; Strikman, Mark
2010-12-01
Photons as well as quarks and gluons are constituents of the infinite momentum frame (IMF) wave function of an energetic particle. They are mostly equivalent photons whose amplitude follows from the Lorentz transformation of the particle rest frame Coulomb field into the IMF and from the conservation of the electromagnetic current. We evaluate in a model independent way the dominant photon contribution \\propto \\alpha_{em}(Z^2/A^{4/3})\\ln(1/R_{A}m_{N}x) to the nuclear structure functions as well as the term \\propto \\alpha_{em}Z/A. In addition we show that the definition of x consistent with the exact kinematics of eA scattering (with exact sum rules) works in the same direction as the nucleus field of equivalent photons. Combined, these effects account for the bulk of the EMC effect for x\\le 0.5 where Fermi motion effects are small. In particular for these x the hadronic mechanism contribution to the EMC effect does not exceed \\sim 3% for all nuclei. Also the A-dependence of the hadronic mechanism of the EMC effect for x > 0.5 is significantly modified.
NASA Astrophysics Data System (ADS)
Bellm, Johannes; Plätzer, Simon; Richardson, Peter; Siódmok, Andrzej; Webster, Stephen
2016-08-01
We report on the possibility of reweighting parton-shower Monte Carlo predictions for scale variations in the parton-shower algorithm. The method is based on a generalization of the Sudakov veto algorithm. We demonstrate the feasibility of this approach using example physical distributions. Implementations are available for both of the parton-shower modules in the Herwig 7 event generator.
Color Effects for Transverse Momentum Dependent Parton Distribution Functions in Hadronic Processes
NASA Astrophysics Data System (ADS)
Buffing, M. G. A.; Mulders, P. J.
2015-09-01
In the Drell-Yan process (DY) a quark and an antiquark, coming from two different protons, produce a colorless virtual photon. In the proton description, we include transverse momentum dependent parton distribution functions (TMD PDFs), which go beyond the ordinary collinear PDFs. As such, we become sensitive to polarization modes of the partons and protons that one cannot probe without accounting for transverse momenta of partons, in particular when one looks at azimuthal asymmetries. Matrix elements used in the description of hadronic processes, such as DY, require the inclusion of gauge links, coming from gluon contributions in the process, which are path-ordered exponentials tracing the color flow. In processes with two hadrons in the initial state the color flow between different parts of the process causes entanglement. We show that in the process of color disentangling each gauge link remains sensitive to this color flow. After disentanglement, we find that particular combinations of TMDs require a different numerical color factor than one might have expected. Such color factors will even play a role for azimuthal asymmetries in the simplest hadronic processes such as the DY process.
Generalized parton distributions from domain wall valence quarks and staggered sea quarks
Renner, Dru; Bratt, Jonathan; Edwards, Robert; Engelhardt, Michael; Fleming, George; Haegler, Philipp; Musch, Bernhard; Negele, John; Orginos, Konstantinos; Pochinsky, Andrew; Richards, David; Schroers, Wolfram
2007-11-01
Moments of the generalized parton distributions of the nucleon, calculated with a mixed action of domain wall valence quarks and asqtad staggered sea quarks, are presented for pion masses extending down to 359 MeV. Results for the moments of the unpolarized, helicity, and transversity distributions are given and compared to the available experimental measurements. Additionally, a selection of the generalized form factors are shown and the implications for the spin decomposition and transverse structure of the nucleon are discussed. Particular emphasis is placed on understanding systematic errors in the lattice calculation and exploring a variety of chiral extrapolations.
Soft-Gluon Resummation and the Valence Parton Distribution Function of the Pion
Aicher, Matthias; Schaefer, Andreas; Vogelsang, Werner
2010-12-17
We determine the valence parton distribution function of the pion by performing a new analysis of data for the Drell-Yan process {pi}{sup -}N{yields}{mu}{sup +}{mu}{sup -}X. Compared to previous analyses, we include next-to-leading-logarithmic threshold resummation effects in the calculation of the Drell-Yan cross section. As a result of these, we find a considerably softer valence distribution at high momentum fractions x than obtained in previous next-to-leading-order analyses, in line with expectations based on perturbative-QCD counting rules or Dyson-Schwinger equations.
The Generalized Parton Distribution program in Hall A at Jefferson Lab
Camacho, C. Munoz
2008-10-13
Recent results on the Generalized Parton Distribution (GPD) program at Jefferson Lab (JLab) will be presented. The emphasis will be in the Hall A program aiming at measuring Q{sup 2}--dependences of different terms of the Deeply Virtual Compton Scattering (DVCS) cross section. This is a fundamental step before one can extract GPD information from JLab DVCS data. Neutral pion production will also be discussed and results from the CLAS collaboration will be shown. Finally, the upcoming program in Hall A, using both a 6 GeV beam ({approx_equal}2010) and a 11 GeV beam ({approx_equal}2015) will be described.
APFEL Web: a web-based application for the graphical visualization of parton distribution functions
NASA Astrophysics Data System (ADS)
Carrazza, Stefano; Ferrara, Alfio; Palazzo, Daniele; Rojo, Juan
2015-05-01
We present APFEL Web, a Web-based application designed to provide a flexible user-friendly tool for the graphical visualization of parton distribution functions. In this note we describe the technical design of the APFEL Web application, motivating the choices and the framework used for the development of this project. We document the basic usage of APFEL Web and show how it can be used to provide useful input for a variety of collider phenomenological studies. Finally we provide some examples showing the output generated by the application.
QCD evolution of naive-time-reversal-odd parton distribution functions
NASA Astrophysics Data System (ADS)
Kang, Zhong-Bo; Qiu, Jian-Wei
2012-07-01
We reexamine the derivation of the leading order QCD evolution equations of twist-3 quark-gluon correlation functions, Tq,F (x , x) and Tq,F (σ) (x , x), which are the first transverse-momentum-moment of the naive-time-reversal-odd parton distribution functions - the Sivers and Boer-Mulders function, respectively. The evolution equations were derived by several groups with apparent differences. We identify the sources that are responsible for the differences, and are able to reconcile the results from various groups.
The asymptotic behaviour of parton distributions at small and large x
NASA Astrophysics Data System (ADS)
Ball, Richard D.; Nocera, Emanuele R.; Rojo, Juan
2016-07-01
It has been argued from the earliest days of quantum chromodynamics that at asymptotically small values of x the parton distribution functions (PDFs) of the proton behave as x^α , where the values of α can be deduced from Regge theory, while at asymptotically large values of x the PDFs behave as (1-x)^β , where the values of β can be deduced from the Brodsky-Farrar quark counting rules. We critically examine these claims by extracting the exponents α and β from various global fits of parton distributions, analysing their scale dependence, and comparing their values to the naive expectations. We find that for valence distributions both Regge theory and counting rules are confirmed, at least within uncertainties, while for sea quarks and gluons the results are less conclusive. We also compare results from various PDF fits for the structure function ratio F_2^n/F_2^p at large x, and caution against unrealistic uncertainty estimates due to overconstrained parametrisations.
Generalized parton distributions and rapidity gap survival in exclusive diffractive pp scattering
Frankfurt, L.; Hyde, C. E.; Strikman, M.; Weiss, C.
2007-03-01
We study rapidity gap survival (RGS) in the production of high-mass systems (H=dijet, heavy quarkonium, Higgs boson) in double-gap exclusive diffractive pp scattering, pp{yields}p+(gap)+H+(gap)+p. Our approach is based on the idea that hard and soft interactions are approximately independent because they proceed over widely different time and distance scales. We implement this idea in a partonic description of proton structure, which allows for a model-independent treatment of the interplay of hard and soft interactions. The high-mass system is produced in a hard scattering process with exchange of two gluons between the protons, whose amplitude is calculable in terms of the gluon generalized parton distribution (GPD), measured in exclusive ep scattering. The hard scattering process is modified by soft spectator interactions, which we calculate neglecting correlations between hard and soft interactions (independent interaction approximation). We obtain an analytic expression for the RGS probability in terms of the phenomenological pp elastic scattering amplitude, without reference to the eikonal approximation. Contributions from inelastic intermediate states are suppressed. The onset of the black-disk limit in pp scattering at TeV energies strongly suppresses diffraction at small impact parameters and is the main factor in determining the RGS probability. Correlations between hard and soft interactions (e.g. due to scattering from the long-range pion field of the proton or due to possible short-range transverse correlations between partons) further decrease the RGS probability. We also investigate the dependence of the diffractive cross section on the transverse momenta of the final-state protons ('diffraction pattern'). By measuring this dependence one can perform detailed tests of the interplay of hard and soft interactions and even extract information about the gluon GPD in the proton. Such studies appear to be feasible with the planned forward detectors at the
New parton distribution functions from a global analysis of quantum chromodynamics
NASA Astrophysics Data System (ADS)
Dulat, Sayipjamal; Hou, Tie-Jiun; Gao, Jun; Guzzi, Marco; Huston, Joey; Nadolsky, Pavel; Pumplin, Jon; Schmidt, Carl; Stump, Daniel; Yuan, C.-P.
2016-02-01
We present new parton distribution functions (PDFs) at next-to-next-to-leading order (NNLO) from the CTEQ-TEA global analysis of quantum chromodynamics. These differ from previous CT PDFs in several respects, including the use of data from LHC experiments and the new D0 charged-lepton rapidity asymmetry data, as well as the use of a more flexible parametrization of PDFs that, in particular, allows a better fit to different combinations of quark flavors. Predictions for important LHC processes, especially Higgs boson production at 13 TeV, are presented. These CT14 PDFs include a central set and error sets in the Hessian representation. For completeness, we also present the CT14 PDFs determined at the LO and the NLO in QCD. Besides these general-purpose PDF sets, we provide a series of (N)NLO sets with various αs values and additional sets in general-mass variable flavor number schemes, to deal with heavy partons, with up to three, four, and six active flavors.
New parton distribution functions from a global analysis of quantum chromodynamics
Dulat, Sayipjamal; Hou, Tie -Jiun; Gao, Jun; Guzzi, Marco; Nadolsky, Pavel; Pumplin, Jon; Schmidt, Carl; Stump, Daniel; Yuan, C. -P.; Huston, Joey
2016-02-16
Here, we present new parton distribution functions (PDFs) up to next-to-next-to-leading order (NNLO) from the CTEQ-TEA global analysis of quantum chromodynamics. These differ from previous CT PDFs in several respects, including the use of data from LHC experiments and the new D0 charged lepton rapidity asymmetry data, as well as the use of more flexible parametrization of PDFs that, in particular, allows a better fit to different combinations of quark flavors. Predictions for important LHC processes, especially Higgs boson production at 13 TeV, are presented. These CT14 PDFs include a central set and error sets in the Hessian representation. Formore » completeness, we also present the CT14 PDFs determined at the leading order (LO) and the next-to-leading order (NLO) in QCD. Besides these general-purpose PDF sets, we provide a series of (N)NLO sets with various αs values and additional sets in general-mass variable flavor number (GM-VFN) schemes, to deal with heavy partons, with up to 3, 4, and 6 active flavors.« less
Huston, Joey [Co-Spokesperson; Ownes, Joseph [Co-Spokesperson
The Coordinated Theoretical-Experimental Project on QCD is a multi-institutional collaboration devoted to a broad program of research projects and cooperative enterprises in high-energy physics centered on Quantum Chromodynamics (QCD) and its implications in all areas of the Standard Model and beyond. The Collaboration consists of theorists and experimentalists at 18 universities and 5 national laboratories. More than 65 sets of Parton Distribution Functions are available for public access. Links to many online software tools, information about Parton Distribution Functions, papers, and other resources are also available.
Transverse dynamics of hard partons in nuclear media and the QCD dipole
NASA Astrophysics Data System (ADS)
Wiedemann, Urs Achim
2000-08-01
We derive the non-abelian generalization of the Furry approximation which describes the transverse dynamical evolution of a hard projectile parton inside a spatially extended colour target field. This provides a unified starting point for the target rest frame description of the nuclear dependence of a large class of observables. For the case of the virtual γ ∗→q q¯ photoabsorption cross section, we investigate then in detail under which conditions the nuclear dependence encoded in the Furry wavefunctions can be parametrized by a q q¯ QCD dipole cross section. The important condition is colour triviality, i.e., the property that for arbitrary N-fold rescattering contributions the only non-vanishing colour trace is N c C FN. We give proofs for the colour triviality of the inelastic, diffractive and total photoabsorption cross section measured inclusively or with one jet resolved in the final state. Also, we list examples for which colour interference effects remain. Colour triviality allows us to write the γ ∗→q q¯ contribution to the DIS nuclear structure function F 2 for small Bjorken x Bj in terms of a path integral which describes the transverse size evolution of the q q¯ pair in the nuclear colour field. This expression reduces in an opacity expansion to the N=1 result of Nikolaev and Zakharov, and in the eikonal approximation to the Glauber-type rescattering formulas first derived by Mueller. In the harmonic oscillator approximation of the path integral, we quantify deviations from the eikonal limit. Their onset is characterized by the scales L/l f and E ⊥tot L which relate the longitudinal extension L of the nuclear target to the coherence length l f and the total transverse energy E ⊥tot accumulated by the q- q¯-pair.
New limits on intrinsic charm in the nucleon from global analysis of parton distributions.
Jimenez-Delgado, P; Hobbs, T J; Londergan, J T; Melnitchouk, W
2015-02-27
We present a new global QCD analysis of parton distribution functions, allowing for possible intrinsic charm (IC) contributions in the nucleon inspired by light-front models. The analysis makes use of the full range of available high-energy scattering data for Q^{2}≳1 GeV^{2} and W^{2}≳3.5 GeV^{2}, including fixed-target proton and deuteron cross sections at lower energies that were excluded in previous global analyses. The expanded data set places more stringent constraints on the momentum carried by IC, with ⟨x⟩_{IC} at most 0.5% (corresponding to an IC normalization of ∼1%) at the 4σ level for Δχ^{2}=1. We also critically assess the impact of older EMC measurements of F_{2}^{c} at large x, which favor a nonzero IC, but with very large χ^{2} values. PMID:25768757
New Angle on the Parton Distribution Functions: Self-Organizing Maps
Honkanen, H.; Liuti, S.
2009-08-04
Neural network (NN) algorithms have been recently applied to construct Parton Distribution Function (PDF) parametrizations, providing an alternative to standard global fitting procedures. Here we explore a novel technique using Self-Organizing Maps (SOMs). SOMs are a class of clustering algorithms based on competitive learning among spatially-ordered neurons. We train our SOMs with stochastically generated PDF samples. On every optimization iteration the PDFs are clustered on the SOM according to a user-defined feature and the most promising candidates are used as a seed for the subsequent iteration using the topology of the map to guide the PDF generating process. Our goal is a fitting procedure that, at variance with the standard neural network approaches, will allow for an increased control of the systematic bias by enabling user interaction in the various stages of the process.
New Limits on Intrinsic Charm in the Nucleon from Global Analysis of Parton Distributions
NASA Astrophysics Data System (ADS)
Jimenez-Delgado, P.; Hobbs, T. J.; Londergan, J. T.; Melnitchouk, W.
2015-02-01
We present a new global QCD analysis of parton distribution functions, allowing for possible intrinsic charm (IC) contributions in the nucleon inspired by light-front models. The analysis makes use of the full range of available high-energy scattering data for Q2≳1 GeV2 and W2≳3.5 GeV2 , including fixed-target proton and deuteron cross sections at lower energies that were excluded in previous global analyses. The expanded data set places more stringent constraints on the momentum carried by IC, with ⟨x ⟩IC at most 0.5% (corresponding to an IC normalization of ˜1 % ) at the 4 σ level for Δ χ2=1 . We also critically assess the impact of older EMC measurements of F2c at large x , which favor a nonzero IC, but with very large χ2 values.
New limits on intrinsic charm in the nucleon from global analysis of parton distributions
Jimenez-Delgado, P.; Hobbs, T. J.; Londergan, J. T.; Melnitchouk, W.
2015-02-27
We present a new global QCD analysis of parton distribution functions, allowing for possible intrinsic charm (IC) contributions in the nucleon inspired by light-front models. The analysis makes use of the full range of available high-energy scattering data for Q2 ≥ 1 GeV2 and W2 ≥ 3.5 GeV2, including fixed-target proton and deuteron deep cross sections at lower energies that were excluded in previously global analyses. The expanded data set places more stringent constraints on the momentum carried by IC, with (x)IC at most 0.5% (corresponding to an IC normalization of ~1%) at the 4σ level for ΔX2 = 1.more » We also assess the impact of older EMC measurements of Fc2c at large x, which favor a nonzero IC, but with very large X2 values.« less
Jo, H S; Girod, F X; Avakian, H; Burkert, V D; Garçon, M; Guidal, M; Kubarovsky, V; Niccolai, S; Stoler, P; Adhikari, K P; Adikaram, D; Amaryan, M J; Anderson, M D; Anefalos Pereira, S; Ball, J; Baltzell, N A; Battaglieri, M; Batourine, V; Bedlinskiy, I; Biselli, A S; Boiarinov, S; Briscoe, W J; Brooks, W K; Carman, D S; Celentano, A; Chandavar, S; Charles, G; Colaneri, L; Cole, P L; Compton, N; Contalbrigo, M; Crede, V; D'Angelo, A; Dashyan, N; De Vita, R; De Sanctis, E; Deur, A; Djalali, C; Dupre, R; Alaoui, A El; Fassi, L El; Elouadrhiri, L; Fedotov, G; Fegan, S; Filippi, A; Fleming, J A; Garillon, B; Gevorgyan, N; Ghandilyan, Y; Gilfoyle, G P; Giovanetti, K L; Goetz, J T; Golovatch, E; Gothe, R W; Griffioen, K A; Guegan, B; Guler, N; Guo, L; Hafidi, K; Hakobyan, H; Harrison, N; Hattawy, M; Hicks, K; Hirlinger Saylor, N; Ho, D; Holtrop, M; Hughes, S M; Ilieva, Y; Ireland, D G; Ishkhanov, B S; Jenkins, D; Joo, K; Joosten, S; Keller, D; Khachatryan, G; Khandaker, M; Kim, A; Kim, W; Klein, A; Klein, F J; Kuhn, S E; Kuleshov, S V; Lenisa, P; Livingston, K; Lu, H Y; MacGregor, I J D; McKinnon, B; Meziani, Z E; Mirazita, M; Mokeev, V; Montgomery, R A; Moutarde, H; Movsisyan, A; Munevar, E; Munoz Camacho, C; Nadel-Turonski, P; Net, L A; Niculescu, G; Osipenko, M; Ostrovidov, A I; Paolone, M; Park, K; Pasyuk, E; Phillips, J J; Pisano, S; Pogorelko, O; Price, J W; Procureur, S; Prok, Y; Puckett, A J R; Raue, B A; Ripani, M; Rizzo, A; Rosner, G; Rossi, P; Roy, P; Sabatié, F; Salgado, C; Schott, D; Schumacher, R A; Seder, E; Simonyan, A; Skorodumina, Iu; Smith, G D; Sokhan, D; Sparveris, N; Stepanyan, S; Strakovsky, I I; Strauch, S; Sytnik, V; Tian, Ye; Tkachenko, S; Ungaro, M; Voskanyan, H; Voutier, E; Walford, N K; Watts, D P; Wei, X; Weinstein, L B; Wood, M H; Zachariou, N; Zana, L; Zhang, J; Zhao, Z W; Zonta, I
2015-11-20
Unpolarized and beam-polarized fourfold cross sections (d^{4}σ/dQ^{2}dx_{B}dtdϕ) for the ep→e^{'}p^{'}γ reaction were measured using the CLAS detector and the 5.75-GeV polarized electron beam of the Jefferson Lab accelerator, for 110 (Q^{2},x_{B},t) bins over the widest phase space ever explored in the valence-quark region. Several models of generalized parton distributions (GPDs) describe the data well at most of our kinematics. This increases our confidence that we understand the GPD H, expected to be the dominant contributor to these observables. Through a leading-twist extraction of Compton form factors, these results support the model predictions of a larger nucleon size at lower quark-momentum fraction x_{B}.
Iterative Monte Carlo analysis of spin-dependent parton distributions
Sato, Nobuo; Melnitchouk, Wally; Kuhn, Sebastian E.; Ethier, Jacob J.; Accardi, Alberto
2016-04-05
We present a comprehensive new global QCD analysis of polarized inclusive deep-inelastic scattering, including the latest high-precision data on longitudinal and transverse polarization asymmetries from Jefferson Lab and elsewhere. The analysis is performed using a new iterative Monte Carlo fitting technique which generates stable fits to polarized parton distribution functions (PDFs) with statistically rigorous uncertainties. Inclusion of the Jefferson Lab data leads to a reduction in the PDF errors for the valence and sea quarks, as well as in the gluon polarization uncertainty at x ≳ 0.1. Furthermore, the study also provides the first determination of the flavor-separated twist-3 PDFsmore » and the d2 moment of the nucleon within a global PDF analysis.« less
Jo, Hyon -Suk
2015-11-17
Unpolarized and beam-polarized four-fold cross sectionsmore » $$\\frac{d^4 \\sigma}{dQ^2 dx_B dt d\\phi}$$ for the $$ep\\to e^\\prime p^\\prime \\gamma$$ reaction were measured using the CLAS detector and the 5.75-GeV polarized electron beam of the Jefferson Lab accelerator, for 110 ($Q^2,x_B,t$) bins over the widest phase space ever explored in the valence-quark region. Several models of Generalized Parton Distributions (GPDs) describe the data well at most of our kinematics. This increases our confidence that we understand the GPD $H$, expected to be the dominant contributor to these observables. Thus, through a leading-twist extraction of Compton Form Factors, these results reveal a tomographic image of the nucleon.« less
New Angle on the Parton Distribution Functions: Self-Organizing Maps
NASA Astrophysics Data System (ADS)
Honkanen, H.; Liuti, S.
2009-08-01
Neural network (NN) algorithms have been recently applied to construct Parton Distribution Function (PDF) parametrizations, providing an alternative to standard global fitting procedures. Here we explore a novel technique using Self-Organizing Maps (SOMs). SOMs are a class of clustering algorithms based on competitive learning among spatially-ordered neurons. We train our SOMs with stochastically generated PDF samples. On every optimization iteration the PDFs are clustered on the SOM according to a user-defined feature and the most promising candidates are used as a seed for the subsequent iteration using the topology of the map to guide the PDF generating process. Our goal is a fitting procedure that, at variance with the standard neural network approaches, will allow for an increased control of the systematic bias by enabling user interaction in the various stages of the process.
Transverse Momentum Dependent Parton Distribution Functions with Domain Wall Valence Fermions
Bernhard Musch, Robert Edwards, Michael Engelhardt, Philipp Haegler, John Negele, Alexey Prokudin, David Richards, Andreas Schaefer
2011-03-01
Transverse Momentum Dependent Parton Distribution Functions (TMDs) reveal the intrinsic motion of quarks inside the nucleon. They are essential ingredients needed to understand angular asymmetries studied in SIDIS experiments, including current and planned experiments at JLab. Within a class B proposal, we ask for time on the Jefferson Lab computer cluster to extract amplitudes for TMDs from existing lattice QCD gauge configurations and propagators calculated by the USQCD/MILC/LHP collaborations [Aubin 2004, Bratt 2010]. The proposal encompasses more comprehensive studies with a simplified operator [Haegler 2010] along with more realistic and more demanding calculations that promise to give access to time reversal odd TMDs such as the Sivers function. We ask for cluster computer time equivalent to 1.26 million J/Psi core hours, plus disk and tape storage worth 159000 J/Psi core hours.
Jo, Hyon -Suk
2015-11-17
Unpolarized and beam-polarized four-fold cross sections $\\frac{d^4 \\sigma}{dQ^2 dx_B dt d\\phi}$ for the $ep\\to e^\\prime p^\\prime \\gamma$ reaction were measured using the CLAS detector and the 5.75-GeV polarized electron beam of the Jefferson Lab accelerator, for 110 ($Q^2,x_B,t$) bins over the widest phase space ever explored in the valence-quark region. Several models of Generalized Parton Distributions (GPDs) describe the data well at most of our kinematics. This increases our confidence that we understand the GPD $H$, expected to be the dominant contributor to these observables. Thus, through a leading-twist extraction of Compton Form Factors, these results reveal a tomographic image of the nucleon.
Lattice QCD Studies of Transverse Momentum-Dependent Parton Distribution Functions
NASA Astrophysics Data System (ADS)
Engelhardt, M.; Musch, B.; Hägler, P.; Negele, J.; Schäfer, A.
2015-09-01
Transverse momentum-dependent parton distributions (TMDs) relevant for semi-inclusive deep inelastic scattering and the Drell-Yan process can be defined in terms of matrix elements of a quark bilocal operator containing a staple-shaped gauge link. Such a definition opens the possibility of evaluating TMDs within lattice QCD. By parametrizing the aforementioned matrix elements in terms of invariant amplitudes, the problem can be cast in a Lorentz frame suited for the lattice calculation. Results for selected TMD observables are presented, including a particular focus on their dependence on a Collins-Soper-type evolution parameter, which quantifies proximity of the staple-shaped gauge links to the light cone.
Partonic Equations of State in High-Energy Nuclear Collisions atRHIC
Xu, Nu
2006-10-01
The authors discuss the recent results on equation of state for partonic matter created at RHIC. Issues of partonic collectivity for multi-strange hadrons and J/{psi} from Au + Au collisions at {radical}s{sub NN} = 200 GeV are the focus of this paper.
Wee partons in large nuclei: From virtual dream to hard reality
Venugopalan, R.
1995-06-01
We construct a weak coupling, many body theory to compute parton distributions in large nuclei for x {much_lt} A{sup {minus} 1/3}. The wee partons are highly coherent, non-Abelian Weizsaecker-Williams fields. Radiative corrections to the classical results axe discussed. The parton distributions for a single nucleus provide the initial conditions for the dynamical evolution of matter formed in ultrarelativistic nuclear collisions.
NASA Astrophysics Data System (ADS)
Hosseinkhani, H.; Modarres, M.
2011-01-01
To overcome the complexity of generalized two hard scale (kt , μ) evolution equation, well known as the Ciafaloni, Catani, Fiorani and Marchesini (CCFM) evolution equations, and calculate the unintegrated parton distribution functions (UPDF), Kimber, Martin and Ryskin (KMR) proposed a procedure based on (i) the inclusion of single-scale (μ) only at the last step of evolution and (ii) the angular ordering constraint (AOC) on the DGLAP terms (the DGLAP collinear approximation), to bring the second scale, kt into the UPDF evolution equations. In this work we intend to use the MSTW2008 (Martin et al.) parton distribution functions (PDF) and try to calculate UPDF for various values of x (the longitudinal fraction of parton momentum), μ (the probe scale) and kt (the parton transverse momentum) to see the general behavior of three-dimensional UPDF at the NLO level up to the LHC working energy scales (μ2). It is shown that there exits some pronounced peaks for the three-dimensional UPDF (fa (x ,kt)) with respect to the two variables x and kt at various energies (μ). These peaks get larger and move to larger values of kt, as the energy (μ) is increased. We hope these peaks could be detected in the LHC experiments at CERN and other laboratories in the less exclusive processes.
NASA Astrophysics Data System (ADS)
Ding, Minghui; Gao, Fei; Chang, Lei; Liu, Yu-Xin; Roberts, Craig D.
2016-03-01
We compute the valence-quark leading twist parton distribution amplitudes (PDAs) of heavy pseudoscalar mesons ηc and ηb and find that they are both broader than the δ-like function while narrower than the asymptotic one. The evolution of distribution amplitude with momentum scale is then considered and PDAs will turn to a asymptotic form when the momentum goes to infinity.
New limits on intrinsic charm in the nucleon from global analysis of parton distributions
Jimenez-Delgado, P.; Hobbs, T. J.; Londergan, J. T.; Melnitchouk, W.
2015-02-27
We present a new global QCD analysis of parton distribution functions, allowing for possible intrinsic charm (IC) contributions in the nucleon inspired by light-front models. The analysis makes use of the full range of available high-energy scattering data for Q^{2} ≥ 1 GeV_{2} and W^{2} ≥ 3.5 GeV^{2}, including fixed-target proton and deuteron deep cross sections at lower energies that were excluded in previously global analyses. The expanded data set places more stringent constraints on the momentum carried by IC, with (x)_{IC} at most 0.5% (corresponding to an IC normalization of ~1%) at the 4σ level for Δ_{X2} = 1. We also assess the impact of older EMC measurements of F^{c}_{2}c at large x, which favor a nonzero IC, but with very large X^{2} values.
Moments of Nucleon's Parton Distribution for the Sea and Valence Quarks from Lattice QCD
Deka, Mridupawan; Streuer, Thomas; Doi, Takumi; Dong, Shao-Jing; Draper, Terrence; Liu, Keh-Fei; Mathur, Nilmani; Thomas, Anthony
2009-01-01
We extend the study of lowest moments, $
Zenaiev, O.; Geiser, A.; Lipka, K.; Blumlein, J.; Cooper-Sarkar, A.; Garzelli, M. -V.; Guzzi, M.; Kuprash, O.; Moch, S. -O.; Nadolsky, P.; et al
2015-08-01
The impact of recent measurements of heavy-flavour production in deep inelastic ep scattering and in pp collisions on parton distribution functions is studied in a QCD analysis in the fixed-flavour number scheme at next-to-leading order. Differential cross sections of charm- and beauty-hadron production measured by LHCb are used together with inclusive and heavy-flavour production cross sections in deep inelastic scattering at HERA. The heavy-flavour data of the LHCb experiment impose additional constraints on the gluon and the sea-quark distributions at low partonic fractions x of the proton momentum, down to x~5×10-6. This kinematic range is currently not covered by othermore » experimental data in perturbative QCD fits.« less
Zenaiev, O.; Geiser, A.; Lipka, K.; Blumlein, J.; Cooper-Sarkar, A.; Garzelli, M. -V.; Guzzi, M.; Kuprash, O.; Moch, S. -O.; Nadolsky, P.; Placakyte, R.; Rabbertz, K.; Schienbein, I.; Starovoitov, P.
2015-08-01
The impact of recent measurements of heavy-flavour production in deep inelastic ep scattering and in pp collisions on parton distribution functions is studied in a QCD analysis in the fixed-flavour number scheme at next-to-leading order. Differential cross sections of charm- and beauty-hadron production measured by LHCb are used together with inclusive and heavy-flavour production cross sections in deep inelastic scattering at HERA. The heavy-flavour data of the LHCb experiment impose additional constraints on the gluon and the sea-quark distributions at low partonic fractions x of the proton momentum, down to x~5×10^{-6}. This kinematic range is currently not covered by other experimental data in perturbative QCD fits.
Transverse parton distribution functions at next-to-next-to-leading order: the quark-to-quark case.
Gehrmann, Thomas; Lübbert, Thomas; Yang, Li Lin
2012-12-14
We present a calculation of the perturbative quark-to-quark transverse parton distribution function at next-to-next-to-leading order based on a gauge invariant operator definition. We demonstrate for the first time that such a definition works beyond the first nontrivial order. We extract from our calculation the coefficient functions relevant for a next-to-next-to-next-to-leading logarithmic Q(T) resummation in a large class of processes at hadron colliders.
Jimenez-Delgado, Pedro; Hobbs, Timothy J.; Londergan, J. T.; Melnitchouk, Wally
2016-01-05
We reply to the Comment of Brodsky and Gardner on our paper "New limits on intrinsic charm in the nucleon from global analysis of parton distributions" [Phys. Rev. Lett. 114, 082002 (2015)]. We address a number of incorrect claims made about our fitting methodology, and elaborate how global QCD analysis of all available high-energy data provides no evidence for a large intrinsic charm component of the nucleon.
NASA Astrophysics Data System (ADS)
Echevarria, Miguel G.; Scimemi, Ignazio; Vladimirov, Alexey
2016-09-01
The transverse momentum dependent parton distribution/fragmentation functions (TMDs) are essential in the factorization of a number of processes like Drell-Yan scattering, vector boson production, semi-inclusive deep inelastic scattering, etc. We provide a comprehensive study of unpolarized TMDs at next-to-next-to-leading order, which includes an explicit calculation of these TMDs and an extraction of their matching coefficients onto their integrated analogues, for all flavor combinations. The obtained matching coefficients are important for any kind of phenomenology involving TMDs. In the present study each individual TMD is calculated without any reference to a specific process. We recover the known results for parton distribution functions and provide new results for the fragmentation functions. The results for the gluon transverse momentum dependent fragmentation functions are presented for the first time at one and two loops. We also discuss the structure of singularities of TMD operators and TMD matrix elements, crossing relations between TMD parton distribution functions and TMD fragmentation functions, and renormalization group equations. In addition, we consider the behavior of the matching coefficients at threshold and make a conjecture on their structure to all orders in perturbation theory.
CT14QED parton distribution functions from isolated photon production in deep inelastic scattering
NASA Astrophysics Data System (ADS)
Schmidt, Carl; Pumplin, Jon; Stump, Daniel; Yuan, C.-P.
2016-06-01
We describe the implementation of quantum electrodynamic (QED) evolution at leading order (LO) along with quantum chromodynamic (QCD) evolution at next-to-leading order (NLO) in the CTEQ-TEA global analysis package. The inelastic contribution to the photon parton distribution function (PDF) is described by a two-parameter ansatz, coming from radiation off the valence quarks, and based on the CT14 NLO PDFs. Setting the two parameters to be equal allows us to completely specify the inelastic photon PDF in terms of the inelastic momentum fraction carried by the photon, p0γ, at the initial scale Q0=1.295 GeV . We obtain constraints on the photon PDF by comparing with ZEUS data [S. Chekanov et al. (ZEUS Collaboration), Phys. Lett. B 687, 16 (2010)] on the production of isolated photons in deep inelastic scattering, e p →e γ +X . For this comparison we present a new perturbative calculation of the process that consistently combines the photon-initiated contribution with the quark-initiated contribution. Comparison with the data allows us to put a constraint at the 90% confidence level of p0γ≲0.14 % for the inelastic photon PDF at the initial scale of Q0=1.295 GeV in the one-parameter radiative ansatz. The resulting inelastic CT14QED PDFs will be made available to the public. In addition, we also provide CT14QEDinc PDFs, in which the inclusive photon PDF at the scale Q0 is defined by the sum of the inelastic photon PDF and the elastic photon distribution obtained from the equivalent photon approximation.
NASA Astrophysics Data System (ADS)
Tuppan, Sam; Budnik, Garrett; Fox, Jordan
2014-09-01
The Meson Cloud Model (MCM) has proven to be a natural explanation for strangeness in the proton because of meson-baryon splitting into kaon-hyperon pairs. Total strangeness is predicted by integrated splitting functions, which represent the probability that the proton will fluctuate into a given meson-baryon pair. However, the momentum distributions s (x) and s (x) in the proton are determined from convolution integrals that depend on the parton distribution functions (PDFs) used for the mesons and baryons in the MCM. Theoretical calculations of these momentum distributions use many different forms for these PDFs. In our investigation, we calculate PDFs for K, K*, Λ, and Σ from two-body wave functions in a Light Cone Model (LCM) of the hadrons. We use these PDFs in conjunction with the MCM to create a hybrid model and compare our results to other theoretical calculations, experimental data from NuTeV, HERMES, ATLAS, and global parton distribution analyses. The Meson Cloud Model (MCM) has proven to be a natural explanation for strangeness in the proton because of meson-baryon splitting into kaon-hyperon pairs. Total strangeness is predicted by integrated splitting functions, which represent the probability that the proton will fluctuate into a given meson-baryon pair. However, the momentum distributions s (x) and s (x) in the proton are determined from convolution integrals that depend on the parton distribution functions (PDFs) used for the mesons and baryons in the MCM. Theoretical calculations of these momentum distributions use many different forms for these PDFs. In our investigation, we calculate PDFs for K, K*, Λ, and Σ from two-body wave functions in a Light Cone Model (LCM) of the hadrons. We use these PDFs in conjunction with the MCM to create a hybrid model and compare our results to other theoretical calculations, experimental data from NuTeV, HERMES, ATLAS, and global parton distribution analyses. This research has been supported in part by the
Jimenez-Delgado, P.; Reya, E.
2009-12-01
Based on our recent next-to-next-to-leading order (NNLO) dynamical parton distributions as obtained in the 'fixed flavor number scheme', we generate radiatively parton distributions in the 'variable flavor number scheme' where the heavy-quark flavors (c,b,t) also become massless partons within the nucleon. Only within this latter factorization scheme are NNLO calculations feasible at present, since the required partonic subprocesses are only available in the approximation of massless initial-state partons. The NNLO predictions for gauge boson production are typically larger (by more than 1{sigma}) than the next-to-leading order (NLO) ones, and rates at LHC energies can be predicted with an accuracy of about 5%, whereas at Tevatron they are more than 2{sigma} above the NLO ones. The NNLO predictions for standard model Higgs-boson production via the dominant gluon fusion process have a total (parton distribution function and scale) uncertainty of about 10% at LHC which almost doubles at the lower Tevatron energies; they are typically about 20% larger than the ones at NLO but the total uncertainty bands overlap.
Engelhardt, M.; Musch, B.; Bhattacharya, T.; Gupta, R.; Hagler, P.; Negele, J.; Pochinsky, A.; Schafer, A.; Syritsyn, S.; Yoon, B.
2014-06-23
Here, lattice QCD calculations of transverse momentum-dependent parton distributions (TMDs) in a nucleon are performed based on a definition of TMDs via hadronic matrix elements of quark bilocal operators containing staple-shaped gauge connections. A parametrization of the matrix elements in terms of invariant amplitudes serves to cast them in the Lorentz frame preferred for the lattice calculation. Using a RBC/UKQCD domain wall fermion ensemble corresponding to a pion mass of 297 MeV, on a lattice with spacing 0.084 fm, selected TMD observables are accessed and compared to previous exploration at heavier pion masses on coarser lattices.
Engelhardt, Michael; Musch, Bernhard; Bhattacharya, Tanmoy; Gupta, Rajan; Hagler, Phillip; Negele, John; Pochinsky, Andrew; Shafer, Andreas; Syritsyn, Sergey; Yoon, Boram
2014-12-01
Lattice QCD calculations of transverse momentum-dependent parton distributions (TMDs) in a nucleon are performed based on a definition of TMDs via hadronic matrix elements of quark bilocal operators containing staple-shaped gauge connections. A parametrization of the matrix elements in terms of invariant amplitudes serves to cast them in the Lorentz frame preferred for the lattice calculation. Using a RBC/UKQCD domain wall fermion ensemble corresponding to a pion mass of 297MeV, on a lattice with spacing 0.084fm, selected TMD observables are accessed and compared to previous explorations at heavier pion masses on coarser lattices.
Charge symmetry at the partonic level
Londergan, J. T.; Peng, J. C.; Thomas, A. W.
2010-07-01
This review article discusses the experimental and theoretical status of partonic charge symmetry. It is shown how the partonic content of various structure functions gets redefined when the assumption of charge symmetry is relaxed. We review various theoretical and phenomenological models for charge symmetry violation in parton distribution functions. We summarize the current experimental upper limits on charge symmetry violation in parton distributions. A series of experiments are presented, which might reveal partonic charge symmetry violation, or alternatively might lower the current upper limits on parton charge symmetry violation.
Glueck, M.; Reya, E.; Pisano, C.
2008-04-01
Recent measurements for F{sub 2}(x,Q{sup 2}) have been analyzed in terms of the 'dynamical' and 'standard' parton model approach at next-to-leading order (NLO) and next-to-next-to-leading order (NNLO) of perturbative QCD. Having fixed the relevant NLO and NNLO parton distributions, we present the implications and predictions for the longitudinal structure function F{sub L}(x,Q{sup 2}). It is shown that the previously noted extreme perturbative NNLO/NLO instability of F{sub L}(x,Q{sup 2}) is an artifact of the commonly utilized 'standard' gluon distributions. In particular it is demonstrated that using the appropriate--dynamically generated--parton distributions at NLO and NNLO, F{sub L}(x,Q{sup 2}) turns out to be perturbatively rather stable already for Q{sup 2}{>=}O(2-3 GeV{sup 2})
Summing threshold logs in a parton shower
NASA Astrophysics Data System (ADS)
Nagy, Zoltán; Soper, Davison E.
2016-10-01
When parton distributions are falling steeply as the momentum fractions of the partons increases, there are effects that occur at each order in α s that combine to affect hard scattering cross sections and need to be summed. We show how to accomplish this in a leading approximation in the context of a parton shower Monte Carlo event generator.
Kovalenko, V. N.
2013-10-15
The soft part of proton-proton interaction is considered within a phenomenological model that involves the formation of color strings. Under the assumption that an elementary collision is associated with the interaction of two color dipoles, the total inelastic cross section and the multiplicity of charged particles are estimated in order to fix model parameters. Particular attention is given to modeling of exclusive parton distributions with allowance for the energy-conservation law and for fixing the center of mass, which are necessary for describing correlations. An algorithm that describes the fusion of strings in the transverse plane and which takes into account their finite rapidity width is developed. The influence of string-fusion effects on long-range correlations is found within this mechanism.
Delineating the polarized and unpolarized partonic structure of the nucleon
Jimenez-Delgado, Pedro
2015-03-01
Our latest results on the extraction of parton distribution functions of the nucleon are reported. First an overview of the recent JR14 upgrade of our unpolarized PDFs, including NNLO determinations of the strong coupling constant and a discussion of the role of the input scale in parton distribution analysis. In the second part of the talk recent results on the determination of spin-dependent PDFs from the JAM collaboration are given, including a careful treatment of hadronic and nuclear corrections, as well as results on the impact of present and future data in our understanding of the spin of the nucleon.
Delineating the polarized and unpolarized partonic structure of the nucleon
Jimenez-Delgado, Pedro
2015-03-01
Reports on our latest extractions of parton distribution functions of the nucleon are given. First an overview of the recent JR14 upgrade of our unpolarized PDFs, including NNLO determinations of the strong coupling constant and a discussion of the role of the input scale in parton distribution analysis. In the second part of the talk recent results on the determination of spin-dependent PDFs from the JAM collaboration are reported, including a careful treatment of hadronic and nuclear corrections, as well as reports on the impact of present and future data in our understanding of the spin of the nucleon.
Gaining analytic control of parton showers
Tackmann, Frank; Bauer, Christian W.; Tackmann, Frank J.
2007-05-14
Parton showers are widely used to generate fully exclusive final states needed to compare theoretical models to experimental observations. While, in general, parton showers give a good description of the experimental data, the precise functional form of the probability distribution underlying the event generation is generally not known. The reason is that realistic parton showers are required to conserve four-momentum at each vertex. In this paper we investigate in detail how four-momentum conservation is enforced in a standard parton shower and why this destroysthe analytic control of the probability distribution. We show how to modify a parton shower algorithm such that it conserves four-momentum at each vertex, but for which the full analytic form of the probability distribution is known. We then comment how this analytic control can be used to match matrix element calculations with parton showers, and to estimate effects of power corrections and other uncertainties in parton showers.
Spin-flavor structure of chiral-odd generalized parton distributions in the large-Nc limit
Schweitzer, P.; Weiss, C.
2016-10-05
We study the spin-flavor structure of the nucleon's chiral-odd generalized parton distributions (transversity GPDs) in the large-Nc limit of QCD. In contrast to the chiral-even case, only three combinations of the four chiral-odd GPDs are nonzero in the leading order of the 1/Nc expansion: E-barT = ET+2H-tildeT, HT, and E-tildeT. The degeneracy is explained by the absence of spin-orbit interactions correlating the transverse momentum transfer with the transverse quark spin. It can also be deduced from the natural Nc scaling of the quark-nucleon helicity amplitudes associated with the GPDs. In the GPD E-barT the flavor-singlet component u+d is leading inmore » the 1/Nc expansion, while in HT and E-tildeT it is the flavor-nonsinglet components u–d. Furthermore, the large-Nc relations are consistent with the spin-flavor structure extracted from hard exclusive π0 and η electroproduction data, if it is assumed that the processes are mediated by twist-3 amplitudes involving the chiral-odd GPDs and the chiral-odd pseudoscalar meson distribution amplitudes.« less
Spin-flavor structure of chiral-odd generalized parton distributions in the large-Nc limit
NASA Astrophysics Data System (ADS)
Schweitzer, P.; Weiss, C.
2016-10-01
We study the spin-flavor structure of the nucleon's chiral-odd generalized parton distributions (transversity GPDs) in the large-Nc limit of QCD. In contrast to the chiral-even case, only three combinations of the four chiral-odd GPDs are nonzero in the leading order of the 1 /Nc expansion: E¯T=ET+2 H˜T,HT , and E˜T. The degeneracy is explained by the absence of spin-orbit interactions correlating the transverse momentum transfer with the transverse quark spin. It can also be deduced from the natural Nc scaling of the quark-nucleon helicity amplitudes associated with the GPDs. In the GPD E¯T the flavor-singlet component u +d is leading in the 1 /Nc expansion, while in HT and E˜T it is the flavor-nonsinglet components u -d . The large-Nc relations are consistent with the spin-flavor structure extracted from hard exclusive π0 and η electroproduction data, if it is assumed that the processes are mediated by twist-3 amplitudes involving the chiral-odd GPDs and the chiral-odd pseudoscalar meson distribution amplitudes.
Measurement of partonic nuclear effects in deep-inelastic neutrino scattering using MINERvA
Mousseau, J.
2016-04-19
Here, the MINERvA Collaboration reports a novel study of neutrino-nucleus charged-current deep inelastic scattering (DIS) using the same neutrino beam incident on targets of polystyrene, graphite, iron, and lead. Results are presented as ratios of C, Fe, and Pb to CH. The ratios of total DIS cross sections as a function of neutrino energy and flux-integrated differential cross sections as a function of the Bjorken scaling variable x are presented in the neutrino-energy range of 5–50 GeV. Based on the predictions of charged-lepton scattering ratios, good agreement is found between the data and prediction at medium x and low neutrino energy.more » However, the ratios appear to be below predictions in the vicinity of the nuclear shadowing region, x < 0.1. This apparent deficit, reflected in the DIS cross-section ratio at high Eν, is consistent with previous MINERvA observations [B. Tice (MINERvA Collaboration), Phys. Rev. Lett. 112, 231801 (2014).] and with the predicted onset of nuclear shadowing with the axial-vector current in neutrino scattering.« less
Measurement of partonic nuclear effects in deep-inelastic neutrino scattering using MINERvA
NASA Astrophysics Data System (ADS)
Mousseau, J.; Wospakrik, M.; Aliaga, L.; Altinok, O.; Bellantoni, L.; Bercellie, A.; Betancourt, M.; Bodek, A.; Bravar, A.; Budd, H.; Cai, T.; Carneiro, M. F.; Christy, M. E.; Chvojka, J.; da Motta, H.; Devan, J.; Dytman, S. A.; Díaz, G. A.; Eberly, B.; Felix, J.; Fields, L.; Fine, R.; Gago, A. M.; Galindo, R.; Gallagher, H.; Ghosh, A.; Golan, T.; Gran, R.; Harris, D. A.; Higuera, A.; Hurtado, K.; Kiveni, M.; Kleykamp, J.; Kordosky, M.; Le, T.; Maher, E.; Manly, S.; Mann, W. A.; Marshall, C. M.; Martinez Caicedo, D. A.; McFarland, K. S.; McGivern, C. L.; McGowan, A. M.; Messerly, B.; Miller, J.; Mislivec, A.; Morfín, J. G.; Naples, D.; Nelson, J. K.; Norrick, A.; Nuruzzaman; Osta, J.; Paolone, V.; Park, J.; Patrick, C. E.; Perdue, G. N.; Rakotondravohitra, L.; Ramirez, M. A.; Ransome, R. D.; Ray, H.; Ren, L.; Rimal, D.; Rodrigues, P. A.; Ruterbories, D.; Schellman, H.; Schmitz, D. W.; Solano Salinas, C. J.; Tagg, N.; Tice, B. G.; Valencia, E.; Walton, T.; Wolcott, J.; Zavala, G.; Zhang, D.; Minerν A Collaboration
2016-04-01
The MINERvA Collaboration reports a novel study of neutrino-nucleus charged-current deep inelastic scattering (DIS) using the same neutrino beam incident on targets of polystyrene, graphite, iron, and lead. Results are presented as ratios of C, Fe, and Pb to CH. The ratios of total DIS cross sections as a function of neutrino energy and flux-integrated differential cross sections as a function of the Bjorken scaling variable x are presented in the neutrino-energy range of 5-50 GeV. Based on the predictions of charged-lepton scattering ratios, good agreement is found between the data and prediction at medium x and low neutrino energy. However, the ratios appear to be below predictions in the vicinity of the nuclear shadowing region, x <0.1 . This apparent deficit, reflected in the DIS cross-section ratio at high Eν, is consistent with previous MINERvA observations [B. Tice et al. (MINERvA Collaboration), Phys. Rev. Lett. 112, 231801 (2014).] and with the predicted onset of nuclear shadowing with the axial-vector current in neutrino scattering.
Strongly interacting parton matter equilibration
Ozvenchuk, V.; Linnyk, O.; Bratkovskaya, E.; Gorenstein, M.; Cassing, W.
2012-07-15
We study the kinetic and chemical equilibration in 'infinite' parton matter within the Parton-Hadron-String Dynamics transport approach. The 'infinite' matter is simulated within a cubic box with periodic boundary conditions initialized at different energy densities. Particle abundances, kinetic energy distributions, and the detailed balance of the off-shell quarks and gluons in the strongly-interacting quarkgluon plasma are addressed and discussed.
Flavor dependence of the pion and kaon form factors and parton distribution functions
NASA Astrophysics Data System (ADS)
Hutauruk, Parada T. P.; Cloët, Ian C.; Thomas, Anthony W.
2016-09-01
The separate quark flavor contributions to the pion and kaon valence quark distribution functions are studied, along with the corresponding electromagnetic form factors in the space-like region. The calculations are made using the solution of the Bethe-Salpeter equation for the model of Nambu and Jona-Lasinio with proper-time regularization. Both the pion and kaon form factors and the valence quark distribution functions reproduce many features of the available empirical data. The larger mass of the strange quark naturally explains the empirical fact that the ratio uK+(x ) /uπ+(x ) drops below unity at large x , with a value of approximately Mu2/Ms2 as x →1 . With regard to the elastic form factors we report a large flavor dependence, with the u -quark contribution to the kaon form factor being an order of magnitude smaller than that of the s -quark at large Q2, which may be a sensitive measure of confinement effects in QCD. Surprisingly though, the total K+ and π+ form factors differ by only 10%. In general we find that flavor breaking effects are typically around 20%.
NASA Astrophysics Data System (ADS)
Tatur, Stanislaw; Bartelski, Jan; Kurzela, Miroslaw
2000-03-01
We have made next to leading order QCD fit to the deep inelastic spin asymmetries on nucleons and we have determined polarised quark and gluon densities. The functional form for such distributions was inspired by the Martin, Roberts and Stirling fit for unpolarised case. In addition to usually used data points (averaged over x and Q2) we have also considered the sample containing points with similar x and different Q2. It seems that splitting of quark densities into valence and sea contribution is strongly model dependent and only their sum (i.e. , Δ u and Δ d) can be precisely determined from the data. Integrated polarised gluon contribution, contrary to some expectations, is relatively small and the sign of it depends on the fact which sample of data points is used.
Parton branching in the color mutation model
NASA Astrophysics Data System (ADS)
Hwa, Rudolph C.; Wu, Yuanfang
1999-11-01
The soft production problem in hadronic collisions as described in the eikonal color mutation branching model is improved in the way that the initial parton distribution is treated. Furry branching of the partons is considered as a means of describing the nonperturbative process of parton reproduction in the soft interaction. The values of all the moments,
Triple parton scattering in collinear approximation of perturbative QCD
NASA Astrophysics Data System (ADS)
Snigirev, A. M.
2016-08-01
Revised formulas for the inclusive cross section of a triple parton scattering process in a hadron collision are suggested based on the modified collinear three-parton distributions. The possible phenomenological issues are discussed.
Deuteron distribution in nuclear matter
NASA Astrophysics Data System (ADS)
Benhar, O.; Fabrocini, A.; Fantoni, S.; Illarionov, A. Yu.; Lykasov, G. I.
2002-05-01
We analyze the properties of deuteron-like structures in infinite, correlated nuclear matter, described by a realistic hamiltonian containing the Urbana v14 two-nucleon and the Urbana TNI many-body potentials. The distribution of neutron-proton pairs, carrying the deuteron quantum numbers, is obtained as a function of the total momentum by computing the overlap between the nuclear matter in its ground state and the deuteron wave functions in correlated basis functions theory. We study the differences between the S- and D-wave components of the deuteron and those of the deuteron-like pair in the nuclear medium. The total number of deuteron type pairs is computed and compared with the predictions of Levinger's quasideuteron model. The resulting Levinger's factor in nuclear matter at equilibrium density is 11.63. We use the local density approximation to estimate the Levinger's factor for heavy nuclei, obtaining results which are consistent with the available experimental data from photoreactions.
NASA Astrophysics Data System (ADS)
Pasquini, B.; Schweitzer, P.
2014-07-01
At leading twist the transverse momentum dependent parton distributions of the pion consist of two functions, the unpolarized f1,π(x,k⊥2) and the Boer-Mulders function h1,π⊥(x ,k⊥2). We study both functions within a light-front constituent model of the pion, comparing the results with different pion models and the corresponding nucleon distributions from a light-front constituent model. After evolution from the model scale to the relevant experimental scales, the results for the collinear pion valence parton distribution function f1,π(x) are in very good agreement with available parametrizations. Using the light-front constituent model results for the Boer-Mulders functions of the pion and nucleon, we calculate the coefficient ν in the angular distribution of Drell-Yan dileptons produced in pion-nucleus scattering, which is responsible for the violation of the Lam-Tung relation. We find a good agreement with the data, and carefully discuss the range of applicability of our approach.
Guegan, Baptiste
2012-11-01
The exclusive leptoproduction of a real photon is considered to be the "cleanest" way to access the Generalized Parton Distribution (GPD). This process is called Deeply Virtual Compton Scattering (DVCS) lN {yields} lN{gamma} , and is sensitive to all the four GPDs. Measuring the DVCS cross section is one of the main goals of this thesis. In this thesis, we present the work performed to extract on a wide phase-space the DVCS cross-section from the JLab data at a beam energy of 6 GeV.
NASA Astrophysics Data System (ADS)
Taghavi-Shahri, F.; Khanpour, Hamzeh; Atashbar Tehrani, S.; Alizadeh Yazdi, Z.
2016-06-01
We present a first QCD analysis of next-to-next-leading-order (NNLO) contributions of the spin-dependent parton distribution functions (PPDFs) in the nucleon and their uncertainties using the Jacobi polynomial approach. Having the NNLO contributions of the quark-quark and gluon-quark splitting functions in perturbative QCD [Nucl. Phys. B889, 351 (2014)], one can obtain the evolution of longitudinally polarized parton densities of hadrons up to NNLO accuracy of QCD. Very large sets of recent and up-to-date experimental data of spin structure functions of the proton g1p, neutron g1n, and deuteron g1d have been used in this analysis. The predictions for the NNLO calculations of the polarized parton distribution functions as well as the proton, neutron and deuteron polarized structure functions are compared with the corresponding results of the NLO approximation. We form a mutually consistent set of polarized PDFs due to the inclusion of the most available experimental data including the recently high-precision measurements from COMPASS16 experiments [Phys. Lett. B 753, 18 (2016)]. We have performed a careful estimation of the uncertainties using the most common and practical method, the Hessian method, for the polarized PDFs originating from the experimental errors. The proton, neutron and deuteron structure functions and also their first moments, Γp ,n ,d , are in good agreement with the experimental data at small and large momentum fractions of x . We will discuss how our knowledge of spin-dependence structure functions can improve at small and large values of x by the recent COMPASS16 measurements at CERN, the PHENIX and STAR measurements at RHIC, and at the future proposed colliders such as the Electron-Ion Collider.
Demartin, Federico; Mariani, Elisa; Forte, Stefano; Vicini, Alessandro; Rojo, Juan
2010-07-01
We present a systematic study of uncertainties due to parton distributions (PDFs) and the strong coupling on the gluon-fusion production cross section of the standard model Higgs at the Tevatron and LHC colliders. We compare procedures and results when three recent sets of PDFs are used, CTEQ6.6, MSTW08, and NNPDF1.2, and we discuss specifically the way PDF and strong coupling uncertainties are combined. We find that results obtained from different PDF sets are in reasonable agreement if a common value of the strong coupling is adopted. We show that the addition in quadrature of PDF and {alpha}{sub s} uncertainties provides an adequate approximation to the full result with exact error propagation. We discuss a simple recipe to determine a conservative PDF+{alpha}{sub s} uncertainty from available global parton sets, and we use it to estimate this uncertainty on the given process to be about 10% at the Tevatron and 5% at the LHC for a light Higgs.
The Polarized TMDs in the covariant parton model approach
A.V. Efremov, P. Schweitzer, O.V. Teryaev, P. Zavada
2011-05-01
We derive relations between polarized transverse momentum dependent distribution functions (TMDs) and the usual parton distribution functions (PDFs) in the 3D covariant parton model, which follow from Lorentz invariance and the assumption of a rotationally symmetric distribution of parton momenta in the nucleon rest frame. Using the known PDF $g_{1}^{q}(x)$ as input we predict the $x$- and $\\mathbf{p}_{T}$-dependence of all polarized twist-2 naively time-reversal even (T-even) TMDs.
Disentangling correlations in multiple parton interactions
Calucci, G.; Treleani, D.
2011-01-01
Multiple Parton Interactions are the tool to obtain information on the correlations between partons in the hadron structure. Partons may be correlated in all degrees of freedom and all different correlation terms contribute to the cross section. The contributions due to the different parton flavors can be isolated, at least to some extent, by selecting properly the final state. In the case of high energy proton-proton collisions, the effects of correlations in the transverse coordinates and in fractional momenta are, on the contrary, unavoidably mixed in the final observables. The standard way to quantify the strength of double parton interactions is by the value of the effective cross section and a small value of the effective cross section may be originated both by the relatively short transverse distance between the pairs of partons undergoing the double interaction and by a large dispersion of the distribution in multiplicity of the multiparton distributions. The aim of the present paper is to show how the effects of longitudinal and transverse correlations may be disentangled by taking into account the additional information provided by double parton interactions in high energy proton-deuteron collisions.
Transverse nucleon structure and diagnostics of hard parton-parton processes at LHC
L. Frankfurt, M. Strikman, C. Weiss
2011-03-01
We propose a new method to determine at what transverse momenta particle production in high-energy pp collisions is governed by hard parton-parton processes. Using information on the transverse spatial distribution of partons obtained from hard exclusive processes in ep/\\gamma p scattering, we evaluate the impact parameter distribution of pp collisions with a hard parton-parton process as a function of p_T of the produced parton (jet). We find that the average pp impact parameters in such events depend very weakly on p_T in the range 2 < p_T < few 100 GeV, while they are much smaller than those in minimum-bias inelastic collisions. The impact parameters in turn govern the observable transverse multiplicity in such events (in the direction perpendicular to the trigger particle or jet). Measuring the transverse multiplicity as a function of p_T thus provides an effective tool for determining the minimum p_T for which a given trigger particle originates from a hard parton-parton process.
The midpoint between dipole and parton showers
Höche, Stefan; Prestel, Stefan
2015-09-28
We present a new parton-shower algorithm. Borrowing from the basic ideas of dipole cascades, the evolution variable is judiciously chosen as the transverse momentum in the soft limit. This leads to a very simple analytic structure of the evolution. A weighting algorithm is implemented that allows one to consistently treat potentially negative values of the splitting functions and the parton distributions. Thus, we provide two independent, publicly available implementations for the two event generators PYTHIA and SHERPA.
Guzey, V.; Teckentrup, T.
2006-09-01
We develop the minimal model of a new leading order parametrization of generalized parton distributions (GPDs) introduced by Polyakov and Shuvaev. The model for GPDs H and E is formulated in terms of the forward quark distributions, the Gegenbauer moments of the D-term, and the forward limit of the GPD E. The model is designed primarily for small and medium-size values of x{sub B}, x{sub B}{<=}0.2. We examine two different models of the t dependence of the GPDs: the factorized exponential model and the nonfactorized Regge-motivated model. Using our model, we successfully described the deeply virtual Compton scattering (DVCS) cross section measured by H1 and ZEUS, the moments of the beam-spin A{sub LU}{sup sin{phi}}, the beam-charge A{sub C}{sup cos{phi}}, and the transversely polarized target A{sub UT}{sup sin{phi}}{sup cos{phi}} DVCS asymmetries measured by HERMES and A{sub LU}{sup sin{phi}} measured by CLAS. The data on A{sub C}{sup cos{phi}} prefer the Regge-motivated model of the t dependence of the GPDs. The data on A{sub UT}{sup sin{phi}}{sup cos{phi}} indicate that the u and d quarks carry only a small fraction of the proton total angular momentum.
The parton orbital angular momentum: Status and prospects
NASA Astrophysics Data System (ADS)
Liu, Keh-Fei; Lorcé, Cédric
2016-06-01
Theoretical progress on the formulation and classification of the quark and gluon orbital angular momenta (OAM) is reviewed. Their relation to parton distributions and open questions and puzzles are discussed. We give a status report on the lattice calculation of the parton kinetic and canonical OAM and point out several strategies to calculate the quark and gluon canonical OAM on the lattice.
Nuclear moment of inertia and spin distribution of nuclear levels
Alhassid, Y.; Fang, L.; Liu, S.; Bertsch, G.F.
2005-12-15
We introduce a simple model to calculate the nuclear moment of inertia at finite temperature. This moment of inertia describes the spin distribution of nuclear levels in the framework of the spin-cutoff model. Our model is based on a deformed single-particle Hamiltonian with pairing interaction and takes into account fluctuations in the pairing gap. We derive a formula for the moment of inertia at finite temperature that generalizes the Belyaev formula for zero temperature. We show that a number-parity projection explains the strong odd-even effects observed in shell model Monte Carlo studies of the nuclear moment of inertia in the iron region.
Parton Charge Symmetry Violation: Electromagnetic Effects and W Production Asymmetries
J.T. Londergan; D.P. Murdock; A.W. Thomas
2006-04-14
Recent phenomenological work has examined two different ways of including charge symmetry violation in parton distribution functions. First, a global phenomenological fit to high energy data has included charge symmetry breaking terms, leading to limits on the magnitude of parton charge symmetry breaking. In a second approach, two groups have included the coupling of partons to photons in the QCD evolution equations. One possible experiment that could search for isospin violation in parton distributions is a measurement of the asymmetry in W production at a collider. In this work we include both of the postulated sources of parton charge symmetry violation. We show that, given charge symmetry violation of a magnitude consistent with existing high energy data, the expected W production asymmetries would be quite small, generally less than one percent.
Central depression of nuclear charge density distribution
Chu Yanyun; Ren Zhongzhou; Wang Zaijun; Dong Tiekuang
2010-08-15
The center-depressed nuclear charge distributions are investigated with the parametrized distribution and the relativistic mean-field theory, and their corresponding charge form factors are worked out with the phase shift analysis method. The central depression of nuclear charge distribution of {sup 46}Ar and {sup 44}S is supported by the relativistic mean-field calculation. According to the calculation, the valence protons in {sup 46}Ar and {sup 44}S prefer to occupy the 1d{sub 3/2} state rather than the 2s{sub 1/2} state, which is different from that in the less neutron-rich argon and sulfur isotopes. As a result, the central proton densities of {sup 46}Ar and {sup 44}S are highly depressed, and so are their central charge densities. The charge form factors of some argon and sulfur isotopes are presented, and the minima of the charge form factors shift upward and inward when the central nuclear charge distributions are more depressed. Besides, the effect of the central depression on the charge form factors is studied with a parametrized distribution, when the root-mean-square charge radii remain constant.
Are partons confined tachyons?
Noyes, H.P.
1996-03-01
The author notes that if hadrons are gravitationally stabilized ``black holes``, as discrete physics suggests, it is possible that partons, and in particular quarks, could be modeled as tachyons, i.e. particles having v{sup 2} > c{sup 2}, without conflict with the observational fact that neither quarks nor tachyons have appeared as ``free particles``. Some consequences of this model are explored.
Double parton scattering: Impact of nonperturbative parton correlations
NASA Astrophysics Data System (ADS)
Ostapchenko, Sergey; Bleicher, Marcus
2016-02-01
We apply the phenomenological Reggeon field theory framework to investigate the relative importance of perturbative and nonperturbative multiparton correlations for the treatment of double parton scattering in proton-proton collisions. We obtain a significant correction to the so-called effective cross section for double parton scattering due to nonperturbative parton splitting. When combined with the corresponding perturbative contribution, this results in a rather weak energy and transverse momentum dependence of the effective cross section, in agreement with experimental observations at the Tevatron and the Large Hadron Collider. In addition, we observe that color fluctuations have a sizable impact on the calculated rate of double parton scattering and on the relative importance of the perturbative parton splitting mechanism.
Absolute nuclear material assay using count distribution (LAMBDA) space
Prasad, Mano K.; Snyderman, Neal J.; Rowland, Mark S.
2015-12-01
A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.
Absolute nuclear material assay using count distribution (LAMBDA) space
Prasad, Manoj K.; Snyderman, Neal J.; Rowland, Mark S.
2012-06-05
A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.
NASA Astrophysics Data System (ADS)
Pesznyak, Csilla
The aim of the investigation is to give answer to some questions of the QC in the mega-voltage therapy for the sake of making the treatments more trouble-free. We investigated the terms of the usage of CT and PET/CT equipments in treatment planning that were made originally for diagnostic purposes. We compared the calculation algorithms of the Varian CadPlan(TM) and CMS XiORTM treatment planning systems (TPS) for photon and electron radiations of different energy. We also investigated the terms of usage of the PTW EPID QC PHANTOMRTM in the quality control of the EPID's and the portal images, as well. We laid down the terms in a protocol that make the diagnostic CT and PET/CT equipments capable for radiation treatment planning. The protocols should contain the exact patient setup, the tube voltage, detailed directions for use of patient immobilization tools, the review and use of the necessary QA/QC devices, the time consumption of the procedure, the frequency of controls and the worksheet to be used during the measurements. On the base of the measurements, it can be stated that on photon energies the superposition algorithm can be used for patient treatments in the case of the CMS XiORTM TPS while in the case of Varian CadPlan(TM) TPS the PBMB algorithm is the proper choice. It is not allowed to use the TPS without inhomogeneity correction. The CIRS Thorax IMRT phantom can be used for electron measurement only at higher than 10 MeV since only the Farmer chamber can be inserted into the holes of the phantom. On the base of the electron measurements, it can be stated that both planning systems give good results in soft tissue. In lung equivalent material the calculated values of the Varian CadPlan(TM) are in better agreement with the measured values, but the calculated values behind the bones are not accurate enough. In the QA/QC process the PTW EPID QC PHANTOMRTM is usable not only for the amorphous silicon EPID's but the image quality can be analysed on the video based devices and on EPID's operating with liquid filled ionisation chamber array detector and even on port films. In the protocol for measurements, the usable file format should be given since the DICOM implementation is not complete in the case of these systems.
Global QCD Analysis of Polarized Parton Densities
Stratmann, Marco
2009-08-04
We focus on some highlights of a recent, first global Quantum Chromodynamics (QCD) analysis of the helicity parton distributions of the nucleon, mainly the evidence for a rather small gluon polarization over a limited region of momentum fraction and for interesting flavor patterns in the polarized sea. It is examined how the various sets of data obtained in inclusive and semi-inclusive deep inelastic scattering and polarized proton-proton collisions help to constrain different aspects of the quark, antiquark, and gluon helicity distributions. Uncertainty estimates are performed using both the robust Lagrange multiplier technique and the standard Hessian approach.
NASA Astrophysics Data System (ADS)
Seng, Chien-Yeah; Ramsey-Musolf, Michael J.
2013-07-01
We study the effect of parton angular momentum on the twist-four correction to the left-right asymmetry in the electron-deuteron parity-violating deep-inelastic scattering (PVDIS). We show that this higher-twist correction is transparent to the dynamics of parton angular momentum needed to account for the Sivers and Boer-Mulders functions and spin-independent parton distribution functions. A sufficiently precise measurement of the PVDIS asymmetry may, thus, provide additional information about the parton dynamics responsible for nucleon spin.
NASA Astrophysics Data System (ADS)
Barbara, Betz; Miklos, Gyulassy
2015-12-01
Not Available Supported by the Helmholtz International Centre for FAIR within the Framework of the LOEWE Program, and the US-DOE Nuclear Science under Grant Nos DE-FG02-93ER40764 and DE-AC02-05CH11231.
Backward dilepton production in color dipole and parton models
Gay Ducati, Maria Beatriz; Graeve de Oliveira, Emmanuel
2010-03-01
The Drell-Yan dilepton production at backward rapidities is studied in proton-nucleus collisions at Relativistic Heavy Ion Collider and LHC energies by comparing two different approaches: the k{sub T} factorization at next-to-leading order with intrinsic transverse momentum and the same process formulated in the target rest frame, i.e., the color dipole approach. Our results are expressed in terms of the ratio between p(d)-A and p-p collisions as a function of transverse momentum and rapidity. Three nuclear parton distribution functions are used: EKS (Eskola, Kolhinen, and Ruuskanen), EPS08, and EPS09 and, in both approaches, dileptons show sensitivity to nuclear effects, specially regarding the intrinsic transverse momentum. Also, there is room to discriminate between formalisms: the color dipole approach lacks soft effects introduced by the intrinsic k{sub T}. Geometric scaling GBW (Golec-Biernat and Wusthoff) and BUW (Boer, Utermann, and Wessels) color dipole cross section models and also a DHJ (Dumitru, Hayashigaki, and Jalilian-Marian) model, which breaks geometric scaling, are used. No change in the ratio between collisions is observed, showing that this observable is not changed by the particular shape of the color dipole cross section. Furthermore, our k{sub T} factorization results are compared with color glass condensate results at forward rapidities: the results agree at Relativistic Heavy Ion Collider although disagree at LHC, mainly due to the different behavior of target gluon and quark shadowing.
Nucleon structure at large x: nuclear effects in deuterium
Wally Melnitchouk
2010-07-01
I review quark momentum distributions in the nucleon at large momentum fractions x. Particular attention is paid to the impact of nuclear effects in deuterium on the d/u quark distribution ratio as x -> 1. A new global study of parton distributions, using less restrictive kinematic cuts in Q^2 and W^2, finds strong suppression of the d quark distribution once nuclear corrections are accounted for.
Large-x connections of nuclear and high-energy physics
Accardi, Alberto
2013-11-20
I discuss how global QCD fits of parton distribution functions can make the somewhat separated fields of high-energy particle physics and lower energy hadronic and nuclear physics interact to the benefit of both. I review specific examples of this interplay from recent works of the CTEQ-Jefferson Lab collaboration, including hadron structure at large parton momentum and gauge boson production at colliders. Particular attention is devoted to quantifying theoretical uncertainties arising in the treatment of large partonic momentum contributions to deep inelastic scattering observables, and to discussing the experimental progress needed to reduce these.
Khachatryan, Vardan
2015-06-26
The inclusive jet cross section for proton–proton collisions at a centre-of-mass energy of 7TeVwas measured by the CMS Collaboration at the LHC with data corresponding to an integrated luminosity of 5.0fb-1. The measurement covers a phase space up to 2TeV in jet transverse momentum and 2.5 in absolute jet rapidity. The statistical precision of these data leads to stringent constraints on the parton distribution functions of the proton. The data provide important input for the gluon density at high fractions of the proton momentum and for the strong coupling constant at large energy scales. Using predictions from perturbative quantum chromodynamicsmore » at next-to-leading order, complemented with electroweak corrections, the constraining power of these data is investigated and the strong coupling constant at the Z boson mass MZ is determined to be αS(MZ)=0.1185±0.0019(exp)+0.0060-0.0037(theo), which is in agreement with the world average.« less
Khachatryan, Vardan
2015-06-26
The inclusive jet cross section for proton–proton collisions at a centre-of-mass energy of 7TeVwas measured by the CMS Collaboration at the LHC with data corresponding to an integrated luminosity of 5.0fb^{-1}. The measurement covers a phase space up to 2TeV in jet transverse momentum and 2.5 in absolute jet rapidity. The statistical precision of these data leads to stringent constraints on the parton distribution functions of the proton. The data provide important input for the gluon density at high fractions of the proton momentum and for the strong coupling constant at large energy scales. Using predictions from perturbative quantum chromodynamics at next-to-leading order, complemented with electroweak corrections, the constraining power of these data is investigated and the strong coupling constant at the Z boson mass M_{Z} is determined to be α_{S}(M_{Z})=0.1185±0.0019(exp)^{+0.0060}_{-0.0037}(theo), which is in agreement with the world average.
HEAVY QUARKS AT RHIC FROM PARTON TRANSPORT THEORY.
MOLNAR, D.
2006-05-15
There are several indications that an opaque partonic medium is created in energetic Au+Au collisions ({radical}s{sub NN} {approx} GeV/nucleon) at the Relativistic Heavy Ion Collider (RHIC). At the extreme densities of {approx} 10-100 times normal nuclear density reached even heavy-flavor hadrons are affected significantly. Heavy-quark observables are presented from the parton transport model MPC, focusing on the nuclear suppression pattern, azimuthal anisotropy (''elliptic flow''), and azimuthal correlations. Comparison with Au + Au data at top RHIC energy {radical}s{sub NN} = 200 GeV indicates significant heavy quark rescattering, corresponding roughly five times higher opacities than estimates based on leading-order perturbative QCD. We propose measurements of charm-anticharm, e.g., D-meson azimuthal correlations as a sensitive, independent probe to corroborate these findings.
Distribution of Corbicula fluminea at nuclear facilities
Counts, C.L. III
1985-11-01
A review of the zoogeographic records for the exotic Asian clam, Corbicula fluminea (Muller, 1774), reveals its presence in 27 states where nuclear powered electric generating plants are either operating or under construction. Nineteen plant sites reported infestation of varying severity in facilities, or source water bodies immediately adjacent to the facility, by C. fluminea. Thirteen plant sites are located within the zoogeographic limits of C. fluminea but have a low risk of infestation due to either salt water cooling systems or locations a great distance from known populations. Eighteen plant sites are located wholly outside of the known zoogeographic range of C. fluminea. Thirty plant sites are located in close proximity to known populations of C. fluminea and therefore should maintain surveillance of the source water body and within plant water systems for possible infestations by these bivalves. 27 figs.
Evolution of anisotropy of a partonic system from relativistic heavy-ion collisions
Jas, Weronika; Mrowczynski, Stanislaw
2007-10-15
The evolution of anisotropy in momentum and coordinate space of the parton system produced in relativistic heavy-ion collisions is discussed within the free-streaming approximation. The momentum distribution evolves from the prolate shape (elongated along the beam) to the oblate one (squeezed along the beam). At the same time, the eccentricity in coordinate space, which occurs at finite values of impact parameter, decreases. It is argued that the parton system reaches local thermodynamic equilibrium before the momentum distribution becomes oblate.
Parton-parton elastic scattering and rapidity gaps at SSC and LHC energies
Duca, V.D.
1993-08-01
The theory of the perturbative pomeron, due to Lipatov and collaborators, is used to compute the probability of observing parton-parton elastic scattering and rapidity gaps between jets in hadron collisions at SSC and LHC energies.
Polarization of partons in the proton
Kobayakawa, K.; Morii, T. ); Tanaka, S. ); Yamanishi, T. )
1992-10-01
The spin-dependent distribution functions of quarks and gluons in a proton are studied so as to explain the European Muon Collaboration {ital g}{sub 1}{sup {ital p}}({ital x}) data by introducing a new model, in which characteristics of both the static quark and the quark-parton model are taken into account. The {ital x} dependence of {ital g}{sub 1}{sup {ital p}}({ital x}) is reproduced well. It is shown that polarized gluons through the anomaly play a significant role and the resultant sum of quark spin is 0.375. Furthermore, {ital g}{sub 1}{sup {ital n}}({ital x}) as well as {ital g}{sub 1}{sup {ital p}}({ital x}) is predicted for future experiments.
Parton shower evolution in a 3D hydrodynamical medium
Renk, Thorsten
2008-09-15
We present a Monte Carlo simulation of the perturbative quantum chromodynamics shower developing after a hard process embedded in a heavy-ion collision. The main assumption is that the cascade of branching partons traverses a medium that (consistent with standard radiative energy loss pictures) is characterized by a local transport coefficient q-circumflex that measures the virtuality per unit length transferred to a parton that propagates in this medium. This increase in parton virtuality alters the development of the shower and in essence leads to extra induced radiation and hence a softening of the momentum distribution in the shower. After hadronization, this leads to the concept of a medium-modified fragmentation function. On the level of observables, this is manifest as the suppression of high-transverse-momentum (P{sub T}) hadron spectra. We simulate the soft medium created in heavy-ion collisions by a 3D hydrodynamical evolution and average the medium-modified fragmentation function over this evolution to compare with data on single inclusive hadron suppression and extract the q-circumflex that characterizes the medium. Finally, we discuss possible uncertainties of the model formulation and argue that the data in a soft momentum show evidence of qualitatively different physics that presumably cannot be described by a medium-modified parton shower.
Parton-Hadron-String Dynamics at relativistic collider energies
NASA Astrophysics Data System (ADS)
Bratkovskaya, E. L.; Cassing, W.; Konchakovski, V. P.; Linnyk, O.
2011-04-01
The novel Parton-Hadron-String Dynamics (PHSD) transport approach is applied to nucleus-nucleus collisions at RHIC energies with respect to differential hadronic spectra in comparison to available data. The PHSD approach is based on a dynamical quasiparticle model for partons (DQPM) matched to reproduce recent lattice-QCD results from the Wuppertal-Budapest group in thermodynamic equilibrium. The transition from partonic to hadronic degrees of freedom is described by covariant transition rates for the fusion of quark-antiquark pairs or three quarks (antiquarks), respectively, obeying flavor current-conservation, color neutrality as well as energy-momentum conservation. Our dynamical studies for heavy-ion collisions at relativistic collider energies are compared to earlier results from the Hadron-String Dynamics (HSD) approach - incorporating no explicit dynamical partonic phase - as well as to experimental data from the STAR, PHENIX, BRAHMS and PHOBOS Collaborations for Au + Au collisions at the top RHIC energy of √{s}=200 GeV. We find a reasonable reproduction of hadron rapidity distributions and transverse mass spectra and also a fair description of the elliptic flow of charged hadrons as a function of the centrality of the reaction and the transverse momentum p. Furthermore, an approximate quark-number scaling of the elliptic flow v of hadrons is observed in the PHSD results, too.
From nuclear structure to nucleon structure
NASA Astrophysics Data System (ADS)
Liu, Keh-Fei
2014-08-01
Similarities between nuclear structure study with many-body theory approach and nucleon structure calculations with lattice QCD are pointed out. We will give an example of how to obtain the connected sea partons from a combination of the experimental data, a global fit of parton distribution functions and a lattice calculation. We also present a complete calculation of the quark and glue decomposition of the proton momentum and angular momentum in the quenched approximation. It is found that the quark orbital angular momentum constitutes about 50% of the proton spin.
KOVCHEGOV,Y.V.
2000-04-25
The authors derive an equation determining the small-x evolution of the F{sub 2} structure function of a large nucleus which resumes a cascade of gluons in the leading logarithmic approximation using Mueller's color dipole model. In the traditional language it corresponds to resummation of the pomeron fan diagrams, originally conjectured in the GLR equation. The authors show that the solution of the equation describes the physics of structure functions at high partonic densities, thus allowing them to gain some understanding of the most interesting and challenging phenomena in small-x physics--saturation.
Process dependent nuclear k⊥ broadening effect
NASA Astrophysics Data System (ADS)
Schäfer, Andreas; Zhou, Jian
2013-10-01
We study the process dependent nuclear k⊥ broadening effect by employing the transverse momentum dependent (TMD) factorization approach in combination with the Mclerran-Venugopalan model. More specifically, we investigate how the parton transverse momentum distributions are affected by the process dependent gauge links in cold nuclear matter. In particular, our analysis also applies to the polarized cases including the nuclear quark Boer-Mulders function and the linearly polarized gluon distribution. Our main focus is on the nuclear TMDs at intermediate or large x.
Multiparticle production in a two-component dual parton model
Aurenche, P. ); Bopp, F.W. ); Capella, A. ); Kwiecinski, J. ); Maire, M. ); Ranft, J.; Tran Thanh Van, J. )
1992-01-01
The dual parton model (DPM) describes soft and semihard multiparticle production. The version of the DPM presented in this paper includes soft and hard mechanisms as well as diffractive processes. The model is formulated as a Monte Carlo event generator. We calculate in this model, in the energy range of the hadron colliders, rapidity distributions and the rise of the rapidity plateau with the collision energy, transverse-momentum distributions and the rise of average transverse momenta with the collision energy, multiplicity distributions in different pseudorapidity regions, and transverse-energy distributions. For most of these quantities we find a reasonable agreement with experimental data.
Parton branching model for pp¯ collisions
NASA Astrophysics Data System (ADS)
Chan, A. H.; Chew, C. K.
1990-02-01
A detailed analysis of the behavior of the initial numbers of gluons and quarks in the generalized multiplicity distribution (GMD) is presented. Two special cases of GMD, namely, the negative-binomial distribution and the Furry-Yule distribution, are also discussed in relation to the non-single-diffractive data at 200, 546, and 900 GeV c.m.-system energies and pseudorapidity intervals ηc. The GMD may provide an alternate distribution to understand parton action for future pp¯ collisions at high TeV energies.
The radial distribution of SNe in nuclear starbursts
NASA Astrophysics Data System (ADS)
Herrero-Illana, R.; Pérez-Torres, M. Á.; Alberdi, A.
2012-10-01
We have probed the radial distribution of supernovae and supernova remnants in the nuclear regions of the starburst galaxies M82, Arp 299-A, and Arp 220, by using high-angular resolution (≤ 0."1) radio observations. We derived scale-length values for the putative nuclear disks, which range from ~20-30 pc for Arp 299-A and Arp 220, up to ~140 pc for M82. The radial distribution of SNe for the nuclear disks in Arp 299-A and Arp 220 is also consistent with a power-law surface density profile of exponent Î³ = 1, as expected from detailed hydrodynamical simulations of nuclear disks. Our results give thus support to scenarios where a nuclear disk of size ~100 pc is formed in (U)LIRGs, and is sustained by gas pressure, in which case the accretion onto the black hole could be lowered due to supernova feedback. This study is detailed in Herrero-Illana et al. (2012). Database: ast
The radial distribution of supernovae in nuclear starbursts
NASA Astrophysics Data System (ADS)
Herrero-Illana, R.; Pérez-Torres, M. A.; Alberdi, A.
2013-05-01
Galaxy-galaxy interactions are expected to be responsible for triggering massive star formation and possibly accretion onto a supermassive black hole, by providing large amounts of dense molecular gas down to the central kiloparsec region. Several scenarios to drive the gas further down to the central ˜100 pc, have been proposed, including the formation of a nuclear disk around the black hole, where massive stars would produce supernovae. Here, we probe the radial distribution of supernovae and supernova remnants in the nuclear regions of the starburst galaxies M82, Arp 299-A, and Arp 220, by using high-angular resolution (≲ 0.''1) radio observations. We derived scale-length values for the putative nuclear disks, which range from ˜20-30 pc for Arp 299-A and Arp 220, up to ˜140 pc for M82. The radial distribution of SNe for the nuclear disks in Arp 299-A and Arp 220 is also consistent with a power-law surface density profile of exponent γ = 1, as expected from detailed hydrodynamical simulations of nuclear disks. This study is detailed in te{herrero-illana12}.
APACIC++ 2.0. A PArton Cascade In C++
NASA Astrophysics Data System (ADS)
Krauss, F.; Schälicke, A.; Soff, G.
2006-06-01
The new version of the parton shower module APACIC++ for the SHERPA event generator framework is presented. It incorporates some features, that are specific for the consistent merging with multi-particle matrix elements at tree-level. This publication also includes some example results and a short description of the upgraded class structure of APACIC++, version 2.0. Program summaryTitle of program:APACIC++, version 2.0 Catalogue identifier:ADNE_v2_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADNE_v2_0 Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Catalogue identifier of previous version: ADNE Authors of previous version: R. Kuhn, F. Krauss, B. Iványi, G. Soff Journal reference of previous version: Comput. Phys. Commun. 134 (2001) 223 Licensing provisions: none Operating system under which the program has been tested: Linux, Unix, Darwin Programming language: C++ No. of lines in distributed program, including test data, etc.: 78 352 No. of bytes in distributed program, including test data, etc.: 2 561 276 External routines/libraries used: The makeinstall requires the autotools package Distribution format: tar gzip file Nature of the physical problem: Modern collider-based experiments in particle physics are characterized by increasing energies that are released and, thus, by a growing number of particles that are produced. The large numbers of involved particles renders it impossible to derive fully analytical predictions for a detailed description of the final state. In addition, the transformation of the partons of perturbative quantum field theory into the experimentally observable hadrons is until now not understood on a quantitative level. These obstacles prevent a direct comparison of analytical predictions with experimental data, and simulation tools need to be employed to bridge this gap. Method of solution: The event generator SHERPA with a new version of the parton shower module APACIC++ is able to
Radon Transform and Light-Cone Distributions
NASA Astrophysics Data System (ADS)
Teryaev, O. V.
2016-08-01
The relevance of Radon transform for generalized and transverse momentum dependent parton distributions is discussed. The new application for conditional (fracture) parton distributions and dihadron fragmentation functions is suggested.
Quantitative velocity distributions via nuclear magnetic resonance flow metering
NASA Astrophysics Data System (ADS)
O'Neill, Keelan T.; Fridjonsson, Einar O.; Stanwix, Paul L.; Johns, Michael L.
2016-08-01
We demonstrate the use of Tikhonov regularisation as a data inversion technique to determine the velocity distributions of flowing liquid streams. Regularisation is applied to the signal produced by a nuclear magnetic resonance (NMR) flow measurement system consisting of a pre-polarising permanent magnet located upstream of an Earth's magnetic field NMR detection coil. A simple free induction decay (FID) NMR signal is measured for the flowing stream in what is effectively a 'time-of-flight' measurement. The FID signal is then modelled as a function of fluid velocity and acquisition time, enabling determination of the velocity probability distributions via regularisation. The mean values of these velocity distributions were successfully validated against in-line rotameters. The ability to quantify multi-modal velocity distributions was also demonstrated using a two-pipe system.
Quantitative velocity distributions via nuclear magnetic resonance flow metering.
O'Neill, Keelan T; Fridjonsson, Einar O; Stanwix, Paul L; Johns, Michael L
2016-08-01
We demonstrate the use of Tikhonov regularisation as a data inversion technique to determine the velocity distributions of flowing liquid streams. Regularisation is applied to the signal produced by a nuclear magnetic resonance (NMR) flow measurement system consisting of a pre-polarising permanent magnet located upstream of an Earth's magnetic field NMR detection coil. A simple free induction decay (FID) NMR signal is measured for the flowing stream in what is effectively a 'time-of-flight' measurement. The FID signal is then modelled as a function of fluid velocity and acquisition time, enabling determination of the velocity probability distributions via regularisation. The mean values of these velocity distributions were successfully validated against in-line rotameters. The ability to quantify multi-modal velocity distributions was also demonstrated using a two-pipe system. PMID:27343484
Quantitative velocity distributions via nuclear magnetic resonance flow metering.
O'Neill, Keelan T; Fridjonsson, Einar O; Stanwix, Paul L; Johns, Michael L
2016-08-01
We demonstrate the use of Tikhonov regularisation as a data inversion technique to determine the velocity distributions of flowing liquid streams. Regularisation is applied to the signal produced by a nuclear magnetic resonance (NMR) flow measurement system consisting of a pre-polarising permanent magnet located upstream of an Earth's magnetic field NMR detection coil. A simple free induction decay (FID) NMR signal is measured for the flowing stream in what is effectively a 'time-of-flight' measurement. The FID signal is then modelled as a function of fluid velocity and acquisition time, enabling determination of the velocity probability distributions via regularisation. The mean values of these velocity distributions were successfully validated against in-line rotameters. The ability to quantify multi-modal velocity distributions was also demonstrated using a two-pipe system.
Study of nuclear matter density distributions using hadronic probes
Kohama, Akihisa; Iida, Kei; Oyamatsu, Kazuhiro
2011-05-06
We briefly review our formula for a proton-nucleus total reaction cross section, {sigma}{sub R}, constructed in the black-sphere approximation of nuclei, in which a nucleus is viewed as a 'black' sphere of radius 'a'. Some years ago, using the Glauber model, one of the authors (A.K.) and his collaborators performed numerical simulations to examine the possibility to probe the nuclear matter density distributions of neutron-rich unstable nuclei from proton elastic scatterings 'model-independently'. The present study is another attempt to seek a 'model-independent' framework for systematically analyzing scattering data for studying the matter density distributions of atomic nuclei.
Chiral dynamics and partonic structure at large transverse distances
Strikman, M.; Weiss, C.
2009-12-30
In this paper, we study large-distance contributions to the nucleon’s parton densities in the transverse coordinate (impact parameter) representation based on generalized parton distributions (GPDs). Chiral dynamics generates a distinct component of the partonic structure, located at momentum fractions x≲M_{π}/M_{N} and transverse distances b~1/M_{π}. We calculate this component using phenomenological pion exchange with a physical lower limit in b (the transverse “core” radius estimated from the nucleon’s axial form factor, R_{core}=0.55 fm) and demonstrate its universal character. This formulation preserves the basic picture of the “pion cloud” model of the nucleon’s sea quark distributions, while restricting its application to the region actually governed by chiral dynamics. It is found that (a) the large-distance component accounts for only ~1/3 of the measured antiquark flavor asymmetry d¯-u¯ at x~0.1; (b) the strange sea quarks s and s¯ are significantly more localized than the light antiquark sea; (c) the nucleon’s singlet quark size for x<0.1 is larger than its gluonic size, (b^{2})_{q+q¯}>(b^{2})_{g}, as suggested by the t-slopes of deeply-virtual Compton scattering and exclusive J/ψ production measured at HERA and FNAL. We show that our approach reproduces the general N_{c}-scaling of parton densities in QCD, thanks to the degeneracy of N and Δ intermediate states in the large-N_{c} limit. Finally, we also comment on the role of pionic configurations at large longitudinal distances and the limits of their applicability at small x.
Cold Nuclear Matter Effects on J/psi Production: Intrinsic and Extrinsic Transverse Momentum Effects
Ferreiro, E.G.; Fleuret, F.; Lansberg, J.P.; Rakotozafindrabe, A.; /SPhN, DAPNIA, Saclay
2010-08-26
Cold nuclear matter effects on J/{psi} production in proton-nucleus and nucleus-nucleus collisions are evaluated taking into account the specific J/{psi}-production kinematics at the partonic level, the shadowing of the initial parton distributions and the absorption in the nuclear matter. We consider two different parton processes for the c{bar c}-pair production: one with collinear gluons and a recoiling gluon in the final state and the other with initial gluons carrying intrinsic transverse momentum. Our results are compared to RHIC observables. The smaller values of the nuclear modification factor R{sub AA} in the forward rapidity region (with respect to the mid rapidity region) are partially explained, therefore potentially reducing the need for recombination effects.
Pre-equilibrium parton dynamics: Proceedings
Wang, Xin-Nian
1993-12-31
This report contains papers on the following topics: parton production and evolution; QCD transport theory; interference in the medium; QCD and phase transition; and future heavy ion experiments. This papers have been indexed separately elsewhere on the data base.
Multiple parton interaction studies at DØ
Lincoln, D.
2016-04-01
Here, we present the results of studies of multiparton interactions done by the DØ collaboration using the Fermilab Tevatron at a center of mass energy of 1.96 TeV. We also present three analyses, involving three distinct final signatures: (a) a photon with at least 3 jets ( γ + 3jets), (b) a photon with a bottom or charm quark tagged jet and at least 2 other jets ( γ + b/c + 2jets), and (c) two J/ ψ mesons. The fraction of photon + jet events initiated by double parton scattering is about 20%, while the fraction for events inmore » which two J/ ψ mesons were produced is 30 ± 10. While the two measurements are statistically compatible, the difference might indicate differences in the quark and gluon distribution within a nucleon. Finally, this speculation originates from the fact that photon + jet events are created by collisions with quarks in the initial states, while J/ ψ events are produced preferentially by a gluonic initial state.« less
Parallelization and automatic data distribution for nuclear reactor simulations
Liebrock, L.M.
1997-07-01
Detailed attempts at realistic nuclear reactor simulations currently take many times real time to execute on high performance workstations. Even the fastest sequential machine can not run these simulations fast enough to ensure that the best corrective measure is used during a nuclear accident to prevent a minor malfunction from becoming a major catastrophe. Since sequential computers have nearly reached the speed of light barrier, these simulations will have to be run in parallel to make significant improvements in speed. In physical reactor plants, parallelism abounds. Fluids flow, controls change, and reactions occur in parallel with only adjacent components directly affecting each other. These do not occur in the sequentialized manner, with global instantaneous effects, that is often used in simulators. Development of parallel algorithms that more closely approximate the real-world operation of a reactor may, in addition to speeding up the simulations, actually improve the accuracy and reliability of the predictions generated. Three types of parallel architecture (shared memory machines, distributed memory multicomputers, and distributed networks) are briefly reviewed as targets for parallelization of nuclear reactor simulation. Various parallelization models (loop-based model, shared memory model, functional model, data parallel model, and a combined functional and data parallel model) are discussed along with their advantages and disadvantages for nuclear reactor simulation. A variety of tools are introduced for each of the models. Emphasis is placed on the data parallel model as the primary focus for two-phase flow simulation. Tools to support data parallel programming for multiple component applications and special parallelization considerations are also discussed.
Nuclear PDFs at NLO - status report and review of the EPS09 results
NASA Astrophysics Data System (ADS)
Eskola, K. J.; Paukkunen, H.; Salgado, C. A.
2011-04-01
We review the current status of the global DGLAP analysis of nuclear parton distribution functions, nPDFs, focusing on the recent EPS09 analysis [K.J. Eskola, H. Paukkunen, C.A. Salgado, JHEP 0904 (2009) 065. [ arXiv:0902.4154 [hep-ph
A global DGLAP analysis of nuclear PDFs
NASA Astrophysics Data System (ADS)
Eskola, K. J.; Kolhinen, V. J.; Paukkunen, H.; Salgado, C. A.
2008-05-01
In this talk, we shortly report results from our recent global DGLAP analysis of nuclear parton distributions. This is an extension of our former EKS98-analysis improved with an automated χ2 minimization procedure and uncertainty estimates. Although our new analysis show no significant deviation from EKS98, a sign of a significantly stronger gluon shadowing could be seen in the RHIC BRAHMS data.
Electroweakino pair production at the LHC: NLO SUSY-QCD corrections and parton-shower effects
NASA Astrophysics Data System (ADS)
Baglio, Julien; Jäger, Barbara; Kesenheimer, Matthias
2016-07-01
We present a set of NLO SUSY-QCD calculations for the pair production of neutralinos and charginos at the LHC, and their matching to parton-shower programs in the framework of the POWHEG-BOX program package. The code we have developed provides a SUSY Les Houches Accord interface for setting supersymmetric input parameters. Decays of the neutralinos and charginos and parton-shower effects can be simulated with PYTHIA. To illustrate the capabilities of our program, we present phenomenological results for a representative SUSY parameter point. We find that NLO-QCD corrections increase the production rates for neutralinos and charginos significantly. The impact of parton-shower effects on distributions of the weakinos is small, but non-negligible for jet distributions.
Parton Propagation and Fragmentation in QCD Matter
Alberto Accardi, Francois Arleo, William Brooks, David D'Enterria, Valeria Muccifora
2009-12-01
We review recent progress in the study of parton propagation, interaction and fragmentation in both cold and hot strongly interacting matter. Experimental highlights on high-energy hadron production in deep inelastic lepton-nucleus scattering, proton-nucleus and heavy-ion collisions, as well as Drell-Yan processes in hadron-nucleus collisions are presented. The existing theoretical frameworks for describing the in-medium interaction of energetic partons and the space-time evolution of their fragmentation into hadrons are discussed and confronted to experimental data. We conclude with a list of theoretical and experimental open issues, and a brief description of future relevant experiments and facilities.
Measurement of parton shower observables with OPAL
NASA Astrophysics Data System (ADS)
Fischer, N.; Gieseke, S.; Kluth, S.; Plätzer, S.; Skands, P.
2016-07-01
A study of QCD coherence is presented based on a sample of about 397,000 e+e- hadronic annihilation events collected at √s = 91 GeV with the OPAL detector at LEP. The study is based on four recently proposed observables that are sensitive to coherence effects in the perturbative regime. The measurement of these observables is presented, along with a comparison with the predictions of different parton shower models. The models include both conventional parton shower models and dipole antenna models. Different ordering variables are used to investigate their influence on the predictions.
Radiocesium Distribution in Bamboo Shoots after the Fukushima Nuclear Accident
Higaki, Takumi; Higaki, Shogo; Hirota, Masahiro; Hasezawa, Seiichiro
2014-01-01
The distribution of radiocesium was examined in bamboo shoots, Phyllostachys pubescens, collected from 10 sites located some 41 to 1140 km from the Fukushima Daiichi nuclear power plant, Japan, in the Spring of 2012, 1 year after the Fukushima nuclear accident. Maximum activity concentrations for radiocesium 134Cs and 137Cs in the edible bamboo shoot parts, 41 km away from the Fukushima Daiichi plant, were in excess of 15.3 and 21.8 kBq/kg (dry weight basis; 1.34 and 1.92 kBq/kg, fresh weight), respectively. In the radiocesium-contaminated samples, the radiocesium activities were higher in the inner tip parts, including the upper edible parts and the apical culm sheath, than in the hardened culm sheath and underground basal parts. The radiocesium/potassium ratios also tended to be higher in the inner tip parts. The radiocesium activities increased with bamboo shoot length in another bamboo species, Phyllostachys bambusoides, suggesting that radiocesium accumulated in the inner tip parts during growth of the shoots. PMID:24831096
Nachtmann, O.
2014-11-15
We review ideas on the structure of the QCD vacuum which had served as motivation for the discussion of various non-standard QCD effects in high-energy reactions in articles from 1984 to 1995. These effects include, in particular, transverse-momentum and spin correlations in the Drell–Yan process and soft photon production in hadron–hadron collisions. We discuss the relation of the approach introduced in the above-mentioned articles to the approach, developed later, using transverse-momentum-dependent parton distributions (TDMs). The latter approach is a special case of our more general one which allows for parton entanglement in high-energy reactions. We discuss signatures of parton entanglement in the Drell–Yan reaction. Also for Higgs-boson production in pp collisions via gluon–gluon annihilation effects of entanglement of the two gluons are discussed and are found to be potentially important. These effects can be looked for in the current LHC experiments. In our opinion studying parton-entanglement effects in high-energy reactions is, on the one hand, very worthwhile by itself and, on the other hand, it allows to perform quantitative tests of standard factorisation assumptions. Clearly, the experimental observation of parton-entanglement effects in the Drell–Yan reaction and/or in Higgs-boson production would have a great impact on our understanding how QCD works in high-energy collisions.
An O([alpha][sub s]) Monte Carlo for W production with parton showering
Baer, H.A.
1991-01-01
We construct an event generator for p[bar p][yields]W[sup +]X[yields]e[sup +][nu]X including complete O([alpha][sub s]) corrections, and interface with initial and final state parton showers. Problems with negative weights and with double counting higher order parton radiation are averted. We present results for W+n-jet production, and compare with results from complete tree-level calculations, and shower calculations off of the lowest order 2[yields]2 sub-process. We also compute the [sub qT](W) distribution, and compare with data.
An O({alpha}{sub s}) Monte Carlo for W production with parton showering
Baer, H.A.
1991-12-31
We construct an event generator for p{bar p}{yields}W{sup +}X{yields}e{sup +}{nu}X including complete O({alpha}{sub s}) corrections, and interface with initial and final state parton showers. Problems with negative weights and with double counting higher order parton radiation are averted. We present results for W+n-jet production, and compare with results from complete tree-level calculations, and shower calculations off of the lowest order 2{yields}2 sub-process. We also compute the {sub qT}(W) distribution, and compare with data.
Fragmentation of parton jets at small x
Kirschner, R.
1985-08-01
The parton fragmentation function is calculated in the region of small x in the doubly logarithmic approximation of QCD. For this, the method of separating the softest particle, which has hitherto been applied only in the Regge kinematic region, is developed. Simple arguments based on unitarity and gauge invariance are used to derive the well known condition of ordering of the emission angles.
QCD parton model at collider energies
Ellis, R.K.
1984-09-01
Using the example of vector boson production, the application of the QCD improved parton model at collider energies is reviewed. The reliability of the extrapolation to SSC energies is assessed. Predictions at ..sqrt..S = 0.54 TeV are compared with data. 21 references.
Systematic Improvement of QCD Parton Showers
Winter, Jan; Hoeche, Stefan; Hoeth, Hendrik; Krauss, Frank; Schonherr, Marek; Zapp, Korinna; Schumann, Steffen; Siegert, Frank; /Freiburg U.
2012-05-17
In this contribution, we will give a brief overview of the progress that has been achieved in the field of combining matrix elements and parton showers. We exemplify this by focusing on the case of electron-positron collisions and by reporting on recent developments as accomplished within the SHERPA event generation framework.
Vadim Guzey, Mark Strikman
2010-04-01
The leading twist theory of nuclear shadowing predicts nuclear parton distributions in the small $x$ shadowing region by connecting them to the leading twist hard diffraction in electron-nucleon scattering. The uncertainties of the predictions are related to the shadowing effects resulting from the interaction of the hard probe with $N \\ge 3$ nucleons. We argue that the pattern of hard diffraction observed at HERA allows one to reduce these uncertainties, and we develop a new approach to the treatment of these multiple collisions. It is based on the concept of the color fluctuations and accounts for the presence of both point-like and hadron-like configurations in the virtual photon. Using the developed framework, we update our predictions for the effect of the leading twist nuclear shadowing in nuclear parton distributions of heavy nuclei at small $x$.
Vesicle Size Distribution as a Novel Nuclear Forensics Tool
Simonetti, Antonio
2016-01-01
The first nuclear bomb detonation on Earth involved a plutonium implosion-type device exploded at the Trinity test site (33°40′38.28″N, 106°28′31.44″W), White Sands Proving Grounds, near Alamogordo, New Mexico. Melting and subsequent quenching of the local arkosic sand produced glassy material, designated “Trinitite”. In cross section, Trinitite comprises a thin (1–2 mm), primarily glassy surface above a lower zone (1–2 cm) of mixed melt and mineral fragments from the precursor sand. Multiple hypotheses have been put forward to explain these well-documented but heterogeneous textures. This study reports the first quantitative textural analysis of vesicles in Trinitite to constrain their physical and thermal history. Vesicle morphology and size distributions confirm the upper, glassy surface records a distinct processing history from the lower region, that is useful in determining the original sample surface orientation. Specifically, the glassy layer has lower vesicle density, with larger sizes and more rounded population in cross-section. This vertical stratigraphy is attributed to a two-stage evolution of Trinitite glass from quench cooling of the upper layer followed by prolonged heating of the subsurface. Defining the physical regime of post-melting processes constrains the potential for surface mixing and vesicle formation in a post-detonation environment. PMID:27658210
Lappi, T.; Venugopalan, R.; Mantysaari, H.
2015-02-25
We argue that the proton multiplicities measured in Roman pot detectors at an electron ion collider can be used to determine centrality classes in incoherent diffractive scattering. Incoherent diffraction probes the fluctuations in the interaction strengths of multi-parton Fock states in the nuclear wavefunctions. In particular, the saturation scale that characterizes this multi-parton dynamics is significantly larger in central events relative to minimum bias events. As an application, we examine the centrality dependence of incoherent diffractive vector meson production. We identify an observable which is simultaneously very sensitive to centrality triggered parton fluctuations and insensitive to details of the model.
New parton structure functions and minijets in the two-component dual parton model
Bopp, F.W.; Pertermann, D. ); Engel, R. ); Ranft, J. )
1994-04-01
We use new fits to parton structure functions, including structure functions with Lipatov behavior at small [ital x] values and discuss the minijet component in the two-component dual parton model with a supercritical Pomeron as demanded by the fits to cross-section data. We find that a consistent model can only be formulated with a [ital p][sub [perpendicular]hr] cutoff for the minijets increasing with energy. The implications for particle production in hadronic collisions at TeV energies are discussed.
Nuclear Shadowing and Select d+Au Observables
NASA Astrophysics Data System (ADS)
Adeluyi, Adeola; Fai, George
2007-04-01
Much of the complexity of the description of d+Au collisions in the framework of perturbative Quantum Chromodynamics (pQCD) derives from effects of the nuclear environment. Here we investigate the effects of the most recent available nuclear shadowing parametrization, the Hirai-Kumano-Nagai (HKN) nuclear parton distribution functions (nPDFs) and the updated Albino-Kniehl-Kramer (AKK) fragmentation functions on three select d+Au collision observables. We compare our results to available experimental data from the STAR and BRAHMS collaborations.
Mudumbi, Krishna C; Schirmer, Eric C; Yang, Weidong
2016-01-01
The normal distribution of nuclear envelope transmembrane proteins (NETs) is disrupted in several human diseases. NETs are synthesized on the endoplasmic reticulum and then transported from the outer nuclear membrane (ONM) to the inner nuclear membrane (INM). Quantitative determination of the distribution of NETs on the ONM and INM is limited in available approaches, which moreover provide no information about translocation rates in the two membranes. Here we demonstrate a single-point single-molecule FRAP microscopy technique that enables determination of distribution and translocation rates for NETs in vivo. PMID:27558844
Mudumbi, Krishna C; Schirmer, Eric C; Yang, Weidong
2016-01-01
The normal distribution of nuclear envelope transmembrane proteins (NETs) is disrupted in several human diseases. NETs are synthesized on the endoplasmic reticulum and then transported from the outer nuclear membrane (ONM) to the inner nuclear membrane (INM). Quantitative determination of the distribution of NETs on the ONM and INM is limited in available approaches, which moreover provide no information about translocation rates in the two membranes. Here we demonstrate a single-point single-molecule FRAP microscopy technique that enables determination of distribution and translocation rates for NETs in vivo. PMID:27558844
Medium Modifications of Hadron Properties and Partonic Processes
Brooks, W. K.; Strauch, S.; Tsushima, K.
2011-06-01
Chiral symmetry is one of the most fundamental symmetries in QCD. It is closely connected to hadron properties in the nuclear medium via the reduction of the quark condensate
Excited nucleon as a van der Waals system of partons
Jenkovszky, L. L.; Muskeyev, A. O. Yezhov, S. N.
2012-06-15
Saturation in deep inelastic scattering (DIS) and deeply virtual Compton scattering (DVCS) is associated with a phase transition between the partonic gas, typical of moderate x and Q{sup 2}, and partonic fluid appearing at increasing Q{sup 2} and decreasing Bjorken x. We suggest the van der Waals equation of state to describe properly this phase transition.
Nuclear Distribution of RNA Polymerase II and mRNA Processing Machinery in Early Mammalian Embryos
Bogolyubova, Irina O.; Bogolyubov, Dmitry S.
2014-01-01
Spatial distribution of components of nuclear metabolism provides a significant impact on regulation of the processes of gene expression. While distribution of the key nuclear antigens and their association with the defined nuclear domains were thoroughly traced in mammalian somatic cells, similar data for the preimplantation embryos are scanty and fragmental. However, the period of cleavage is characterized by the most drastic and dynamic nuclear reorganizations accompanying zygotic gene activation. In this minireview, we try to summarize the results of studies concerning distribution of major factors involved in RNA polymerase II-dependent transcription, pre-mRNA splicing mRNA export that have been carried out on early embryos of mammals. PMID:24868542
Effect of Particle Size Distribution on Slurry Rheology: Nuclear Waste Simulant Slurries
Chun, Jaehun; Oh, Takkeun; Luna, Maria L.; Schweiger, Michael J.
2011-07-05
Controlling the rheological properties of slurries has been of great interest in various industries such as cosmetics, ceramic processing, and nuclear waste treatment. Many physicochemical parameters, such as particle size, pH, ionic strength, and mass/volume fraction of particles, can influence the rheological properties of slurry. Among such parameters, the particle size distribution of slurry would be especially important for nuclear waste treatment because most nuclear waste slurries show a broad particle size distribution. We studied the rheological properties of several different low activity waste nuclear simulant slurries having different particle size distributions under high salt and high pH conditions. Using rheological and particle size analysis, it was found that the percentage of colloid-sized particles in slurry appears to be a key factor for rheological characteristics and the efficiency of rheological modifiers. This behavior was shown to be coupled with an existing electrostatic interaction between particles under a low salt concentration. Our study suggests that one may need to implement the particle size distribution as a critical factor to understand and control rheological properties in nuclear waste treatment plants, such as the U.S. Department of Energy’s Hanford and Savannah River sites, because the particle size distributions significantly vary over different types of nuclear waste slurries.
Nuclear distribution of claudin-2 increases cell proliferation in human lung adenocarcinoma cells.
Ikari, Akira; Watanabe, Ryo; Sato, Tomonari; Taga, Saeko; Shimobaba, Shun; Yamaguchi, Masahiko; Yamazaki, Yasuhiro; Endo, Satoshi; Matsunaga, Toshiyuki; Sugatani, Junko
2014-09-01
Claudin-2 is expressed in human lung adenocarcinoma tissue and cell lines, although it is absent in normal lung tissue. However, the role of claudin-2 in cell proliferation and the regulatory mechanism of intracellular distribution remain undefined. Proliferation of human adenocarcinoma A549 cells was decreased by claudin-2 knockdown together with a decrease in the percentage of S phase cells. This knockdown decreased the expression levels of ZONAB and cell cycle regulators. Claudin-2 was distributed in the nucleus in human adenocarcinoma tissues and proliferating A549 cells. The nuclear distribution of ZONAB and percentage of S phase cells were higher in cells exogenously expressing claudin-2 with a nuclear localization signal than in cells expressing claudin-2 with a nuclear export signal. Nuclear claudin-2 formed a complex with ZO-1, ZONAB, and cyclin D1. Nuclear distribution of S208A mutant, a dephosphorylated form of claudin-2, was higher than that of wild type. We suggest that nuclear distribution of claudin-2 is up-regulated by dephosphorylation and claudin-2 serves to retain ZONAB and cyclin D1 in the nucleus, resulting in the enhancement of cell proliferation in lung adenocarcinoma cells.
Azimuthal Asymmetries for eA/eN Semi-Inclusive DIS and Its Nuclear Dependence
NASA Astrophysics Data System (ADS)
Song, Yu-Kun
2016-02-01
We applied collinear expansion to the semi-inclusive deeply inelastic lepton-nucleon (nucleus) scattering process e + N(A) → e + q + X with both polarized beam and polarized target up to twist-3, and unpolarized process up to twist-4. The differential cross section and azimuthal asymmetries are expressed in terms of gauge invariant twist-3 and twist-4 TMD parton distribution/correlation functions. Measurements of such azimuthal asymmetries provide methods to study different spin and transverse momentum aspects of the partonic structure of nucleon. We further study the nuclear dependence of azimuthal asymmetries and adopt Gaussian ansatz for TMD distribution/correlation functions to estimat the semi-quantitive behaviour of the nuclear dependence. We predict the A-dependence of azimuthal asymmetries which can be tested in the planned EIC’s.
PACIAE 2.1: An updated issue of the parton and hadron cascade model PACIAE 2.0
NASA Astrophysics Data System (ADS)
Sa, Ben-Hao; Zhou, Dai-Mei; Yan, Yu-Liang; Dong, Bao-Guo; Cai, Xu
2013-05-01
a given impact parameter possesses an almond-like spatial asymmetry. Because of the strong parton rescattering, the local thermal equilibrium and asymmetric pressure gradient may build up in this initial fireball. The asymmetric pressure gradient then drives a collective anisotropic expansion. The expansion along the almond minor axis (along the large pressure gradient) is faster than the one along the major axis. This results in a strong asymmetric transverse momentum azimuthal distribution and hence a large elliptic flow coefficient v2 of the final hadronic state. As mentioned in [6], PACIAE is a parton and hadron cascade model for the ultra-relativistic nuclear collisions and is based on PYTHIA [7]. In the PACIAE model, a nucleus-nucleus collision is decomposed into a sequence of nucleon-nucleon (NN) collisions according to the collision geometry and the NN total cross section. Each NN collision is performed, in turn, by the PYTHIA model with the string fragmentation switched-off temporarily and the diquark (anti-diquark) broken into quark pairs (anti-quark pairs) randomly. The parton rescattering then proceeds. This parton evolution stage is followed by the hadronization at the moment of partonic freeze-out (exhausting the partonic collisions). The Lund string fragmentation regime and/or phenomenological coalescence model is provided for the hadronization. Then the rescattering among produced hadrons is dealt with by the usual two body collision model [6]. In the PYTHIA model [7] once the transverse momentum pT of a final state hadron generated from the string fragmentation and/or the unstable particle decay is randomly sampled, the px and py components are randomly placed on the circle with radius of pT. This px and py determination may strongly cancel the final state transverse momentum anisotropy developed dynamically. The charged particle transverse sphericity [8-10] may reach to unity (isotropic). This is inconsistent with the experimental observation that
Redux on "When is the top quark a parton?"
NASA Astrophysics Data System (ADS)
Dawson, S.; Ismail, A.; Low, Ian
2014-07-01
If a new heavy particle ϕ is produced in association with the top quark in a hadron collider, the production cross section exhibits a collinear singularity of the form log(mϕ/mt), which can be resummed by introducing a top quark parton distribution function (PDF). We reassess the necessity of such resummation in the context of a high-energy pp collider. We find that the introduction of a top PDF typically has a small effect at √S ˜100 TeV due to three factors: (1) αs at the scale μ =mϕ, which is quite small when log(mϕ/mt) is large, (2) the Bjorken x≪1 for mϕ≲10 TeV, and (3) the kinematic region where log(mϕ/mt)≫1 is suppressed by phase space. We consider the example of pp→tH+ at next-to-leading logarithm (NLL) order and show that, in terms of the total cross section, the effect of a top PDF is generically smaller than that of a bottom PDF in the associated production of bϕ. However, in the pT distribution of the charged Higgs, the NLL calculation using a top PDF is crucial to generate the pT distribution for pT≲mt.
NASA Astrophysics Data System (ADS)
Kutak, Krzysztof; Maciuła, Rafał; Serino, Mirko; Szczurek, Antoni; van Hameren, Andreas
2016-07-01
In the present paper, we discuss how to maximize the double-parton scattering (DPS) contribution in four-jet production by selecting kinematical cuts. Here both single-parton and double-parton scattering effects are calculated in the kT -factorization approach, following our recent developments of relevant methods and tools. Several differential distributions are shown and discussed in the context of future searches for DPS effects, such as rapidity of jets, rapidity distance, and azimuthal correlations between jets. The dependence of the relative DPS amount is studied as a function of those observables. The regions with an enhanced DPS contribution are identified. Future experimental explorations could extract more precise values of σeff and its potential dependence on kinematical variables.
Evolution effects on parton energy loss with detailed balance
Cheng Luan; Wang Enke
2010-07-15
The initial conditions in the chemically nonequilibrated medium and Bjorken expanding medium at Relativistic Heavy Ion Collider (RHIC) are determined. With a set of rate equations describing the chemical equilibration of quarks and gluons based on perturbative QCD, we investigate the consequence for parton evolution at RHIC. With considering parton evolution, it is shown that the Debye screening mass and the inverse mean free-path of gluons reduce with increasing proper time in the QGP medium. The parton evolution affects the parton energy loss with detailed balance, both parton energy loss from stimulated emission in the chemically nonequilibrated expanding medium and in Bjorken expanding medium are linear dependent on the propagating distance rather than square dependent in the static medium. The energy absorption cannot be neglected at intermediate jet energies and small propagating distance of the energetic parton in contrast with that it is important only at intermediate jet energy in the static medium. This will increase the energy and propagating distance dependence of the parton energy loss and will affect the shape of suppression of moderately high P{sub T} hadron spectra.
Nuclear momentum distribution and potential energy surface in hexagonal ice
NASA Astrophysics Data System (ADS)
Lin, Lin; Morrone, Joseph; Car, Roberto; Parrinello, Michele
2011-03-01
The proton momentum distribution in ice Ih has been recently measured by deep inelastic neutron scattering and calculated from open path integral Car-Parrinello simulation. Here we report a detailed investigation of the relation between momentum distribution and potential energy surface based on both experiment and simulation results. The potential experienced by the proton is largely harmonic and characterized by 3 principal frequencies, which can be associated to weighted averages of phonon frequencies via lattice dynamics calculations. This approach also allows us to examine the importance of quantum effects on the dynamics of the oxygen nuclei close to the melting temperature. Finally we quantify the anharmonicity that is present in the potential acting on the protons. This work is supported by NSF and by DOE.
Temperature Distribution within a Cold Cap during Nuclear Waste Vitrification
Dixon, Derek R.; Schweiger, Michael J.; Riley, Brian J.; Pokorny, Richard; Hrma, Pavel R.
2015-07-21
The kinetics of the feed-to-glass conversion affects the waste vitrification rate in an electric melter. The primary area of interest in this conversion process is the cold cap, a layer of reacting feed on top of molten glass. Knowing the temperature profile within a cold cap will help determine its characteristics and relate them to the rate of glass production. The work presented here provides an experimental determination of the temperature distribution within the cold cap. Since a direct measurement of the temperature field within the cold cap is impracticable, an indirect method was developed where the textural features in a laboratory-made cold cap with a high-level waste feed were mapped as a function of position using optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. To correlate the temperature distribution to microstructures within the cold cap, microstructures were identified of individual feed samples that were heat treated to set temperatures between 400°C and 1200°C and quenched. The temperature distribution within the cold cap was then established by correlating cold-cap regions with the feed samples of nearly identical structures and was compared with the temperature profile from a mathematical model.
Evidence of nuclear disks in starburst galaxies from their radial distribution of supernovae
NASA Astrophysics Data System (ADS)
Herrero-Illana, R.; Pérez-Torres, M. Á.; Alberdi, A.
2012-04-01
Galaxy-galaxy interactions are expected to be responsible for triggering massive star formation and possibly accretion onto a supermassive black hole, by providing large amounts of dense molecular gas down to the central kiloparsec region. Several scenarios to drive the gas further down to the central ~100 pc, have been proposed, including the formation of a nuclear disk around the black hole, where massive stars would produce supernovae. Here, we probe the radial distribution of supernovae and supernova remnants in the nuclear regions of the starburst galaxies M 82, Arp 299-A, and Arp 220, by using high-angular resolution (≲ 0.''1) radio observations published in the literature (for M 82 and Arp 220), or obtained by ourselves from the European VLBI Network (Arp 299-A). Our main goal was to characterize the nuclear starbursts in those galaxies and thus test scenarios that propose that nuclear disks of sizes ~100 pc form in the central regions of starburst galaxies. We obtained the radial distribution of supernovae (SNe) in the nuclear starbursts of M 82, Arp 299-A, and Arp 220, and derived scale-length values for the putative nuclear disks powering the bursts in those central regions. The scale lengths for the (exponential) disks range from ~20-30 pc for Arp 299-A and Arp 220, up to ~140 pc for M 82. The radial distribution of SNe for the nuclear disks in Arp 299-A and Arp 220 is also consistent with a power-law surface density profile of exponent γ = 1, as expected from detailed hydrodynamical simulations of nuclear disks. Our results support scenarios where a nuclear disk of size ~100 pc is formed in (U)LIRGs, and sustained by gas pressure, in which case the accretion onto the black hole could be lowered by supernova feedback. Appendices are available in electronic form at http://www.aanda.org
Temperature Distribution within a Cold Cap during Nuclear Waste Vitrification.
Dixon, Derek R; Schweiger, Michael J; Riley, Brian J; Pokorny, Richard; Hrma, Pavel
2015-07-21
The kinetics of the feed-to-glass conversion affects the waste vitrification rate in an electric glass melter. The primary area of interest in this conversion process is the cold cap, a layer of reacting feed on top of the molten glass. The work presented here provides an experimental determination of the temperature distribution within the cold cap. Because direct measurement of the temperature field within the cold cap is impracticable, an indirect method was developed in which the textural features in a laboratory-made cold cap with a simulated high-level waste feed were mapped as a function of position using optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. The temperature distribution within the cold cap was established by correlating microstructures of cold-cap regions with heat-treated feed samples of nearly identical structures at known temperatures. This temperature profile was compared with a mathematically simulated profile generated by a cold-cap model that has been developed to assess the rate of glass production in a melter.
Mass and charge distributions in chlorine-induced nuclear reactions
Marchetti, A.A.
1991-12-31
Projectile-like fragments were detected and characterized in terms of A, Z, and energy for the reactions {sup 37}Cl on {sup 40}Ca and {sup 209}Bi at E/A = 7.3 MeV, and {sup 35}Cl, on {sup 209}Bi at E/A = 15 MeV, at angles close to the grazing angle. Mass and charge distributions were generated in the N-Z plane as a function of energy loss, and have been parameterized in terms of their centroids, variances, and coefficients of correlation. Due to experimental problems, the mass resolution corresponding to the {sup 31}Cl on {sup 209}Bi reaction was very poor. This prompted the study and application of a deconvolution technique for peak enhancement. The drifts of the charge and mass centroids for the system {sup 37}Cl on {sup 40}Ca are consistent with a process of mass and charge equilibration mediated by nucleon exchange between the two partners, followed by evaporation. The asymmetric systems show a strong drift towards larger asymmetry, with the production of neutron-rich nuclei. It was concluded that this is indicative of a net transfer of protons from the light to the heavy partner, and a net flow of neutrons in the opposite direction. The variances for all systems increase with energy loss, as it would be expected from a nucleon exchange mechanism; however, the variances for the reaction {sup 37}Cl on {sup 40}Ca are higher than those expected from that mechanism. The coefficients of correlation indicate that the transfer of nucleons between projectile and target is correlated. The results were compared to the predictions of two current models based on a stochastic nucleon exchange mechanism. In general, the comparisons between experimental and predicted variances support this mechanism; however, the need for more realistic driving forces in the model calculations is indicated by the disagreement between predicted and experimental centroids.
Long, Fuhui; Peng, Hanchuan; Sudar, Damir; Levievre, Sophie A.; Knowles, David W.
2006-09-05
Background: The distribution of the chromatin-associatedproteins plays a key role in directing nuclear function. Previously, wedeveloped an image-based method to quantify the nuclear distributions ofproteins and showed that these distributions depended on the phenotype ofhuman mammary epithelial cells. Here we describe a method that creates ahierarchical tree of the given cell phenotypes and calculates thestatistical significance between them, based on the clustering analysisof nuclear protein distributions. Results: Nuclear distributions ofnuclear mitotic apparatus protein were previously obtained fornon-neoplastic S1 and malignant T4-2 human mammary epithelial cellscultured for up to 12 days. Cell phenotype was defined as S1 or T4-2 andthe number of days in cultured. A probabilistic ensemble approach wasused to define a set of consensus clusters from the results of multipletraditional cluster analysis techniques applied to the nucleardistribution data. Cluster histograms were constructed to show how cellsin any one phenotype were distributed across the consensus clusters.Grouping various phenotypes allowed us to build phenotype trees andcalculate the statistical difference between each group. The resultsshowed that non-neoplastic S1 cells could be distinguished from malignantT4-2 cells with 94.19 percent accuracy; that proliferating S1 cells couldbe distinguished from differentiated S1 cells with 92.86 percentaccuracy; and showed no significant difference between the variousphenotypes of T4-2 cells corresponding to increasing tumor sizes.Conclusion: This work presents a cluster analysis method that canidentify significant cell phenotypes, based on the nuclear distributionof specific proteins, with high accuracy.
From C to Parton Sea: How Supercomputing Reveals Nucleon Structure
NASA Astrophysics Data System (ADS)
Lin, Huey-Wen
2016-03-01
Studying the structure of nucleons is not only important to understanding the strong interactions of quarks and gluons, but also to improving the precision of new-physics searches. Since a broad class of experiments, including the LHC and dark-matter detection, require interactions with nucleons, the mission to probe femtoscale physics is also essential for disentangling Standard-Model contributions from potential new physics. These SM backgrounds require parton distribution functions (PDFs) as inputs. However, after decades of experiments and theoretical efforts, there still remain many unknowns, especially in the sea flavor structure and transversely polarized structure. In a discrete spacetime, we can make a direct numerical calculation of the implications of QCD using sufficiently large supercomputing resources. A nonperturbative approach from first principles, lattice QCD, provides hope to expand our understanding of nucleon structure, especially in regions that are difficult to observe in experiments. In this work, we present a first direct calculation of the Bjorken-x dependence of the PDFs using Large-Momentum Effective Theory (LaMET) and comment on the surprising result revealed for the nucleon sea-flavor asymmetry. The work of HWL is supported in part by the M. Hildred Blewett Fellowship of the American Physical Society, www.aps.org.
Evidence of Nuclear Disks from the Radial Distribution of CCSNe in Starburst Galaxies
NASA Astrophysics Data System (ADS)
Herrero-Illana, Rubén; Pérez-Torres, Miguel Ángel; Alberdi, Antxon
Galaxy-galaxy interactions are expected to be responsible for triggering massive star formation and possibly accretion onto a supermassive black hole, by providing large amounts of dense molecular gas down to the central kiloparsec region. Several scenarios to drive the gas further down to the central ˜ 100 pc, have been proposed, including the formation of a nuclear disk around the black hole, where massive stars would produce supernovae. Here, we probe the radial distribution of supernovae and supernova remnants in the nuclear regions of the starburst galaxies M82, Arp 299-A, and Arp 220, by using high-angular resolution (≲ 0.'1) radio observations. We derived scale-length values for the putative nuclear disks, which range from ˜ 20-30 pc for Arp 299-A and Arp 220, up to ˜ 140 pc for M82. The radial distribution of SNe for the nuclear disks in Arp 299-A and Arp 220 is also consistent with a power-law surface density profile of exponent γ = 1, as expected from detailed hydrodynamical simulations of nuclear disks. This study is detailed in Herrero-Illana, Perez-Torres, and Alberdi [11].
NASA Astrophysics Data System (ADS)
Papoulia, A.; Carlsson, B. G.; Ekman, J.
2016-10-01
Atomic spectral lines from different isotopes display a small shift in energy, commonly referred to as the line isotope shift. One of the components of the isotope shift is the field shift, which depends on the extent and the shape of the nuclear charge density distribution. The purpose of this work is to investigate how sensitive field shifts are with respect to variations in the nuclear size and shape and what information of nuclear charge distributions can be extracted from measurements. Nuclear properties are obtained from nuclear density functional theory calculations based on the Skyrme-Hartree-Fock-Bogoliubov approach. These results are combined with multiconfiguration Dirac-Hartree-Fock methods to obtain realistic field shifts and it is seen that phenomena such as nuclear deformation and variations in the diffuseness of nuclear charge distributions give measurable contributions to the isotope shifts. Using a different approach, we demonstrate the possibility to extract information concerning the nuclear charge densities from the observed field shifts. We deduce that combining methods used in atomic and nuclear structure theory gives an improved description of field shifts and that extracting additional nuclear information from measured isotope shifts is possible in the near future with improved experimental methods.
HERA Diffractive Structure Function Data and Parton Distributions
Laycock, Paul; Newman, Paul; Schilling, Frank-Peter
2005-10-06
The high precision diffractive DIS data from the H1 and ZEUS collaborations discussed elsewhere in these proceedings are compared. NLO DGLAP QCD fits are performed separately to the H1 and ZEUS data samples and the resulting diffractive PDFs are compared.
Analysis of aerosol distribution inside the object "shelter" at the Chernobyl nuclear reactor site.
Bondarenko, O A; Aryasov, P B; Melnichuk, D V; Medvedev, S Y
2001-08-01
Results of the aerosol sampling inside the Object Shelter at the Chornobyl nuclear reactor site are considered in the work. The results show a consistent and significant contribution of submicron fraction to the total aerosol activity. Different methods of interpretation of impactor data series are compared in order to indicate and detect in the most effective way the submicron fraction as a separate component of the distribution. The methods used are as follows-method of probabilistic-logarithmic scale, method of likelihood function, non-linear approximation by sum of several log-normal distributions, and restoration of the initial distribution using passage functions of impactor cascades. Practically all the collected data on aerosol distribution inside the Shelter show a distinct submicron component. The contribution of the submicron component into the total aerosol activity is about 35%. Influence of the actual aerosol distribution on the dose coefficients is analyzed.
NASA Astrophysics Data System (ADS)
Nefedov, M. A.; Saleev, V. A.
2015-11-01
The hadroproduction of prompt isolated photon pairs at high energies is studied in the framework of the parton Reggeization approach. The real part of the NLO corrections is computed (the NLO⋆ approximation), and the procedure for the subtraction of double counting between real parton emissions in the hard-scattering matrix element and unintegrated parton distribution function is constructed for the amplitudes with Reggeized quarks in the initial state. The matrix element of the important next-to-next-to-leading-order subprocess R R →γ γ with full dependence on the transverse momenta of the initial-state Reggeized gluons is obtained. We compare obtained numerical results with diphoton spectra measured at the Tevatron and the LHC and find a good agreement of our predictions with experimental data at the high values of diphoton transverse momentum, pT, and especially at the pT larger than the diphoton invariant mass, M . In this multi-Regge kinematics region, the NLO correction is strongly suppressed, demonstrating the self-consistency of the parton Reggeization approach.
VBFNLO: A parton level Monte Carlo for processes with electroweak bosons
NASA Astrophysics Data System (ADS)
Arnold, K.; Bähr, M.; Bozzi, G.; Campanario, F.; Englert, C.; Figy, T.; Greiner, N.; Hackstein, C.; Hankele, V.; Jäger, B.; Klämke, G.; Kubocz, M.; Oleari, C.; Plätzer, S.; Prestel, S.; Worek, M.; Zeppenfeld, D.
2009-09-01
VBFNLO is a fully flexible parton level Monte Carlo program for the simulation of vector boson fusion, double and triple vector boson production in hadronic collisions at next-to-leading order in the strong coupling constant. VBFNLO includes Higgs and vector boson decays with full spin correlations and all off-shell effects. In addition, VBFNLO implements CP-even and CP-odd Higgs boson via gluon fusion, associated with two jets, at the leading-order one-loop level with the full top- and bottom-quark mass dependence in a generic two-Higgs-doublet model. A variety of effects arising from beyond the Standard Model physics are implemented for selected processes. This includes anomalous couplings of Higgs and vector bosons and a Warped Higgsless extra dimension model. The program offers the possibility to generate Les Houches Accord event files for all processes available at leading order. Program summaryProgram title:VBFNLO Catalogue identifier: AEDO_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEDO_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GPL version 2 No. of lines in distributed program, including test data, etc.: 339 218 No. of bytes in distributed program, including test data, etc.: 2 620 847 Distribution format: tar.gz Programming language: Fortran, parts in C++ Computer: All Operating system: Linux, should also work on other systems Classification: 11.1, 11.2 External routines: Optionally Les Houches Accord PDF Interface library and the GNU Scientific library Nature of problem: To resolve the large scale dependence inherent in leading order calculations and to quantify the cross section error induced by uncertainties in the determination of parton distribution functions, it is necessary to include NLO corrections. Moreover, whenever stringent cuts are required on decay products and/or identified jets the question arises whether the scale dependence and a k-factor, defined
Ottley, D.B.
1995-05-01
Settled dust from nuclear operations may be contaminated with radionuclides and become resuspended and subsequently breathed. This is the predominate radionuclide inhalation hazard scenario in nuclear facilities that have been deactivated and no longer have liquid in their process systems that may become directly airborne in accident situations. Comparisons were made between indoor ambient airborne particulate size distribution and that of resuspended dust that could become contaminated and subsequently airborne during decommissioning operations at selected nuclear facilities on the Hanford Site. Results indicate that only 5% of the particles, by count, above the breathing zone are greater than ten (10) {mu}m in size and that the particulates that could be resuspended into the breathing zone had a mean aerodynamic equivalent diameter of four (4) {mu}m or less.
NASA Astrophysics Data System (ADS)
Maltoni, Fabio; Mawatari, Kentarou; Zaro, Marco
2014-01-01
Vector-boson fusion and associated production at the LHC can provide key information on the strength and structure of the Higgs couplings to the Standard Model particles. Using an effective field theory approach, we study the effects of next-to-leading order (NLO) QCD corrections matched to a parton shower on selected observables for various spin-0 hypotheses. We find that inclusion of NLO corrections is needed to reduce the theoretical uncertainties on the total rates as well as to reliably predict the shapes of the distributions. Our results are obtained in a fully automatic way via FeynRules and MadGraph5_aMC@NLO.
A Higher Order Perturbative Parton Evolution Toolkit (HOPPET)
NASA Astrophysics Data System (ADS)
Salam, G. P.; Rojo, J.
2009-01-01
This document describes a Fortran 95 package for carrying out DGLAP evolution and other common manipulations of parton distribution functions (PDFs). The PDFs are represented on a grid in x-space so as to avoid limitations on the functional form of input distributions. Good speed and accuracy are obtained through the representation of splitting functions in terms of their convolution with a set of piecewise polynomial basis functions, and Runge-Kutta techniques are used for the evolution in Q. Unpolarised evolution is provided to NNLO, including heavy-quark thresholds in the MS¯ scheme, and longitudinally polarised evolution to NLO. The code is structured so as to provide simple access to the objects representing splitting functions and PDFs, making it possible for a user to extend the facilities already provided. A streamlined interface is also available, facilitating use of the evolution part of the code from F77 and C/C++. Program summaryProgram title: HOPPET Catalogue identifier: AEBZ_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEBZ_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU Public License No. of lines in distributed program, including test data, etc.: 61 001 No. of bytes in distributed program, including test data, etc.: 270 312 Distribution format: tar.gz Programming language: Fortran 95 Computer: All Operating system: All RAM: ≲10 MB Classification: 11.5 Nature of problem: Solution of the DGLAP evolution equations up to NNLO (NLO) for unpolarised (longitudinally polarised) PDFs, and provision of tools to facilitate manipulation (convolutions, etc.) of PDFs with user-defined coefficient and splitting functions. Solution method: Representation of PDFs on a grid in x, adaptive integration of splitting functions to reduce them to a discretised form, obtaining fast convolutions that are equivalent to integration with an interpolated form of the PDFs; Runge
Kinoshita, Norikazu; Sueki, Keisuke; Sasa, Kimikazu; Kitagawa, Jun-ichi; Ikarashi, Satoshi; Nishimura, Tomohiro; Wong, Ying-Shee; Satou, Yukihiko; Handa, Koji; Takahashi, Tsutomu; Sato, Masanori; Yamagata, Takeyasu
2011-01-01
A tremendous amount of radioactivity was discharged because of the damage to cooling systems of nuclear reactors in the Fukushima No. 1 nuclear power plant in March 2011. Fukushima and its adjacent prefectures were contaminated with fission products from the accident. Here, we show a geographical distribution of radioactive iodine, tellurium, and cesium in the surface soils of central-east Japan as determined by gamma-ray spectrometry. Especially in Fukushima prefecture, contaminated area spreads around Iitate and Naka-Dori for all the radionuclides we measured. Distributions of the radionuclides were affected by the physical state of each nuclide as well as geographical features. Considering meteorological conditions, it is concluded that the radioactive material transported on March 15 was the major contributor to contamination in Fukushima prefecture, whereas the radioactive material transported on March 21 was the major source in Ibaraki, Tochigi, Saitama, and Chiba prefectures and in Tokyo. PMID:22084070
Kinoshita, Norikazu; Sueki, Keisuke; Sasa, Kimikazu; Kitagawa, Jun-ichi; Ikarashi, Satoshi; Nishimura, Tomohiro; Wong, Ying-Shee; Satou, Yukihiko; Handa, Koji; Takahashi, Tsutomu; Sato, Masanori; Yamagata, Takeyasu
2011-12-01
A tremendous amount of radioactivity was discharged because of the damage to cooling systems of nuclear reactors in the Fukushima No. 1 nuclear power plant in March 2011. Fukushima and its adjacent prefectures were contaminated with fission products from the accident. Here, we show a geographical distribution of radioactive iodine, tellurium, and cesium in the surface soils of central-east Japan as determined by gamma-ray spectrometry. Especially in Fukushima prefecture, contaminated area spreads around Iitate and Naka-Dori for all the radionuclides we measured. Distributions of the radionuclides were affected by the physical state of each nuclide as well as geographical features. Considering meteorological conditions, it is concluded that the radioactive material transported on March 15 was the major contributor to contamination in Fukushima prefecture, whereas the radioactive material transported on March 21 was the major source in Ibaraki, Tochigi, Saitama, and Chiba prefectures and in Tokyo. PMID:22084070
Kinoshita, Norikazu; Sueki, Keisuke; Sasa, Kimikazu; Kitagawa, Jun-ichi; Ikarashi, Satoshi; Nishimura, Tomohiro; Wong, Ying-Shee; Satou, Yukihiko; Handa, Koji; Takahashi, Tsutomu; Sato, Masanori; Yamagata, Takeyasu
2011-12-01
A tremendous amount of radioactivity was discharged because of the damage to cooling systems of nuclear reactors in the Fukushima No. 1 nuclear power plant in March 2011. Fukushima and its adjacent prefectures were contaminated with fission products from the accident. Here, we show a geographical distribution of radioactive iodine, tellurium, and cesium in the surface soils of central-east Japan as determined by gamma-ray spectrometry. Especially in Fukushima prefecture, contaminated area spreads around Iitate and Naka-Dori for all the radionuclides we measured. Distributions of the radionuclides were affected by the physical state of each nuclide as well as geographical features. Considering meteorological conditions, it is concluded that the radioactive material transported on March 15 was the major contributor to contamination in Fukushima prefecture, whereas the radioactive material transported on March 21 was the major source in Ibaraki, Tochigi, Saitama, and Chiba prefectures and in Tokyo.
Leading twist nuclear shadowing phenomena in hard processes with nuclei
L. Franfurt; Guzey, V.; Strikman, M.
2012-01-08
We present and discuss the theory and phenomenology of the leading twist theory of nuclear shadowing which is based on the combination of the generalization of Gribov-Glauber theory, QCD factorization theorems, and HERA QCD analysis of diffraction in lepton-proton deep inelastic scattering (DIS). We apply this technique for the analysis of a wide range of hard processes with nuclei-inclusive DIS on deuterons, medium-range and heavy nuclei, coherent and incoherent diffractive DIS with nuclei, and hard diffraction in proton-nucleus scattering - and make predictions for the effect of nuclear shadowing in the corresponding sea quark and gluon parton distributions. We also analyze the role of the leading twist nuclear shadowing in generalized parton distributions in nuclei and certain characteristics of final states in nuclear DIS. We discuss the limits of applicability of the leading twist approximation for small x scattering off nuclei and the onset of the black disk regime and methods of detecting it. It will be possible to check many of our predictions in the near future in the studies of the ultraperipheral collisions at the Large Hadron Collider (LHC). Further checks will be possible in pA collisions at the LHC and forward hadron production at Relativistic Heavy Ion Collider (RHIC). As a result, detailed tests will be possible at an Electon-Ion Collider (EIC) in USA and at the Large Hadron-Electron Collider (LHeC) at CERN.
Leading twist nuclear shadowing phenomena in hard processes with nuclei
L. Franfurt; Guzey, V.; Strikman, M.
2012-01-08
We present and discuss the theory and phenomenology of the leading twist theory of nuclear shadowing which is based on the combination of the generalization of Gribov-Glauber theory, QCD factorization theorems, and HERA QCD analysis of diffraction in lepton-proton deep inelastic scattering (DIS). We apply this technique for the analysis of a wide range of hard processes with nuclei-inclusive DIS on deuterons, medium-range and heavy nuclei, coherent and incoherent diffractive DIS with nuclei, and hard diffraction in proton-nucleus scattering - and make predictions for the effect of nuclear shadowing in the corresponding sea quark and gluon parton distributions. We alsomore » analyze the role of the leading twist nuclear shadowing in generalized parton distributions in nuclei and certain characteristics of final states in nuclear DIS. We discuss the limits of applicability of the leading twist approximation for small x scattering off nuclei and the onset of the black disk regime and methods of detecting it. It will be possible to check many of our predictions in the near future in the studies of the ultraperipheral collisions at the Large Hadron Collider (LHC). Further checks will be possible in pA collisions at the LHC and forward hadron production at Relativistic Heavy Ion Collider (RHIC). As a result, detailed tests will be possible at an Electon-Ion Collider (EIC) in USA and at the Large Hadron-Electron Collider (LHeC) at CERN.« less
Polarized 3 parton production in inclusive DIS at small x
NASA Astrophysics Data System (ADS)
Ayala, Alejandro; Hentschinski, Martin; Jalilian-Marian, Jamal; Tejeda-Yeomans, Maria Elena
2016-10-01
Azimuthal angular correlations between produced hadrons/jets in high energy collisions are a sensitive probe of the dynamics of QCD at small x. Here we derive the triple differential cross section for inclusive production of 3 polarized partons in DIS at small x. The target proton or nucleus is described using the Color Glass Condensate (CGC) formalism. The resulting expressions are used to study azimuthal angular correlations between produced partons in order to probe the gluon structure of the target hadron or nucleus. Our analytic expressions can also be used to calculate the real part of the Next to Leading Order (NLO) corrections to di-hadron production in DIS by integrating out one of the three final state partons.
Results on the neutron energy distribution measurements at the RECH-1 Chilean nuclear reactor
NASA Astrophysics Data System (ADS)
Aguilera, P.; Molina, F.; Romero-Barrientos, J.
2016-07-01
Neutron activations experiments has been perform at the RECH-1 Chilean Nuclear Reactor to measure its neutron flux energy distribution. Samples of pure elements was activated to obtain the saturation activities for each reaction. Using - ray spectroscopy we identify and measure the activity of the reaction product nuclei, obtaining the saturation activities of 20 reactions. GEANT4 and MCNP was used to compute the self shielding factor to correct the cross section for each element. With the Expectation-Maximization algorithm (EM) we were able to unfold the neutron flux energy distribution at dry tube position, near the RECH-1 core. In this work, we present the unfolding results using the EM algorithm.
Nuclear shape dependence of Gamow-Teller distributions in neutron-deficient Pb isotopes
Sarriguren, P.; Moreno, O.; Alvarez-Rodriguez, R.; Moya de Guerra, E.
2005-11-01
We study Gamow-Teller strength distributions in the neutron-deficient even isotopes {sup 184-194}Pb in a search for signatures of deformation. The microscopic formalism used is based on a deformed quasiparticle random-phase approximation (QRPA) approach, which involves a self-consistent quasiparticle deformed Skyrme Hartree-Fock (HF) basis and residual spin-isospin forces in both the particle-hole and particle-particle channels. By analyzing the sensitivity of the Gamow-Teller strength distributions to the various ingredients in the formalism, we conclude that the {beta} decay of these isotopes could be a useful tool to look for fingerprints of nuclear deformation.
Thermionic nuclear reactor with internal heat distribution and multiple duct cooling
Fisher, C.R.; Perry, L.W. Jr.
1975-11-01
A Thermionic Nuclear Reactor is described having multiple ribbon-like coolant ducts passing through the core, intertwined among the thermionic fuel elements to provide independent cooling paths. Heat pipes are disposed in the core between and adjacent to the thermionic fuel elements and the ribbon ducting, for the purpose of more uniformly distributing the heat of fission among the thermionic fuel elements and the ducts.
Energy dependence of nuclear charge distribution in neutron induced fission of Z-even nuclei
NASA Astrophysics Data System (ADS)
Roshchenko, V. A.; Piksaikin, V. M.; Isaev, S. G.; Goverdovski, A. A.
2006-07-01
For the first time the distribution of nuclear charge of fission products with mass numbers 87, 88, 89, 91, 93, 94, 95, 137, 138, 139, and 140 and their complementary products have been studied for neutron induced fission of U235 and Pu239 in the energy range from thermal up to 1.2 MeV. The energy dependences of the cumulative yields of Br87, Br88, Br89, Br91, Kr93, Rb94, Rb95, I137, I138, I139, and I140 have been obtained by delayed neutron measurements. The most probable charge ZP(A)in the appropriate isobaric β-decay chains was estimated. The results were analyzed in terms of the deviation ΔZP(A') of the most probable charge of isobaric β-decay chains from the unchanged charge distribution before prompt neutron emission (nuclear charge polarization) and they are compared with experimental data of other authors and with predictions from Nethaway's ZP-formula and Wahl's ZP-model. We show that the nuclear charge polarization of primary fission fragments <ΔZP(A')> before prompt neutron evaporation decreases as the excitation energy of the compound nucleus increases. This decrease is more pronounced for fission of U235. The energy dependencies of ΔZP(A') and ΔZP(ZP) obtained in the present work show an attenuation of the odd-even effects in the charge distribution as the excitation energy of the compound nucleus increases.
Nuclear distribution of eIF3g and its interacting nuclear proteins in breast cancer cells
ZHENG, QIAOLI; LIU, HAO; YE, JINGJIA; ZHANG, HUI; JIA, ZHENYU; CAO, JIANG
2016-01-01
Eukaryotic translation initiation factor 3 subunit g (eIF3g) is a core subunit of the eukaryotic translation initiation factor 3 complex, and is important in the initiation of translation. It is also involved in caspase-mediated apoptosis, and is upregulated in multidrug-resistant cancer cells. In the present study, the nuclear distribution of eIF3g was determined by performing co-immunoprecipitation of proteins that potentially interact with eIF3g in the nucleus. Mass spectrometry characterization showed that three proteins, heterogeneous nuclear ribonucleoprotein U/scaffold attachment factor A, HSZFP36/zinc finger protein 823 and β-actin, were among the candidate eIF3g-interacting proteins in the nucleus. The protein-protein interaction was further confirmed by cross-linking and a glutathione S-transferase pull-down assay, followed by western blotting. The co-localization of these proteins was determined by confocal microscopy. These findings provide novel insight into the possible functions of eIF3g in the nucleus and serves as an important first step for further investigation of the roles of eIF3g in cancer development. PMID:26935993
NASA Astrophysics Data System (ADS)
Chen, Yan; Liu, Min; Compton, Stephen G.; Chen, Xiao-Yong
2014-05-01
Nuclear mitochondrial pseudogenes (NUMTs) are nuclear sequences transferred from mitochondrial genomes. Although widespread, their distribution patterns among populations or closely related species are rarely documented. We amplified and sequenced the mitochondrial cytochrome b (Cytb) gene to check for NUMTs in three fig wasp species that pollinate Ficus pumila (Wiebesia sp. 1, 2 and 3) in Southeastern China using direct and cloned sequencing. Unambiguous sequences (332) of 487 bp in length belonging to 33 haplotypes were found by direct sequencing. Their distribution was highly concordant with those of cytochrome c oxidase subunit I (COI). Obvious signs of co-amplification of NUMTs were indicated by their uneven distribution. NUMTs were observed in all individuals of 12 populations of Wiebesia sp. 3, and 13 individuals of three northern populations of Wiebesia sp. 1. Sequencing clones of potential co-amplification products confirmed that they were NUMTs. These NUMTs either clustered as NUMT clades basal to mtDNA Cytb clades (basal NUMTs), or together with Cytb haplotypes. Basal NUMTs had either stop codons or frame-shifting mutations resulting from deletion of a 106 bp fragment. In addition, no third codon or synonymous substitutions were detected within each NUMT clade. The phylogenetic tree indicated that basal NUMTs had been inserted into nuclei before divergence of the three species. No significant pairwise differences were detected in their ratios of third codon substitutions, suggesting that these NUMTs originated from one transfer event, with duplication in the nuclear genome resulting in the coexistence of the 381 bp copy. No significant substitution differences were detected between Cytb haplotypes and NUMTs that clustered with Cytb haplotypes. However, these NUMTs coexisted with Cytb haplotypes in multiple populations, suggesting that these NUMT haplotypes were recently inserted into the nuclear genome. Both basal and recently inserted NUMTs were rare
Evaluation of population density and distribution criteria in nuclear power plant siting
Young, M.
1994-06-01
The NRC has proposed revisions to 10 CFR 100 which include the codification of nuclear reactor site population density limits to 500 people per square mile, at the siting stage, averaged over any radial distance out to 30 miles, and 1,000 people per square mile within the 40-year lifetime of a nuclear plant. This study examined whether there are less restrictive alternative population density and/or distribution criteria which would provide equivalent or better protection to human health in the unlikely event of a nuclear accident. This study did not attempt to directly address the issue of actual population density limits because there are no US risk standards established for the evaluation of population density limits. Calculations were performed using source terms for both a current generation light water reactor (LWR) and an advanced light water reactor (ALWR) design. The results of this study suggest that measures which address the distribution of the population density, including emergency response conditions, could result in lower average individual risks to the public than the proposed guidelines that require controlling average population density. Studies also indicate that an exclusion zone size, determined by emergency response conditions and reactor design (power level and safety features), would better serve to protect public health than a rigid standard applied to all sites.
Martínez-Herrera, Alejandro; Aragón, Jorge; Bermúdez-Cruz, Rosa Ma.; Bazán, Ma. Luisa; Soid-Raggi, Gabriela; Ceja, Víctor; Santos Coy-Arechavaleta, Andrea; Alemán, Víctor; Depardón, Francisco; Montañez, Cecilia
2015-01-01
Dystrophin Dp40 is the shortest protein encoded by the DMD (Duchenne muscular dystrophy) gene. This protein is unique since it lacks the C-terminal end of dystrophins. In this data article, we describe the subcellular localization, nuclear export signals and the three-dimensional structure modeling of putative Dp40 proteins using bioinformatics tools. The Dp40 wild type protein was predicted as a cytoplasmic protein while the Dp40n4 was predicted to be nuclear. Changes L93P and L170P are involved in the nuclear localization of Dp40n4 protein. A close analysis of Dp40 protein scored that amino acids 93LEQEHNNLV101 and 168LLLHDSIQI176 could function as NES sequences and the scores are lost in Dp40n4. In addition, the changes L93/170P modify the tertiary structure of putative Dp40 mutants. The analysis showed that changes of residues 93 and 170 from leucine to proline allow the nuclear localization of Dp40 proteins. The data described here are related to the research article entitled “EF-hand domains are involved in the differential cellular distribution of dystrophin Dp40” (J. Aragón et al. Neurosci. Lett. 600 (2015) 115–120) [1]. PMID:26217814
Ko, Young-Joon
2016-01-01
Nuclear mitochondrial DNA segment (Numt) insertion describes a well-known phenomenon of mitochondrial DNA transfer into a eukaryotic nuclear genome. However, it has not been well understood, especially in plants. Numt insertion patterns vary from species to species in different kingdoms. In this study, the patterns were surveyed in nine plant species, and we found some tip-offs. First, when the mitochondrial genome size is relatively large, the portion of the longer Numt is also larger than the short one. Second, the whole genome duplication event increases the ratio of the shorter Numt portion in the size distribution. Third, Numt insertions are enriched in exon regions. This analysis may be helpful for understanding plant evolution. PMID:27729838
Armesto, Nestor; Dainese, Andrea; Salgado, Carlos A.; Wiedemann, Urs Achim
2005-03-01
The ratio of nuclear modification factors of high-p{sub T} heavy-flavored mesons to light-flavored hadrons ('heavy-to-light ratio') in nucleus-nucleus collisions tests the partonic mechanism expected to underlie jet quenching. Heavy-to-light ratios are mainly sensitive to the mass and color-charge dependences of medium-induced parton energy loss. Here, we assess the potential for identifying these two effects in D and B meson production at RHIC and at the LHC. To this end, we supplement the perturbative QCD factorized formalism for leading hadron production with radiative parton energy loss. For D meson spectra at high but experimentally accessible transverse momentum (10 < or approx. p{sub T} < or approx. 20 GeV) in Pb-Pb collisions at the LHC, we find that charm quarks behave essentially like light quarks. However, since light-flavored hadron yields are dominated by gluon parents, the heavy-to-light ratio of D mesons is a sensitive probe of the color-charge dependence of parton energy loss. In contrast, due to the larger b quark mass, the medium modification of B mesons in the same kinematical regime provides a sensitive test of the mass dependence of parton energy loss. At RHIC energies, the strategies for identifying and disentangling the color charge and mass dependence of parton energy loss are more involved because of the smaller kinematical range accessible. We argue that at RHIC, the kinematical regime best suited for such an analysis of D mesons is 7 < or approx. p{sub T} < or approx. 12 GeV, whereas the study of lower transverse momenta is further complicated due to the known dominant contribution of additional, particle species dependent, nonperturbative effects.
Alpha-Particle Angular Distributions of At and Rn Isotopes and Their Relation to Nuclear Structure
NICOLE Collaboration and ISOLDE Collaboration
1996-12-01
We report on an extensive on-line nuclear orientation study of the angular distribution of {alpha} particles emitted in the favored decay of neutron deficient At and Rn nuclei near the {ital N}=126 shell closure. Surprisingly large anisotropies were observed, showing pronounced changes from one isotope to another. Comparing these data with several theoretical models shows that anisotropic {alpha} emission in favored decays from near-spherical nuclei can well be explained within the shell model, implying that it is mainly determined by the structure of the decaying nucleus. {copyright} {ital 1996 The American Physical Society.}
NASA Astrophysics Data System (ADS)
Stingaciu, Laura R.; Weihermüller, Lutz; Haber-Pohlmeier, Sabina; Stapf, Siegfried; Vereecken, Harry; Pohlmeier, Andreas
2010-05-01
Known pore size distributions can be directly linked to the water retention characteristic which is essential for the prognosis of water and solute movement through the material. In our study, we evaluated the feasibility to use Nuclear Magnetic Resonance (NMR) relaxometry measurements for the characterization of pore size distribution in four porous samples with different texture and composition. Therefore, NMR T2 and T1 relaxation measurements at 6.47 MHz were carried out for three model samples (medium sand; fine sand; and a homogenous sand / kaolin clay mixture) and a natural soil. To quantify the goodness of the approach, the NMR measurements were compared in terms of cumulated pore size distribution functions and mean pore diameter with the two classical techniques based on water retention and mercury porosimetry measurements. The results showed that T1 and T2 derived mean pore size diameters are in good agreement with each other but deviate from retention curve derived ones. This is especially the case for well sorted sands with n values > 2.7. For finer materials differences are less pronounced. A short study was performed to evaluate the influence of the variations observed in the pore diameter distributions on the hydraulic properties of the samples: θS, α, and n. In conclusion, NMR T1 and T2 relaxation measurements can be used to estimate pore size distribution, mean pore diameter, as well as the retention function and corresponding hydraulic properties.
NASA Astrophysics Data System (ADS)
Chang, Wen-Chen
2016-02-01
The observation of the violation of Lam-Tung relation in the πN Drell-Yan process triggered many theoretical speculations. The TMD Boer-Mulders functions characterizing the correlation of transverse momentum and transverse spin for partons in unpolarized hadrons could nicely account for the violation. The COMPASS experiment at CERN will measure the angular distributions of dimuons from the unpolarized Drell-Yan process over a wide kinematic region and study the beam particle dependence. Significant statistics is expected from a successful run in 2015 which will bring further understanding of the origin of the violation of Lam-Tung relation and of the partonic transverse spin structure of the nucleon.
Neutron angular distribution in a plasma focus obtained using nuclear track detectors.
Castillo-Mejía, F; Herrera, J J E; Rangel, J; Golzarri, J I; Espinosa, G
2002-01-01
The dense plasma focus (DPF) is a coaxial plasma gun in which a high-density, high-temperature plasma is obtained in a focused column for a few nanoseconds. When the filling gas is deuterium, neutrons can be obtained from fusion reactions. These are partially due to a beam of deuterons which are accelerated against the background hot plasma by large electric fields originating from plasma instabilities. Due to a beam-target effect, the angular distribution of the neutron emission is anisotropic, peaked in the forward direction along the axis of the gun. The purpose of this work is to illustrate the use of CR-39 nuclear track detectors as a diagnostic tool in the determination of the time-integrated neutron angular distribution. For the case studied in this work, neutron emission is found to have a 70% contribution from isotropic radiation and a 30% contribution from anisotropic radiation.
Distribution of tritium in water vapour and precipitation around Wolsung nuclear power plant.
Chae, Jung-Seok; Lee, Sang-Kuk; Kim, Yongjae; Lee, Jung-Min; Cho, Heung-Joon; Cho, Yong-Woo; Yun, Ju-Yong
2011-07-01
The distribution of tritium in water vapour and precipitation with discharge of tritiated water vapour and meteorological factors was studied around the Wolsung nuclear power plant (NPP) site during the period 2004-2008. The tritium concentrations in atmospheric water vapour and precipitation had a temporal variation with relatively high values in the early summer. Spatial distribution of tritium concentrations was affected by various factors such as distance from the NPP site, wind direction, tritium discharge into the atmosphere and atmospheric dispersion factor. The annual mean concentrations of atmospheric HTO and precipitation were correlated with the amount of gaseous tritium released from the Wolsung NPP. The tritium concentrations in precipitation decrease exponentially with an increase of the distance from the Wolsung NPP site.
Integration of distributed plant process computer systems to nuclear power generation facilities
Bogard, T.; Finlay, K.
1996-11-01
Many operating nuclear power generation facilities are replacing their plant process computer. Such replacement projects are driven by equipment obsolescence issues and associated objectives to improve plant operability, increase plant information access, improve man machine interface characteristics, and reduce operation and maintenance costs. This paper describes a few recently completed and on-going replacement projects with emphasis upon the application integrated distributed plant process computer systems. By presenting a few recent projects, the variations of distributed systems design show how various configurations can address needs for flexibility, open architecture, and integration of technological advancements in instrumentation and control technology. Architectural considerations for optimal integration of the plant process computer and plant process instrumentation & control are evident from variations of design features.
Intrinsic transverse momentum and parton correlations from dynamical chiral symmetry breaking
Peter Schweitzer, Mark Strikman, Christian Weiss
2013-01-01
The dynamical breaking of chiral symmetry in QCD is caused by nonperturbative interactions on a distance scale rho ~ 0.3 fm, much smaller than the typical hadronic size R ~ 1 fm. These short-distance interactions influence the intrinsic transverse momentum distributions of partons and their correlations at a low normalization point. We study this phenomenon in an effective description of the low-energy dynamics in terms of chiral constituent quark degrees of freedom, which refers to the large-N_c limit of QCD. The nucleon is obtained as a system of constituent quarks and antiquarks moving in a self-consistent classical chiral field (relativistic mean-field approximation, or chiral quark-soliton model). The calculated transverse momentum distributions of constituent quarks and antiquarks are matched with QCD quarks, antiquarks and gluons at the chiral symmetry--breaking scale rho^{-2}. We find that the transverse momentum distribution of valence quarks is localized at p_T^2 ~ R^{-2} and roughly of Gaussian shape. The distribution of unpolarized sea quarks exhibits a would-be power-like tail ~1/p_T^2 extending up to the chiral symmetry-breaking scale. Similar behavior is observed in the flavor-nonsinglet polarized sea. The high-momentum tails are the result of short-range correlations between sea quarks in the nucleon's light-cone wave function, which are analogous to short-range NN correlations in nuclei. We show that the nucleon's light-cone wave function contains correlated pairs of transverse size rho << R with scalar-isoscalar (Sigma) and pseudoscalar-isovector (Pi) quantum numbers, whose internal wave functions have a distinctive spin structure and become identical at p_T^2 ~ rho^{-2} (restoration of chiral symmetry). These features are model-independent and represent an effect of dynamical chiral symmetry breaking on the nucleon's partonic structure. Our results have numerous implications for the transverse momentum distributions of particles produced in hard
Active Degradation Explains the Distribution of Nuclear Proteins during Cellular Senescence
Giampieri, Enrico; De Cecco, Marco; Remondini, Daniel; Sedivy, John; Castellani, Gastone
2015-01-01
The amount of cellular proteins is a crucial parameter that is known to vary between cells as a function of the replicative passages, and can be important during physiological aging. The process of protein degradation is known to be performed by a series of enzymatic reactions, ranging from an initial step of protein ubiquitination to their final fragmentation by the proteasome. In this paper we propose a stochastic dynamical model of nuclear proteins concentration resulting from a balance between a constant production of proteins and their degradation by a cooperative enzymatic reaction. The predictions of this model are compared with experimental data obtained by fluorescence measurements of the amount of nuclear proteins in murine tail fibroblast (MTF) undergoing cellular senescence. Our model provides a three-parameter stationary distribution that is in good agreement with the experimental data even during the transition to the senescent state, where the nuclear protein concentration changes abruptly. The estimation of three parameters (cooperativity, saturation threshold, and maximal velocity of the reaction), and their evolution during replicative passages shows that only the maximal velocity varies significantly. Based on our modeling we speculate the reduction of functionality of the protein degradation mechanism as a possible competitive inhibition of the proteasome. PMID:26115222
Nuclear microscopy: a tool for imaging elemental distribution and percutaneous absorption in vivo.
Veríssimo, Ana; Alves, Luís C; Filipe, Paulo; Silva, João N; Silva, Raquel; Ynsa, Maria Dolores; Gontier, Etienne; Moretto, Philippe; Pallon, Jan; Pinheiro, Teresa
2007-04-01
Nuclear microscopy is a technique based on a focused beam of accelerated particles that has the ability of imaging the morphology of the tissue in vivo and of producing the correspondent elemental maps, whether in major, minor, or trace concentrations. These characteristics constitute a strong advantage in studying the morphology of human skin, its elemental distributions and the permeation mechanisms of chemical compounds. In this study, nuclear microscopy techniques such as scanning transmission ion microscopy and particle induced X-ray emission were applied simultaneously, to cryopreserved human skin samples with the purpose of obtaining high-resolution images of cells and tissue morphology. In addition, quantitative elemental profiling and mapping of phosphorus, calcium, chlorine, and potassium in skin cross-sections were obtained. This procedure accurately distinguishes the epidermal strata and dermis by overlapping in real time the elemental information with density images obtained from the transmitted beam. A validation procedure for elemental distributions in human skin based on differential density of epidermal strata and dermis was established. As demonstrated, this procedure can be used in future studies as a tool for the in vivo examination of trans-epidermal and -dermal delivery of products.
Nuclear Effects in Neutrino-Nucleus Interactions and the MINERvA Neutrino Nucleus Scattering Program
NASA Astrophysics Data System (ADS)
Morfín, Jorge G.
2011-09-01
Nuclear effects of charged current deep inelastic neutrino-iron scattering have been studied in the frame-work of a χ2 analysis of parton distribution functions (PDFs)1. A set of iron PDFs have been extracted which are then used to compute xBj-dependent and Q2-dependent nuclear correction factors for iron structure functions which are required in global analyses of free nucleon PDFs. Upon comparing our results with nuclear correction factors from neutrino-nucleus scattering models and correction factors for l±-iron scattering we find that, except for very high xBj, our correction factors differ in both shape and magnitude from the correction factors of the models and charged-lepton scattering. The MINERvA neutrino-nucleus scattering experiment at Fermilab, will systematically study neutrino nuclear effects off of He, C, Fe and Pb for a more thorough A-dependent study of nuclear PDFs and these correction factors.
Polarised Parton Densities from the Fits to the Deep Inelastic Spin Asymmetries on Nucleons
NASA Astrophysics Data System (ADS)
Bartelski, Jan; Tatur, Stanislaw
2001-07-01
We have updated our next to leading order QCD fit for polarised parton densities [S. Tatur, J. Bartelski, M. Kurzela, Acta Phys. Pol. B31, 647 (2000)] using recent experimental data on the deep inelastic spin asymmetries on nucleons. Our distributions have functional form inspired by the unpolarised ones given by MRST (Martin, Roberts, Stirling and Thorne) fit. In addition to usually used data sample (averaged over variable Q2 for the same value of x variable) we have also considered the points with the same x and different Q2. Our fits to both groups of data give very similar results with substantial antiquark contribution in the measured region of x. In the first case we get rather small (Δ G=0.31) gluon polarisation. For the non averaged data the best fit is obtained when gluon contribution vanishes at Q2=1GeV2. Our new parametrisation of parton densities and additional experimental data taken into account do not change much our previous results.
B-meson production in the Parton Reggeization Approach at Tevatron and the LHC
NASA Astrophysics Data System (ADS)
Karpishkov, A. V.; Nefedov, M. A.; Saleev, V. A.; Shipilova, A. V.
2015-02-01
We study the inclusive hadroproduction of B0, B+ and Bs0 mesons at leading order in the Parton Reggeization Approach using the universal fragmentation functions extracted from the combined e+e- annihilation data from CERN LEP1 and SLAC SLC colliders. We have described B-meson transverse momentum distributions measured in the central region of rapidity by the CDF Collaboration at Fermilab Tevatron and CMS Collaboration at LHC within uncertainties and without free parameters, applying Kimber-Martin-Ryskin unintegrated gluon distribution function in a proton. The forward B-meson production (2.0
Double Parton Fragmentation Function and its Evolution in Quarkonium Production
NASA Astrophysics Data System (ADS)
Kang, Zhong-Bo
2014-01-01
We summarize the results of a recent study on a new perturbative QCD factorization formalism for the production of heavy quarkonia of large transverse momentum pT at collider energies. Such a new factorization formalism includes both the leading power (LP) and next-to-leading power (NLP) contributions to the cross section in the mQ2/p_T^2 expansion for heavy quark mass mQ. For the NLP contribution, the so-called double parton fragmentation functions are involved, whose evolution equations have been derived. We estimate fragmentation functions in the non-relativistic QCD formalism, and found that their contribution reproduce the bulk of the large enhancement found in explicit NLO calculations in the color singlet model. Heavy quarkonia produced from NLP channels prefer longitudinal polarization, in contrast to the single parton fragmentation function. This might shed some light on the heavy quarkonium polarization puzzle.
Small-x parton content of the photon
NASA Astrophysics Data System (ADS)
Forshaw, J. R.; Harriman, P. N.
1992-11-01
The parton content of the photon is examined systematically. In the low-Q2 region (Q2<1 GeV2) we assume the photon behaves largely according to the vector-meson-dominance (VMD) hypothesis, while for higher Q2 we supplement the VMD with a purely perturbative pointlike component and QCD corrections. Special care is taken in the region of small x: we work in the leading-logarithm approximation (LLA) in 1/x at low Q2 and in the LLA in Q2 for Q2>4 GeV2. We include small-x shadowing effects in the VMD sector and show that they need not be considered in the pointlike sector where the parton content is much less.
Projective symmetry of partons in Kitaev's honeycomb model
NASA Astrophysics Data System (ADS)
Mellado, Paula
2015-03-01
Low-energy states of quantum spin liquids are thought to involve partons living in a gauge-field background. We study the spectrum of Majorana fermions of Kitaev's honeycomb model on spherical clusters. The gauge field endows the partons with half-integer orbital angular momenta. As a consequence, the multiplicities reflect not the point-group symmetries of the cluster, but rather its projective symmetries, operations combining physical and gauge transformations. The projective symmetry group of the ground state is the double cover of the point group. We acknowledge Fondecyt under Grant No. 11121397, Conicyt under Grant No. 79112004, and the Simons Foundation (P.M.); the Max Planck Society and the Alexander von Humboldt Foundation (O.P.); and the US DOE Grant No. DE-FG02-08ER46544 (O.T.).
Parton interpretation of the nucleon spin-dependent structure functions
Mankiewicz, L. ); Ryzak, Z. )
1991-02-01
We discuss the interpretation of the nucleon's polarized structure function {ital g}{sub 2}({ital x}). If the target state is represented by its Fock decomposition on the light cone, the operator-product expansion allows us to demonstrate that moments of {ital g}{sub 2}({ital x}) are related to overlap integrals between wave functions of opposite longitudinal polarizations. In the light-cone formalism such wave functions are related by the kinematical operator {ital scrY}, or light-cone parity. As a consequence, it can be shown that moments of {ital g}{sub 2} give information about the same parton wave function, or probability amplitude to find a certain parton configuration in the target which defines {ital g}{sub 1}({ital x}) or {ital F}{sub 2}({ital x}). Specific formulas are given, and possible applications to the phenomenology of the nucleon structure in QCD are discussed.
Costabel, Stephan; Yaramanci, Ugur
2013-01-01
[1] For characterizing water flow in the vadose zone, the water retention curve (WRC) of the soil must be known. Because conventional WRC measurements demand much time and effort in the laboratory, alternative methods with shortened measurement duration are desired. The WRC can be estimated, for instance, from the cumulative pore size distribution (PSD) of the investigated material. Geophysical applications of nuclear magnetic resonance (NMR) relaxometry have successfully been applied to recover PSDs of sandstones and limestones. It is therefore expected that the multiexponential analysis of the NMR signal from water-saturated loose sediments leads to a reliable estimation of the WRC. We propose an approach to estimate the WRC using the cumulative NMR relaxation time distribution and approximate it with the well-known van-Genuchten (VG) model. Thereby, the VG parameter n, which controls the curvature of the WRC, is of particular interest, because it is the essential parameter to predict the relative hydraulic conductivity. The NMR curves are calibrated with only two conventional WRC measurements, first, to determine the residual water content and, second, to define a fixed point that relates the relaxation time to a corresponding capillary pressure. We test our approach with natural and artificial soil samples and compare the NMR-based results to WRC measurements using a pressure plate apparatus and to WRC predictions from the software ROSETTA. We found that for sandy soils n can reliably be estimated with NMR, whereas for samples with clay and silt contents higher than 10% the estimation fails. This is the case when the hydraulic properties of the soil are mainly controlled by the pore constrictions. For such samples, the sensitivity of the NMR method for the pore bodies hampers a plausible WRC estimation. Citation: Costabel, S., and U. Yaramanci (2013), Estimation of water retention parameters from nuclear magnetic resonance relaxation time distributions, Water
Nuclear EMC effect in a statistical model
NASA Astrophysics Data System (ADS)
Zhang, Yunhua; Shao, Lijing; Ma, Bo-Qiang
2009-09-01
A simple statistical model in terms of light-front kinematic variables is used to explain the nuclear EMC effect in the range x∈[0.2,0.7], which was constructed by us previously to calculate the parton distribution functions (PDFs) of the nucleon. Here, we treat the temperature T as a parameter of the atomic number A, and get reasonable results in agreement with the experimental data. Our results show that the larger A, the lower T thus the bigger volume V, and these features are consistent with other models. Moreover, we give the predictions of the quark distribution ratios, i.e., q(x)/q(x), q(x)/q(x), and s(x)/s(x), and also the gluon ratio g(x)/g(x) for iron as an example. The predictions are different from those by other models, thus experiments aiming at measuring the parton ratios of anti-quarks, strange quarks, and gluons can provide a discrimination of different models.
Electroweak W+W- jj prodution at NLO in QCD matched with parton shower in the POWHEG-BOX
NASA Astrophysics Data System (ADS)
Jäger, Barbara; Zanderighi, Giulia
2013-04-01
We present an implementation of electroweak W + W - jj production at hadron colliders in the POWHEG framework, a method that allows the interfacing of a next-to-leading order QCD calculation with parton shower Monte Carlo programs. We provide results for both, fully and semi-leptonic decay modes of the weak bosons, taking resonant and non-resonant contributions and spin correlations of the final-state particles into account. To illustrate the versatility of our implementation, we provide phenomenological results for two representative scenarios with a light and with a heavy Higgs boson, respectively, and in a kinematic regime of highly boosted gauge bosons. The impact of the parton shower is found to depend on the setup and the observable under investigation. In particular, distributions related to a central-jet veto are more sensitive to these effects. Therefore the impact of radiation by the parton shower on next-to-leading order predictions should be assessed carefully on a case-by-case basis.
Partonic Flow and phi-Meson production in Au+Au collisions at sqrt radical sNN = 200 GeV.
Abelev, B I; Aggarwal, M M; Ahammed, Z; Anderson, B D; Arkhipkin, D; Averichev, G S; Bai, Y; Balewski, J; Barannikova, O; Barnby, L S; Baudot, J; Baumgart, S; Belaga, V V; Bellingeri-Laurikainen, A; Bellwied, R; Benedosso, F; Betts, R R; Bhardwaj, S; Bhasin, A; Bhati, A K; Bichsel, H; Bielcik, J; Bielcikova, J; Bland, L C; Blyth, S-L; Bombara, M; Bonner, B E; Botje, M; Bouchet, J; Brandin, A V; Bravar, A; Burton, T P; Bystersky, M; Cadman, R V; Cai, X Z; Caines, H; Calderón de la Barca Sánchez, M; Callner, J; Catu, O; Cebra, D; Chajecki, Z; Chaloupka, P; Chattopadhyay, S; Chen, H F; Chen, J H; Chen, J Y; Cheng, J; Cherney, M; Chikanian, A; Christie, W; Chung, S U; Coffin, J P; Cormier, T M; Cosentino, M R; Cramer, J G; Crawford, H J; Das, D; Dash, S; Daugherity, M; de Moura, M M; Dedovich, T G; DePhillips, M; Derevschikov, A A; Didenko, L; Dietel, T; Djawotho, P; Dogra, S M; Dong, X; Drachenberg, J L; Draper, J E; Du, F; Dunin, V B; Dunlop, J C; Dutta Mazumdar, M R; Eckardt, V; Edwards, W R; Efimov, L G; Emelianov, V; Engelage, J; Eppley, G; Erazmus, B; Estienne, M; Fachini, P; Fatemi, R; Fedorisin, J; Feng, A; Filip, P; Finch, E; Fine, V; Fisyak, Y; Fu, J; Gagliardi, C A; Gaillard, L; Ganti, M S; Garcia-Solis, E; Ghazikhanian, V; Ghosh, P; Gorbunov, Y G; Gos, H; Grebenyuk, O; Grosnick, D; Grube, B; Guertin, S M; Guimaraes, K S F F; Gupta, N; Haag, B; Hallman, T J; Hamed, A; Harris, J W; He, W; Heinz, M; Henry, T W; Heppelmann, S; Hippolyte, B; Hirsch, A; Hjort, E; Hoffman, A M; Hoffmann, G W; Hofman, D J; Hollis, R S; Horner, M J; Huang, H Z; Hughes, E W; Humanic, T J; Igo, G; Iordanova, A; Jacobs, P; Jacobs, W W; Jakl, P; Jia, F; Jones, P G; Judd, E G; Kabana, S; Kang, K; Kapitan, J; Kaplan, M; Keane, D; Kechechyan, A; Kettler, D; Khodyrev, V Yu; Kim, B C; Kiryluk, J; Kisiel, A; Kislov, E M; Klein, S R; Knospe, A G; Kocoloski, A; Koetke, D D; Kollegger, T; Kopytine, M; Kotchenda, L; Kouchpil, V; Kowalik, K L; Kravtsov, P; Kravtsov, V I; Krueger, K; Kuhn, C; Kulikov, A I; Kumar, A; Kurnadi, P; Kuznetsov, A A; Lamont, M A C; Landgraf, J M; Lange, S; LaPointe, S; Laue, F; Lauret, J; Lebedev, A; Lednicky, R; Lee, C-H; Lehocka, S; LeVine, M J; Li, C; Li, Q; Li, Y; Lin, G; Lin, X; Lindenbaum, S J; Lisa, M A; Liu, F; Liu, H; Liu, J; Liu, L; Ljubicic, T; Llope, W J; Longacre, R S; Love, W A; Lu, Y; Ludlam, T; Lynn, D; Ma, G L; Ma, J G; Ma, Y G; Mahapatra, D P; Majka, R; Mangotra, L K; Manweiler, R; Margetis, S; Markert, C; Martin, L; Matis, H S; Matulenko, Yu A; McClain, C J; McShane, T S; Melnick, Yu; Meschanin, A; Millane, J; Miller, M L; Minaev, N G; Mioduszewski, S; Mironov, C; Mischke, A; Mitchell, J; Mohanty, B; Morozov, D A; Munhoz, M G; Nandi, B K; Nattrass, C; Nayak, T K; Nelson, J M; Nepali, C; Netrakanti, P K; Nogach, L V; Nurushev, S B; Odyniec, G; Ogawa, A; Okorokov, V; Oldenburg, M; Olson, D; Pachr, M; Pal, S K; Panebratsev, Y; Pavlinov, A I; Pawlak, T; Peitzmann, T; Perevoztchikov, V; Perkins, C; Peryt, W; Phatak, S C; Planinic, M; Pluta, J; Poljak, N; Porile, N; Poskanzer, A M; Potekhin, M; Potrebenikova, E; Potukuchi, B V K S; Prindle, D; Pruneau, C; Putschke, J; Qattan, I A; Raniwala, R; Raniwala, S; Ray, R L; Relyea, D; Ridiger, A; Ritter, H G; Roberts, J B; Rogachevskiy, O V; Romero, J L; Rose, A; Roy, C; Ruan, L; Russcher, M J; Sahoo, R; Sakrejda, I; Sakuma, T; Salur, S; Sandweiss, J; Sarsour, M; Sazhin, P S; Schambach, J; Scharenberg, R P; Schmitz, N; Seger, J; Selyuzhenkov, I; Seyboth, P; Shabetai, A; Shahaliev, E; Shao, M; Sharma, M; Shen, W Q; Shimanskiy, S S; Sichtermann, E P; Simon, F; Singaraju, R N; Smirnov, N; Snellings, R; Sorensen, P; Sowinski, J; Speltz, J; Spinka, H M; Srivastava, B; Stadnik, A; Stanislaus, T D S; Staszak, D; Stock, R; Strikhanov, M; Stringfellow, B; Suaide, A A P; Suarez, M C; Subba, N L; Sumbera, M; Sun, X M; Sun, Z; Surrow, B; Symons, T J M; Szanto de Toledo, A; Takahashi, J; Tang, A H; Tarnowsky, T; Thomas, J H; Timmins, A R; Timoshenko, S; Tokarev, M; Trainor, T A; Trentalange, S; Tribble, R E; Tsai, O D; Ulery, J; Ullrich, T; Underwood, D G; Van Buren, G; van der Kolk, N; van Leeuwen, M; Vander Molen, A M; Varma, R; Vasilevski, I M; Vasiliev, A N; Vernet, R; Vigdor, S E; Viyogi, Y P; Vokal, S; Voloshin, S A; Waggoner, W T; Wang, F; Wang, G; Wang, J S; Wang, X L; Wang, Y; Watson, J W; Webb, J C; Westfall, G D; Wetzler, A; Whitten, C; Wieman, H; Wissink, S W; Witt, R; Wu, J; Wu, Y; Xu, N; Xu, Q H; Xu, Z; Yepes, P; Yoo, I-K; Yue, Q; Yurevich, V I; Zhan, W; Zhang, H; Zhang, W M; Zhang, Y; Zhang, Z P; Zhao, Y; Zhong, C; Zhou, J; Zoulkarneev, R; Zoulkarneeva, Y; Zubarev, A N; Zuo, J X
2007-09-14
We present first measurements of the phi-meson elliptic flow (v2(pT)) and high-statistics pT distributions for different centralities from radical sNN=200 GeV Au+Au collisions at RHIC. In minimum bias collisions the v2 of the phi meson is consistent with the trend observed for mesons. The ratio of the yields of the Omega to those of the phi as a function of transverse momentum is consistent with a model based on the recombination of thermal s quarks up to pT approximately 4 GeV/c, but disagrees at higher momenta. The nuclear modification factor (R CP) of phi follows the trend observed in the K S 0 mesons rather than in Lambda baryons, supporting baryon-meson scaling. These data are consistent with phi mesons in central Au+Au collisions being created via coalescence of thermalized s quarks and the formation of a hot and dense matter with partonic collectivity at RHIC. PMID:17930430
Aging Management Guideline for commercial nuclear power plants: Power and distribution transformers
Toman, G.; Gazdzinski, R.
1994-05-01
This Aging Management Guideline (AMG) provides recommended methods for effective detection and mitigation of age-related degradation mechanisms in power and distribution transformers important to license renewal in commercial nuclear power plants. The intent of this AMG to assist plant maintenance and operations personnel in maximizing the safe, useful life of these components. It also supports the documentation of effective aging management programs required under the License Renewal Rule 10 CFR Part 54. This AMG is presented in a manner which allows personnel responsible for performance analysis and maintenance to compare their plant-specific aging mechanisms (expected or already experienced) and aging management program activities to the more generic results and recommendations presented herein.
Dose distributions in phantoms irradiated in thermal columns of two different nuclear reactors.
Gambarini, G; Agosteo, S; Altieri, S; Bortolussi, S; Carrara, M; Gay, S; Nava, E; Petrovich, C; Rosi, G; Valente, M
2007-01-01
In-phantom dosimetry studies have been carried out at the thermal columns of a thermal- and a fast-nuclear reactor for investigating: (a) the spatial distribution of the gamma dose and the thermal neutron fluence and (b) the accuracy at which the boron concentration should be estimated in an explanted organ of a boron neutron capture therapy patient. The phantom was a cylinder (11 cm in diameter and 12 cm in height) of tissue-equivalent gel. Dose images were acquired with gel dosemeters across the axial section of the phantom. The thermal neutron fluence rate was measured with activation foils in a few positions of this phantom. Dose and fluence rate profiles were also calculated with Monte Carlo simulations. The trend of these profiles do not show significant differences for the thermal columns considered in this work.
NASA Astrophysics Data System (ADS)
Bhaduri, Susmita; Ghosh, Dipak
2016-08-01
There are numerous existing works on investigating the dynamics of particle production process in ultrarelativistic nuclear collision. In the past, fluctuation of spatial pattern has been analyzed in terms of the scaling behavior of voids. But analysis of the scaling behavior of the void in fractal scenario has not been explored yet. In this work, we have analyzed the fractality of void probability distribution with a completely different and rigorous method called visibility graph analysis, analyzing the void-data produced out of fluctuation of pions in 32S-AgBr interaction at 200 GeV in pseudo-rapidity (η) and azimuthal angle (ϕ) space. The power of scale-freeness of visibility graph denoted by PSVG is a measure of fractality, which can be used as a quantitative parameter for the assessment of the state of chaotic system. As the behavior of particle production process depends on the target excitation, we can dwell down the void probability distribution in the event-wise fluctuation resulted out of the high energy interaction for different degree of target excitation, with respect to the fractal scenario and analyze the scaling behavior of the voids. From the analysis of the PSVG parameter, we have observed that scaling behavior of void probability distribution in multipion production changes with increasing target excitation. Since visibility graph method is a classic method of complex network analysis, has been applied over fractional Brownian motion (fBm) and fractional Gaussian noises (fGn) to measure the fractality and long-range dependence of a time series successfully, we can quantitatively confirm that fractal behavior of the void probability distribution in particle production process depends on the target excitation.
Higgs pair production at the LHC with NLO and parton-shower effects
NASA Astrophysics Data System (ADS)
Frederix, R.; Frixione, S.; Hirschi, V.; Maltoni, F.; Mattelaer, O.; Torrielli, P.; Vryonidou, E.; Zaro, M.
2014-05-01
We present predictions for the SM-Higgs-pair production channels of relevance at the LHC: gluon-gluon fusion, VBF, and top-pair, W, Z and single-top associated production. All these results are at the NLO accuracy in QCD, and matched to parton showers by means of the MC@NLO method; hence, they are fully differential. With the exception of the gluon-gluon fusion process, for which a special treatment is needed in order to improve upon the infinite-top-mass limit, our predictions are obtained in a fully automatic way within the publicly available MADGRAPH5_AMC@NLO framework. We show that for all channels in general, and for gluon-gluon fusion and top-pair associated production in particular, NLO corrections reduce the theoretical uncertainties, and are needed in order to arrive at reliable predictions for total rates as well as for distributions.
Neufeld, Richard B.; Vitev, Ivan M.
2011-01-01
We derive the distribution of energy and momentumtransmitted from a primary fast parton and its medium-induced bremsstrahlung gluons to a thermalized quark-gluon plasma. Our calculation takes into account the important and thus far neglected effects of quantum interference between the resulting color currents. We use our result to obtain the rate at which energy is absorbed by the medium as a function of time and find that the rate is modified by the quantum interference between the primary parton and secondary gluons. This Landau-Pomeranchuk-Migdal type interference persists for time scales relevant to heavy ion phenomenology. We further couple the newly derived source of energy and momentum deposition to linearized hydrodynamics to obtain the bulk medium response to realistic parton propagation and splitting in the quark-gluon plasma. We find that because of the characteristic large angle in-medium gluon emission and the multiple sources of energy deposition in a parton shower, formation of well defined Mach cones by energetic jets in heavy ion reactions is not likely.
Intermediate/high energy nuclear physics. [Iowa State Univ. , Ames, Iowa
Vary, J.P.
1992-01-01
Progress during the last year is reviewed under the following topics: relativistic hadron--nucleus and nucleus--nucleus collisions (heavy meson production, photon production and fragmentation functions--direct photon production with the QCM and photon fragmentation functions, Cronin efffect and multiple scattering, effective nuclear parton distributions); solving quantum field theories in nonperturbative regime; light-front dynamics and high-spin states (soft form factor of the pion and nucleon for transverse and longitudinal momentum transfers, light front spinors for high-spin objects); high-energy spin physics; relativistic wave equations, quarkonia, and e[sup +]e[sup [minus
Implementing the LPM effect in a parton cascade model
NASA Astrophysics Data System (ADS)
Coleman-Smith, C. E.; Bass, S. A.; Srivastava, D. K.
2011-07-01
Parton Cascade Models (PCM [K. Geiger, B. Muller, Nucl. Phys. B369 (1992) 600-654; S. A. Bass, B. Muller, D. K. Srivastava, Phys. Lett. B551 (2003) 277-283; Z. Xu and C. Greiner, Phys. Rev. C 76, 024911 (2007); D. Molnar and M. Gyulassy, Phys. Rev. C 62, 054907 (2000)]), which describe the full time-evolution of a system of quarks and gluons using pQCD interactions are ideally suited for the description of jet production, including the emission, evolution and energy-loss of the full parton shower in a hot and dense QCD medium. The Landau-Pomeranchuk-Migdal (LPM) effect [L. D. Landau, I. J. Pomeranchuk, Dolk. Akad. Nauk. SSSR 92 (92); A. B. Migdal, Phys. Rev. 103 (6) (1956) 1811-1820], the quantum interference of parton wave functions due to repeated scatterings against the background medium, is likely the dominant in-medium effect affecting jet suppression. We have implemented a probabilistic implementation of the LPM effect [K. Zapp, J. Stachel, U. A. Wiedemann, Phys. Rev. Lett. 103 (2009) 152302] within the PCM which can be validated against previously derived analytical calculations by Baier et al (BDMPS-Z) [R. Baier, Y. L. Dokshitzer, A. H. Mueller, S. Peigne, D. Schiff, Nucl. Phys. B478 (1996) 577-597; R. Baier, Y. L. Dokshitzer, S. Peigne, D. Schiff, Phys. Lett. B345 (1995) 277-286; R. Baier, Y. L. Dokshitzer, A. H. Mueller, S. Peigne, D. Schiff, Nucl. Phys. B483 (1997) 291-320; B. Zakharov, JETP Lett. 63 (1996) 952-957; B. Zakharov, JETP Lett. 65 (1997) 615-620]. Presented at the 6th International Conference on Physics and Astrophysics of Quark Gluon Plasma (ICPAQGP 2010).
PHANTOM: A Monte Carlo event generator for six parton final states at high energy colliders
NASA Astrophysics Data System (ADS)
Ballestrero, Alessandro; Belhouari, Aissa; Bevilacqua, Giuseppe; Kashkan, Vladimir; Maina, Ezio
2009-03-01
PHANTOM is a tree level Monte Carlo for six parton final states at proton-proton, proton-antiproton and electron-positron colliders at O(αEM6) and O(αEM4αS2) including possible interferences between the two sets of diagrams. This comprehends all purely electroweak contributions as well as all contributions with one virtual or two external gluons. It can generate unweighted events for any set of processes and it is interfaced to parton shower and hadronization packages via the latest Les Houches Accord protocol. It can be used to analyze the physics of boson-boson scattering, Higgs boson production in boson-boson fusion, tt¯ and three boson production. Program summaryProgram title:PHANTOM (V. 1.0) Catalogue identifier: AECE_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AECE_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 175 787 No. of bytes in distributed program, including test data, etc.: 965 898 Distribution format: tar.gz Programming language: Fortran 77 Computer: Any with a UNIX, LINUX compatible Fortran compiler Operating system: UNIX, LINUX RAM: 500 MB Classification: 11.1 External routines: LHAPDF (Les Houches Accord PDF Interface, http://projects.hepforge.org/lhapdf/), CIRCE (beamstrahlung for ee ILC collider). Nature of problem: Six fermion final state processes have become important with the increase of collider energies and are essential for the study of top, Higgs and electroweak symmetry breaking physics at high energy colliders. Since thousands of Feynman diagrams contribute in a single process and events corresponding to hundreds of different final states need to be generated, a fast and stable calculation is needed. Solution method:PHANTOM is a tree level Monte Carlo for six parton final states at proton-proton, proton-antiproton and
Parton-hadron matter in- and out-off equilibrium
NASA Astrophysics Data System (ADS)
Bratkovskaya, E. L.; Ozvenchuk, V.; Cassing, W.; Konchakovski, V. P.; Linnyk, O.
2013-08-01
We study the shear and bulk viscosities of partonic and hadronic matter - as well as the electric conductivity - as functions of temperature T within the Parton-Hadron-String Dynamics (PHSD) off-shell transport approach. Dynamical hadronic and partonic systems in equilibrium are studied by the PHSD simulations in a finite box with periodic boundary conditions. The ratio of the shear viscosity to entropy density η(T)/s(T) from PHSD shows a minimum (with a value of about 0.1) close to the critical temperature Tc, while it approaches the perturbative QCD (pQCD) limit at higher temperatures in line with lattice QCD results. For T < Tc, i.e. in the hadronic phase, the ratio η/s rises fast with decreasing temperature due to a lower interaction rate of the hadronic system and a significantly smaller number of degrees-of-freedom. The bulk viscosity ζ(T) - evaluated in the relaxation time approach - is found to strongly depend on the effects of mean fields (or potentials) in the partonic phase. We find a significant rise of the ratio ζ(T)/s(T) in the vicinity of the critical temperature Tc, when consistently including the scalar mean-field from PHSD, which is also in agreement with that from lQCD calculations. Furthermore, we present the results for the ratio (η + 3ζ/4)/s, which is found to depend non-trivially on temperature and to generally agree with the lQCD calculations as well. Within the PHSD calculations, the strong maximum of ζ(T)/η(T) close to Tc has to be attributed to mean-fields (or potential) effects that in PHSD are encoded in the temperature dependence of the quasiparticle masses, which is related to the infrared enhancement of the resummed (effective) coupling g(T). We also find that the dimensionless ratio of the electric conductivity over temperature σ0/T rises above Tc approximately linearly with T up to T = 2.5Tc, but approaches a constant above 5Tc, as expected qualitatively from perturbative QCD (pQCD).
An emergent world of gauge force and partons
NASA Astrophysics Data System (ADS)
Ma, Yao; Weng, Zheng-Yu
2014-09-01
We illustrate how a completely new world of gauge force emerges from a conventional condensed matter system in a rigorous way. A characteristic energy scale (Mott gap) separates such an exotic universe from the ordinary one that we condensed matter physicists are more familiar with at higher energies. The governing physical law is no longer about individual electrons but concerns fractionalized particles, i.e., partons, as the new collective modes resulted from strong correlation among the electrons. Novel phenomena in this low-energy universe are clearly distinguished from Landau's Fermi liquid described by the perturbative quantum many-body theory.
Litvinchuk, Spartak N; Rosanov, Jury M; Borkin, Leo J
2007-04-01
We used flow cytometry to measure the nuclear DNA content in erythrocytes of 27 salamandrid species. Across these species, diploid genome size varied more than 2 fold (51.3-104.4 pg). According to genome size and geographic distribution, 3 groups of newt species were recognized: West Palearctics with smaller amounts of nuclear DNA; Nearctic, with intermediate values; and East Asiatic, with higher genome sizes. Viviparous West Palearctic salamanders differed from most of the oviparous West Palearctic newts in possessing larger genome sizes. The nuclear DNA content strongly correlates with species range limits. At the same temperature, embryos of salamandrid species with larger genome sizes have a markedly longer developmental time than those with smaller genomes. We present an analysis of the relationships between the amount of nuclear DNA and water temperature at the breeding sites.
NASA Astrophysics Data System (ADS)
Chang, Ning-Bo; Qin, Guang-You
2016-08-01
We study the evolution of the full jet shower in quark-gluon plasma by solving a set of coupled differential transport equations for the three-dimensional momentum distributions of quarks and gluons contained in full jets. In our jet evolution equations, we include all partonic splitting processes as well as the collisional energy loss and transverse momentum broadening for both the leading and radiated partons of the full jets. Combining with a realistic (2 +1 )-dimensional viscous hydrodynamic simulation for the spacetime profiles of the hot and dense nuclear medium produced in heavy-ion collisions, we apply our formalism to calculate the nuclear modification of single inclusive full jet spectra, the momentum imbalance of photon-jet and dijet pairs, and the jet shape function (at partonic level) in Pb+Pb collisions at 2.76 A TeV. The roles of various jet-medium interaction mechanisms on the full jet modification are studied. We find that the nuclear modification of jet shape is sensitive to the interplay of different interaction mechanisms as well as the energies of the full jets.
Distribution of Pico- and Nanosecond Motions in Disordered Proteins from Nuclear Spin Relaxation.
Khan, Shahid N; Charlier, Cyril; Augustyniak, Rafal; Salvi, Nicola; Déjean, Victoire; Bodenhausen, Geoffrey; Lequin, Olivier; Pelupessy, Philippe; Ferrage, Fabien
2015-09-01
Intrinsically disordered proteins and intrinsically disordered regions (IDRs) are ubiquitous in the eukaryotic proteome. The description and understanding of their conformational properties require the development of new experimental, computational, and theoretical approaches. Here, we use nuclear spin relaxation to investigate the distribution of timescales of motions in an IDR from picoseconds to nanoseconds. Nitrogen-15 relaxation rates have been measured at five magnetic fields, ranging from 9.4 to 23.5 T (400-1000 MHz for protons). This exceptional wealth of data allowed us to map the spectral density function for the motions of backbone NH pairs in the partially disordered transcription factor Engrailed at 11 different frequencies. We introduce an approach called interpretation of motions by a projection onto an array of correlation times (IMPACT), which focuses on an array of six correlation times with intervals that are equidistant on a logarithmic scale between 21 ps and 21 ns. The distribution of motions in Engrailed varies smoothly along the protein sequence and is multimodal for most residues, with a prevalence of motions around 1 ns in the IDR. We show that IMPACT often provides better quantitative agreement with experimental data than conventional model-free or extended model-free analyses with two or three correlation times. We introduce a graphical representation that offers a convenient platform for a qualitative discussion of dynamics. Even when relaxation data are only acquired at three magnetic fields that are readily accessible, the IMPACT analysis gives a satisfactory characterization of spectral density functions, thus opening the way to a broad use of this approach. PMID:26331256
Distribution of Pico- and Nanosecond Motions in Disordered Proteins from Nuclear Spin Relaxation
Khan, Shahid N.; Charlier, Cyril; Augustyniak, Rafal; Salvi, Nicola; Déjean, Victoire; Bodenhausen, Geoffrey; Lequin, Olivier; Pelupessy, Philippe; Ferrage, Fabien
2015-01-01
Intrinsically disordered proteins and intrinsically disordered regions (IDRs) are ubiquitous in the eukaryotic proteome. The description and understanding of their conformational properties require the development of new experimental, computational, and theoretical approaches. Here, we use nuclear spin relaxation to investigate the distribution of timescales of motions in an IDR from picoseconds to nanoseconds. Nitrogen-15 relaxation rates have been measured at five magnetic fields, ranging from 9.4 to 23.5 T (400–1000 MHz for protons). This exceptional wealth of data allowed us to map the spectral density function for the motions of backbone NH pairs in the partially disordered transcription factor Engrailed at 11 different frequencies. We introduce an approach called interpretation of motions by a projection onto an array of correlation times (IMPACT), which focuses on an array of six correlation times with intervals that are equidistant on a logarithmic scale between 21 ps and 21 ns. The distribution of motions in Engrailed varies smoothly along the protein sequence and is multimodal for most residues, with a prevalence of motions around 1 ns in the IDR. We show that IMPACT often provides better quantitative agreement with experimental data than conventional model-free or extended model-free analyses with two or three correlation times. We introduce a graphical representation that offers a convenient platform for a qualitative discussion of dynamics. Even when relaxation data are only acquired at three magnetic fields that are readily accessible, the IMPACT analysis gives a satisfactory characterization of spectral density functions, thus opening the way to a broad use of this approach. PMID:26331256
LHAPDF6: parton density access in the LHC precision era
NASA Astrophysics Data System (ADS)
Buckley, Andy; Ferrando, James; Lloyd, Stephen; Nordström, Karl; Page, Ben; Rüfenacht, Martin; Schönherr, Marek; Watt, Graeme
2015-03-01
The Fortran LHAPDF library has been a long-term workhorse in particle physics, providing standardised access to parton density functions for experimental and phenomenological purposes alike, following on from the venerable PDFLIB package. During Run 1 of the LHC, however, several fundamental limitations in LHAPDF's design have became deeply problematic, restricting the usability of the library for important physics-study procedures and providing dangerous avenues by which to silently obtain incorrect results. In this paper we present the LHAPDF 6 library, a ground-up re-engineering of the PDFLIB/LHAPDF paradigm for PDF access which removes all limits on use of concurrent PDF sets, massively reduces static memory requirements, offers improved CPU performance, and fixes fundamental bugs in multi-set access to PDF metadata. The new design, restricted for now to interpolated PDFs, uses centralised numerical routines and a powerful cascading metadata system to decouple software releases from provision of new PDF data and allow completely general parton content. More than 200 PDF sets have been migrated from LHAPDF 5 to the new universal data format, via a stringent quality control procedure. LHAPDF 6 is supported by many Monte Carlo generators and other physics programs, in some cases via a full set of compatibility routines, and is recommended for the demanding PDF access needs of LHC Run 2 and beyond.
Radiation dose distribution for workers in South Korean nuclear power plants.
Lee, Byoung-il; Kim, So-i; Suh, Dong-hee; Jin, Young-woo; Kim, Jeong-in; Choi, Hoon; Lim, Young-khi
2010-07-01
A total of 33 680 nuclear power plants (NPPs) workers were monitored and recorded from 1990 to 2007. According to the record, the average individual radiation dose has been decreasing continually from 3.20 mSv man(-1) in 1990 to 1.12 mSv man(-1) at the end of 2007. After the International Commission on Radiological Protection 60 recommendation was generalised in South Korea, no NPP workers received >20 mSv radiation, and the numbers of relatively highly exposed workers have been decreasing continuously. The age distribution of radiation workers in NPPs was composed mainly of 20-30 y olds (83 %) for 1990-1994 and 30-40 y olds (75 %) for 2003-2007. The difference in individual average dose by age was not significant. Most (77 %) of the NPP radiation exposures from 1990 to 2007 occurred mostly during the refueling period. With regard to exposure type, the majority of exposures was external exposures, representing 95 % of the total exposures, whereas internal exposures represented only 5 %. External effective dose was affected mainly by gamma radiation exposure, with an insignificant amount of neutron exposure. As for internal effective dose, tritium in the pressurised heavy water reactor was the biggest cause of exposure.
Woo, Tai-Ting; Chao, Ju-Lan; Yao, Meng-Chao
2016-03-01
Bi-directional non-coding transcripts and their ∼29-nt small RNA products are known to guide DNA deletion in Tetrahymena, leading to the removal of one-third of the genome from developing somatic nuclei. Using an antibody specific for long double-stranded RNAs (dsRNAs), we determined the dynamic subcellular distributions of these RNAs. Conjugation-specific dsRNAs were found and show sequential appearances in parental germline, parental somatic nuclei and finally in new somatic nuclei of progeny. The dsRNAs in germline nuclei and new somatic nuclei are likely transcribed from the sequences destined for deletion; however, the dsRNAs in parental somatic nuclei are unexpected, and PCR analyses suggested that they were transcribed in this nucleus. Deficiency in the RNA interference (RNAi) pathway led to abnormal aggregations of dsRNA in both the parental and new somatic nuclei, whereas accumulation of dsRNAs in the germline nuclei was only seen in the Dicer-like gene mutant. In addition, RNAi mutants displayed an early loss of dsRNAs from developing somatic nuclei. Thus, long dsRNAs are made in multiple nuclear compartments and some are linked to small RNA production whereas others might participate in their regulations. PMID:26769902
Hawkley, Gavin
2014-01-01
Atmospheric dispersion modeling within the near field of a nuclear facility typically applies a building wake correction to the Gaussian plume model, whereby a point source is modeled as a plane source. The plane source results in greater near field dilution and reduces the far field effluent concentration. However, the correction does not account for the concentration profile within the near field. Receptors of interest, such as the maximally exposed individual, may exist within the near field and thus the realm of building wake effects. Furthermore, release parameters and displacement characteristics may be unknown, particularly during upset conditions. Therefore, emphasis is placed upon the need to analyze and estimate an enveloping concentration profile within the near field of a release. This investigation included the analysis of 64 air samples collected over 128 wk. Variables of importance were then derived from the measurement data, and a methodology was developed that allowed for the estimation of Lorentzian-based dispersion coefficients along the lateral axis of the near field recirculation cavity; the development of recirculation cavity boundaries; and conservative evaluation of the associated concentration profile. The results evaluated the effectiveness of the Lorentzian distribution methodology for estimating near field releases and emphasized the need to place air-monitoring stations appropriately for complete concentration characterization. Additionally, the importance of the sampling period and operational conditions were discussed to balance operational feedback and the reporting of public dose.
Kinase, Sakae; Takahashi, Tomoyuki; Sato, Satoshi; Sakamoto, Ryuichi; Saito, Kimiaki
2014-08-01
Preliminary prediction models have been studied for the radioactive caesium distribution within the 80-km radius of the Fukushima Daiichi nuclear power plant. The models were represented by exponential functions using ecological half-life of radioactive caesium in the environment. The ecological half-lives were derived from the changes in ambient dose equivalent rates through vehicle-borne surveys. It was found that the ecological half-lives of radioactive caesium were not constant within the 80-km radius of the Fukushima Daiichi nuclear power plant. The ecological half-life of radioactive caesium in forest areas was found to be much larger than that in urban and water areas.
A New Insight into Energy Distribution of Electrons in Fuel-Rod Gap in VVER-1000 Nuclear Reactor
NASA Astrophysics Data System (ADS)
Fereshteh, Golian; Ali, Pazirandeh; Saeed, Mohammadi
2015-06-01
In order to calculate the electron energy distribution in the fuel rod gap of a VVER-1000 nuclear reactor, the Fokker-Planck equation (FPE) governing the non-equilibrium behavior of electrons passing through the fuel-rod gap as an absorber has been solved in this paper. Besides, the Monte Carlo Geant4 code was employed to simulate the electron migration in the fuel-rod gap and the energy distribution of electrons was found. As for the results, the accuracy of the FPE was compared to the Geant4 code outcomes and a satisfactory agreement was found. Also, different percentage of the volatile and noble gas fission fragments produced in fission reactions in fuel rod, i.e. Krypton, Xenon, Iodine, Bromine, Rubidium and Cesium were employed so as to investigate their effects on the electrons' energy distribution. The present results show that most of the electrons in the fuel rod's gap were within the thermal energy limitation and the tail of the electron energy distribution was far from a Maxwellian distribution. The interesting outcome was that the electron energy distribution is slightly increased due to the accumulation of fission fragments in the gap. It should be noted that solving the FPE for the energy straggling electrons that are penetrating into the fuel-rod gap in the VVER-1000 nuclear reactor has been carried out for the first time using an analytical approach.
Microwave Field Distribution in a Magic Angle Spinning Dynamic Nuclear Polarization NMR Probe
Nanni, Emilio A.; Barnes, Alexander B.; Matsuki, Yoh; Woskov, Paul P.; Corzilius, Björn; Griffin, Robert G.; Temkin, Richard J.
2011-01-01
We present a calculation of the microwave field distribution in a magic angle spinning (MAS) probe utilized in dynamic nuclear polarization (DNP) experiments. The microwave magnetic field (B1S) profile was obtained from simulations performed with the High Frequency Structure Simulator (HFSS) software suite, using a model that includes the launching antenna, the outer Kel-F stator housing coated with Ag, the RF coil, and the 4 mm diameter sapphire rotor containing the sample. The predicted average B1S field is 13µT/W1/2, where S denotes the electron spin. For a routinely achievable input power of 5 W the corresponding value is γ SB1S = 0.84 MHz. The calculations provide insights into the coupling of the microwave power to the sample, including reflections from the RF coil and diffraction of the power transmitted through the coil. The variation of enhancement with rotor wall thickness was also successfully simulated. A second, simplified calculation was performed using a single pass model based on Gaussian beam propagation and Fresnel diffraction. This model provided additional physical insight and was in good agreement with the full HFSS simulation. These calculations indicate approaches to increasing the coupling of the microwave power to the sample, including the use of a converging lens and fine adjustment of the spacing of the windings of the RF coil. The present results should prove useful in optimizing the coupling of microwave power to the sample in future DNP experiments. Finally, the results of the simulation were used to predict the cross effect DNP enhancement (ε) vs. ω1S/(2π) for a sample of 13C-urea dissolved in a 60:40 glycerol/water mixture containing the polarizing agent TOTAPOL; very good agreement was obtained between theory and experiment. PMID:21382733
The distribution of nuclear genetic variation and historical demography of sea otters
Aguilar, A.; Jessup, David A.; Estes, James; Garza, J.C.
2008-01-01
The amount and distribution of population genetic variation is crucial information for the design of effective conservation strategies for endangered species and can also be used to provide inference about demographic processes and patterns of migration. Here, we describe variation at a large number of nuclear genes in sea otters Enhydra lutris ssp. We surveyed 14 variable microsatellite loci and two genes of the major histocompatibility complex (MHC) in up to 350 California sea otters Enhydra lutris nereis, which represents ???10% of the subspecies' population, and 46 otters from two Alaskan sites. We utilized methods for detecting past reductions in effective population size to examine the effects of near extinction from the fur trade. Summary statistic tests largely failed to find a signal of a recent population size reduction (within the past 200years), but a Bayesian method found a signal of a strong reduction over a longer time scale (up to 500years ago). These results indicate that the reduction in size began long enough ago that much genetic variation was lost before the 19th century fur trade. A comparison of geographic distance and pairwise relatedness for individual otters found no evidence of kin-based spatial clustering for either gender. This indicates that there is no population structure, due to extended family groups, within the California population. A survey of population genetic variation found that two of the MHC genes, DQB and DRB, had two alleles present and one of the genes, DRA, was monomorphic in otters. This contrasts with other mammals, where they are often the most variable coding genes known. Genetic variation in the sea otter is among the lowest observed for a mammal and raises concerns about the long-term viability of the species, particularly in the face of future environmental changes. ?? Journal compilation ?? 2007 The Zoological Society of London No claim to original US government works.
Double parton effects for jets with large rapidity separation
Szczurek, Antoni; Cisek, Anna; Maciuła, Rafal
2015-04-10
We discuss production of four jets pp → jjjjX with at least two jets with large rapidity separation in proton-proton collisions at the LHC through the mechanism of double-parton scattering (DPS). The cross section is calculated in a factorizaed approximation. Each hard subprocess is calculated in LO collinear approximation. The LO pQCD calculations are shown to give a reasonably good descritption of CMS and ATLAS data on inclusive jet production. It is shown that relative contribution of DPS is growing with increasing rapidity distance between the most remote jets, center-of-mass energy and with decreasing (mini)jet transverse momenta. We show also result for angular azimuthal dijet correlations calculated in the framework of k{sub t} -factorization approximation.
Storch, Kirsten N; Taatjes, Douglas J; Bouffard, Nicole A; Locknar, Sarah; Bishop, Nicole M; Langevin, Helene M
2007-05-01
Alpha smooth muscle actin (alpha-SMA) was recently shown to be present in mouse subcutaneous tissue fibroblasts in the absence of tissue injury. In this study, we used a combination of immunohistochemistry and correlative confocal scanning laser and electron microscopy to investigate the structural organization of alpha-SMA in relation to the nucleus. Furthermore, we explored colocalization analysis as a method for quantifying the amount of alpha-SMA in close approximation to the nucleic acid marker, 4',6-diamidino-2-phenyl-indole, dihydrochloride. Our findings indicate the presence of alpha-SMA within nuclear invaginations in close proximity to the nuclear membrane, but not in the nucleoplasm. Although the function of these alpha-SMA-rich nuclear invaginations is at present unknown, the morphology of these structures suggests their possible involvement in cellular and nuclear mechanotransduction as well as nuclear transport.
Bouhouche, Khaled; Zickler, Denise; Debuchy, Robert; Arnaise, Sylvie
2004-01-01
Repeat-induced point mutation (RIP) is a homology-dependent gene-silencing mechanism that introduces C:G-to-T:A transitions in duplicated DNA segments. Cis-duplicated sequences can also be affected by another mechanism called premeiotic recombination (PR). Both are active over the sexual cycle of some filamentous fungi, e.g., Neurospora crassa and Podospora anserina. During the sexual cycle, several developmental steps require precise nuclear movement and positioning, but connections between RIP, PR, and nuclear distributions have not yet been established. Previous work has led to the isolation of ami1, the P. anserina ortholog of the Aspergillus nidulans apsA gene, which is required for nuclear positioning. We show here that ami1 is involved in nuclear distribution during the sexual cycle and that alteration of ami1 delays the fruiting-body development. We also demonstrate that ami1 alteration affects loss of transgene functions during the sexual cycle. Genetically linked multiple copies of transgenes are affected by RIP and PR much more frequently in an ami1 mutant cross than in a wild-type cross. Our results suggest that the developmental slowdown of the ami1 mutant during the period of RIP and PR increases time exposure to the duplication detection system and thus increases the frequency of RIP and PR. PMID:15166143
NASA Astrophysics Data System (ADS)
Godinho, R. M.; Cabrita, M. T.; Alves, L. C.; Pinheiro, T.
2015-04-01
Studies of the elemental composition of whole marine diatoms cells have high interest as they constitute a direct measurement of environmental changes, and allow anticipating consequences of anthropogenic alterations to organisms, ecosystems and global marine geochemical cycles. Nuclear microscopy is a powerful tool allowing direct measurement of whole cells giving qualitative imaging of distribution, and quantitative determination of intracellular concentration. Major obstacles to the analysis of marine microalgae are high medium salinity and the recurrent presence of extracellular exudates produced by algae to maintain colonies in natural media and in vitro. The objective of this paper was to optimize the methodology of sample preparation of marine unicellular algae for elemental analysis with nuclear microscopy, allowing further studies on cellular response to metals. Primary cultures of Coscinodiscus wailesii maintained in vitro were used to optimize protocols for elemental analysis with nuclear microscopy techniques. Adequate cell preparation procedures to isolate the cells from media components and exudates were established. The use of chemical agents proved to be inappropriate for elemental determination and for intracellular morphological analysis. The assessment of morphology and elemental partitioning in cell compartments obtained with nuclear microscopy techniques enabled to infer their function in natural environment and imbalances in exposure condition. Exposure to metal affected C. wailesii morphology and internal elemental distribution.
Proposal for Drell-Yan Measurements of Nucleon and Nuclear Structure with the FNAL Main Injector
Isenhower, L.D.; Sadler, M.E.; Arrinton, J.; Geesamn, D.F.; Holt, R.J.; Jackson, H.E.; Reimer, P.E.; Potterveld, D.H.; Brown, C.N.; Garvey, G.T.; Leitch, M.J.; /Los Alamos /Rutgers U. /Texas A-M /Valparaiso U.
2001-04-01
We propose measuring the fractional momentum (x) dependence of the ratio of the anti-down to anti-up quark distributions in the proton, {bar d}(x)/{bar u}(x), using proton induced Drell-Yan reactions at 120 GeV. Recent measurements by FNAL E866 unexpectedly show considerable x dependence in this ratio for x > 0.2. A lower energy primary proton beam from the Main Injector makes it possible to extend the E866 measurements to larger x with much higher precision. The apparatus will also be used with nuclear targets to measure parton energy loss and modifications to anti-quark distributions in nuclear targets at large x (x > 0.2).
Virtual photon structure functions and the parton content of the electron
Drees, M. ); Godbole, R.M. )
1994-09-01
We point out that in processes involving the parton content of the photon the usual effective photon approximation should be modified. The reason is that the parton content of virtual photons is logarithmically suppressed compared to real photons. We describe this suppression using several simple, physically motivated [ital Ansa]$[ital uml---tze]. Although the parton content of the electron in general no longer factorizes into an electron flux function and a photon structure function, it can still be expressed as a single integral. Numerical examples are given for the [ital e][sup +][ital e][sup [minus
Hard photon production and matrix-element parton-shower merging
Hoeche, Stefan; Schumann, Steffen; Siegert, Frank
2010-02-01
We present a Monte Carlo approach to prompt-photon production, where photons and QCD partons are treated democratically. The photon fragmentation function is modeled by an interleaved QCD+QED parton shower. This known technique is improved by including higher-order real-emission matrix elements. To this end, we extend a recently proposed algorithm for merging matrix elements and truncated parton showers. We exemplify the quality of the Monte Carlo predictions by comparing them to measurements of the photon fragmentation function at LEP and to measurements of prompt photon and diphoton production from the Tevatron experiments.
Tools for the Future of Nuclear Physics
NASA Astrophysics Data System (ADS)
Geesaman, Donald
2014-03-01
The challenges of Nuclear Physics, especially in understanding strongly interacting matter in all its forms in the history of the universe, place ever higher demands on the tools of the field, including the workhorse, accelerators. These demands are not just higher energy and higher luminosity. To recreate the matter that fleetingly was formed in the origin of the heavy elements, we need higher power heavy-ion accelerators and creative techniques to harvest the isotopes. We also need high-current low-energy accelerators deep underground to detect the very slow rate reactions in stellar burning. To explore the three dimensional distributions of high-momentum quarks in hadrons and to search for gluonic excitations we need high-current CW electron accelerators. Understanding the gluonic structure of nuclei and the three dimensional distributions of partons at lower x, we need high-luminosity electron-ion colliders that also have the capabilities to prepare, preserve and manipulate the polarization of both beams. A search for the critical point in the QCD phase diagram demands high luminosity beams over a broad range of species and energy. With advances in cavity design and construction, beam manipulation and cooling, and ion sources and targets, the Nuclear Physics community, in the U.S. and internationally has a coordinated vision to deliver this exciting science. This work is supported by DOE, Office of Nuclear Physics, under contract DE-AC02-06CH11357.
Miyamoto, Yutaka; Yasuda, Kenichiro; Magara, Masaaki
2014-06-01
Airborne radioactive particles released by the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident in 2011 were collected with a cascade low-pressure impactor at the Japan Atomic Energy Agency (JAEA) in Tokai, Japan, 114 km south of the FDNPP. Size-fractionated samples were collected twice, in the periods of March 17-April 1, 2011, and May 9-13, 2011. These size-fractionated samplings were carried out in the earliest days at a short distance from the FDNPP. Radioactivity of short-lived nuclides (several ten days of half-life) was determined as well as (134)Cs and (137)Cs. The elemental composition of size-fractionated samples was also measured. In the first collection, the activity median aerodynamic diameter (AMAD) of (129m)Te, (140)Ba, (134)Cs, (136)Cs and (137)Cs was 1.5-1.6 μm, while the diameter of (131)I was 0.45 μm. The diameters of (134)Cs and (137)Cs in the second collection were expressed as three peaks at <0.5 μm, 0.94 μm, and 7.8 μm. The (134)Cs/(137)Cs ratio of the first collection was 1.02 in total, but the ratio in the fine fractions was 0.91. A distribution map of (134)Cs/(137)Cs - (136)Cs/(137)Cs ratios was helpful in understanding the change of radioactive Cs composition. The Cs composition of size fractions <0.43 μm and the composition in the 1.1-2.1 μm range (including the AMAD of 1.5-1.6 μm) were similar to the calculated compositions of fuels in the reactors No. 1 and No. 3 at the FDNPP using the ORIGEN-II code. The Cs composition collected in May, 2011 was similar to the calculation results of reactor No. 2 fuel composition. The change of Cs composition implies that the radioactive Cs was released from the three reactors at the FDNPP via different processes.
Computer program for afterheat temperature distribution for mobile nuclear power plant
NASA Technical Reports Server (NTRS)
Parker, W. G.; Vanbibber, L. E.
1972-01-01
ESATA computer program was developed to analyze thermal safety aspects of post-impacted mobile nuclear power plants. Program is written in FORTRAN 4 and designed for IBM 7094/7044 direct coupled system.
Direct Estimation of Power Distribution in Reactors for Nuclear Thermal Space Propulsion
NASA Astrophysics Data System (ADS)
Aldemir, Tunc; Miller, Don W.; Burghelea, Andrei
2004-02-01
A recently proposed constant temperature power sensor (CTPS) has the capability to directly measure the local power deposition rate in nuclear reactor cores proposed for space thermal propulsion. Such a capability reduces the uncertainties in the estimated power peaking factors and hence increases the reliability of the nuclear engine. The CTPS operation is sensitive to the changes in the local thermal conditions. A procedure is described for the automatic on-line calibration of the sensor through estimation of changes in thermal .conditions.
Direct Estimation of Power Distribution in Reactors for Nuclear Thermal Space Propulsion
Aldemir, Tunc; Miller, Don W.; Burghelea, Andrei
2004-02-04
A recently proposed constant temperature power sensor (CTPS) has the capability to directly measure the local power deposition rate in nuclear reactor cores proposed for space thermal propulsion. Such a capability reduces the uncertainties in the estimated power peaking factors and hence increases the reliability of the nuclear engine. The CTPS operation is sensitive to the changes in the local thermal conditions. A procedure is described for the automatic on-line calibration of the sensor through estimation of changes in thermal conditions.
Rosinski, S.T. ); Kennedy, E.L.; Foulds, J.R. )
1990-01-01
Pressurized water reactor pressure vessels operate under US Nuclear Regulatory Commission (NRC) rules and regulatory guides that are intended to maintain a low probability of vessel failure. The NRC has also addressed neutron embrittlement of pressurized water reactor pressure vessels by imposing regulations on plant operation. Plants failing to meet the operating criteria specified by these rules and regulations are required, among other things, to analytically demonstrate fitness for service in order to continue safe operation. The initial flaw size or distribution of initial vessel flaws is a key input to the required vessel integrity analyses. A fracture mechanics sensitivity study was performed to quantify the effect of the assumed flaw distribution on the predicted vessel performance under a specified pressurized thermal shock transient and to determine the critical crack size. Results of the analysis indicate that vessel performance in terms of the estimated probability of failure is very sensitive to the assumed flaw distribution. 20 refs., 3 figs., 2 tabs.
Thornton, Blair; Ohnishi, Seiki; Ura, Tamaki; Odano, Naoteru; Sasaki, Shun; Fujita, Tsuneo; Watanabe, Tomowo; Nakata, Kaoru; Ono, Tsuneo; Ambe, Daisuke
2013-09-15
An estimated 3.5±0.7×10(15) Bq of (137)Cs is thought to have been discharged into the ocean following the melt down at Fukushima Dai-ichi Nuclear Power Plant (F1NPP). While efforts have been made to monitor seafloor radiation levels, the sampling techniques used cannot capture the continuous distribution of radionuclides. In this work, we apply in situ measurement techniques using a towed gamma ray spectrometer to map the continuous distribution of (137)Cs on the seafloor within 20 km of the F1NPP. The results reveal the existence of local (137)Cs anomalies, with levels of (137)Cs an order of magnitude higher than the surrounding seafloors. The sizes of the anomalies mapped in this work range from a few meters to a few hundreds of meters in length, and it is demonstrated that the distribution of these anomalies is strongly influenced by meter scale features of the terrain.
NASA Astrophysics Data System (ADS)
Grabitz, P.; Andrianov, V.; Bishop, S.; Blanc, A.; Dubey, S.; Echler, A.; Egelhof, P.; Faust, H.; Gönnenwein, F.; Gomez-Guzman, J. M.; Köster, U.; Kraft-Bermuth, S.; Mutterer, M.; Scholz, P.; Stolte, S.
2016-08-01
Calorimetric low temperature detectors (CLTD's) for heavy-ion detection have been combined with the LOHENGRIN recoil separator at the ILL Grenoble for the determination of nuclear charge distributions of fission fragments produced by thermal neutron-induced fission of ^{235}U. The LOHENGRIN spectrometer separates fission fragments according to their mass-to-ionic-charge ratio and their kinetic energy, but has no selectivity with respect to nuclear charges Z. For the separation of the nuclear charges, one can exploit the nuclear charge-dependent energy loss of the fragments passing through an energy degrader foil (absorber method). This separation requires detector systems with high energy resolution and negligible pulse height defect, as well as degrader foils which are optimized with respect to thickness, homogeneity, and energy loss straggling. In the present, contribution results of test measurements at the Maier Leibnitz tandem accelerator facility in Munich with ^{109}Ag and ^{127}I beams with the aim to determine the most suitable degrader material, as well as measurements at the Institut Laue-Langevin will be presented. These include a systematic study of the quality of Z-separation of fission fragments in the mass range 82le A le 132 and a systematic measurement of ^{92}Rb fission yields, as well as investigations of fission yields toward the symmetry region.
Comparing multiparticle production within a two-component dual parton model with collider data
Hahn, K.; Ranft, J. )
1990-03-01
The dual parton model (DPM) is very successful in describing hadronic multiparticle production. The version of DPM presented includes both soft and hard mechanisms. The hard component is described according to the lowest-order perturbative QCD--parton-model cross section. The model is formulated in the form of a Monte Carlo event generator. Results obtained with this event generator are compared with data on inclusive reactions in the TeV energy range of the CERN and Fermilab hadron colliders.
Lappi, T; Mäntysaari, H; Venugopalan, R
2015-02-27
We argue that the proton multiplicities measured in Roman pot detectors at an electron ion collider can be used to determine centrality classes in incoherent diffractive scattering. Incoherent diffraction probes the fluctuations in the interaction strengths of multiparton Fock states in the nuclear wave functions. In particular, the saturation scale that characterizes this multiparton dynamics is significantly larger in central events relative to minimum bias events. As an application, we study the centrality dependence of incoherent diffractive vector meson production. We identify an observable which is simultaneously very sensitive to centrality triggered parton fluctuations and insensitive to details of the model.
Lappi, T; Mäntysaari, H; Venugopalan, R
2015-02-27
We argue that the proton multiplicities measured in Roman pot detectors at an electron ion collider can be used to determine centrality classes in incoherent diffractive scattering. Incoherent diffraction probes the fluctuations in the interaction strengths of multiparton Fock states in the nuclear wave functions. In particular, the saturation scale that characterizes this multiparton dynamics is significantly larger in central events relative to minimum bias events. As an application, we study the centrality dependence of incoherent diffractive vector meson production. We identify an observable which is simultaneously very sensitive to centrality triggered parton fluctuations and insensitive to details of the model. PMID:25768758
3D structure and nuclear targets
NASA Astrophysics Data System (ADS)
Dupré, Raphaël; Scopetta, Sergio
2016-06-01
Recent experimental and theoretical ideas are laying the ground for a new era in the knowledge of the parton structure of nuclei. We report on two promising directions beyond inclusive deep inelastic scattering experiments, aimed at, among other goals, unveiling the three-dimensional structure of the bound nucleon. The 3D structure in coordinate space can be accessed through deep exclusive processes, whose non-perturbative content is parametrized in terms of generalized parton distributions. In this way the distribution of partons in the transverse plane will be obtained, providing a pictorial view of the realization of the European Muon Collaboration effect. In particular, we show how, through the generalized parton distribution framework, non-nucleonic degrees of freedom in nuclei can be unveiled. Analogously, the momentum space 3D structure can be accessed by studying transverse-momentum-dependent parton distributions in semi-inclusive deep inelastic scattering processes. The status of measurements is also summarized, in particular novel coincidence measurements at high-luminosity facilities, such as Jefferson Laboratory. Finally the prospects for the next years at future facilities, such as the 12GeV Jefferson Laboratory and the Electron Ion Collider, are presented.
NASA Astrophysics Data System (ADS)
Gaunt, Jonathan R.; Maciuła, Rafał; Szczurek, Antoni
2014-09-01
The double parton distributions (dPDF), both conventional (i.e. double ladder) and those corresponding to 1→2 ladder splitting, are calculated and compared for different two-parton combinations. The conventional and splitting dPDFs have very similar shape in x1 and x2. We make a first quantitative evaluation of the single-ladder-splitting contribution to double parton scattering (DPS) production of two S- or P-wave quarkonia, two Higgs bosons and cc ¯cc ¯. The ratio of the single-ladder-splitting to conventional (i.e. double ladder against double ladder) contributions is discussed as a function of center-of-mass energy, mass of the produced system and other kinematical variables. Using a simple model for the dependence of the conventional two-parton distribution on transverse parton separation (Gaussian and independent of xi and scales), we find that the single-ladder-splitting (or 2v1) contribution is as big as the conventional (or 2v2) contribution discussed in recent years in the literature. In many experimental studies of DPS, one extracts the quantity 1/σeff=σDPS/(σSPS ,1σSPS,2), with σSPS ,1 and σSPS ,2 being the single scattering cross sections for the two subprocesses in the DPS process. Many past phenomenological studies of DPS have only considered the conventional contribution and have obtained values a factor of ˜2 too small for 1/σeff. Our analysis shows that it is important also to consider the ladder-splitting mechanism, and that this might resolve the discrepancy (this was also pointed out in a recent study by Blok et al.). The differential distributions in rapidity and transverse momenta calculated for conventional and single-ladder-splitting DPS processes are however very similar which causes their experimental separation to be rather difficult, if not impossible. The direct consequence of the existence of the two components (conventional and splitting) is the energy and process dependence of the empirical parameter σeff. This is
Automated parton-shower variations in pythia 8
NASA Astrophysics Data System (ADS)
Mrenna, S.; Skands, P.
2016-10-01
In the era of precision physics measurements at the LHC, efficient and exhaustive estimations of theoretical uncertainties play an increasingly crucial role. In the context of Monte Carlo (MC) event generators, the estimation of such uncertainties traditionally requires independent MC runs for each variation, for a linear increase in total run time. In this work, we report on an automated evaluation of the dominant (renormalization-scale and nonsingular) perturbative uncertainties in the pythia 8 event generator, with only a modest computational overhead. Each generated event is accompanied by a vector of alternative weights (one for each uncertainty variation), with each set separately preserving the total cross section. Explicit scale-compensating terms can be included, reflecting known coefficients of higher-order splitting terms and reducing the effect of the variations. The formalism also allows for the enhancement of rare partonic splittings, such as g →b b ¯ and q →q γ , to obtain weighted samples enriched in these splittings while preserving the correct physical Sudakov factors.
Energy flow along the medium-induced parton cascade
NASA Astrophysics Data System (ADS)
Blaizot, J.-P.; Mehtar-Tani, Y.
2016-05-01
We discuss the dynamics of parton cascades that develop in dense QCD matter, and contrast their properties with those of similar cascades of gluon radiation in vacuum. We argue that such cascades belong to two distinct classes that are characterized respectively by an increasing or a constant (or decreasing) branching rate along the cascade. In the former class, of which the BDMPS, medium-induced, cascade constitutes a typical example, it takes a finite time to transport a finite amount of energy to very soft quanta, while this time is essentially infinite in the latter case, to which the DGLAP cascade belongs. The medium induced cascade is accompanied by a constant flow of energy towards arbitrary soft modes, leading eventually to the accumulation of the initial energy of the leading particle at zero energy. It also exhibits scaling properties akin to wave turbulence. These properties do not show up in the cascade that develops in vacuum. There, the energy accumulates in the spectrum at smaller and smaller energy as the cascade develops, but the energy never flows all the way down to zero energy. Our analysis suggests that the way the energy is shared among the offsprings of a splitting gluon has little impact on the qualitative properties of the cascades, provided the kernel that governs the splittings is not too singular.
NASA Astrophysics Data System (ADS)
Regnier, D.; Dubray, N.; Schunck, N.; Verrière, M.
2016-05-01
Background: Accurate knowledge of fission fragment yields is an essential ingredient of numerous applications ranging from the formation of elements in the r process to fuel cycle optimization for nuclear energy. The need for a predictive theory applicable where no data are available, together with the variety of potential applications, is an incentive to develop a fully microscopic approach to fission dynamics. Purpose: In this work, we calculate the pre-neutron emission charge and mass distributions of the fission fragments formed in the neutron-induced fission of 239Pu using a microscopic method based on nuclear density functional theory (DFT). Methods: Our theoretical framework is the nuclear energy density functional (EDF) method, where large-amplitude collective motion is treated adiabatically by using the time-dependent generator coordinate method (TDGCM) under the Gaussian overlap approximation (GOA). In practice, the TDGCM is implemented in two steps. First, a series of constrained EDF calculations map the configuration and potential-energy landscape of the fissioning system for a small set of collective variables (in this work, the axial quadrupole and octupole moments of the nucleus). Then, nuclear dynamics is modeled by propagating a collective wave packet on the potential-energy surface. Fission fragment distributions are extracted from the flux of the collective wave packet through the scission line. Results: We find that the main characteristics of the fission charge and mass distributions can be well reproduced by existing energy functionals even in two-dimensional collective spaces. Theory and experiment agree typically within two mass units for the position of the asymmetric peak. As expected, calculations are sensitive to the structure of the initial state and the prescription for the collective inertia. We emphasize that results are also sensitive to the continuity of the collective landscape near scission. Conclusions: Our analysis confirms
Electron energy distribution in a helium plasma created by nuclear radiations
NASA Technical Reports Server (NTRS)
Lo, R. H.; Miley, G. H.
1974-01-01
An integral balance technique for calculation of the electron energy distribution in a radiation-induced plasma is described. Results predict W-values reasonably well and compare favorably with more complicated Monte-Carlo calculations. The distribution found differs from that in a normal electrical discharge and is of interest in radiation-pumped laser research.
Effects of pore-size and shape distributions on diffusion pore imaging by nuclear magnetic resonance
NASA Astrophysics Data System (ADS)
Kuder, Tristan Anselm; Laun, Frederik Bernd
2015-08-01
In medical imaging and porous media research, NMR diffusion measurements are extensively used to investigate the structure of diffusion restrictions such as cell membranes. Recently, several methods have been proposed to unambiguously determine the shape of arbitrary closed pores or cells filled with an NMR-visible medium by diffusion experiments. The first approach uses a combination of a long and a short diffusion-weighting gradient pulse, while the other techniques employ short gradient pulses only. While the eventual aim of these methods is to determine pore-size and shape distributions, the focus has been so far on identical pores. Thus, the aim of this work is to investigate the ability of these different methods to resolve pore-size and orientation distributions. Simulations were performed comparing the various pore imaging techniques employing different distributions of pore size and orientation and varying timing parameters. The long-narrow gradient profile is most advantageous to investigate pore distributions, because average pore images can be directly obtained. The short-gradient methods suppress larger pores or induce a considerable blurring. Moreover, pore-shape-specific artifacts occur; for example, the central part of a distribution of cylinders may be largely underestimated. Depending on the actual pore distribution, short-gradient methods may nonetheless yield good approximations of the average pore shape. Furthermore, the application of short-gradient methods can be advantageous to differentiate whether pore-size distributions or intensity distributions, e.g., due to surface relaxation, are predominant.
Vázquez-López, C.; Zendejas-Leal, B. E.; Bogard, James S; Golzarri, J. I.; Espinosa Garcia, Guillermo
2009-01-01
This paper presents a device to measure the angular distribution of the diffuse optical transmittance produced by etched nuclear tracks in polyallyl diglycol carbonate (PADC) detector. The device makes use of a stepper motor to move an array of four photodetectors around the sample in 1.8-degree steps. The integrated transmitted light was observed to increase monotonically with the etched track density in a range from zero to 2.8 x 10^5 per cm^2, using a neutron Am Be source.
Two jet energy and rapidity distributions
Blazey, G.C.; For the D {O} Collaboration
1992-11-01
The D0 detector has been recording data at the Tevatron {bar p}p Collider since May 1992. Because the D0 calorimeter is hermetic and has large acceptance it is well suited for semi-exclusive final state jet studies. We present a primary measurement of the distribution d{sup 3}N/dE{sub t1}/d{eta}{sub 1}/d{eta}{sub 2} at {radical}s TeV over a large range of {eta}. The sensitivity of this cross-section to parton momentum distributions and the ability of D0 to discriminate between possible parton distributions is discussed.
Two jet energy and rapidity distributions
Blazey, G.C.
1992-11-01
The D0 detector has been recording data at the Tevatron [bar p]p Collider since May 1992. Because the D0 calorimeter is hermetic and has large acceptance it is well suited for semi-exclusive final state jet studies. We present a primary measurement of the distribution d[sup 3]N/dE[sub t1]/d[eta][sub 1]/d[eta][sub 2] at [radical]s TeV over a large range of [eta]. The sensitivity of this cross-section to parton momentum distributions and the ability of D0 to discriminate between possible parton distributions is discussed.
Altstetter, C.J.
1981-01-01
The use of ion beams for materials analysis has made a successful transition from the domain of the particle physicist to that of the materials scientist. The subcategory of this field, nuclear reaction analysis, is just now undergoing the transition, particularly in applications to hydrogen in materials. The materials scientist must locate the nearest accelerator, because now he will find that using it can solve mysteries that do not yield to other techniques. 9 figures
Leal Neto, Viriato; Vieira, José Wilson; Lima, Fernando Roberto de Andrade
2014-01-01
Objective This article presents a way to obtain estimates of dose in patients submitted to radiotherapy with basis on the analysis of regions of interest on nuclear medicine images. Materials and Methods A software called DoRadIo (Dosimetria das Radiações Ionizantes [Ionizing Radiation Dosimetry]) was developed to receive information about source organs and target organs, generating graphical and numerical results. The nuclear medicine images utilized in the present study were obtained from catalogs provided by medical physicists. The simulations were performed with computational exposure models consisting of voxel phantoms coupled with the Monte Carlo EGSnrc code. The software was developed with the Microsoft Visual Studio 2010 Service Pack and the project template Windows Presentation Foundation for C# programming language. Results With the mentioned tools, the authors obtained the file for optimization of Monte Carlo simulations using the EGSnrc; organization and compaction of dosimetry results with all radioactive sources; selection of regions of interest; evaluation of grayscale intensity in regions of interest; the file of weighted sources; and, finally, all the charts and numerical results. Conclusion The user interface may be adapted for use in clinical nuclear medicine as a computer-aided tool to estimate the administered activity. PMID:25741101
Turck, Natacha; Gross, Isabelle; Gendry, Patrick; Stutzmann, Jeanne; Freund, Jean-Noel; Kedinger, Michele; Simon-Assmann, Patricia; Launay, Jean-Francois . E-mail: Jean-Francois.Launay@inserm.u-strasbg.fr
2005-02-15
Laminins are structurally and functionally major components of the extracellular matrix. Four isoforms of laminins (laminin-1, -2, -5 and -10) are expressed in a specific pattern along the crypt-villus axis of the intestine. Previous works indicated that expression of these isoforms is developmentally regulated and that laminins could modulate the behaviour of intestinal cells, but the exact role of each isoform remained unclear. Here, we report the first systematic analysis of the cellular functions of the four isoforms using the human colon adenocarcinoma Caco2/TC7 cell line as a model. We compared the respective abilities of each isoform to modulate adhesion, proliferation and differentiation of intestinal epithelial cells. We found that the isoforms were functionally distinct, with laminin-10 being the most adhesive substratum, laminin-2, laminin-5 and laminin-10 enhancing cellular proliferation and at the opposite, laminin-1 stimulating intestinal cell differentiation. To begin to characterise the molecular events induced by the different isoforms, we examined by immunofluorescence the intracellular distribution of several nuclear proteins, recently highlighted by a nuclear proteomic approach. We observed clear nucleocytoplasmic redistribution of these proteins, which depended on the laminin isoform. These results provide evidence for a distinct functional role of laminins in intestinal cell functions characterised by specific localisation of nuclear proteins.
Intermediate/high energy nuclear physics. Technical progress report, June 15, 1992--June 14, 1993
Vary, J.P.
1992-12-31
Progress during the last year is reviewed under the following topics: relativistic hadron--nucleus and nucleus--nucleus collisions (heavy meson production, photon production and fragmentation functions--direct photon production with the QCM and photon fragmentation functions, Cronin efffect and multiple scattering, effective nuclear parton distributions); solving quantum field theories in nonperturbative regime; light-front dynamics and high-spin states (soft form factor of the pion and nucleon for transverse and longitudinal momentum transfers, light front spinors for high-spin objects); high-energy spin physics; relativistic wave equations, quarkonia, and e{sup +}e{sup {minus}} resonances; associated production of Higgs boson at collider energies, and microscopic nuclear many-body theory and reactions. 135 refs.
NASA Astrophysics Data System (ADS)
Nishimura, Daiki; Fukuda, M.; Takechi, M.; Mihara, M.; Ishikawa, D.; Matsuta, K.; Matsumiya, R.; Kuboki, T.; Suzuki, T.; Yamaguchi, T.; Hachiuma, I.; Namihira, K.; Ohtsubo, T.; Shinbara, Y.; Ohkuma, Y.; Izumikawa, T.; Tanaka, K.; Ozawa, A.; Yasuda, Y.; Moriguchi, T.; Momota, S.; Fukuda, S.; Sato, S.; Kanazawa, M.; Kitagawa, A.
2009-10-01
The halo and skin structures at the nuclear surface have attracted much interest for their exotic nature. By utilizing the isospin asymmetry of nucleon-nucleon total cross sections in the intermediate energy region, in principle, the proton- and neutron-density distributions can be determined independently. To demonstrate this isospin asymmetric effect, we have studied σR for the neutron-halo nucleus ^11 Be and the proton-halo nucleus ^8B on proton targets. We measured σR for ^11Be and ^8B on C and proton targets by the transmission method in the intermidiate energy region using HIMAC heavy ion synchrotron at NIRS. The present result for ^11Be is consistent with that the tail of ^11Be density consists of a neutron. On the other hand, the experimental result for ^8B is in agreement with the calculation with a proton tail in ^8B. Thus, the proton and neutron density distributions at the nuclear surface can be distinguished successfully by the σR on C and proton targets.
Bithell, J. F.; Dutton, S. J.; Draper, G. J.; Neary, N. M.
1994-01-01
OBJECTIVE--To examine the relation between the risk of childhood leukaemia and non-Hodgkin's lymphoma and proximity of residence to nuclear installations in England and Wales. DESIGN--Observed and expected numbers of cases were calculated and analysed by standard methods based on ratios of observed to expected counts and by a new statistical test, the linear risk score test, based on ranks and designed to be sensitive to excess incidence in close proximity to a putative source of risk. SETTING--Electoral wards within 25 km of 23 nuclear installations and six control sites that had been investigated for suitability for generating stations but never used. SUBJECTS--Children below age 15 in England and Wales, 1966-87. MAIN OUTCOME MEASURE--Registration of any leukaemia or non-Hodgkin's lymphoma. RESULTS--In none of the 25 km circles around the installations was the incidence ratio significantly greater than 1.0. The only significant results for the linear risk score test were for Sellafield (P = 0.00002) and Burghfield (P = 0.031). The circles for Aldermaston and Burghfield overlap; the incidence ratio was 1.10 in each. One of the control sites gave a significant linear risk score test result (P = 0.020). All the tests carried out were one sided with P values estimated by simulation. CONCLUSION--There is no evidence of a general increase of childhood leukaemia or non-Hodgkin's lymphoma around nuclear installations. Apart from Sellafield, the evidence for distance related risk is very weak. PMID:8086902
Bithell, J F; Stone, R A
1989-03-01
There is great public concern, often based on anecdotal reports, about risks from ionising radiation. Recent interest has been directed at an excess of leukaemia cases in the locality of civil nuclear installations at Sellafield and Sizewell, and epidemiologists have a duty to pursue such information vigorously. This paper sets out to show that the epidemiological methods most commonly used can be improved upon. When analysing geographical data it is necessary to consider location. The most obvious quantification of location is ranked distance, though other measures which may be more meaningful in relation to aetiology may be substituted. A test based on distance ranks, the "Poisson maximum test", depends on the maximum of observed relative risk in regions of increasing size, but with significance level adjusted for selection. Applying this test to data from Sellafield and Sizewell shows that the excess of leukaemia incidence observed at Seascale, near Sellafield, is not an artefact due to data selection by region, and that the excess probably results from a genuine, if as yet unidentified cause (there being little evidence of any other locational association once the Seascale cases have been removed). So far as Sizewell is concerned, geographical proximity to the nuclear power station does not seem particularly important. PMID:2592896
Bithell, J F; Stone, R A
1989-01-01
There is great public concern, often based on anecdotal reports, about risks from ionising radiation. Recent interest has been directed at an excess of leukaemia cases in the locality of civil nuclear installations at Sellafield and Sizewell, and epidemiologists have a duty to pursue such information vigorously. This paper sets out to show that the epidemiological methods most commonly used can be improved upon. When analysing geographical data it is necessary to consider location. The most obvious quantification of location is ranked distance, though other measures which may be more meaningful in relation to aetiology may be substituted. A test based on distance ranks, the "Poisson maximum test", depends on the maximum of observed relative risk in regions of increasing size, but with significance level adjusted for selection. Applying this test to data from Sellafield and Sizewell shows that the excess of leukaemia incidence observed at Seascale, near Sellafield, is not an artefact due to data selection by region, and that the excess probably results from a genuine, if as yet unidentified cause (there being little evidence of any other locational association once the Seascale cases have been removed). So far as Sizewell is concerned, geographical proximity to the nuclear power station does not seem particularly important. PMID:2592896
Estimation of Ground-Level Radioisotope Distributions for Underground Nuclear Test Leakage
Ely, James H.; Fast, James E.; Seifert, Carolyn E.; Warren, Glen A.
2009-06-19
On-site inspections (OSI) will be an important process to deter and help verify compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). An important tool in narrowing the possible locations to collect evidence of a nuclear test during an on-site inspection may be over-flights of the general area using aerial gamma spectroscopy which can measure the energy and intensity of gamma radiation and help identify areas that may warrant further investigation of areas of high concentrations of radioactivity. This paper will investigate the capabilities of gamma ray detectors that are typically used in aerial searches. Modeling and simulation results of the detector response for radionuclide species for an OSI will be presented for a variety of assumed releases, depositions on the ground, and times after a suspected Treaty violation for typical over flight heights and speeds. This data will provide information on the possible applicability for airborne spectroscopy and the challenges and limitations of this tool for OSI. Of particular interest will be analysis of the data for gross count, regions of interest, and isotope identification types of algorithms and the characteristics of each.
Teramage, Mengistu T; Onda, Yuichi; Patin, Jeremy; Kato, Hiroaki; Gomi, Takashi; Nam, Sooyoun
2014-11-01
This study deals with the description of the vertical distribution of radiocaesium ((137)Cs and (134)Cs) in a representative coniferous forest soil, investigated 10 months after the Fukushima radioactive fallout. During soil sampling, the forest floor components (understory plants, litter (Ol-) and fermented layers (Of)) were collected and treated separately. The results indicate that radiocesium is concentrated in the forest floor, and high radiocesium transfer factor observed in the undergrowth plants (3.3). This made the forest floor an active exchanging interphase for radiocesium. The raw organic layer (Ol + Of) holds 52% (5.3 kBq m(-2)) of the Fukushima-derived and 25% (0.7 kBq m(-2)) of the pre-Fukushima (137)Cs at the time of the soil sampling. Including the pre-Fukushima (137)Cs, 99% of the total soil inventory was in the upper 10 cm, in which the organic matter (OM) content was greater than 10%, suggesting the subsequent distribution most likely depends on the OM turnover. However, the small fraction of the Fukushima-derived (137)Cs at a depth of 16 cm is most likely due to the infiltration of radiocesium-circumscribed rainwater during the fallout before that selective adsorption prevails and reduces the migration of soluble (137)Cs. The values of the depth distribution parameters revealed that the distribution of the Fukushima-derived (137)Cs was somewhat rapid.
NASA Astrophysics Data System (ADS)
Jiang, Yijie; Wang, Qiming; Cui, Yi; Huo, Yongzhong; Ding, Shurong; Zhang, Lin; Li, Yuanming
2011-11-01
Dispersion nuclear fuel elements have promising prospects to be used in advanced nuclear reactors and disposal of nuclear wastes. They consist of fuel meat and cladding, and the fuel meat is a kind of composite fuel in which the fuel particles are embedded in the non-fissile matrix. Prediction of the micro-thermo-mechanical behaviors in dispersion nuclear plates is of importance to their irradiation safety and optimal design. In this study, the heterogeneity of the fuel particles along the thickness direction in the fuel meat is considered. The 3D finite element models have been developed respectively for two cases: (1) variation of fuel particle-particle (PP) distances for the particles near the mid-plane of the fuel meat; (2) variation of the particle-cladding (PC) distances for the fuel particles near the interface between the fuel meat and the cladding. The respective finite strain constitutive relations are developed for the fuel particle, metal matrix and cladding. The developed virtual temperature method is used to simulate irradiation swelling of the fuel particles and irradiation growth of the metal cladding. Effects of the heterogeneous distributions of the fuel particles on the micro temperature fields and the micro stress-strain fields are investigated. The obtained results indicate that: (1) as a whole, the maximum Mises stress, equivalent plastic strain and first principal stress at the matrix between the two closest particles increase with decreasing the particle-particle (PP) distance; existence of large first principal stresses there may be the main factor that induces the matrix failure; (2) variation of the particle-cladding (PC) distance has remarkable effects on the interfacial normal stress and shear stress at the interface between the fuel meat and the cladding; the first principal stress at the cladding near the interface increases dramatically when the fuel particle is closer and closer to the cladding. Thus, the proper distance between the
NASA Astrophysics Data System (ADS)
Sato, Haruo; Niizato, Tadafumi; Tanaka, Shingo; Abe, Hironobu; Aoki, Kazuhiro
2014-05-01
This work was conducted as one of the researches relating to distribution maps of radiation dose rate etc. which the government has promoted as one of the counter-measures to the Fukushima Dai-ichi Nuclear Power Plant accident in March 2011, and the 2nd investigation on the depth distribution of radionuclides (RNs) in soil was conducted after about 1 year from the accident, succeedingly to the 1st investigation which was conducted after about 3 months from the accident. Soil core samples to about 50cm deep were taken at 11 locations in Nihonmatsu-city, Kawamata-town and Namie-town. Sorption-desorption experiments of Cs-137 and I-131, CEC and AEC measurements and mineralogical analyses by XRD were conducted for 3 types of soils (sandy, clayey, organic) and those elutriated components (clay, silt, sand). Radiocaesium (Cs-134 and Cs-137) and Ag-110m were detected at all locations investigated and only at locations where radiation dose rate is high, respectively. Radiocaesium more than 95% and 99% of the inventory distributed within 5cm and 10cm deep in soil in the surface layer (mainly sandy soil), respectively, and distributed within 16cm and 20cm deep in organic soil and soil at locations where are supposed to have been used as farmland, respectively. Radiocaesium tended to extend to deeper parts in soil that organic and clayey soils are the support layer, particularly in organic soil, compared with the 1st investigation. Distribution coefficients of Cs-137 onto organic soil and its elutriated components were also lower than that onto other soils. This is consistent with trend of penetration profile.
Huntley, J M; Tarvaz, T; Mantle, M D; Sederman, A J; Gladden, L F; Sheikh, N A; Wildman, R D
2014-05-13
We report the results of nuclear magnetic resonance imaging experiments on granular beds of mustard grains fluidized by vertical vibration at ultrasonic frequencies. The variation of both granular temperature and packing fraction with height was measured within the three-dimensional cell for a range of vibration frequencies, amplitudes and numbers of grains. Small increases in vibration frequency were found--contrary to the predictions of classical 'hard-sphere' expressions for the energy flux through a vibrating boundary--to result in dramatic reductions in granular temperature. Numerical simulations of the grain-wall interactions, using experimentally determined Hertzian contact stiffness coefficients, showed that energy flux drops significantly as the vibration period approaches the grain-wall contact time. The experiments thus demonstrate the need for new models for 'soft-sphere' boundary conditions at ultrasonic frequencies.
Huntley, J M; Tarvaz, T; Mantle, M D; Sederman, A J; Gladden, L F; Sheikh, N A; Wildman, R D
2014-05-13
We report the results of nuclear magnetic resonance imaging experiments on granular beds of mustard grains fluidized by vertical vibration at ultrasonic frequencies. The variation of both granular temperature and packing fraction with height was measured within the three-dimensional cell for a range of vibration frequencies, amplitudes and numbers of grains. Small increases in vibration frequency were found--contrary to the predictions of classical 'hard-sphere' expressions for the energy flux through a vibrating boundary--to result in dramatic reductions in granular temperature. Numerical simulations of the grain-wall interactions, using experimentally determined Hertzian contact stiffness coefficients, showed that energy flux drops significantly as the vibration period approaches the grain-wall contact time. The experiments thus demonstrate the need for new models for 'soft-sphere' boundary conditions at ultrasonic frequencies. PMID:24711488
Osvay, M; Deme, S
2006-01-01
Al2O3:Mg,Y ceramic thermoluminescence dosemeters were developed at the Institute of Isotopes for high dose applications at room temperatures. The glow curve of Al2O3:Mg,Y exhibits two peaks--one at 250 degrees C (I) and another peak at approximately 400 degrees C (II). In order to extend the application of these dosemeters to high temperatures, the effect of irradiation temperature was investigated using temperature controlled heating system during high dose irradiation at various temperatures (20-100 degrees C). The new calibration and measuring method has been successfully applied for dose mapping within the hermetic zone of the Paks Nuclear Power Plant even at high temperature parts of blocks.
Yu, Wen; He, Jianhua; Lin, Wuhui; Li, Yiliang; Men, Wu; Wang, Fenfen; Huang, Jiang
2015-04-01
In order to understand the impact of Fukushima Nuclear Accident (FNA) on the marine environment, seawater and a composite squid (Ommastrephe bartrami) sample were collected on the monitoring cruise XT01 during June 16-July 4, 2011. The concentration levels of Cesium-134, Cesium-137, Strontium-90, Silver-110 m, Cobalt-58 and Cobalt-60 were measured both for the seawater and squid samples. The elevated activity levels of Cesium-134 and Cesium-137 were found in the sampling area. Cesium-134 and Silver-110 m, which were usually undetectable before FNA, were also found in the squid sample, with the activity levels of 1.65 ± 0.13 Bq/kg-wet and 0.07 ± 0.01 Bq/kg-wet, respectively. The radiological assessment result showed that the radioactive release from the FNA would not have a significant adverse effect on marine biota at the population level.
NASA Astrophysics Data System (ADS)
Lee, S. J.; Mekjian, A. Z.
1992-03-01
Partition functions for a canonical and microcanonical ensemble are developed which are then used to describe various properties of excited hadronic systems. Relating multinomial coefficients to a generating function of these partition functions, it is shown that the average value of various moments of cluster sizes are of a quite simple form in terms of canonical partition functions. Specific applications of the results are to partitioning problems as in the partitioning of nucleons into clusters arising from a nuclear collision and to branching processes as in Furry branching. The underlying dynamical evolution of a system is studied by parametrizing the multinomial variables of the theory. A Fokker-Planck equation can be obtained from these evolutionary equations. By relating the parameters and variables of the theory to thermodynamic variables, the thermal properties of excited hadronic systems are studied.
Huntley, J. M.; Tarvaz, T.; Mantle, M. D.; Sederman, A. J.; Gladden, L. F.; Sheikh, N. A.; Wildman, R. D.
2014-01-01
We report the results of nuclear magnetic resonance imaging experiments on granular beds of mustard grains fluidized by vertical vibration at ultrasonic frequencies. The variation of both granular temperature and packing fraction with height was measured within the three-dimensional cell for a range of vibration frequencies, amplitudes and numbers of grains. Small increases in vibration frequency were found—contrary to the predictions of classical ‘hard-sphere’ expressions for the energy flux through a vibrating boundary—to result in dramatic reductions in granular temperature. Numerical simulations of the grain–wall interactions, using experimentally determined Hertzian contact stiffness coefficients, showed that energy flux drops significantly as the vibration period approaches the grain–wall contact time. The experiments thus demonstrate the need for new models for ‘soft-sphere’ boundary conditions at ultrasonic frequencies. PMID:24711488
DESHPANDE,A.; VOGELSANG, W.
2007-10-08
The determination of the polarized gluon distribution is a central goal of the RHIC spin program. Recent achievements in polarization and luminosity of the proton beams in RHIC, has enabled the RHIC experiments to acquire substantial amounts of high quality data with polarized proton beams at 200 and 62.4 GeV center of mass energy, allowing a first glimpse of the polarized gluon distribution at RHIC. Short test operation at 500 GeV center of mass energy has also been successful, indicating absence of any fundamental roadblocks for measurements of polarized quark and anti-quark distributions planned at that energy in a couple of years. With this background, it has now become high time to consider how all these data sets may be employed most effectively to determine the polarized parton distributions in the nucleon, in general, and the polarized gluon distribution, in particular. A global analysis of the polarized DIS data from the past and present fixed target experiments jointly with the present and anticipated RHIC Spin data is needed.
Zhang, Xiaoli; Wen, Zhifeng; Sun, Limei; Wang, Jian; Song, Min; Wang, Enhua; Mi, Xiaoyi
2013-06-28
Highlights: •TRAF2 appears to interact with TRAF4 in breast cancer cell lines. •TRAF2 affects the localization and function of TRAF4 in breast cancer cell lines. •TRAF4 may play an important role in the activation of NF-κB via TRAF2. -- Abstract: Although numerous studies have shown that tumor necrosis factor receptor-associated factor 4 (TRAF4) plays an important role in the carcinogenesis of many tumor types, its exact molecular mechanism remains elusive. In this study, we examined the regulation function of TRAF2 to the cytoplasmic/nuclear distribution of TRAF4 in the breast cancer cell line. Using cell immunofluorescent staining, we found that TRAF2 and TRAF4 were co-localized to the cytoplasm in MCF-7 cells. Co-immunoprecipitation showed that TRAF2 could interact with TRAF4 in MCF-10A, MCF-7 and MDA-MB-231 cell lines. Western blotting showed TRAF2 depletion by targeted siRNA in MDA-MB-231 cells led to reduced TRAF4 expression in the cytoplasm and augmented TRAF4 expression in the nucleus. Cytoplasmic expression of TRAF4 was augmented and nuclear expression was reduced when MCF-7 cells were transfected with hTRAF2pLPCX-HA-Flag/P874. MCF-7 cells expressing hTRAF2pLPCX-HA-Flag/P874 had enhanced cell proliferation rates. The nuclear expression of NF-κB significantly increased after TNF-α treatment. When hTRAF2pLPCX-HA-Flag/P874 and the siRNA-TRAF4 plasmid were cotransfected, the nuclear expression of NF-κB was significantly reduced compared with cells transfected with hTRAF2pLPCX-HA-Flag/P874 only. In conclusion, TRAF2 appears to interact with TRAF4 and affect the localization of TRAF4 in breast cancer cell lines. The overexpression of TRAF2 augmented the cytoplasmic expression of TRAF4 which promoted cell proliferation and inhibited cell apoptosis by activating NF-κB nuclear transcription. TRAF4 may play an important role in the activation of NF-κB via TRAF2.
Tannenbaum, M.J.
1990-04-01
As part of AGS Experiment 802, an array of 245 Lead Glass blocks, covering half the azimuth, with a polar angular acceptance approximately 8{degree} {le} {theta} {le} 32{degree}, which corresponds roughly to a laboratory pseudo rapidity range 1.25 {le} {eta} {le} 2.50 with good acceptance, when edges and corners are taken into account, measured the transverse energy (E{sub T}) distributions from primary beams of protons, {sup 16}O, and {sup 28}Si, at 14.6 A Gev/c, incident on targets of Be, Al, Cu and Au. The lead glass is most sensitive to electromagnetic radiation, but also responds to charged hadrons. The total detector response provides a good measure of the global pion yield in the central rapidity region of these reactions. Correlations among the 4 detector systems in E802 are shown to be a powerful diagnostic tool. Latest results of the analysis in progress, including dE{sub T}/d{eta} distributions, are presented, with emphasis on the proton -- nucleus data. Additionally, these data, and previous measurements of pseudorapidity distributions of multiplicity and Transverse Energy at both the AGS and CERN are analyzed in an acceptance-independent and model-independent method, with the conclusion that simple considerations of nuclear geometry do not provide an explanation of the different {radical}{sup s}NN dependences observed in {sup 16}O + Au and p-p reactions. 37 refs., 25 figs.
Angular distribution of products of ternary nuclear fission induced by cold polarized neutrons
Bunakov, V. E. Kadmensky, S. G. Kadmensky, S. S.
2008-11-15
Within quantum fission theory, angular distributions of products originating from the ternary fission of nuclei that is induced by polarized cold and thermal neutrons are investigated on the basis of a non-evaporative mechanism of third-particle emission and a consistent description of fission-channel coupling. It is shown that the inclusion of Coriolis interaction both in the region of the discrete and in the region of the continuous spectrum of states of the system undergoing fission leads to T-odd correlations in the aforementioned angular distributions. The properties of the TRI and ROT effects discovered recently, which are due to the interference between the fission amplitudes of neutron resonances, are explored. The results obtained here are compared with their counterparts from classic calculations based on the trajectory method.
First Results on Angular Distributions of Thermal Dileptons in Nuclear Collisions
Arnaldi, R.; Colla, A.; Cortese, P.; Ferretti, A.; Oppedisano, C.; Scomparin, E.; Banicz, K.; Damjanovic, S.; Castor, J.; Devaux, A.; Fargeix, J.; Force, P.; Manso, F.; Chaurand, B.; Cicalo, C.; Falco, A. de; Floris, M.; Masoni, A.; Puddu, G.; Serci, S.
2009-06-05
The NA60 experiment at the CERN Super Proton Synchrotron has studied dimuon production in 158A GeV In-In collisions. The strong excess of pairs above the known sources found in the complete mass region 0.2
Biased distributions and decay of long interspersed nuclear elements in the chicken genome.
Abrusán, György; Krambeck, Hans-Jürgen; Junier, Thomas; Giordano, Joti; Warburton, Peter E
2008-01-01
The genomes of birds are much smaller than mammalian genomes, and transposable elements (TEs) make up only 10% of the chicken genome, compared with the 45% of the human genome. To study the mechanisms that constrain the copy numbers of TEs, and as a consequence the genome size of birds, we analyzed the distributions of LINEs (CR1's) and SINEs (MIRs) on the chicken autosomes and Z chromosome. We show that (1) CR1 repeats are longest on the Z chromosome and their length is negatively correlated with the local GC content; (2) the decay of CR1 elements is highly biased, and the 5'-ends of the insertions are lost much faster than their 3'-ends; (3) the GC distribution of CR1 repeats shows a bimodal pattern with repeats enriched in both AT-rich and GC-rich regions of the genome, but the CR1 families show large differences in their GC distribution; and (4) the few MIRs in the chicken are most abundant in regions with intermediate GC content. Our results indicate that the primary mechanism that removes repeats from the chicken genome is ectopic exchange and that the low abundance of repeats in avian genomes is likely to be the consequence of their high recombination rates.
3D dose and TCP distribution for radionuclide therapy in nuclear medicine
Valente, M.; Malano, F.; Perez, P.
2010-08-04
A common feature to any radiant therapy is that lesion and health tissue dosimetry provides relevant information for treatment optimization along with dose-efficacy and dose-complication correlation studies. Nowadays, different radionuclide therapies are commonly available, assessing both systemic and loco-regional approach and using different alfa-, beta-and gamma-emitting isotopes and binding molecules. It is well established, that specific dosimetric approaches become necessary according to each therapy modality. Sometimes, observed activity distribution can be satisfactory represented by simple geometrical models. However, Monte Carlo techniques are capable of better approaches, therefore becoming sometimes the only way to get dosimetric data since the patient-specific situation can not be adequately represented by conventional dosimetry techniques. Therefore, due to strong limitations of traditional and standard methods, this work concentrates on the development of a dedicated and novel calculation system in order to assess the dose distribution within the irradiated patient. However, physical dose may not be enough information in order to establish real deterministic biological/metabolic effects; therefore complementary radiobiological models have been suitably introduced with the aim of performing realistic 3D dose as well as corresponding Tumor Control Probability distribution calculation.
Sound Produced by a Fast Parton in the Quark-Gluon Plasma is a ``Crescendo''
NASA Astrophysics Data System (ADS)
Neufeld, R. B.; Müller, B.
2009-07-01
We calculate the total energy deposited into the medium per unit length by fast partons traversing a quark-gluon plasma. The medium excitation due to collisions is taken to be given by the well-known expression for the collisional drag force. The radiative energy loss of the parton contributes to the energy deposition because each radiated gluon acts as an additional source of collisional energy loss in the medium. We derive a differential equation which governs how the spectrum of radiated gluons is modified when this energy loss is taken into account. This modified spectrum is then used to calculate the additional energy deposition due to the interactions of radiated gluons with the medium. Numerical results are presented for the medium response for the case of two energetic back-to-back partons created in a hard interaction.
The sound generated by a fast parton in the quark-gluon plasma is a crescendo
NASA Astrophysics Data System (ADS)
Neufeld, R. B.; Müller, B.
2009-11-01
The total energy deposited into the medium per unit length by a fast parton traversing a quarkgluon plasma is calculated. We take the medium excitation due to collisions to be given by the well known expression for the collisional drag force. The parton's radiative energy loss contributes to the energy deposition because each radiated gluon acts as an additional source of collisional energy loss in the medium. In our model, this leads to a length dependence on the differential energy loss due to the interactions of radiated gluons with the medium. The final result, which is a sum of the primary and the secondary contributions, is then treated as the coefficient of a local hydrodynamic source term. Results are presented for energy density wave induced by two fast, back-to-back partons created in an initial hard interaction.
Sound produced by a fast parton in the quark-gluon plasma is a "crescendo".
Neufeld, R B; Müller, B
2009-07-24
We calculate the total energy deposited into the medium per unit length by fast partons traversing a quark-gluon plasma. The medium excitation due to collisions is taken to be given by the well-known expression for the collisional drag force. The radiative energy loss of the parton contributes to the energy deposition because each radiated gluon acts as an additional source of collisional energy loss in the medium. We derive a differential equation which governs how the spectrum of radiated gluons is modified when this energy loss is taken into account. This modified spectrum is then used to calculate the additional energy deposition due to the interactions of radiated gluons with the medium. Numerical results are presented for the medium response for the case of two energetic back-to-back partons created in a hard interaction.
QCD-aware partonic jet clustering for truth-jet flavour labelling
NASA Astrophysics Data System (ADS)
Buckley, Andy; Pollard, Chris
2016-02-01
We present an algorithm for deriving partonic flavour labels to be applied to truth particle jets in Monte Carlo event simulations. The inputs to this approach are final pre-hadronisation partons, to remove dependence on unphysical details such as the order of matrix element calculation and shower generator frame recoil treatment. These are clustered using standard jet algorithms, modified to restrict the allowed pseudojet combinations to those in which tracked flavour labels are consistent with QCD and QED Feynman rules. The resulting algorithm is shown to be portable between the major families of shower generators, and largely insensitive to many possible systematic variations: it hence offers significant advantages over existing ad hoc labelling schemes. However, it is shown that contamination from multi-parton scattering simulations can disrupt the labelling results. Suggestions are made for further extension to incorporate more detailed QCD splitting function kinematics, robustness improvements, and potential uses for truth-level physics object definitions and tagging.
The heavy quark parton oxymoron: A mini-review of heavy quark production theory in PQCD
Tung, W.-K.
1997-04-20
Conventional perturbative QCD calculations on the production of a heavy quark 'H' consist of two contrasting approaches: the usual QCD parton formalism uses the zero-mass approximation (m{sub H}=0) once above threshold, and treats H just like the other light partons; on the other hand, most recent 'NLO' heavy quark calculations treat m{sub H} as a large parameter and always consider H as a heavy particle, never as a parton, irrespective of the energy scale of the physical process. By their very nature, both these approaches are limited in their regions of applicability. This dichotomy can be resolved in a unified general-mass variable-flavor-number scheme, which retains the m{sub H} dependence at all energies, and which naturally reduces to the two conventional approaches in their respective region of validity. Recent applications to lepto- and hadro-production of heavy quarks are briefly summarized.
Künzle, H; Rehkämper, G
1992-01-01
Using retrograde axonal flow and wheatgerm agglutinin conjugated to horseradish peroxidase, we studied the distribution of cortical neurons giving rise to spinal and dorsal column nuclear projections, and correlated the regions involved in the projections with the cytoarchitectonic areas recently identified in the lesser hedgehog tenrec, Echinops telfairi (Insectivora). Labeled cortical neurons were most numerous following injections of tracer into higher cervical segments, whereas almost none were found following thoracic injections. The cortical labeling appeared more prominent ipsilaterally than contralaterally after spinal injections, although it was more prominent on the contralateral side after injection into the dorsal column nuclear complex. The majority of labeled neurons found in lamina V occupied the neocortex adjacent to the interhemispheric fissure along the rostrocaudal extent of the small corpus callosum. This location corresponded to an intermediate rostrocaudal portion of the hemisphere, and particularly to area 2 of Rehkämper. In some cases, adjacent portions of areas 1 and 3 were also involved, as well as neocortical regions of the lateral hemisphere. The present data did not suggest a somatotopic organization of the projections; likewise, evidence for the presence of more than one somatosensorimotor representation was sparse.
Validation of nuclear models in Geant4 using the dose distribution of a 177 MeV proton pencil beam.
Hall, David C; Makarova, Anastasia; Paganetti, Harald; Gottschalk, Bernard
2016-01-01
A proton pencil beam is associated with a surrounding low-dose envelope, originating from nuclear interactions. It is important for treatment planning systems to accurately model this envelope when performing dose calculations for pencil beam scanning treatments, and Monte Carlo (MC) codes are commonly used for this purpose. This work aims to validate the nuclear models employed by the Geant4 MC code, by comparing the simulated absolute dose distribution to a recent experiment of a 177 MeV proton pencil beam stopping in water. Striking agreement is observed over five orders of magnitude, with both the shape and normalisation well modelled. The normalisations of two depth dose curves are lower than experiment, though this could be explained by an experimental positioning error. The Geant4 neutron production model is also verified in the distal region. The entrance dose is poorly modelled, suggesting an unaccounted upstream source of low-energy protons. Recommendations are given for a follow-up experiment which could resolve these issues.
Validation of nuclear models in Geant4 using the dose distribution of a 177 MeV proton pencil beam
NASA Astrophysics Data System (ADS)
Hall, David C.; Makarova, Anastasia; Paganetti, Harald; Gottschalk, Bernard
2016-01-01
A proton pencil beam is associated with a surrounding low-dose envelope, originating from nuclear interactions. It is important for treatment planning systems to accurately model this envelope when performing dose calculations for pencil beam scanning treatments, and Monte Carlo (MC) codes are commonly used for this purpose. This work aims to validate the nuclear models employed by the Geant4 MC code, by comparing the simulated absolute dose distribution to a recent experiment of a 177 MeV proton pencil beam stopping in water. Striking agreement is observed over five orders of magnitude, with both the shape and normalisation well modelled. The normalisations of two depth dose curves are lower than experiment, though this could be explained by an experimental positioning error. The Geant4 neutron production model is also verified in the distal region. The entrance dose is poorly modelled, suggesting an unaccounted upstream source of low-energy protons. Recommendations are given for a follow-up experiment which could resolve these issues.
Validation of nuclear models in Geant4 using the dose distribution of a 177 MeV proton pencil beam.
Hall, David C; Makarova, Anastasia; Paganetti, Harald; Gottschalk, Bernard
2016-01-01
A proton pencil beam is associated with a surrounding low-dose envelope, originating from nuclear interactions. It is important for treatment planning systems to accurately model this envelope when performing dose calculations for pencil beam scanning treatments, and Monte Carlo (MC) codes are commonly used for this purpose. This work aims to validate the nuclear models employed by the Geant4 MC code, by comparing the simulated absolute dose distribution to a recent experiment of a 177 MeV proton pencil beam stopping in water. Striking agreement is observed over five orders of magnitude, with both the shape and normalisation well modelled. The normalisations of two depth dose curves are lower than experiment, though this could be explained by an experimental positioning error. The Geant4 neutron production model is also verified in the distal region. The entrance dose is poorly modelled, suggesting an unaccounted upstream source of low-energy protons. Recommendations are given for a follow-up experiment which could resolve these issues. PMID:26611861
NASA Technical Reports Server (NTRS)
Khandelwal, Govind S.; Khan, Ferdous
1989-01-01
An optical model description of energy and momentum transfer in relativistic heavy-ion collisions, based upon composite particle multiple scattering theory, is presented. Transverse and longitudinal momentum transfers to the projectile are shown to arise from the real and absorptive part of the optical potential, respectively. Comparisons of fragment momentum distribution observables with experiments are made and trends outlined based on our knowledge of the underlying nucleon-nucleon interaction. Corrections to the above calculations are discussed. Finally, use of the model as a tool for estimating collision impact parameters is indicated.
Distribution of properties in nuclear reactor vessel shells in the unirradiated state
NASA Astrophysics Data System (ADS)
Skundin, M. A.; Chernobaeva, A. A.; Zhurko, D. A.; Krasikov, E. A.; Medvedev, K. I.
2013-04-01
The distributions of the chemical composition, the strength characteristics, and critical ductile-brittle transition temperature T cr are studied in the axial, radial, and tangential directions of the material of a test ring cut from a standard forging used for a VVER-1000 reactor vessel shell. The values of T cr of specimens cut from the test ring are shown to be well below those of the internal volume of the shell, which can explain the substantial scatter of the results obtained on reference specimens cut from the base metal.
Universal scaling of pT distribution of particles in relativistic nuclear collisions
NASA Astrophysics Data System (ADS)
Zhu, L. L.; Yang, C. B.
2007-04-01
With the experimental data from the STAR, PHENIX, and BRAHMS programs on the centrality and rapidity dependence of the pT spectrum in Au+Au and d+Au collisions, we show that a scaling distribution exists that is independent of the colliding system, centrality, and rapidity. The parameter for the average transverse momentum
Coherent radiative parton energy loss beyond the BDMPS-Z limit
NASA Astrophysics Data System (ADS)
Zapp, Korinna Christine; Wiedemann, Urs Achim
2012-06-01
It is widely accepted that a phenomenologically viable theory of jet quenching for heavy ion collisions requires the understanding of medium-induced parton energy loss beyond the limit of eikonal kinematics formulated by Baier-Dokshitzer-Mueller-Peigné-Schiff and Zakharov (BDMPS-Z). Here, we supplement a recently developed exact Monte Carlo implementation of the BDMPS-Z formalism with elementary physical requirements including exact energy-momentum conservation, a refined formulation of jet-medium interactions and a treatment of all parton branchings on the same footing. We document the changes induced by these physical requirements and we describe their kinematic origin.
Studies of Parton Propagation and Hadron Formation in the Space-Time Domain
Brooks, Will; Hakobyan, Hayk
2008-10-13
Over the past decade, new data from HERMES, Jefferson Lab, Fermilab, and RHIC that connect to parton propagation and hadron formation have become available. Semi-inclusive DIS on nuclei, the Drell-Yan reaction, and heavy-ion collisions all bring different kinds of information on parton propagation within a medium, while the most direct information on hadron formation comes from the DIS data. Over the next decade one can hope to begin to understand these data within a unified picture. We briefly survey the most relevant data and the common elements of the physics picture, then highlight the new Jefferson Lab data, and close with a prospective for the future.
Examining the Crossover from the Hadronic to Partonic Phase in QCD
Xu Mingmei; Yu Meiling; Liu Lianshou
2008-03-07
A mechanism, consistent with color confinement, for the transition between perturbative and physical vacua during the gradual crossover from the hadronic to partonic phase is proposed. The essence of this mechanism is the appearance and growing up of a kind of grape-shape perturbative vacuum inside the physical one. A percolation model based on simple dynamics for parton delocalization is constructed to exhibit this mechanism. The crossover from hadronic matter to sQGP (strongly coupled quark-gluon plasma) as well as the transition from sQGP to weakly coupled quark-gluon plasma with increasing temperature is successfully described by using this model.
Nondestructive Experimental Determination of the Pin-Power Distribution in Nuclear Fuel Assemblies
Svaerd, Staffan Jacobsson; Hakansson, Ane; Baecklin, Anders; Osifo, Otasowie; Willman, Christopher; Jansson, Peter
2005-07-15
A need for validation of modern production codes with respect to the calculated pin-power distribution has been recognized. A nondestructive experimental method for such validation has been developed based on a tomographic technique. The gamma-ray flux distribution is recorded in each axial node of the fuel assembly separately, whereby the relative rod-by-rod content of the fission product {sup 140}Ba is determined. Measurements indicate that 1 to 2% accuracy (1{sigma}) is achievable.A device has been constructed for in-pool measurements at reactor sites. The applicability has been demonstrated in measurements at the Swedish boiling water reactor (BWR) Forsmark 2 on irradiated fuel with a cooling time of 4 to 5 weeks. Data from the production code POLCA-7 have been compared to measured rod-by-rod contents of {sup 140}Ba. An agreement of 3.1% (1{sigma}) has been demonstrated.It is estimated that measurements can be performed on a complete BWR assembly in 25 axial nodes within an 8-h work shift. As compared to the conventional method, involving gamma scanning of individual fuel rods, this method does not require the fuel to be disassembled nor does the fuel channel have to be removed. The cost per measured fuel rod is estimated to be an order of magnitude lower than the conventional method.
NASA Astrophysics Data System (ADS)
Rawlins, B. G.; Scheib, C.; Tyler, A. N.; Jones, D.; Webster, R.; Young, M. E.
2009-04-01
The spatial distribution of caesium-137 (137Cs) across the land is of much interest because it can tell us about the redistribution of the radionuclide as a result of soil erosion, differential migration through the soil—or its complement, differential retention in the soil. Any such inferences from survey measurements depend on the assumption of a broadly even distribution from weapons testing fallout, and the substantial deposition of 137Cs in rain following the Chernobyl accident on 26 April 1986. Deposition from the latter was not uniform over large areas, of course, and measurements across northern England showed that the magnitude of 137Cs deposition depended largely on the distribution of convective rainfall in the days immediately after the accident. There were too few measurements of 137Cs deposition at close spacings to estimate local variation. Twenty years after the deposition from Chernobyl a detailed airborne radiometric survey of the whole of Northern Ireland was flown. Flights were made along transects 200 m apart with recordings at 80 m intervals along the flight lines to give more than one million data in total. We have used the data to investigate the spatial distribution of 137Cs. Our initial geostatistical analyses suggested substantial short-range variation in the distribution of 137Cs. We wished to determine whether soil erosion or soil type could account for this. We made further detailed analyses using the terrain parameter compound topographic index as an index of soil erosion and deposition and soil maps to account for the migration or retention of 137Cs. The concentration of 137Cs in the soil is greatest where most rain fell in the few days after the accident. However, the local variances are of similar magnitudes across the the majority of the province. The global variogram of the radionuclide shows a large proportion of the spatially correlated variance occurring within 700 m and a longer-range structure extending to 15 km. Local
NASA Astrophysics Data System (ADS)
Ozvenchuk, V.; Linnyk, O.; Gorenstein, M. I.; Bratkovskaya, E. L.; Cassing, W.
2013-06-01
We study the shear and bulk viscosities of partonic and hadronic matter as functions of temperature T within the parton-hadron-string dynamics (PHSD) off-shell transport approach. Dynamical hadronic and partonic systems in equilibrium are studied by the PHSD simulations in a finite box with periodic boundary conditions. The ratio of the shear viscosity to entropy density η(T)/s(T) from PHSD shows a minimum (with a value of about 0.1) close to the critical temperature Tc, while it approaches the perturbative QCD limit at higher temperatures in line with lattice QCD (lQCD) results. For T
A dynamic model for evaluating radionuclide distribution in forests from nuclear accidents.
Schell, W R; Linkov, I; Myttenaere, C; Morel, B
1996-03-01
The Chernobyl Nuclear Power Plant accident in 1986 caused radionuclide contamination in most countries in Eastern and Western Europe. A prime example is Belarus where 23% of the total land area received chronic levels; about 1.5 x 10(6) ha of forested lands were contaminated with 40--190 kBq m-2 and 2.5 x 10(4) ha received greater than 1,480 kBq m-2 of 137Cs and other long-lived radionuclides such as 90Sr and 239,240Pu. Since the radiological dose to the forest ecosystem will tend to accumulate over long time periods (decades to centuries), we need to determine what countermeasures can be taken to limit this dose so that the affected regions can, once again, safely provide habitat and natural forest products. To address some of these problems, our initial objective is to formulate a generic model, FORESTPATH, which describes the major kinetic processes and pathways of radionuclide movement in forests and natural ecosystems and which can be used to predict future radionuclide concentrations. The model calculates the time-dependent radionuclide concentrations in different compartments of the forest ecosystem based on the information available on residence half-times in two forest types: coniferous and deciduous. The results show that the model reproduces well the radionuclide cycling pattern found in the literature for deciduous and coniferous forests. Variability analysis was used to access the relative importance of specific parameter values in the generic model performance. The FORESTPASTH model can be easily adjusted for site-specific applications.
Sato, Itaru; Okada, Keiji; Sasaki, Jun; Chida, Hiroyuki; Satoh, Hiroshi; Miura, Kiyoshi; Kikuchi, Kaoru; Otani, Kumiko; Sato, Shusuke
2015-07-01
Radioactivity inspection of slaughtered cattle is generally conducted using a portion of the neck muscle; however, there is limited information about the distribution of radioactive cesium in cattle. In this study, therefore, we measured not only radioactive cesium but also stable cesium in various tissues of 19 cattle that had been kept in the area highly contaminated by the Fukushima nuclear accident. Skeletal muscles showed approximately 1.5-3.0 times higher concentration of radioactive cesium than internal organs. Radioactive cesium concentration in the tenderloin and top round was about 1.2 times as high as that in the neck muscle. The kidney showed the highest concentration of radioactive cesium among internal organs, whereas the liver was lowest. Radioactive cesium concentration in the blood was about 8% of that in the neck muscle. Characteristics of stable cesium distribution were almost the same as those of radioactive cesium. Correlation coefficient between radioactive cesium and stable cesium in tissues of individual cattle was 0.981 ± 0.012. When a suspicious level near 100 Bq/kg is detected in the neck of slaughtered cattle, re-inspection should be conducted using a different region of muscle, for example top round, to prevent marketing of beef that violates the Food Sanitation Act.
Probing the spatial distribution of nuclear magnetism in francium by optical spectroscopy
NASA Astrophysics Data System (ADS)
Aubin, S.; Tandecki, M.; Behr, J. A.; Pearson, M. R.; Zhang, J.; Orozco, L. A.; Collister, R.; Gwinner, G.; Gomez, E.
2013-10-01
The recently commissioned Francium Trapping Facility at TRIUMF in Vancouver, Canada will enable experiments to study weak interactions in francium atoms. We have successfully trapped and cooled 206 , 207 , 209 , 213 , 221Fr isotopes in large quantities (104 to 105) with trap lifetimes comparable to the radioactive lifetimes of the shortest lived trapped isotope (t1/2 = 14.8s). We use a combination of radio-frequency and optical spectroscopy to determine the hyperfine splittings of the 7P1 / 2 level of isotopes 206 , 207 , 209 , 213Fr to the 100 ppm level. These measurements, in combination with the known hyperfine ground state splittings, can be used to study the hyperfine anomaly in these isotopes. Our results extend previous work on the neutron distribution to a closed neutron shell isotope (213) and to neutron deficient isotopes (206, 207). These spectroscopic measurements also allow us to extract the isotope shifts to study changes in the charge radius. Work supported by NSERC and NRC from Canada, NSF and DOE from USA, and CONACYT from Mexico.
Jeon, Jae-Deok; Kwak, Seung-Yeop
2007-08-16
Nafion/sb-CD membranes were prepared by mixing 5 wt% Nafion solution with H+-form sulfated beta-cyclodextrin (sb-CD), and their water uptakes, ion exchange capacities (IECs), and ionic cluster size distributions were measured. Gravimetric and thermogravimetric measurements showed that the water uptake of the membranes increased with increases in their sb-CD content. The IECs of the membrane were measured with acid-base titration and found to increase with increases in the sb-CD content, reaching 0.96 mequiv/g for NC5 ("NCx" denotes a Nafion/sb-CD composite membrane containing x wt% of sb-CD). The cluster-correlation peaks and ionic cluster size distributions of the water-swollen membranes were determined using small-angle X-ray scattering (SAXS) and 1H nuclear magnetic resonance (NMR) cryoporometry, respectively. The SAXS experiments confirmed that increases in the sb-CD content of the membranes shifted the maximum SAXS peaks to lower angles, indicating an increase in the cluster correlation peak. NMR cryoporometry is based on the theory of the melting point depression, Delta Tm, of a liquid confined within a pore, which is dependent on the pore diameter. The melting point depression was determined by analyzing the variation of the NMR signal intensity with temperature. Our analysis of the intensity-temperature (IT) curves showed that the ionic cluster size distribution gradually became broader with increases in the membrane sb-CD content due to the increased water content, indicating an increase in the ionic cluster size. This result indicates that the presence of sb-CD with its many sulfonic acid sites in the Nafion membranes results in increases in the ionic cluster size as well as in the water uptake and the IEC. We conclude that NMR cryoporometry provides a method for determining the ionic cluster size on the nanometer scale in an aqueous environment, which cannot be obtained using other methods.
Nuclear analysis of the chornobyl fuel containing masses with heterogeneous fuel distribution.
Turski, R. B.
1998-10-14
Although significant data has been obtained on the condition and composition of the fuel containing masses (FCM) located in the concrete chambers under the Chernobyl Unit 4 reactor cavity, there is still uncertainty regarding the possible recriticality of this material. The high radiation levels make access extremely difficult, and most of the samples are from the FCM surface regions. There is little information on the interior regions of the FCM, and one cannot assume with confidence that the surface measurements are representative of the interior regions. Therefore, reasonable assumptions on the key parameters such as fuel concentration, the concentrations of impurities and neutron poisons (especially boron), the void fraction of the FCM due to its known porosity, and the degrees of fuel heterogeneity, are necessary to evaluate the possibility of recriticality. The void fraction is important since it introduces the possibility of water moderator being distributed throughout the FCM. Calculations indicate that the addition of 10 to 30 volume percent (v/o) water to the FCM has a significant impact on the calculated reactivity of the FCM. Therefore, water addition must be considered carefully. The other possible moderators are graphite and silicone dioxide. As discussed later in this paper, silicone dioxide moderation does not represent a criticality threat. For graphite, both heterogeneous fuel arrangements and very large volume fractions of graphite are necessary for a graphite moderated system to go critical. Based on the observations and measurements of the FCM compositions, these conditions do not appear creditable for the Chernobyl FCM. Therefore, the focus of the analysis reported in this paper will be on reasonable heterogeneous fuel arrangements and water moderation. The analysis will evaluate a range of fuel and diluent compositions.
Making Sense in the City: Dolly Parton, Early Reading and Educational Policy-Making
ERIC Educational Resources Information Center
Hall, Christine; Jones, Susan
2016-01-01
In this paper, we present a case study of a philanthropic literacy initiative, Dolly Parton's Imagination Library, a book-gifting scheme for under 5s, and consider the impact of the scheme on literacy policy in the English city where it was introduced. We bring four lenses to bear on the case study. First, we analyse the operation of the scheme in…
Drell-Yan Lepton pair production at NNLO QCD with parton showers
Hoeche, Stefan; Li, Ye; Prestel, Stefan
2015-04-13
We present a simple approach to combine NNLO QCD calculations and parton showers, based on the UNLOPS technique. We apply the method to the computation of Drell-Yan lepton-pair production at the Large Hadron Collider. We comment on possible improvements and intrinsic uncertainties.
Energy dependence of jet transport parameter and parton saturationin quark-gluon plasma
Casalderrey-Solana, Jorge; Wang, Xin-Nian
2007-06-24
We study the evolution and saturation of the gluondistribution function in the quark-gluon plasma as probed by apropagating parton and its effect on the computation of jet quenching ortransport parameter $\\hat q $. For thermal partons, the saturation scale$Q2_s$ is found to be proportional to the Debye screening mass $\\mu_D2$.For hard probes, evolution at small $x=Q2_s/6ET$ leads to jet energydependence of hat q. We study this dependence for both a conformal gaugetheory in weak and strong coupling limit and for (pure gluon) QCD. Theenergy dependence can be used to extract the shear viscosity $\\eta$ ofthe medium since $\\eta$ can be related to the transport parameter forthermal partons in a transport description. We also derive upper boundson the transport parameter for both energetic and thermal partons. Thelater leads to a lower bound on shear viscosity-to-entropy density ratiowhich is consistent with the conjectured lower bound $\\eta/s\\geq 1/4\\pi$.Implications on the study of jet quenching at RHIC and LHC and the bulkproperties of the dense matter are discussed.
J. J. Sakurai Prize for Theoretical Particle Physics Talk: Partons, QCD, and Factorization
NASA Astrophysics Data System (ADS)
Soper, Davison
2009-05-01
Many important cross sections in high-energy collisions are analyzed using factorization properties. I review the nature of factorization, how it arose from the parton model, and current issues in its development. This talk will be coordinated with the one by Collins.
Double distributions and evolution equations
A.V. Radyushkin
1998-05-01
Applications of perturbative QCD to deeply virtual Compton scattering and hard exclusive meson electroproduction processes require a generalization of usual parton distributions for the case when long-distance information is accumulated in nonforward matrix elements < p{prime} {vert_bar}O(0,z){vert_bar}p > of quark and gluon light-cone operators. In their previous papers the authors used two types of nonperturbative functions parameterizing such matrix elements: double distributions F(x,y;t) and nonforward distribution functions F{sub {zeta}}(X;t). Here they discuss in more detail the double distributions (DD's) and evolution equations which they satisfy. They propose simple models for F(x,y;t=0) DD's with correct spectral and symmetry properties which also satisfy the reduction relations connecting them to the usual parton densities f(x). In this way, they obtain self-consistent models for the {zeta}-dependence of nonforward distributions. They show that, for small {zeta}, one can easily obtain nonforward distributions (in the X > {zeta} region) from the parton densities: F{sub {zeta}} (X;t=0) {approx} f(X{minus}{zeta}/2).
Nuclear physics with a medium-energy Electron-Ion Collider
A. Accardi, V. Guzey, A. Prokudin, C. Weiss
2012-06-01
A polarized ep/eA collider (Electron-Ion Collider, or EIC) with variable center-of-mass energy {radical}s {approx} 20-70 GeV and a luminosity {approx}10{sup 34} cm{sup -2} s{sup -1} would be uniquely suited to address several outstanding questions of Quantum Chromodynamics (QCD) and the microscopic structure of hadrons and nuclei: (i) the three-dimensional structure of the nucleon in QCD (sea quark and gluon spatial distributions, orbital motion, polarization, correlations); (ii) the fundamental color fields in nuclei (nuclear parton densities, shadowing, coherence effects, color transparency); (iii) the conversion of color charge to hadrons (fragmentation, parton propagation through matter, in-medium jets). We briefly review the conceptual aspects of these questions and the measurements that would address them, emphasizing the qualitatively new information that could be obtained with the collider. Such a medium-energy EIC could be realized at Jefferson Lab after the 12 GeV Upgrade (MEIC), or at Brookhaven National Lab as the low-energy stage of eRHIC.
NASA Astrophysics Data System (ADS)
Higashi, H.; Morino, Y.; Furuichi, N.; Ohara, T.
2015-12-01
Massive amounts of anthropogenic radiocaesium 137Cs that were released into the environment by the Fukushima Daiichi Nuclear Power Plant accident in March 2011 are widely known to have extensively migrated to Pacific Ocean sediment off of eastern Japan. Several recent reports have stated that the sedimentary 137Cs is now stable with a remarkably heterogeneous distribution. The present study elucidates ocean dynamic processes causing this heterogeneous sedimentary 137Cs distribution in and around the shelf off Fukushima and adjacent prefectures. We performed a numerical simulation of oceanic 137Cs behaviour for about 10 months after the accident, using a comprehensive dynamic model involving advection-diffusion transport in seawater, adsorption and desorption to and from particulate matter, sedimentation and suspension on and from the bottom, and vertical diffusion transport in the sediment. A notable simulated result was that the sedimentary 137Cs significantly accumulated in a swath just offshore of the shelf break (along the 50-100 m isobath) as in recent observations, although the seabed in the entire simulation domain was assumed to have ideal properties such as identical bulk density, uniform porosity, and aggregation of particles with a single grain diameter. This result indicated that the heterogeneous sedimentary 137Cs distribution was not necessarily a result of the spatial distribution of 137Cs sediment adsorptivity. The present simulation suggests that the shape of the swath is mainly associated with spatiotemporal variation between bottom shear stress in the shallow shelf (< 50 m depths) and that offshore of the shelf break. In a large part of the shallow shelf, the simulation indicated that strong bottom friction suspending particulate matter from the seabed frequently occurred via a periodic spring tide about every 2 weeks and via occasional strong wind. The sedimentary 137Cs thereby could hardly stay on the surface of the seabed with the result that
Photo nuclear energy loss term for muon-nucleus interactions based on xi scaling model of QCD
NASA Technical Reports Server (NTRS)
Roychoudhury, R.
1985-01-01
Extensive air showers (EMC) experiments discovered a significant deviation of the ratio of structure functions of iron and deuteron from unity. It was established that the quark parton distribution in nuclei are different from the corresponding distribution in the nucleus. It was examined whether these results have an effect on the calculation of photo nucleus energy loss term for muon-nucleus nuclear interaction. Though the EMC and SLAC data were restricted to rather large q sq region it is expected that the derivation would persist even in the low q sq domain. For the ratio of iron and deuteron structure function a rather naive least square fit of the form R(x) = a + bx was taken and it is assumed that the formula is valid for the whole q sq region the absence of any knowledge of R(x) for small q sq.
Diño, Maria. R.; Mugnaini, Enrico
2009-01-01
In most mammals the cochlear nuclear complex (CN) contains a distributed system of granule cells (GCS), whose parallel fiber axons innervate the dorsal cochlear nucleus (DCN). Like their counterpart in cerebellum, CN granules are innervated by mossy fibers of various origins. The GCS is complemented by unipolar brush (UBCs) and Golgi cells, and by stellate and cartwheel cells of the DCN. This cerebellum-like microcircuit modulates the activity of the DCN’s main projection neurons, the pyramidal, giant and tuberculoventral neurons, and is thought to improve auditory performance by integrating acoustic and proprioceptive information. In this paper, we focus on the UBCs, a chemically heterogeneous neuronal population, using antibodies to calretinin, mGluR1α epidermal growth factor substrate 8 (Eps8) and the transcription factor Tbr2. Eps8 and Tbr2 labeled most of the CN’s UBCs, if not the entire population, while calretinin and mGluR1α distinguished two largely separate subsets with overlapping distributions. By double labeling with antibodies to Tbr2 and the α6 GABAA-receptor subunit, we found that UBCs populate all regions of the GCS and occur at remarkably high densities in the DCN and subpeduncular corner, but rarely in the lamina. Although GCS subregions likely share the same microcircuitry, their dissimilar UBC densities suggest they may be functionally distinct. UBCs and granules are also present in regions previously not included in the GCS, namely the rostrodorsal magnocellular portions of VCN, vestibular nerve root, trapezoid body, spinal tract and sensory and principal nuclei of the trigeminal nerve, and cerebellar peduncles. The UBC’s dendritic brush receives AMPA- and NMDA-mediated input from an individual mossy fiber, favoring singularity of input, and its axon most likely forms several mossy fiber-like endings that target numerous granule cells and other UBCs, as in the cerebellum. The UBCs therefore, may amplify afferent signals temporally and
NASA Astrophysics Data System (ADS)
Vavpetič, P.; Vogel-Mikuš, K.; Jeromel, L.; Ogrinc Potočnik, N.; Pongrac, P.; Drobne, D.; Pipan Tkalec, Ž.; Novak, S.; Kos, M.; Koren, Š.; Regvar, M.; Pelicon, P.
2015-04-01
The analysis of biological samples in frozen-hydrated state with micro-PIXE technique at Jožef Stefan Institute (JSI) nuclear microprobe has matured to a point that enables us to measure and examine frozen tissue samples routinely as a standard research method. Cryotome-cut slice of frozen-hydrated biological sample is mounted between two thin foils and positioned on the sample holder. The temperature of the cold stage in the measuring chamber is kept below 130 K throughout the insertion of the samples and the proton beam exposure. Matrix composition of frozen-hydrated tissue is consisted mostly of ice. Sample deterioration during proton beam exposure is monitored during the experiment, as both Elastic Backscattering Spectrometry (EBS) and Scanning Transmission Ion Microscopy (STIM) in on-off axis geometry are recorded together with the events in two PIXE detectors and backscattered ions from the chopper in a single list-mode file. The aim of this experiment was to determine differences and similarities between two kinds of biological sample preparation techniques for micro-PIXE analysis, namely freeze-drying and frozen-hydrated sample preparation in order to evaluate the improvements in the elemental localisation of the latter technique if any. In the presented work, a standard micro-PIXE configuration for tissue mapping at JSI was used with five detection systems operating in parallel, with proton beam cross section of 1.0 × 1.0 μm2 and a beam current of 100 pA. The comparison of the resulting elemental distributions measured at the biological tissue prepared in the frozen-hydrated and in the freeze-dried state revealed differences in elemental distribution of particular elements at the cellular level due to the morphology alteration in particular tissue compartments induced either by water removal in the lyophilisation process or by unsatisfactory preparation of samples for cutting and mounting during the shock-freezing phase of sample preparation.
Harada, Naoki; Nonaka, Masanori
2012-11-01
A magnitude 9.0 earthquake and subsequent large tsunami hit the northeastern coast of Japan on March 11, 2011. This resulted in serious damage to the reactors of the Fukushima Dai-ichi Nuclear Power Plant (FDNPP), operated by the Tokyo Electric Power Company. Large amounts of radionuclides were released from the FDNPP, a proportion of which were deposited onto the ground. In this study, we investigated soil radiocesium contamination of rice fields in Aga and Minamiuonuma, Niigata, ~130 and 200 km away from the FDNPP, respectively, as Niigata is one of the largest rice growing regions in Japan. Soil samples were collected from the plow layer of five rice fields in August and September, 5-6 months after the FDNPP accident. Results showed that radiocesium concentrations (the sum of Cs-134 and Cs-137) in the rice soil samples were ~300 Bq (kg dry soil)(-1). All samples contained a Cs-134/Cs-137 activity ratio of 0.68-0.96 after correction to March 11, 2011, showing that the radiocesium released from the FDNPP were deposited on these areas. Although the rice fields had been disturbed by farming processes after the FDNPP accident, the depth distribution of radiocesium concentrations in the plow layers showed higher concentrations in the upper soil layers. This suggests that spring tillage, flooding and puddling performed before rice transplantation may not disperse radiocesium deposited on the surface through the whole plow layer. In addition, the planar distribution of radiocesium concentrations was examined near the water inlet in one of the rice fields. Highest activities were found aligned with the direction of irrigation water discharge, indicating that radioactivity levels in rice fields may be elevated by an influx of additional radionuclides, probably in irrigation water, during farming.
NASA Astrophysics Data System (ADS)
Raepsaet, C.; Bossis, Ph.; Hamon, D.; Béchade, J. L.; Brachet, J. C.
2008-05-01
Hydrogen content and its distribution in in-core materials of nuclear plants are known to have a strong influence on their behaviour, especially on their mechanical properties but also on their corrosion resistance. This point has to be largely investigated in the case of the nuclear fuel cladding (Zr based alloys) of pressurized water reactors (PWR). Two situations have been considered here, with regards to the hydrogen content and its spatial distribution within the thickness of the tubes: Irradiated fuel cladding tubes after a nominal period under working conditions in a PWR core. Non-irradiated fuel cladding previously exposed to conditions representative of an hypothetical "loss of coolant accident" scenario (LOCA). As far as micrometric distributions of H were required, μ-ERDA has been performed at the nuclear microprobe of the Pierre Süe Laboratory. This facility is fitted with two beam lines. In the first one, used for non-active sample analysis, the μ-ERDA configuration has been improved to reduce the limits of detection and the reliability of the results. The second one offers the unique feature of being dedicated to radioactive samples. We will present the nuclear microprobe and emphasize on the μ-ERDA configuration of the two beam lines. We will illustrate the performance of the setup by describing the results obtained for Zircaloy-4 cladding both on non-irradiated and irradiated samples.
Tinsley, J H; Minke, P F; Bruno, K S; Plamann, M
1996-01-01
Dynactin is a multisubunit complex that is required for cytoplasmic dynein, a minus-end-directed, microtubule-associated motor, to efficiently transport vesicles along microtubules in vitro. p150Glued, the largest subunit of dynactin, has been identified in vertebrates and Drosophila and recently has been shown to interact with cytoplasmic dynein intermediate chains in vitro. The mechanism by which dynactin facilitates cytoplasmic dynein-dependent vesicle transport is unknown. We have devised a genetic screen for cytoplasmic dynein/dynactin mutants in the filamentous fungus Neurospora crassa. In this paper, we report that one of these mutants, ro-3, defines a gene encoding an apparent homologue of p150Glued, and we provide genetic evidence that cytoplasmic dynein and dynactin interact in vivo. The major structural features of vertebrate and Drosophila p150Glued, a microtubule-binding site at the N-terminus and two large alpha-helical coiled-coil regions contained within the distal two-thirds of the polypeptide, are conserved in Ro3. Drosophila p150Glued is essential for viability; however, ro-3 null mutants are viable, indicating that dynactin is not an essential complex in N. crassa. We show that N. crassa cytoplasmic dynein and dynactin mutants have abnormal nuclear distribution but retain the ability to organize cytoplasmic microtubules and actin in anucleate hyphae. Images PMID:8744947
Höche, Stefan; Schönherr, Marek
2012-11-01
We quantify uncertainties in the Monte Carlo simulation of inclusive and dijet final states, which arise from using the MC@NLO technique for matching next-to-leading order parton-level calculations and parton showers. We analyse a large variety of data from early measurements at the LHC. In regions of phase space where Sudakov logarithms dominate over high-energy effects, we observe that the main uncertainty can be ascribed to the free parameters of the parton shower. In complementary regions, the main uncertainty stems from the considerable freedom in the simulation of underlying events.
NASA Astrophysics Data System (ADS)
Matsuzaki, Hiroyuki; Muramatsu, Yasuyuki; Toyama, Chiaki; Ohno, Takeshi; Kusuno, Haruka; Miyake, Yasuto; Honda, Maki
2014-05-01
Among various radioactive nuclides emitted from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, Iodine-131 displayed high radioactivity just after the accident. Moreover if taken into human body, Iodine-131 concentrates in the thyroid and may cause the thyroid cancer. The recognition about the risk of Iodine-131 dose originated from the experience of the Chernobyl accident based on the epidemiological study [1]. It is thus important to investigate the detailed deposition distribution of I-131 to evaluate the radiation dose due to I-131 and watch the influence on the human health. However I-131 decays so rapidly (half life = 8.02 d) that it cannot be detected several months after the accident. At the recognition of the risk of I-131 on the Chernobyl occasion, it had gone several years after the accident. The reconstruction of I-131 distribution from Cs-137 distribution was not successful because the behavior of iodine and cesium was different because they have different chemical properties. Long lived radioactive isotope I-129 (half life = 1.57E+7 yr,), which is also a fission product as well as I-131, is ideal proxy for I-131 because they are chemically identical. Several studies had tried to quantify I-129 in 1990's but the analytical technique, especially AMS (Accelerator Mass Spectrometry), had not been developed well and available AMS facility was limited. Moreover because of the lack of enough data on I-131 just after the accident, the isotopic ratio I-129/I-131 of the Chernobyl derived iodine could not been estimated precisely [2]. Calculated estimation of the isotopic ratio showed scattered results. On the other hand, at the FDNPP accident detailed I-131 distribution is going to be successfully reconstructed by the systematical I-129 measurements by our group. We measured soil samples selected from a series of soil collection taken from every 2 km (or 5km, in the distant area) meshed region around FDNPP conducted by the Japanese Ministry of
Doye, V.; Wepf, R.; Hurt, E. C.
1994-01-01
Temperature-sensitive nucleoporin nup49-316 mutant cells accumulate poly(A)+ RNA inside the nucleus when shifted to restrictive temperature. We performed a synthetic lethal screen with this mutant allele to identify further components of the mRNA export machinery. A synthetic lethal mutant slv21 was isolated, which exhibited a ts phenotype and showed nuclear accumulation of poly(A)+ RNA at 37 degrees C. The wild-type gene complementing slv21 was cloned and sequenced. It encodes a novel protein Nup133p which is located at the nuclear pore complex. NUP133 is not an essential gene, but cells in which NUP133 is disrupted grow slowly at permissive temperatures and stop growing at 37 degrees C. Concomitant with the growth inhibition, nup133- cells accumulate poly(A)+ RNA inside the nucleus whereas nuclear import of a karyophilic reporter protein is not altered. Strikingly, nup133- cells display extensive clustering of nuclear pore complexes at a few sites on the nuclear envelope. However, the nuclear pore clustering phenotype and intranuclear accumulation of poly(A)+ RNA are not obligatorily linked, since an amino-terminally truncated Nup133p allows normal poly(A)+ RNA export, but does not complement the clustering phenotype of nup133- cells. Images PMID:7813444
Lattice QCD calculations of transverse momentum-dependent parton distributions (TMDs)
NASA Astrophysics Data System (ADS)
Engelhardt, M.; Musch, B.; Bhattacharya, T.; Green, J. R.; Gupta, R.; Hägler, P.; Krieg, S.; Negele, J.; Pochinsky, A.; Schäfer, A.; Syritsyn, S.; Yoon, B.
2016-03-01
An ongoing program of evaluating TMD observables within Lattice QCD is reviewed, summarizing recent progress with respect to several challenges faced by such calculations. These lattice calculations are based on a definition of TMDs through hadronic matrix elements of quark bilocal operators containing staple-shaped gauge connections. A parametrization of the matrix elements in terms of invariant amplitudes serves to cast them in the Lorentz frame preferred for a lattice calculation. Data on the naively T-odd Sivers and Boer-Mulders effects as well as the transversity TMD are presented.
Bedlinskiy, Ivan; Niccolai, Silvia; Stoler, Paul; Adhikari, Krishna; Aghasyan, Mher; Amaryan, Moskov; Anghinolfi, Marco; Avagyan, Harutyun; Baghdasaryan, Hovhannes; Ball, Jacques; Baltzell, Nathan; Battaglieri, Marco; Bennett, Robert; Biselli, Angela; Bookwalter, Craig; Boyarinov, Sergey; Briscoe, William; Brooks, Williams; Burkert, Volker; Carman, Daniel; Celentano, Andrea; Chandavar, Shloka; Charles, Gabriel; Contalbrigo, Marco; Crede, Volker; D'Angelo, Annalisa; Daniel, Aji; Dashyan, Natalya; De Vita, Raffaella; De Sanctis, Enzo; Deur, Alexandre; Djalali, Chaden; Doughty, David; Dupre, Raphael; Egiyan, Hovanes; El Alaoui, Ahmed; Elfassi, Lamiaa; Elouadrhiri, Latifa; Eugenio, Paul; Fedotov, Gleb; Fegan, Stuart; Fleming, Jamie; Forest, Tony; Garcon, Michel; Gevorgyan, Nerses; Giovanetti, Kevin; Girod, Francoi-Xavier; Gohn, Wesley; Gothe, Ralf; Graham, Lewis; Griffioen, Keith; Guegan, Baptiste; Guidal, Michel; Guo, Lei; Hafidi, Kawtar; Hakobyan, Hayk; Hanretty, Charles; Heddle, David; Hicks, Kenneth; Holtrop, Maurik; Ilieva, Yordanka; Ireland, David; Ishkhanov, Boris; Isupov, Evgeny; Jo, Hyon-Suk; Joo, Kyungseon; Keller, Dustin; Khanddaker, Mahbubul; Khertarpal, Puneet; Kim, Andrey; Kim, Wooyoung; Klein, Franz; Koirala, Suman; Kubarovsky, A; Kuhn, Sebastian; Kuleshov, Sergey; Kvaltine, Nicholas; Livingston, Kenneth; Lu, Haiyun; MacGregor, Ian; Mao, Yuqing; Markov, Nikolai; Martinez, D; Mayer, Michael; McKinnon, Bryan; Meyer, Curtis; Mineeva, Taisiya; Mirazita, Marco; Mokeev, Viktor; Moutarde, Herve; Munevar Espitia, Edwin; Munoz Camacho, Carlos; Nadel-Turonski, Pawel; Niculescu, Gabriel; Niculescu, Maria-Ioana; Osipenko, Mikhail; Ostrovidov, Alexander; Pappalardo, Luciano; Permuzyan, Rafayel; Park, Kijun; Park, Sungkyun; Pasyuk, Eugene; Pereira, Sergio; Phelps, Evan; Pisano, Silvia; Pogorelko, Oleg; Pozdnyakov, Sergey; Price, John; Procureur, Sebastien; Prok, Yelena; Protopopescu, Dan; Puckett, Andrew; Raue, Brian; Ricco, Giovanni; Rimal, Dipak; Ripani, Marco; Rosner, Guenther; Rossi, Patrizia; Sabatie, Franck; Saini, Mukesh; Salgado, Carlos; Saylor, Nicholas; Schott, Diane; Schumacher, Reinhard; Seder, Erin; Seraydaryan, Heghine; Sharabian, Youri; Smith, Gregory; Sober, Daniel; Sokhan, Daria; Stepanyan, Samuel; Strauch, Steffen; Taiuti, Mauro; Tang, Wei; Taylor, Charles; Tian, Ye; Tkachenko, Svyatoslav; Ungaro, Maurizio; Vineyard, Michael; Vlasov, Alexander; Voskanyan, Hakob; Voutier, Eric; Walford, Natalie; Watts, Daniel; Weinstein, Lawrence; Weygan, Dennis; Wood, Michael; Zachariou, Nicholas; Zhang, Jixie; Zhao, Zhiwen; Zonta, Irene
2012-09-01
Exclusive $\\pi^0$ electroproduction at a beam energy of 5.75 GeV has been measured with the Jefferson Lab CLAS spectrometer. Differential cross sections were measured at more than 1800 kinematic values in $Q^2$, $x_B$, $t$, and $\\phi_\\pi$, in the $Q^2$ range from 1.0 to 4.6 GeV$^2$,\\ $-t$ up to 2 GeV$^2$, and $x_B$ from 0.1 to 0.58. Structure functions $\\sigma_T +\\epsilon \\sigma_L, \\sigma_{TT}$ and $\\sigma_{LT}$ were extracted as functions of $t$ for each of 17 combinations of $Q^2$ and $x_B$. The data were compared directly with two handbag-based calculations including both longitudinal and transversity GPDs. Inclusion of only longitudinal GPDs very strongly underestimates $\\sigma_T +\\epsilon \\sigma_L$ and fails to account for $\\sigma_{TT}$ and $\\sigma_{LT}$, while inclusion of transversity GPDs brings the calculations into substantially better agreement with the data. There is very strong sensitivity to the relative contributions of nucleon helicity flip and helicity non-flip processes. The results confirm that exclusive $\\pi^0$ electroproduction offers direct experimental access to the transversity GPDs.
Marčiulionienė, D; Mažeika, J; Lukšienė, B; Jefanova, O; Mikalauskienė, R; Paškauskas, R
2015-07-01
Based on γ-ray emitting artificial radionuclide spectrometric measurements, an assessment of areal and vertical distribution of (137)Cs, (60)Co and (54)Mn activity concentrations in bottom sediments of Lake Drūkšiai was performed. Samples of bottom sediments from seven monitoring stations within the cooling basin were collected in 1988-1996 and 2007-2010 (in July-August). For radionuclide areal distribution analysis, samples from the surface 0-5 cm layer were used. Multi sample cores sliced 2 cm, 3 cm or 5 cm thick were used to study the vertical distribution of radionuclides. The lowest (137)Cs activity concentrations were obtained for two stations that were situated close to channels with radionuclide discharges, but with sediments that had a significantly smaller fraction of organic matter related to finest particles and consequently smaller radionuclide retention potential. The (137)Cs activity concentration was distributed quite evenly in the bottom sediments from other investigated monitoring stations. The highest (137)Cs activity concentrations in the bottom sediments of Lake Drūkšiai were measured in the period of 1988-1989; in 1990, the (137)Cs activity concentrations slightly decreased and they varied insignificantly over the investigation period. The obtained (238)Pu/(239,240)Pu activity ratio values in the bottom sediments of Lake Drūkšiai represented radioactive pollution with plutonium from nuclear weapon tests. Higher (60)Co and (54)Mn activity concentrations were observed in the monitoring stations that were close to the impact zones of the technical water outlet channel and industrial rain drainage system channel. (60)Co and (54)Mn activity concentrations in the bottom sediments of Lake Drūkšiai significantly decreased when operations at both INPP reactor units were stopped. The vertical distribution of radionuclides in bottom sediments revealed complicated sedimentation features, which may have been affected by a number of natural and
Marčiulionienė, D; Mažeika, J; Lukšienė, B; Jefanova, O; Mikalauskienė, R; Paškauskas, R
2015-07-01
Based on γ-ray emitting artificial radionuclide spectrometric measurements, an assessment of areal and vertical distribution of (137)Cs, (60)Co and (54)Mn activity concentrations in bottom sediments of Lake Drūkšiai was performed. Samples of bottom sediments from seven monitoring stations within the cooling basin were collected in 1988-1996 and 2007-2010 (in July-August). For radionuclide areal distribution analysis, samples from the surface 0-5 cm layer were used. Multi sample cores sliced 2 cm, 3 cm or 5 cm thick were used to study the vertical distribution of radionuclides. The lowest (137)Cs activity concentrations were obtained for two stations that were situated close to channels with radionuclide discharges, but with sediments that had a significantly smaller fraction of organic matter related to finest particles and consequently smaller radionuclide retention potential. The (137)Cs activity concentration was distributed quite evenly in the bottom sediments from other investigated monitoring stations. The highest (137)Cs activity concentrations in the bottom sediments of Lake Drūkšiai were measured in the period of 1988-1989; in 1990, the (137)Cs activity concentrations slightly decreased and they varied insignificantly over the investigation period. The obtained (238)Pu/(239,240)Pu activity ratio values in the bottom sediments of Lake Drūkšiai represented radioactive pollution with plutonium from nuclear weapon tests. Higher (60)Co and (54)Mn activity concentrations were observed in the monitoring stations that were close to the impact zones of the technical water outlet channel and industrial rain drainage system channel. (60)Co and (54)Mn activity concentrations in the bottom sediments of Lake Drūkšiai significantly decreased when operations at both INPP reactor units were stopped. The vertical distribution of radionuclides in bottom sediments revealed complicated sedimentation features, which may have been affected by a number of natural and
Modified Dihadron Fragmentation Functions in Hot and Nuclear Matter
Majumder, A.; Wang Enke; Wang Xinnian
2007-10-12
Medium modification of dihadron fragmentation functions due to gluon bremsstrahlung induced by multiple partonic scattering is studied in both deep-inelastic scattering (DIS) off large nuclei and high-energy heavy-ion collisions within the same framework of twist expansion. The modification for dihadrons is found to closely follow that for single hadrons, leading to a weak nuclear suppression of their ratios in DIS experiments. A mild enhancement of the near-side correlation of two high transverse momentum hadrons with increasing centrality is found in heavy-ion collisions due to trigger bias and the rise in parton energy loss with centrality. Successful comparisons between theory and experiment for multihadron observables in both confining and deconfined media offer comprehensive evidence for partonic energy loss as the mechanism of jet modification in dense matter.
Momentum broadening of a fast parton in a perturbative quark-gluon plasma
Majumder, Abhijit; Mueller, Berndt; Mrowczynski, Stanislaw
2009-12-15
The average transverse momentum transfer per unit path length to a fast parton scattering elastically in a perturbative quark-gluon plasma is related to the radiative energy loss of the parton. We first calculate the momentum transfer coefficient q-circumflex in terms of a classical Langevin problem and then define it quantum mechanically through a scattering matrix element. After treating the well-known case of a quark-gluon plasma in equilibrium, we consider an off-equilibrium unstable plasma. As a specific example, we treat the two-stream plasma with unstable modes of longitudinal chromoelectric field. In the presence of the instabilities, q-circumflex is shown to exponentially grow in time.
COLLINEAR SPLITTING, PARTON EVOLUTION AND THE STRANGE-QUARK ASYMMETRY OF THE NUCLEON IN NNLO QCD.
RODRIGO,G.CATANI,S.DE FLORIAN, D.VOGELSANG,W.
2004-04-25
We consider the collinear limit of QCD amplitudes at one-loop order, and their factorization properties directly in color space. These results apply to the multiple collinear limit of an arbitrary number of QCD partons, and are a basic ingredient in many higher-order computations. In particular, we discuss the triple collinear limit and its relation to flavor asymmetries in the QCD evolution of parton densities at three loops. As a phenomenological consequence of this new effect, and of the fact that the nucleon has non-vanishing quark valence densities, we study the perturbative generation of a strange-antistrange asymmetry s(x)-{bar s}(x) in the nucleon's sea.
Off-shell single-top production at NLO matched to parton showers
NASA Astrophysics Data System (ADS)
Frederix, R.; Frixione, S.; Papanastasiou, A. S.; Prestel, S.; Torrielli, P.
2016-06-01
We study the hadroproduction of a W b pair in association with a light jet, focusing on the dominant t-channel contribution and including exactly at the matrix-element level all non-resonant and off-shell effects induced by the finite top-quark width. Our simulations are accurate to the next-to-leading order in QCD, and are matched to the Herwig6 and Pythia8 parton showers through the MC@NLO method. We present phenomenological results relevant to the 8 TeV LHC, and carry out a thorough comparison to the case of on-shell t-channel single-top production. We formulate our approach so that it can be applied to the general case of matrix elements that feature coloured intermediate resonances and are matched to parton showers.
Off-shell single-top production at NLO matched to parton showers
Frederix, R.; Frixione, S.; Papanastasiou, A. S.; Prestel, S.; Torrielli, P.
2016-06-06
We study the hadroproduction of a W b pair in association with a light jet, focusing on the dominant t -channel contribution and including exactly at the matrix-element level all non-resonant and off-shell effects induced by the finite top-quark width. Our simulations are accurate to the next-to-leading order in QCD, and are matched to the Herwig6 and Pythia8 parton showers through the MC@NLO method. We present phenomenological results relevant to the 8 TeV LHC, and carry out a thorough comparison to the case of on-shell t -channel single-top production. Furthermore, we formulate our approach so that it can be appliedmore » to the general case of matrix elements that feature coloured intermediate resonances and are matched to parton showers.« less
Ma, Guo -Liang; Bzdak, Adam
2014-11-04
In this study, we show that the incoherent elastic scattering of partons, as present in a multi-phase transport model (AMPT), with a modest parton–parton cross-section of σ = 1.5 – 3 mb, naturally explains the long-range two-particle azimuthal correlation as observed in proton–proton and proton–nucleus collisions at the Large Hadron Collider.
Alwall, J.; Hoche, S.; Krauss, F.; Lavesson, N.; Lonnblad, L.; Maltoni, F.; Mangano, M.L.; Moretti, M.; Papadopoulos, C.G.; Piccinini, F.; Schumann, S.; Treccani, M.; Winter, J.; Worek, M.; /SLAC /Durham U., IPPP /Lund U. /Louvain U. /CERN /Ferrara U. /INFN, Ferrara /Athens U. /INFN, Pavia /Dresden, Tech. U. /Karlsruhe U., TP /Silesia U.
2007-06-27
We compare different procedures for combining fixed-order tree-level matrix-element generators with parton showers. We use the case of W-production at the Tevatron and the LHC to compare different implementations of the so-called CKKW and MLM schemes using different matrix-element generators and different parton cascades. We find that although similar results are obtained in all cases, there are important differences.
Studies of partonic transverse momentum and spin structure of the nucleon
NASA Astrophysics Data System (ADS)
Contalbrigo, M.
2014-06-01
The investigation of the partonic degrees of freedom beyond collinear approximation (3D description) has been gained increasing interest in the last decade. The Thomas Jefferson National Laboratory, after the CEBAF upgrade to 12 GeV, will become the most complete facility for the investigation of the hadron structure in the valence region by scattering of polarized electron off various polarized nucleon targets. A compendium of the planned experiments is here presented.
One-Loop Multi-Parton Amplitudes with a Vector Boson for the LHC
Berger, C.F.; Bern, Z.; Dixon, L.J.; Cordero, F.Febres; Forde, D.; Ita, H.; Kosower, D.A.; Maitre, D.; /SLAC
2008-08-11
In this talk, we present the first, numerically stable, results for the one-loop amplitudes needed for computing W; Z + 3 jet cross sections at the LHC to next-to-leading order in the QCD coupling. We implemented these processes in BlackHat, an automated program based on on-shell methods. These methods scale very well with increasing numbers of external partons, and are applicable to a wide variety of problems of phenomenological interest at the LHC.
Engel, R.; Bopp, F.W.; Pertermann, D.; Ranft, J. )
1992-12-01
In the framework of a two-component dual parton model we perform a fit to {ital p{bar p}} total, elastic, inelastic, and single-diffractive cross-section data at collider energies. The fit including diffractive data gives better results using the supercritical soft Pomeron instead of the critical one. Because of the different structure function parametrizations the predictions of cross sections at supercollider energies are subject to large uncertainties.
Studies of Multi-Parton Interactions in Photon+Jets Events at D0
Bandurin, Dmitry; /Florida State U.
2011-09-01
We consider sample of inclusive {gamma} + 3 jet events collected by the D0 experiment. The double parton fraction (f{sub DP}) and effective cross section {sigma}{sub eff}, a process-independent scale parameter related to the parton density inside the nucleon, are measured in three intervals of the second (ordered in p{sub T}) jet transverse momentum p{sub T}{sup jet2} within the 15 {le} p{sub T}{sup jet2} {le} 30 GeV range. Also we measured cross sections as a function of the angle in the plane transverse to the beam direction between the transverse momentum (p{sub T}) of the {gamma} + leading jet system and p{sub T} of the other jet for {gamma} + 2 jet, or p{sub T} sum of the two other jets for {gamma} + 3 jet events. The results are compared to different models of multiple parton interactions (MPI) in the PYTHIA and SHERPA Monte Carlo (MC) generators.
Multi-parton loop amplitudes and next-to-leading order jet cross-sections
Bern, Z.; Dixon, L.; Kosower, D.A.; Signer, A.
1998-02-01
The authors review recent developments in the calculation of QCD loop amplitudes with several external legs, and their application to next-to-leading order jet production cross-sections. When a number of calculational tools are combined together--helicity, color and supersymmetry decompositions, plus unitarity and factorization properties--it becomes possible to compute multi-parton one-loop QCD amplitudes without ever evaluating analytically standard one-loop Feynman diagrams. One-loop helicity amplitudes are now available for processes with five external partons (ggggg, q{anti q}ggg and q{anti q}q {anti q}{prime} g), and for an intermediate vector boson V {equivalent_to} {gamma}{sup *}, Z, W plus four external partons (V q{anti q} and V q{anti q}q{prime}{anti q}{prime}). Using these amplitudes, numerical programs have been constructed for the next-to-leading order corrections to the processes p{anti p} {yields} 3 jets (ignoring quark contributions so far) and e{sup +}e{sup -} {yields} 4 jets.
NASA Astrophysics Data System (ADS)
Armbruster, P.; Bernas, M.; Czajkowski, S.; Geissel, H.; Aumann, T.; Dessagne, Ph.; Donzaud, C.; Hanelt, E.; Heinz, A.; Hesse, M.; Kozhuharov, C.; Miehe, Ch.; Münzenberg, G.; Pfützner, M.; Schmidt, K.-H.; Schwab, W.; Stéphan, C.; Sümmerer, K.; Tassan-Got, L.; Voss, B.
1996-12-01
Charge distributions of fragments from low energy nuclear fission are investigated in reactions of highly fissile238U projectiles at relativistic energies (750 A·MeV) with a heavy (Pb) and a light (Be) target. The fully stripped fission fragments are separated by the Fragment Separator (FRS). Their high kinetic energies in the laboratory system allow the identification of all atomic numbers by using Multiple-Sampling Ionization Chambers (MUSIC). The elemental distributions of fragments observed at larger magnetic rigidities than the238U projectiles show asymmetric break-up and odd-even effects. They indicate a low energy fission process, induced mainly by dissociation in the electro-magnetic field for the U/Pb-system, or by peripheral nuclear interactions for the U/Be-system.
Collins, John; Rogers, Ted
2015-04-01
There is considerable controversy about the size and importance of non-perturbative contributions to the evolution of transverse momentum dependent (TMD) parton distribution functions. Standard fits to relatively high-energy Drell-Yan data give evolution that when taken to lower Q is too rapid to be consistent with recent data in semi-inclusive deeply inelastic scattering. Some authors provide very different forms for TMD evolution, even arguing that non-perturbative contributions at large transverse distance bT are not needed or are irrelevant. Here, we systematically analyze the issues, both perturbative and non-perturbative. We make a motivated proposal for the parameterization of the non-perturbative part of the TMD evolution kernel that could give consistency: with the variety of apparently conflicting data, with theoretical perturbative calculations where they are applicable, and with general theoretical non-perturbative constraints on correlation functions at large distances. We propose and use a scheme- and scale-independent function A(bT) that gives a tool to compare and diagnose different proposals for TMD evolution. We also advocate for phenomenological studies of A(bT) as a probe of TMD evolution. The results are important generally for applications of TMD factorization. In particular, they are important to making predictions for proposed polarized Drell- Yan experiments to measure the Sivers function.
Collins, John; Rogers, Ted
2015-04-01
There is considerable controversy about the size and importance of non-perturbative contributions to the evolution of transverse momentum dependent (TMD) parton distribution functions. Standard fits to relatively high-energy Drell-Yan data give evolution that when taken to lower Q is too rapid to be consistent with recent data in semi-inclusive deeply inelastic scattering. Some authors provide very different forms for TMD evolution, even arguing that non-perturbative contributions at large transverse distance bT are not needed or are irrelevant. Here, we systematically analyze the issues, both perturbative and non-perturbative. We make a motivated proposal for the parameterization of the non-perturbative part ofmore » the TMD evolution kernel that could give consistency: with the variety of apparently conflicting data, with theoretical perturbative calculations where they are applicable, and with general theoretical non-perturbative constraints on correlation functions at large distances. We propose and use a scheme- and scale-independent function A(bT) that gives a tool to compare and diagnose different proposals for TMD evolution. We also advocate for phenomenological studies of A(bT) as a probe of TMD evolution. The results are important generally for applications of TMD factorization. In particular, they are important to making predictions for proposed polarized Drell- Yan experiments to measure the Sivers function.« less
Cha, Keith; Sen, Progga; Raghunayakula, Sarita; Zhang, Xiang-Dong
2015-01-01
The Ran GTPase activating protein RanGAP1 plays an essential role in nuclear transport by stimulating RanGTP hydrolysis in the cytoplasmic compartment. In mammalian cells, unmodified RanGAP1 is predominantly cytoplasmic, whereas modification by small ubiquitin-related modifier protein (SUMO) targets RanGAP1 to the cytoplasmic filaments of nuclear pore complex (NPC). Although RanGAP1 contains nine putative nuclear export signals and a nuclear localization signal, little is known if RanGAP1 shuttles between the nuclear and cytoplasmic compartments and how its primary localization in the cytoplasm and at the NPC is regulated. Here we show that inhibition of CRM1-mediated nuclear export using RNAi-knockdown of CRM1 and inactivation of CRM1 by leptomycin B (LMB) results in nuclear accumulation of RanGAP1. LMB treatment induced a more robust redistribution of RanGAP1 from the cytoplasm to the nucleoplasm compared to CRM1 RNAi and also uniquely triggered a decrease or loss of RanGAP1 localization at the NPC, suggesting that LMB treatment is more effective in inhibiting CRM1-mediated nuclear export of RanGAP1. Our time-course analysis of LMB treatment reveals that the NPC-associated RanGAP1 is much more slowly redistributed to the nucleoplasm than the cytoplasmic RanGAP1. Furthermore, LMB-induced nuclear accumulation of RanGAP1 is positively correlated with an increase in levels of SUMO-modified RanGAP1, suggesting that SUMOylation of RanGAP1 may mainly take place in the nucleoplasm. Lastly, we demonstrate that the nuclear localization signal at the C-terminus of RanGAP1 is required for its nuclear accumulation in cells treated with LMB. Taken together, our results elucidate that RanGAP1 is actively transported between the nuclear and cytoplasmic compartments, and that the cytoplasmic and NPC localization of RanGAP1 is dependent on CRM1-mediated nuclear export. PMID:26506250
Energy loss in a partonic transport model including bremsstrahlung processes
Fochler, Oliver; Greiner, Carsten; Xu Zhe
2010-08-15
A detailed investigation of the energy loss of gluons that traverse a thermal gluonic medium simulated within the perturbative QCD-based transport model BAMPS (a Boltzmann approach to multiparton scatterings) is presented in the first part of this work. For simplicity the medium response is neglected in these calculations. The energy loss from purely elastic interactions is compared with the case where radiative processes are consistently included based on the matrix element by Gunion and Bertsch. From this comparison, gluon multiplication processes gg{yields}ggg are found to be the dominant source of energy loss within the approach employed here. The consequences for the quenching of gluons with high transverse momentum in fully dynamic simulations of Au+Au collisions at the BNL Relativistic Heavy Ion Collider (RHIC) energy of {radical}(s)=200A GeV are discussed in the second major part of this work. The results for central collisions as discussed in a previous publication are revisited, and first results on the nuclear modification factor R{sub AA} for noncentral Au+Au collisions are presented. They show a decreased quenching compared to central collisions while retaining the same shape. The investigation of the elliptic flow v{sub 2} is extended up to nonthermal transverse momenta of 10 GeV, exhibiting a maximum v{sub 2} at roughly 4 to 5 GeV and a subsequent decrease. Finally the sensitivity of the aforementioned results on the specific implementation of the effective modeling of the Landau-Pomeranchuk-Migdal (LPM) effect via a formation-time-based cutoff is explored.
Taira, Yasuyuki; Hayashida, Naomi; Tsuchiya, Rimi; Yamaguchi, Hitoshi; Takahashi, Jumpei; Kazlovsky, Alexander; Urazalin, Marat; Rakhypbekov, Tolebay; Yamashita, Shunichi; Takamura, Noboru
2013-01-01
For the current on-site evaluation of the environmental contamination and contributory external exposure after the accident at the Chernobyl Nuclear Power Plant (CNPP) and the nuclear tests at the Semipalatinsk Nuclear Testing Site (SNTS), the concentrations of artificial radionuclides in soil samples from each area were analyzed by gamma spectrometry. Four artificial radionuclides ((241)Am, (134)Cs, (137)Cs, and (60)Co) were detected in surface soil around CNPP, whereas seven artificial radionuclides ((241)Am, (57)Co, (137)Cs, (95)Zr, (95)Nb, (58)Co, and (60)Co) were detected in surface soil around SNTS. Effective doses around CNPP were over the public dose limit of 1 mSv/y (International Commission on Radiological Protection, 1991). These levels in a contaminated area 12 km from Unit 4 were high, whereas levels in a decontaminated area 12 km from Unit 4 and another contaminated area 15 km from Unit 4 were comparatively low. On the other hand, the effective doses around SNTS were below the public dose limit. These findings suggest that the environmental contamination and effective doses on the ground definitely decrease with decontamination such as removing surface soil, although the effective doses of the sampling points around CNPP in the present study were all over the public dose limit. Thus, the remediation of soil as a countermeasure could be an extremely effective method not only for areas around CNPP and SNTS but also for areas around the Fukushima Dai-ichi Nuclear Power Plant (FNPP), and external exposure levels will be certainly reduced. Long-term follow-up of environmental monitoring around CNPP, SNTS, and FNPP, as well as evaluation of the health effects in the population residing around these areas, could contribute to radiation safety and reduce unnecessary exposure to the public. PMID:23469013
Taira, Yasuyuki; Hayashida, Naomi; Tsuchiya, Rimi; Yamaguchi, Hitoshi; Takahashi, Jumpei; Kazlovsky, Alexander; Urazalin, Marat; Rakhypbekov, Tolebay; Yamashita, Shunichi; Takamura, Noboru
2013-01-01
For the current on-site evaluation of the environmental contamination and contributory external exposure after the accident at the Chernobyl Nuclear Power Plant (CNPP) and the nuclear tests at the Semipalatinsk Nuclear Testing Site (SNTS), the concentrations of artificial radionuclides in soil samples from each area were analyzed by gamma spectrometry. Four artificial radionuclides ((241)Am, (134)Cs, (137)Cs, and (60)Co) were detected in surface soil around CNPP, whereas seven artificial radionuclides ((241)Am, (57)Co, (137)Cs, (95)Zr, (95)Nb, (58)Co, and (60)Co) were detected in surface soil around SNTS. Effective doses around CNPP were over the public dose limit of 1 mSv/y (International Commission on Radiological Protection, 1991). These levels in a contaminated area 12 km from Unit 4 were high, whereas levels in a decontaminated area 12 km from Unit 4 and another contaminated area 15 km from Unit 4 were comparatively low. On the other hand, the effective doses around SNTS were below the public dose limit. These findings suggest that the environmental contamination and effective doses on the ground definitely decrease with decontamination such as removing surface soil, although the effective doses of the sampling points around CNPP in the present study were all over the public dose limit. Thus, the remediation of soil as a countermeasure could be an extremely effective method not only for areas around CNPP and SNTS but also for areas around the Fukushima Dai-ichi Nuclear Power Plant (FNPP), and external exposure levels will be certainly reduced. Long-term follow-up of environmental monitoring around CNPP, SNTS, and FNPP, as well as evaluation of the health effects in the population residing around these areas, could contribute to radiation safety and reduce unnecessary exposure to the public.
NASA Astrophysics Data System (ADS)
Geiger, Klaus
1997-08-01
VNI is a general-purpose Monte Carlo event generator, which includes the simulation of lepton-lepton, lepton-hadron, lepton-nucleus, hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions. On the basis of renormalization-group improved parton description and quantum-kinetic theory, it uses the real-time evolution of parton cascades in conjunction with a self-consistent hadronization scheme that is governed by the dynamics itself. The causal evolution from a specific initial state (determined by the colliding beam particles) is followed by the time development of the phase-space densities of partons, pre-hadronic parton clusters, and final-state hadrons, in position space, momentum space and color space. The parton evolution is described in terms of a space-time generalization of the familiar momentum-space description of multiple (semi) hard interactions in QCD, involving 2 → 2 parton collisions, 2 → 1 parton fusion processes, and 1 → 2 radiation processes. The formation of color-singlet pre-hadronic clusters and their decays into hadrons, on the other hand, is treated by using a spatial criterion motivated by confinement and a non-perturbative model for hadronization. This article gives a brief review of the physics underlying VNI, which is followed by a detailed description of the program itself. The latter program description emphasizes easy-to-use pragmatism and explains how to use the program (including a simple example), annotates input and control parameters, and discusses output data provided by it.
Randrup, Jørgen; Möller, Peter
2011-04-01
Although nuclear fission can be understood qualitatively as an evolution of the nuclear shape, a quantitative description has proven to be very elusive. In particular, until now, there existed no model with demonstrated predictive power for the fission-fragment mass yields. Exploiting the expected strongly damped character of nuclear dynamics, we treat the nuclear shape evolution in analogy with Brownian motion and perform random walks on five-dimensional fission potential-energy surfaces which were calculated previously and are the most comprehensive available. Test applications give good reproduction of highly variable experimental mass yields. This novel general approach requires only a single new global parameter, namely, the critical neck size at which the mass split is frozen in, and the results are remarkably insensitive to its specific value.
Randrup, Joergen; Moeller, Peter
2011-04-01
Although nuclear fission can be understood qualitatively as an evolution of the nuclear shape, a quantitative description has proven to be very elusive. In particular, until now, there existed no model with demonstrated predictive power for the fission-fragment mass yields. Exploiting the expected strongly damped character of nuclear dynamics, we treat the nuclear shape evolution in analogy with Brownian motion and perform random walks on five-dimensional fission potential-energy surfaces which were calculated previously and are the most comprehensive available. Test applications give good reproduction of highly variable experimental mass yields. This novel general approach requires only a single new global parameter, namely, the critical neck size at which the mass split is frozen in, and the results are remarkably insensitive to its specific value.
NASA Astrophysics Data System (ADS)
Alvioli, M.; Ciofi degli Atti, C.; Morita, H.
2016-10-01
Background: The two-nucleon momentum distributions of nucleons N1 and N2 in a nucleus A , nAN1N2(krel,Kc .m .) , is a relevant quantity that determines the probability of finding two nucleons with relative momentum krel and center-of-mass (c.m.) momentum Kc .m .; at high values of the relative momentum and, at the same time, low values of the c.m. momentum, nAN1N2(krel,Kc .m .) provides information on the short-range structure of nuclei. Purpose: Our purpose is to calculate the momentum distributions of proton-neutron and proton-proton pairs in 3He, 4He, 12C, 16O, and 40Ca, in correspondence to various values of krel and Kc .m .. Methods: The momentum distributions for A >4 nuclei are calculated as a function of the relative, krel, and center-of-mass, Kc.m., momenta and relative angle Θ , within a linked cluster many-body expansion approach, based upon realistic local two-nucleon interaction of the Argonne family and variational wave functions featuring central, tensor, and spin-isospin correlations. Results: Independently of the mass number A , at values of the relative momentum krel≳1.5 -2 fm-1 the momentum distributions exhibit the property of factorization, nAN1N2(krel,Kc .m .) ≃nrelN1N2(krel) nc.m . N1N2(Kc .m .) ; in particular, for p n back-to-back pairs one has nAp n(krel,Kc .m .=0 ) ≃CAp nnD(krel) nc.m . p n(Kc .m .=0 ) , where nD is the deuteron momentum distribution, nc.m . p n(Kc .m .=0 ) the c.m. motion momentum distribution of the pair, and CAp n the p n nuclear contact measuring the number of back-to-back p n pairs with deuteron-like momenta (kp≃-kn,Kc .m .=0 ). Conclusions: The values of the p n nuclear contact are extracted from the general properties of the two-nucleon momentum distributions corresponding to Kc .m .=0 . The Kc .m .-integrated p n momentum distributions exhibit the property nAp n(krel) ≃CAp nnD(krel) but only at very high values of krel, ≳3.5 -4 fm-1. The theoretical ratio of the p p /p n momentum distributions of 4He
NASA Astrophysics Data System (ADS)
Aaij, R.; Abellán Beteta, C.; Adeva, B.; Adinolfi, M.; Affolder, A.; Ajaltouni, Z.; Akar, S.; Albrecht, J.; Alessio, F.; Alexander, M.; Ali, S.; Alkhazov, G.; Alvarez Cartelle, P.; Alves, A. A.; Amato, S.; Amerio, S.; Amhis, Y.; An, L.; Anderlini, L.; Anderson, J.; Andreassi, G.; Andreotti, M.; Andrews, J. E.; Appleby, R. B.; Aquines Gutierrez, O.; Archilli, F.; d'Argent, P.; Artamonov, A.; Artuso, M.; Aslanides, E.; Auriemma, G.; Baalouch, M.; Bachmann, S.; Back, J. J.; Badalov, A.; Baesso, C.; Baldini, W.; Barlow, R. J.; Barschel, C.; Barsuk, S.; Barter, W.; Batozskaya, V.; Battista, V.; Bay, A.; Beaucourt, L.; Beddow, J.; Bedeschi, F.; Bediaga, I.; Bel, L. J.; Bellee, V.; Belloli, N.; Belyaev, I.; Ben-Haim, E.; Bencivenni, G.; Benson, S.; Benton, J.; Berezhnoy, A.; Bernet, R.; Bertolin, A.; Bettler, M.-O.; van Beuzekom, M.; Bien, A.; Bifani, S.; Billoir, P.; Bird, T.; Birnkraut, A.; Bizzeti, A.; Blake, T.; Blanc, F.; Blouw, J.; Blusk, S.; Bocci, V.; Bondar, A.; Bondar, N.; Bonivento, W.; Borghi, S.; Borisyak, M.; Borsato, M.; Bowcock, T. J. V.; Bowen, E.; Bozzi, C.; Braun, S.; Britsch, M.; Britton, T.; Brodzicka, J.; Brook, N. H.; Buchanan, E.; Burr, C.; Bursche, A.; Buytaert, J.; Cadeddu, S.; Calabrese, R.; Calvi, M.; Calvo Gomez, M.; Campana, P.; Campora Perez, D.; Capriotti, L.; Carbone, A.; Carboni, G.; Cardinale, R.; Cardini, A.; Carniti, P.; Carson, L.; Carvalho Akiba, K.; Casse, G.; Cassina, L.; Castillo Garcia, L.; Cattaneo, M.; Cauet, Ch.; Cavallero, G.; Cenci, R.; Charles, M.; Charpentier, Ph.; Chefdeville, M.; Chen, S.; Cheung, S.-F.; Chiapolini, N.; Chrzaszcz, M.; Cid Vidal, X.; Ciezarek, G.; Clarke, P. E. L.; Clemencic, M.; Cliff, H. V.; Closier, J.; Coco, V.; Cogan, J.; Cogneras, E.; Cogoni, V.; Cojocariu, L.; Collazuol, G.; Collins, P.; Comerma-Montells, A.; Contu, A.; Cook, A.; Coombes, M.; Coquereau, S.; Corti, G.; Corvo, M.; Couturier, B.; Cowan, G. A.; Craik, D. C.; Crocombe, A.; Cruz Torres, M.; Cunliffe, S.; Currie, R.; D'Ambrosio, C.; Dall'Occo, E.; Dalseno, J.; David, P. N. Y.; Davis, A.; De Aguiar Francisco, O.; De Bruyn, K.; De Capua, S.; De Cian, M.; De Miranda, J. M.; De Paula, L.; De Simone, P.; Dean, C.-T.; Decamp, D.; Deckenhoff, M.; Del Buono, L.; Déléage, N.; Demmer, M.; Derkach, D.; Deschamps, O.; Dettori, F.; Dey, B.; Di Canto, A.; Di Ruscio, F.; Dijkstra, H.; Donleavy, S.; Dordei, F.; Dorigo, M.; Dosil Suárez, A.; Dossett, D.; Dovbnya, A.; Dreimanis, K.; Dufour, L.; Dujany, G.; Durante, P.; Dzhelyadin, R.; Dziurda, A.; Dzyuba, A.; Easo, S.; Egede, U.; Egorychev, V.; Eidelman, S.; Eisenhardt, S.; Eitschberger, U.; Ekelhof, R.; Eklund, L.; El Rifai, I.; Elsasser, Ch.; Ely, S.; Esen, S.; Evans, H. M.; Evans, T.; Falabella, A.; Färber, C.; Farley, N.; Farry, S.; Fay, R.; Ferguson, D.; Fernandez Albor, V.; Ferrari, F.; Ferreira Rodrigues, F.; Ferro-Luzzi, M.; Filippov, S.; Fiore, M.; Fiorini, M.; Firlej, M.; Fitzpatrick, C.; Fiutowski, T.; Fohl, K.; Fol, P.; Fontana, M.; Fontanelli, F.; Forshaw, D. C.; Forty, R.; Frank, M.; Frei, C.; Frosini, M.; Fu, J.; Furfaro, E.; Gallas Torreira, A.; Galli, D.; Gallorini, S.; Gambetta, S.; Gandelman, M.; Gandini, P.; Gao, Y.; García Pardiñas, J.; Garra Tico, J.; Garrido, L.; Gascon, D.; Gaspar, C.; Gauld, R.; Gavardi, L.; Gazzoni, G.; Gerick, D.; Gersabeck, E.; Gersabeck, M.; Gershon, T.; Ghez, Ph.; Gianì, S.; Gibson, V.; Girard, O. G.; Giubega, L.; Gligorov, V. V.; Göbel, C.; Golubkov, D.; Golutvin, A.; Gomes, A.; Gotti, C.; Grabalosa Gándara, M.; Graciani Diaz, R.; Granado Cardoso, L. A.; Graugés, E.; Graverini, E.; Graziani, G.; Grecu, A.; Greening, E.; Gregson, S.; Griffith, P.; Grillo, L.; Grünberg, O.; Gui, B.; Gushchin, E.; Guz, Yu.; Gys, T.; Hadavizadeh, T.; Hadjivasiliou, C.; Haefeli, G.; Haen, C.; Haines, S. C.; Hall, S.; Hamilton, B.; Han, X.; Hansmann-Menzemer, S.; Harnew, N.; Harnew, S. T.; Harrison, J.; He, J.; Head, T.; Heijne, V.; Hennessy, K.; Henrard, P.; Henry, L.; van Herwijnen, E.; Heß, M.; Hicheur, A.; Hill, D.; Hoballah, M.; Hombach, C.; Hulsbergen, W.; Humair, T.; Hussain, N.; Hutchcroft, D.; Hynds, D.; Idzik, M.; Ilten, P.; Jacobsson, R.; Jaeger, A.; Jalocha, J.; Jans, E.; Jawahery, A.; John, M.; Johnson, D.; Jones, C. R.; Joram, C.; Jost, B.; Jurik, N.; Kandybei, S.; Kanso, W.; Karacson, M.; Karbach, T. M.; Karodia, S.; Kecke, M.; Kelsey, M.; Kenyon, I. R.; Kenzie, M.; Ketel, T.; Khairullin, E.; Khanji, B.; Khurewathanakul, C.; Klaver, S.; Klimaszewski, K.; Kochebina, O.; Kolpin, M.; Komarov, I.; Koopman, R. F.; Koppenburg, P.; Kozeiha, M.; Kravchuk, L.; Kreplin, K.; Kreps, M.; Krocker, G.; Krokovny, P.; Kruse, F.; Krzemien, W.; Kucewicz, W.; Kucharczyk, M.; Kudryavtsev, V.; Kuonen, A. K.; Kurek, K.; Kvaratskheliya, T.; Lacarrere, D.; Lafferty, G.; Lai, A.; Lambert, D.; Lanfranchi, G.; Langenbruch, C.; Langhans, B.; Latham, T.; Lazzeroni, C.; Le Gac, R.; van Leerdam, J.; Lees, J.-P.; Lefèvre, R.; Leflat, A.; Lefrançois, J.; Lemos Cid, E.; Leroy, O.; Lesiak, T.; Leverington, B.; Li, Y.; Likhomanenko, T.; Liles, M.; Lindner, R.; Linn, C.; Lionetto, F.; Liu, B.; Liu, X.; Loh, D.; Longstaff, I.; Lopes, J. H.; Lucchesi, D.; Lucio Martinez, M.; Luo, H.; Lupato, A.; Luppi, E.; Lupton, O.; Lusiani, A.; Machefert, F.; Maciuc, F.; Maev, O.; Maguire, K.; Malde, S.; Malinin, A.; Manca, G.; Mancinelli, G.; Manning, P.; Mapelli, A.; Maratas, J.; Marchand, J. F.; Marconi, U.; Marin Benito, C.; Marino, P.; Marks, J.; Martellotti, G.; Martin, M.; Martinelli, M.; Martinez Santos, D.; Martinez Vidal, F.; Martins Tostes, D.; Massafferri, A.; Matev, R.; Mathad, A.; Mathe, Z.; Matteuzzi, C.; Mauri, A.; Maurin, B.; Mazurov, A.; McCann, M.; McCarthy, J.; McNab, A.; McNulty, R.; Meadows, B.; Meier, F.; Meissner, M.; Melnychuk, D.; Merk, M.; Michielin, E.; Milanes, D. A.; Minard, M.-N.; Mitzel, D. S.; Molina Rodriguez, J.; Monroy, I. A.; Monteil, S.; Morandin, M.; Morawski, P.; Mordà, A.; Morello, M. J.; Moron, J.; Morris, A. B.; Mountain, R.; Muheim, F.; Müller, D.; Müller, J.; Müller, K.; Müller, V.; Mussini, M.; Muster, B.; Naik, P.; Nakada, T.; Nandakumar, R.; Nandi, A.; Nasteva, I.; Needham, M.; Neri, N.; Neubert, S.; Neufeld, N.; Neuner, M.; Nguyen, A. D.; Nguyen, T. D.; Nguyen-Mau, C.; Niess, V.; Niet, R.; Nikitin, N.; Nikodem, T.; Novoselov, A.; O'Hanlon, D. P.; Oblakowska-Mucha, A.; Obraztsov, V.; Ogilvy, S.; Okhrimenko, O.; Oldeman, R.; Onderwater, C. J. G.; Osorio Rodrigues, B.; Otalora Goicochea, J. M.; Otto, A.; Owen, P.; Oyanguren, A.; Palano, A.; Palombo, F.; Palutan, M.; Panman, J.; Papanestis, A.; Pappagallo, M.; Pappalardo, L. L.; Pappenheimer, C.; Parker, W.; Parkes, C.; Passaleva, G.; Patel, G. D.; Patel, M.; Patrignani, C.; Pearce, A.; Pellegrino, A.; Penso, G.; Pepe Altarelli, M.; Perazzini, S.; Perret, P.; Pescatore, L.; Petridis, K.; Petrolini, A.; Petruzzo, M.; Picatoste Olloqui, E.; Pietrzyk, B.; Pilař, T.; Pinci, D.; Pistone, A.; Piucci, A.; Playfer, S.; Plo Casasus, M.; Poikela, T.; Polci, F.; Poluektov, A.; Polyakov, I.; Polycarpo, E.; Popov, A.; Popov, D.; Popovici, B.; Potterat, C.; Price, E.; Price, J. D.; Prisciandaro, J.; Pritchard, A.; Prouve, C.; Pugatch, V.; Puig Navarro, A.; Punzi, G.; Qian, W.; Quagliani, R.; Rachwal, B.; Rademacker, J. H.; Rama, M.; Ramos Pernas, M.; Rangel, M. S.; Raniuk, I.; Rauschmayr, N.; Raven, G.; Redi, F.; Reichert, S.; Reid, M. M.; dos Reis, A. C.; Ricciardi, S.; Richards, S.; Rihl, M.; Rinnert, K.; Rives Molina, V.; Robbe, P.; Rodrigues, A. B.; Rodrigues, E.; Rodriguez Lopez, J. A.; Rodriguez Perez, P.; Roiser, S.; Romanovsky, V.; Romero Vidal, A.; Ronayne, J. W.; Rotondo, M.; Ruf, T.; Ruiz Valls, P.; Saborido Silva, J. J.; Sagidova, N.; Sail, P.; Saitta, B.; Salustino Guimaraes, V.; Sanchez Mayordomo, C.; Sanmartin Sedes, B.; Santacesaria, R.; Santamarina Rios, C.; Santimaria, M.; Santovetti, E.; Sarti, A.; Satriano, C.; Satta, A.; Saunders, D. M.; Savrina, D.; Schiller, M.; Schindler, H.; Schlupp, M.; Schmelling, M.; Schmelzer, T.; Schmidt, B.; Schneider, O.; Schopper, A.; Schubiger, M.; Schune, M.-H.; Schwemmer, R.; Sciascia, B.; Sciubba, A.; Semennikov, A.; Serra, N.; Serrano, J.; Sestini, L.; Seyfert, P.; Shapkin, M.; Shapoval, I.; Shcheglov, Y.; Shears, T.; Shekhtman, L.; Shevchenko, V.; Shires, A.; Siddi, B. G.; Silva Coutinho, R.; Silva de Oliveira, L.; Simi, G.; Sirendi, M.; Skidmore, N.; Skwarnicki, T.; Smith, E.; Smith, E.; Smith, I. T.; Smith, J.; Smith, M.; Snoek, H.; Sokoloff, M. D.; Soler, F. J. P.; Soomro, F.; Souza, D.; Souza De Paula, B.; Spaan, B.; Spradlin, P.; Sridharan, S.; Stagni, F.; Stahl, M.; Stahl, S.; Stefkova, S.; Steinkamp, O.; Stenyakin, O.; Stevenson, S.; Stoica, S.; Stone, S.; Storaci, B.; Stracka, S.; Straticiuc, M.; Straumann, U.; Sun, L.; Sutcliffe, W.; Swientek, K.; Swientek, S.; Syropoulos, V.; Szczekowski, M.; Szumlak, T.; T'Jampens, S.; Tayduganov, A.; Tekampe, T.; Teklishyn, M.; Tellarini, G.; Teubert, F.; Thomas, C.; Thomas, E.; van Tilburg, J.; Tisserand, V.; Tobin, M.; Todd, J.; Tolk, S.; Tomassetti, L.; Tonelli, D.; Topp-Joergensen, S.; Torr, N.; Tournefier, E.; Tourneur, S.; Trabelsi, K.; Tran, M. T.; Tresch, M.; Trisovic, A.; Tsaregorodtsev, A.; Tsopelas, P.; Tuning, N.; Ukleja, A.; Ustyuzhanin, A.; Uwer, U.; Vacca, C.; Vagnoni, V.; Valenti, G.; Vallier, A.; Vazquez Gomez, R.; Vazquez Regueiro, P.; Vázquez Sierra, C.; Vecchi, S.; Velthuis, J. J.; Veltri, M.; Veneziano, G.; Vesterinen, M.; Viaud, B.; Vieira, D.; Vieites Diaz, M.; Vilasis-Cardona, X.; Volkov, V.; Vollhardt, A.; Volyanskyy, D.; Voong, D.; Vorobyev, A.; Vorobyev, V.; Voß, C.; de Vries, J. A.; Waldi, R.; Wallace, C.; Wallace, R.; Walsh, J.; Wandernoth, S.; Wang, J.; Ward, D. R.; Watson, N. K.; Websdale, D.; Weiden, A.; Whitehead, M.; Wilkinson, G.; Wilkinson, M.; Williams, M.; Williams, M. P.; Williams, M.; Williams, T.; Wilson, F. F.; Wimberley, J.; Wishahi, J.; Wislicki, W.; Witek, M.; Wormser, G.; Wotton, S. A.; Wright, S.; Wyllie, K.; Xie, Y.; Xu, Z.; Yang, Z.; Yu, J.; Yuan, X.; Yushchenko, O.; Zangoli, M.; Zavertyaev, M.; Zhang, L.; Zhang, Y.; Zhelezov, A.; Zhokhov, A.; Zhong, L.; Zucchelli, S.
2016-07-01
Associated production of bottomonia and open charm hadrons in pp collisions at √{s}=7 and 8 TeV is observed using data corresponding to an integrated luminosity of 3 fb-1 accumulated with the LHCb detector. The observation of five combinations, Y(1S)D0, Y(2S)D0, Y(1S)D+, Y(2S)D+ and Y(1S)D s + , is reported. Production crosssections are measured for Y(1S)D0 and Y(1S)D+ pairs in the forward region. The measured cross-sections and the differential distributions indicate the dominance of double parton scattering as the main production mechanism. [Figure not available: see fulltext.
Short range structure of hadron and nuclear wave functions at high x
Hoyer, P.; Brodsky, S.J.
1990-11-01
We discuss the short-range structure of hadronic and nuclear wave functions expected in QCD. In addition to the extrinsic'' contributions associated with radiation from single partons, there is an intrinsic'' hardness of the high-mass fluctuations of the wave function due to the spatial overlap of two or more partons. We argue that intrinsically-hard partons, having large mass and/or large transverse momentum, will dominate in the region of large Feynman x{sub F}. Their rescattering in nuclear targets is expected to be larger than for extrinsically-hard partons, leading to a suppressed production cross section for hadrons scattering on heavy nuclei. Experimental evidence for this exists for open chars. J/{psi}, and {gamma} production at large x{sub F}. The effects of intrinsic hardness may be particularly striking in nuclear wave functions, where the overlap of partons belonging to different nucleons can give rise to cumulative (x > 1) phenomena. The data on backward cumulative particle production from nuclei supports the existence of an intrinsically-hard component in nuclear wave functions. Partons at large x{sub F} may also be associated with the enhanced subthreshold production of particles observed in hadron-nucleus and nucleus-nucleus collisions. We discuss the evidence for anomalies in the large angle pp {yields} pp cross section near the charm threshold. Arguments are presented that chromium states may bind to nuclei through the QCD Van der Waals force. This would lead to a striking signal in charm production near threshold. 49 refs., 7 figs.
D0 results on diphoton direct production and double parton interactions in photon + 3 jet events
Sawyer, Lee; /Louisiana Tech. U.
2010-01-01
We report the measurement of differential diphoton direct production cross sections and a study of photon + 3-jet events with double parton (DP) interactions, based on data taken with the D0 experiment at the Fermilab Tevatron proton-antiproton collider. We measure single differential cross sections as a function of the diphoton mass, the transverse momentum of the diphoton system, the azimuthal angle between the photons, and the polar scattering angle of the photons. In addition, we measure double differential cross sections considering the last three kinematic variables in three diphoton mass bins. The results are compared with different perturbative QCD predictions and event generators. We have used a sample of photon + 3-jet events collected by the D0 experiment with an integrated luminosity of about 1 fb{sup -1} to determine the fraction of events with double parton scattering (f{sub DP}) in a single p{bar p} collision at {radical}s = 1.96 TeV. The DP fraction and effective cross section ({sigma}{sub eff}), a process-independent scale parameter related to the parton density inside the nucleon, are measured in three intervals of the second (ordered in p{sub T}) jet transverse momentum p{sub T}{sup jet2} within the range 15 < p{sub T}{sup jet} < 30 GeV. In this range, f{sub DP} varies between 0.23 < f{sub DP} < 0.47, while {sigma}{sub eff} has the average value {sigma}{sub eff}{sup ave} = 16.4 {+-} 0.3(stat) {+-} 2.3(syst) mb.
Investigating GPDs in the framework of the double distribution model
NASA Astrophysics Data System (ADS)
Nazari, F.; Mirjalili, A.
2016-06-01
In this paper, we construct the generalized parton distribution (GPD) in terms of the kinematical variables x, ξ, t, using the double distribution model. By employing these functions, we could extract some quantities which makes it possible to gain a three-dimensional insight into the nucleon structure function at the parton level. The main objective of GPDs is to combine and generalize the concepts of ordinary parton distributions and form factors. They also provide an exclusive framework to describe the nucleons in terms of quarks and gluons. Here, we first calculate, in the Double Distribution model, the GPD based on the usual parton distributions arising from the GRV and CTEQ phenomenological models. Obtaining quarks and gluons angular momenta from the GPD, we would be able to calculate the scattering observables which are related to spin asymmetries of the produced quarkonium. These quantities are represented by AN and ALS. We also calculate the Pauli and Dirac form factors in deeply virtual Compton scattering. Finally, in order to compare our results with the existing experimental data, we use the difference of the polarized cross-section for an initial longitudinal leptonic beam and unpolarized target particles (ΔσLU). In all cases, our obtained results are in good agreement with the available experimental data.
Transverse-Momentum Parton Densities:. Gauge Links, Divergences and Soft Factor
NASA Astrophysics Data System (ADS)
Cherednikov, I. O.; Stefanis, N. G.
2011-02-01
We discuss the state-of-the-art of the theory of transverse-momentum dependent parton densities (TMDs), paying special attention to their renormalization properties, the structure of the gauge links in the operator definition, and the role of the soft factor in the factorization formula within the TMD approach to the semi-inclusive processes. We argue that the use of the lightcone axial gauge offers certain advantages for a consistent definition of TMDs as compared to the off-the-light-cone gauges, or covariant gauges with off-the-lightcone gauge links.
Double parton interactions as a background to associated HW production at the Tevatron
Bandurin, Dmitry; Golovanov, Georgy; Skachkov, Nikolai
2010-11-01
In this paper we study events with W+jets final state, produced in double parton (DP) interactions, as a background to the associated Higgs boson (H) and W production, with H {yields} b{bar b} decay, at the Tevatron. We have found that the event yield from the DP background can be quite sizable, what necessitates a choice of selection criteria to separate the HW and DP production processes. We suggest a set of variables sensitive to the kinematics of DP and HW events. We show that these variables, being used as an input to the artificial neural network, allow one to significantly improve a sensitivity to the Higgs boson production.
Multiple Parton Interactions in ppbar Collisions in D0 Experiment at the Tevatron Collider
Golovanov, Georgy
2016-01-01
The thesis is devoted to the study of processes with multiple parton interactions (MPI) in a ppbar collision collected by D0 detector at the Fermilab Tevatron collider at sqrt(s) = 1.96 TeV. The study includes measurements of MPI event fraction and effective cross section, a process-independent parameter related to the effective interaction region inside the nucleon. The measurements are done using events with a photon and three hadronic jets in the final state. The measured effective cross section is used to estimate background from MPI for WH production at the Tevatron energy
Anomalous coupling, top-mass and parton-shower effects in W + W - production
NASA Astrophysics Data System (ADS)
Bellm, J.; Gieseke, S.; Greiner, N.; Heinrich, G.; Plätzer, S.; Reuschle, C.; von Soden-Fraunhofen, J. F.
2016-05-01
We calculate the process ppto {W}+{W}-to {e}+{ν}_e{μ}-{overline{ν}}_{μ } at NLO QCD, including also effective field theory (EFT) operators mediating the ggW + W - interaction, which first occur at dimension eight. We further combine the NLO and EFT matrix elements produced by G oS am with the H erwig7/M atchbox framework, which offers the possibility to study the impact of a parton shower. We assess the effects of the anomalous couplings by comparing them to top-mass effects as well as uncertainties related to variations of the renormalisation, factorisation and hard shower scales.
Matching next-to-leading order predictions to parton showers in supersymmetric QCD
Degrande, Céline; Fuks, Benjamin; Hirschi, Valentin; Proudom, Josselin; Shao, Hua-Sheng
2016-02-03
We present a fully automated framework based on the FeynRules and MadGraph5_aMC@NLO programs that allows for accurate simulations of supersymmetric QCD processes at the LHC. Starting directly from a model Lagrangian that features squark and gluino interactions, event generation is achieved at the next-to-leading order in QCD, matching short-distance events to parton showers and including the subsequent decay of the produced supersymmetric particles. As an application, we study the impact of higher-order corrections in gluino pair-production in a simplified benchmark scenario inspired by current gluino LHC searches.
Hadronic and partonic sources of direct photons in relativistic heavy-ion collisions
NASA Astrophysics Data System (ADS)
Linnyk, O.; Konchakovski, V.; Steinert, T.; Cassing, W.; Bratkovskaya, E. L.
2015-11-01
The direct photon spectra and flow (v2, v3) in heavy-ion collisions at CERN Super Proton Synchrotron, BNL Relativistic Heavy Ion Collider, and CERN Large Hadron Collider energies are investigated within a relativistic transport approach incorporating both hadronic and partonic phases, the parton-hadron-string dynamics (PHSD). In the present work, four extensions are introduced compared to our previous calculations: (i) going beyond the soft-photon approximation (SPA) in the calculation of the bremsstrahlung processes meson +meson →meson +meson +γ , (ii) quantifying the suppression owing to the Landau-Pomeranchuk-Migdal (LPM) coherence effect, (iii) adding the additional channels V +N →N +γ and Δ →N +γ , and (iv) providing PHSD calculations for Pb +Pb collisions at √{sN N}=2.76 TeV . The first issue extends the applicability of the bremsstrahlung calculations to higher photon energies to understand the relevant sources in the region pT=0.5 -1.5 GeV , while the LPM correction turns out to be important for pT<0.4 GeV in the partonic phase. The results suggest that a large elliptic flow v2 of the direct photons signals a significant contribution of photons produced in interactions of secondary mesons and baryons in the late (hadronic) stage of the heavy-ion collision. To further differentiate the origin of the direct photon azimuthal asymmetry (late hadron interactions vs electromagnetic fields in the initial stage), we provide predictions for the photon spectra, elliptic flow, and triangular flow v3(pT) of direct photons at different centralities to be tested by the experimental measurements at the LHC energies. Additionally, we illustrate the magnitude of the photon production in the partonic and hadronic phases as functions of time and local energy density. Finally, the "cocktail" method for an estimation of the background photon elliptic flow, which is widely used in the experimental works, is supported by the calculations within the PHSD transport
Matching next-to-leading order predictions to parton showers in supersymmetric QCD
NASA Astrophysics Data System (ADS)
Degrande, Céline; Fuks, Benjamin; Hirschi, Valentin; Proudom, Josselin; Shao, Hua-Sheng
2016-04-01
We present a fully automated framework based on the FEYNRULES and MADGRAPH5_aMC@NLO programs that allows for accurate simulations of supersymmetric QCD processes at the LHC. Starting directly from a model Lagrangian that features squark and gluino interactions, event generation is achieved at the next-to-leading order in QCD, matching short-distance events to parton showers and including the subsequent decay of the produced supersymmetric particles. As an application, we study the impact of higher-order corrections in gluino pair-production in a simplified benchmark scenario inspired by current gluino LHC searches.
QCD CORRECTIONS TO DILEPTON PRODUCTION NEAR PARTONIC THRESHOLD IN PP SCATTERING.
SHIMIZU, H.; STERMAN, G.; VOGELSANG, W.; YOKOYA, H.
2005-10-02
We present a recent study of the QCD corrections to dilepton production near partonic threshold in transversely polarized {bar p}p scattering, We analyze the role of the higher-order perturbative QCD corrections in terms of the available fixed-order contributions as well as of all-order soft-gluon resummations for the kinematical regime of proposed experiments at GSI-FAIR. We find that perturbative corrections are large for both unpolarized and polarized cross sections, but that the spin asymmetries are stable. The role of the far infrared region of the momentum integral in the resummed exponent and the effect of the NNLL resummation are briefly discussed.
Nuclear Theory - Nuclear Power
NASA Astrophysics Data System (ADS)
Svenne, J. P.; Canton, L.; Kozier, K. S.
2008-01-01
The results from modern nuclear theory are accurate and reliable enough to be used for practical applications, in particular for scattering that involves few-nucleon systems of importance to nuclear power. Using well-established nucleon-nucleon (NN) interactions that fit well the NN scattering data, and the AGS form of the three-body theory, we have performed precise calculations of low-energy neutron-deuteron (
Sycheva, A M; Kel, A; Nikolaev, E N; Moshkovskii, S A
2014-06-01
There are two physical processes that influence the spatial distribution of transcription factor molecules entering the nucleus of a eukaryotic cell, the binding to genomic DNA and the diffusion throughout the nuclear volume. Comparison of the DNA-protein association rate constant and the protein diffusion constant may determine which one is the limiting factor. If the process is diffusion-limited, transcription factor molecules are captured by DNA before their even distribution in the nuclear volume. Otherwise, if the reaction rate is limiting, these molecules diffuse evenly and then find their binding sites. Using well-studied human NF-κB dimer as an example, we calculated its diffusion constant using the Debye-Smoluchowski equation. The value of diffusion constant was about 10(-15) cm(3)/s, and it was comparable to the NF-κB association rate constant for DNA binding known from previous studies. Thus, both diffusion and DNA binding play an equally important role in NF-κB spatial distribution. The importance of genome 3D-structure in gene expression regulation and possible dependence of gene expression on the local concentration of open chromatin can be hypothesized from our theoretical estimate.
Regnier, D.; Dubray, N.; Schunck, N.; Verriere, M.
2016-05-13
Here, accurate knowledge of fission fragment yields is an essential ingredient of numerous applications ranging from the formation of elements in the r process to fuel cycle optimization for nuclear energy. The need for a predictive theory applicable where no data are available, together with the variety of potential applications, is an incentive to develop a fully microscopic approach to fission dynamics.
1990-01-01
Nuclear pore complexes (NPCs) prepared from Xenopus laevis oocyte nuclear envelopes were studied in "intact" form (i.e., unexposed to detergent) and after detergent treatment by a combination of conventional transmission electron microscopy (CTEM) and quantitative scanning transmission electron microscopy (STEM). In correlation- averaged CTEM pictures of negatively stained intact NPCs and of distinct NPC components (i.e., "rings," "spoke" complexes, and "plug- spoke" complexes), several fine structural features arranged with octagonal symmetry about a central axis could reproducibly be identified. STEM micrographs of unstained/freeze-dried intact NPCs as well as of their components yielded comparable but less distinct features. Mass determination by STEM revealed the following molecular masses: intact NPC with plug, 124 +/- 11 MD; intact NPC without plug, 112 +/- 11 MD; heavy ring, 32 +/- 5 MD; light ring, 21 +/- 4 MD; plug- spoke complex, 66 +/- 8 MD; and spoke complex, 52 +/- 3 MD. Based on these combined CTEM and STEM data, a three-dimensional model of the NPC exhibiting eightfold centrosymmetry about an axis perpendicular to the plane of the nuclear envelope but asymmetric along this axis is proposed. This structural polarity of the NPC across the nuclear envelope is in accord with its well-documented functional polarity facilitating mediated nucleocytoplasmic exchange of molecules and particles. PMID:2324201
Sasaki, Keisuke; Hayashi, Masayuki; Narita, Takumi; Motoyama, Michiyo; Oe, Mika; Ojima, Koichi; Nakajima, Ikuyo; Muroya, Susumu; Chikuni, Koichi; Aikawa, Katsuhiro; Ide, Yasuyuki; Nakanishi, Naoto; Suzuki, Nobuaki; Shioya, Shigeru; Takenaka, Akio
2012-01-01
This study examined the accumulation and tissue distribution of radioactive cesium nuclides in Japanese Black beef heifers raised on roughage contaminated with radioactive fallout due to the accident at the Fukushima Daiichi Nuclear Power Station on March 2011. Radiocesium feeding increased both (134)Cs and (137)Cs levels in all tissues tested. The kidney had the highest level and subcutaneous adipose had the lowest of radioactive cesium in the tissues. Different radioactive cesium levels were not found among parts of the muscles. These results indicate that radiocesium accumulated highly in the kidney and homogenously in the skeletal muscles in the heifers.
Dinh, L. N.; Mayer, B. P.; Maiti, A.; Chinn, S. C.; Maxwell, R. S.
2011-05-01
The statistical methodology of population balance (PB) has been applied in order to predict the effects of cross-linking and chain-scissioning induced by ionizing radiation on the distribution of molecular weight between cross-links (MWBC) of a siloxane-based elastomer. Effective molecular weight distributions were extracted from the quantification of residual dipolar couplings via multiple quantum nuclear magnetic resonance (MQ-NMR) measurements and are taken to reflect actual MWBC distributions. The PB methodology is then applied to the unirradiated MWBC distribution and considers both chain-scissioning and the possibility of the formation of three types of cross-links: random recombination of scissioned-chain ends (end-linking), random covalent bonds of free radicals on scissioned-chain ends (Y-cross-linking), and the formation of random cross-links from free radicals on side groups (H-cross-linking). The qualitative agreement between the statistical modeling approach and the NMR data confirms that it is possible to predict trends for the evolution of the distribution of MWBC of polymers under irradiation. The approach described herein can also discern heterogeneities in radiation effects in different structural motifs in the polymer network.
Transverse Momentum Dependent Distributions in Hard Scattering
Alexie Prokudin
2011-05-01
Transverse Momentum Dependent Distributions (TMDs) describe the spin structure of the proton. At leading twist spin structure of spin-1/2 hadron can be described by 8 TMDs. TMDs reveal three-dimensional distribution of partons inside polarised nucleon. Experimentally these functions can be studied in polarised experiments using Spin Asymmetries in particular Single Spin Asymmetries (SSAs). We discuss transversity that measures distribution of transversely polarised quarks in a transversely polarised nucleon and Sivers distribution function that describes distribution of unpolarised quarks in a transversely polarised nucleon.
Hard scattering of partons as a probe of collisions at RHIC using the STAR detector system
Christie, W.B.
1995-07-15
Presented here is the current state of the author`s investigations into the use of hard probes to study pp, pA, and AA collisions at the Relativistic Heavy Ion Collider (RHIC) being built at Brookhaven National Laboratory. The overall goal of the RHIC program is the discovery and study of the Quark-Gluon Plasma (QGP), which is predicted to be formed at the high energy densities reached at RHIC in high energy AA collisions. The term {open_quotes}Hard probes{close_quotes} as used in this document includes those particles whose origin is the result of a direct hard parton scatter (i.e qq, qg, or gg). The final states of these hard parton scatters which the author proposes to study include dijets, gamma-jet coincidences, and inclusive high P{sub t} particle spectra. A brief discussion of the physics objectives is given in section 1. This is followed by an introduction to the STAR detector system in section 2, with particular details given for the proposed STAR Electromagnetic Calorimeter (EMC). The present simulation studies and results are given in section 3. The author concludes with a summary and a discussion of future plans in section 4.
Thermalization of parton spectra in the colour-flux-tube model
NASA Astrophysics Data System (ADS)
Ryblewski, Radoslaw
2016-09-01
A detailed study of thermalization of the momentum spectra of partons produced via decays of colour flux tubes due to the Schwinger tunnelling mechanism is presented. The collisions between particles are included in the relaxation-time approximation specified by different values of the shear viscosity to entropy density ratio. At first we show that, to a good approximation, the transverse-momentum spectra of the produced partons are exponential, irrespective of the assumed value of the viscosity of the system and the freeze-out time. This thermal-like behaviour may be attributed to specific properties of the Schwinger tunnelling process. In the next step, in order to check the approach of the system towards genuine local equilibrium, we compare the local slope of the model transverse-momentum spectra with the local slope of the fully equilibrated reference spectra characterized by the effective temperature that reproduces the energy density of the system. We find that the viscosity corresponding to the anti-de Sitter/conformal field theory lower bound is necessary for thermalization of the system within about two fermis.
Campelo, Riward; Díaz Lozano, Isabel; Figarella, Katherine; Osuna, Antonio
2014-01-01
In its canonical role the reverse transcriptase telomerase recovers the telomeric repeats that are lost during DNA replication. Other locations and activities have been recently described for the telomerase protein subunit TERT in mammalian cells. In the present work, using biochemistry, molecular biology, and electron microscopy techniques, we found that in the human parasite Leishmania major, TERT (and telomerase activity) shared locations between the nuclear, mitochondrial, and cytoplasmic compartments. Also, some telomerase activity and TERT protein could be found in ∼100-nm nanovesicles. In the mitochondrial compartment, TERT appears to be mainly associated with the kinetoplast DNA. When Leishmania cells were exposed to H2O2, TERT changed its relative abundance and activity between the nuclear and mitochondrial compartments, with the majority of activity residing in the mitochondrion. Finally, overexpression of TERT in Leishmania transfected cells not only increased the parasitic cell growth rate but also increased their resistance to oxidative stress. PMID:25312950
Amirov, R. Kh. Vorona, N. A.; Gavrikov, A. V.; Lizyakin, G. D.; Polishchuk, V. P.; Samoilov, I. S.; Smirnov, V. P.; Usmanov, R. A.; Yartsev, I. M.
2015-10-15
Results from experimental studies of a vacuum arc with a distributed cathode spot on the heated cathode are presented. Such an arc can be used as a plasma source for plasma separation of spent nuclear fuel and radioactive waste. The experiments were performed with a gadolinium cathode, the properties of which are similar to those of an uranium arc cathode. The heat flux from the plasma to the cathode (and its volt equivalent) at discharge voltages of 4-15 V and discharge currents of 44-81 A, the radial distribution of the emission intensity of gadolinium atoms and singly charged ions in the arc channel at a voltage of 4.3 V, and the plasma electron temperature behind the anode were measured. The average charge of plasma ions at arc voltages of 3.5-8 V and a discharge current of 52 A and the average rate of gadolinium evaporation in the discharge were also determined.
Lacey, Roy A; Wei, R; Ajitanand, N N; Alexander, J M; Gong, X; Jia, J; Mawi, A; Mohapatra, S; Reynolds, D; Salnikov, S; Taranenko, A
2009-10-01
The scaling properties of jet-suppression measurements are compared for nonphotonic electrons (e+/-) and neutral pions (pi(0)) in Au+Au collisions at sqrt[S(NN)]=200 GeV. For a broad range of transverse momenta and collision centralities, the comparison is consistent with jet quenching dominated by radiative energy loss for both heavy and light partons. Less quenching is indicated for heavy quarks via e+/-; this gives an independent estimate of the transport coefficient q that agrees with its magnitude obtained from quenching of light partons via pi(0)'s.
Asaturyan, R.; Ent, R.; Mkrtchyan, H.; Navasardyan, T.; Tadevosyan, V.; Adams, G. S.; Ahmidouch, A.; Angelescu, T.; Arrington, J.; Asaturyan, A.; et al
2012-01-01
A large set of cross sections for semi-inclusive electroproduction of charged pions (π±) from both proton and deuteron targets was measured. The data are in the deep-inelastic scattering region with invariant mass squared W2 > 4 GeV2 and range in four-momentum transfer squared 2 < Q2 < 4 (GeV/c)2, and cover a range in the Bjorken scaling variable 0.2 < x < 0.6. The fractional energy of the pions spans a range 0.3 < z < 1, with small transverse momenta with respect to the virtual-photon direction, Pt2 < 0.2 (GeV/c)2. The invariant mass that goes undetected, Mx or W',more » is in the nucleon resonance region, W' < 2 GeV. The new data conclusively show the onset of quark-hadron duality in this process, and the relation of this phenomenon to the high-energy factorization ansatz of electron-quark scattering and subsequent quark → pion production mechanisms. The x, z and Pt2 dependences of several ratios (the ratios of favored-unfavored fragmentation functions, charged pion ratios, deuteron-hydrogen and aluminum-deuteron ratios for π+ and π-) have been studied. The ratios are found to be in good agreement with expectations based upon a high-energy quark-parton model description. We find the azimuthal dependences to be small, as compared to exclusive pion electroproduction, and consistent with theoretical expectations based on tree-level factorization in terms of transverse-momentum-dependent parton distribution and fragmentation functions. In the context of a simple model, the initial transverse momenta of d quarks are found to be slightly smaller than for u quarks, while the transverse momentum width of the favored fragmentation function is about the same as for the unfavored one, and both fragmentation widths are larger than the quark widths.« less
NASA Astrophysics Data System (ADS)
Cuevas Vivas, Gabriel Francisco
A methodology to optimize enrichment distributions in Light Water Reactor (LWR) fuel assemblies is developed and tested. The optimization technique employed is the linear programming revised simplex method, and the fuel assembly's performance is evaluated with a neutron transport code that is also utilized in the calculation of sensitivity coefficients. The enrichment distribution optimization procedure begins from a single-value (flat) enrichment distribution until a target, maximum local power peaking factor, is achieved. The optimum rod enrichment distribution, with 1.00 for the maximum local power peaking factor and with each rod having its own enrichment, is calculated at an intermediate stage of the analysis. Later, the best locations and values for a reduced number of rod enrichments is obtained as a function of a target maximum local power peaking factor by applying sensitivity to change techniques. Finally, a shuffling process that assigns individual rod enrichments among the enrichment groups is performed. The relative rod power distribution is then slightly modified and the rod grouping redefined until the optimum configuration is attained. To verify the accuracy of the relative rod power distribution, a full computation with the neutron transport code using the optimum enrichment distribution is carried out. The results are compared and tested for assembly designs loaded with fresh Low Enriched Uranium (LEU) and plutonium Mixed OXide (MOX) fuels. MOX isotopics for both reactor-grade and weapons-grade plutonium were utilized to demonstrate the wide-range of applicability of the optimization technique. The features of the assembly designs used for evaluation purposes included burnable absorbers and internal water regions, and were prepared to resemble the configurations of modern assemblies utilized in commercial Boiling Water Reactors (BWRs) and Pressurized Water Reactors (PWRs). In some cases, a net improvement in the relative rod power distribution or
Watabe, Teruhisa; Oikawa, Shinji; Isoyama, Naohiko; Suzuki, Chiyoshi; Misonoo, Jun; Morizono, Shigemitsu
2013-10-01
The historic spatiotemporal distribution of 137Cs in the seawaters and sea-floor sediments adjacent to nuclear power plants in Japan are summarized, using data obtained over a period of time more than 20 years prior to the disaster at the Fukushima Daiichi Nuclear Power Plant in 2011. Relatively uniform distributions of 137Cs were observed both in the surface seawaters (1 m in depth) and in deeper seawaters (10 to 30 m above the seabed and ranging from tens to hundreds of meters in depth) independent of the geographical position, although lower concentrations were observed in significantly deeper bottom seawaters. Conversely, there were wide variations in 137Cs levels between sediments, such that higher 137Cs concentrations were observed in the deeper sampling locations. A mathematical model describing the successive transfer of 137Cs from surface waters through deeper waters to sediments suggested that the transfer rate of 137Cs from deep water to the sediments, and the loss rate from bottom sediments, were both greater than the transfer rate from surface water to deeper water. It was found that the calculated regression lines for 137Cs depletion rates over time for surface waters, deeper waters, and sediments were approximately parallel when plotted on a semi-logarithmic coordinate system, regardless of the sampling location. A radionuclide depletion half-life was calculated to be 4 months to 16 years with the geometric mean of 2.22 y for the sediments in the Fukushima region, suggesting that nuclear contamination will be remediated over time through sediment redistribution processes such as remobilization, bioturbation, and migration due to sea currents.
Peemoeller, H; Pintar, M M
1979-01-01
The proton free-induction decays, spin-spin relaxation times, local fields in the rotating frame, and spin-lattice relaxation times in the laboratory and rotating frames, in natural and fully deuterated mouse muscle, are reported. Measurements were taken above and below freezing temperature and at two time windows on the free-induction decay. A comparative analysis show that the magnetization fractions deduced from the different experiments are in good agreement. The main conclusion is that the resolution of the (heterogeneous) muscle nuclear magnetic resonance (NMR) response is improved by the multiwindow analysis. PMID:262554
Sullivan, T.
2014-09-24
ZionSolutions is in the process of decommissioning the Zion Nuclear Power Plant. The site contains two reactor Containment Buildings, a Fuel Building, an Auxiliary Building, and a Turbine Building that may be contaminated. The current decommissioning plan involves removing all above grade structures to a depth of 3 feet below grade. The remaining underground structures will be backfilled. The remaining underground structures will contain low amounts of residual licensed radioactive material. An important component of the decommissioning process is the demonstration that any remaining activity will not cause a hypothetical individual to receive a dose in excess of 25 mrem/y as specified in 10CFR20 SubpartE.
Sullivan T.
2014-06-09
ZionSolutions is in the process of decommissioning the Zion Nuclear Power Plant. The site contains two reactor Containment Buildings, a Fuel Building, an Auxiliary Building, and a Turbine Building that may be contaminated. The current decommissioning plan involves removing all above grade structures to a depth of 3 feet below grade. The remaining underground structures will be backfilled. The remaining underground structures will contain low amounts of residual licensed radioactive material. An important component of the decommissioning process is the demonstration that any remaining activity will not cause a hypothetical individual to receive a dose in excess of 25 mrem/y as specified in 10CFR20 SubpartE.
NASA Technical Reports Server (NTRS)
Friedlander, A. L.; Wells, W. C.
1980-01-01
A study of long term risks is presented that treats an additional pathway that could result in earth reentry, namely, small radioactive particles released in solar orbit due to payload fragmentation by accidental explosion or meteoroid impact. A characterization of such an event and of the initial mass size distribution of particles is given for two extremes of waste form strength. Attention is given to numerical results showing the mass-time distribution of material and the fraction of initial mass intercepted by earth. It is concluded that it appears that program planners need not be to concerned about the risks of this particular failure mechanism and return pathway.
Novel High Transverse Momentum Phenomena in Hadronic and Nuclear Collisions
Brodsky, Stanley J.; /SLAC
2009-04-10
I discuss a number of novel phenomenological features of QCD in high transverse momentum reactions. The presence of direct higher-twist processes, where a proton is produced directly in the hard subprocess, can explain the 'baryon anomaly' - the large proton-to-pion ratio seen at RHIC in high centrality heavy ion collisions. Direct hadronic processes can also account for the deviation from leading-twist PQCD scaling at fixed x{sub T} = 2 p{sub T}/{radical}s. I suggest that the 'ridge' --the same-side long-range rapidity correlation observed at RHIC in high centrality heavy ion collisions is due to the imprint of semihard DGLAP gluon radiation from initial-state partons which have transverse momenta biased toward the trigger. A model for early thermalization of the quark-gluon medium is also outlined. Rescattering interactions from gluon-exchange, normally neglected in the parton model, have a profound effect in QCD hard-scattering reactions, leading to leading-twist single-spin asymmetries, diffractive deep inelastic scattering, diffractive hard hadronic reactions, the breakdown of the Lam-Tung relation in Drell-Yan reactions, nuclear shadowing--all leading-twist dynamics not incorporated in the light-front wavefunctions of the target computed in isolation. Anti shadowing is shown to be quark flavor specific and thus different in charged and neutral deep inelastic lepton-nucleus scattering. I also discuss other aspects of quantum effects in heavy ion collisions, such as tests of hidden color in nuclear wavefunctions, the use of diffraction to materialize the Fock states of a hadronic projectile and test QCD color transparency, and the important consequences of color-octet intrinsic heavy quark distributions in the proton for particle and Higgs production at high x{sub F}. I also discuss how the AdS/CFT correspondence between Anti-de Sitter space and conformal gauge theories allows one to compute the analytic form of frame-independent light-front wavefunctions of
Boost covariant gluon distributions in large nuclei
NASA Astrophysics Data System (ADS)
McLerran, Larry; Venugopalan, Raju
1998-04-01
It has been shown recently that there exist analytical solutions of the Yang-Mills equations for non-Abelian Weizsäcker-Williams fields which describe the distribution of gluons in large nuclei at small x. These solutions however depend on the color charge distribution at large rapidities. We here construct a model of the color charge distribution of partons in the fragmentation region and use it to compute the boost covariant momentum distributions of wee gluons. The phenomenological applications of our results are discussed.
NASA Astrophysics Data System (ADS)
Stumpf, H.
2003-01-01
Generalized de Broglie-Bargmann-Wigner (BBW) equations are relativistically invariant quantum mechanical many body equations with nontrivial interaction, selfregularization and probability interpretation. Owing to these properties these equations are a suitable means for describing relativistic bound states of fermions. In accordance with de Broglie's fusion theory and modern assumptions about the partonic substructure of elementary fermions, i.e., leptons and quarks, the three-body generalized BBW-equations are investigated. The transformation properties and quantum numbers of the three-parton equations under the relevant group actions are elaborated in detail. Section 3 deals with the action of the isospin group SU(2), a U(1) global gauge group for the fermion number, the hypercharge and charge generators. The resulting quantum numbers of the composite partonic systems can be adapted to those of the phenomenological particles to be described. The space-time transformations and in particular rotations generated by angular momentum operators are considered in Section 4. Based on the compatibility of the BBW-equations and the group theoretical constraints, in Sect. 5 integral equations are formulated in a representation with diagonal energy and total angular momentum variables. The paper provides new insight into the solution space and quantum labels of resulting integral equations for three parton states and prepares the ground for representing leptons and quarks as composite systems.
Accessing the quark orbital angular momentum with Wigner distributions
Lorce, Cedric
2013-04-15
The quark orbital angular momentum (OAM) has been recognized as an important piece of the proton spin puzzle. A lot of effort has been invested in trying to extract it quantitatively from the generalized parton distributions (GPDs) and the transverse-momentum dependent parton distributions (TMDs), which are accessed in high-energy processes and provide three-dimensional pictures of the nucleon. Recently, we have shown that it is more natural to access the quark OAM from the phase-space or Wigner distributions. We discuss the concept of Wigner distributions in the context of quantum field theory and show how they are related to the GPDs and the TMDs. We summarize the different definitions discussed in the literature for the quark OAM and show how they can in principle be extracted from the Wigner distributions.
NASA Astrophysics Data System (ADS)
Wotawa, Gerhard; Becker, Andreas; Kalinowski, Martin; Saey, Paul; Tuma, Matthias; Zähringer, Matthias
2010-05-01
Monitoring of radioactive noble gases, in particular xenon isotopes, is a crucial element of the verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). The capability of the noble gas network, which is currently under construction, to detect signals from a nuclear explosion critically depends on the background created by other sources. Therefore, the global distribution of these isotopes based on emissions and transport patterns needs to be understood. A significant xenon background exists in the reactor regions of North America, Europe and Asia. An emission inventory of the four relevant xenon isotopes has recently been created, which specifies source terms for each power plant. As the major emitters of xenon isotopes worldwide, a few medical radioisotope production facilities have been recently identified, in particular the facilities in Chalk River (Canada), Fleurus (Belgium), Pelindaba (South Africa) and Petten (Netherlands). Emissions from these sites are expected to exceed those of the other sources by orders of magnitude. In this study, emphasis is put on 133Xe, which is the most prevalent xenon isotope. First, based on the emissions known, the resulting 133Xe concentration levels at all noble gas stations of the final CTBT verification network were calculated and found to be consistent with observations. Second, it turned out that emissions from the radioisotope facilities can explain a number of observed peaks, meaning that atmospheric transport modelling is an important tool for the categorization of measurements. Third, it became evident that Nuclear Power Plant emissions are more difficult to treat in the models, since their temporal variation is high and not generally reported. Fourth, there are indications that the assumed annual emissions may be underestimated by factors of two to ten, while the general emission patterns seem to be well understood. Finally, it became evident that 133Xe sources mainly influence the sensitivity of the
Heavy quarkonium production at collider energies: Partonic cross section and polarization
Qiu, Jian -Wei; Kang, Zhong -Bo; Ma, Yan -Qing; Sterman, George
2015-01-27
We calculate the O(α³s) short-distance, QCD collinear-factorized coefficient functions for all partonic channels that include the production of a heavy quark pair at short distances. Thus, this provides the first power correction to the collinear-factorized inclusive hadronic production of heavy quarkonia at large transverse momentum, pT, including the full leading-order perturbative contributions to the production of heavy quark pairs in all color and spin states employed in NRQCD treatments of this process. We discuss the role of the first power correction in the production rates and the polarizations of heavy quarkonia in high-energy hadronic collisions. The consistency of QCD collinearmore » factorization and nonrelativistic QCD factorization applied to heavy quarkonium production is also discussed.« less
Heavy quarkonium production at collider energies: Partonic cross section and polarization
Qiu, Jian -Wei; Kang, Zhong -Bo; Ma, Yan -Qing; Sterman, George
2015-01-27
We calculate the O(α³_{s}) short-distance, QCD collinear-factorized coefficient functions for all partonic channels that include the production of a heavy quark pair at short distances. Thus, this provides the first power correction to the collinear-factorized inclusive hadronic production of heavy quarkonia at large transverse momentum, _{pT}, including the full leading-order perturbative contributions to the production of heavy quark pairs in all color and spin states employed in NRQCD treatments of this process. We discuss the role of the first power correction in the production rates and the polarizations of heavy quarkonia in high-energy hadronic collisions. The consistency of QCD collinear factorization and nonrelativistic QCD factorization applied to heavy quarkonium production is also discussed.
NASA Astrophysics Data System (ADS)
Greif, Moritz; Bouras, Ioannis; Greiner, Carsten; Xu, Zhe
2014-11-01
Electric conductivity is sensitive to effective cross sections among the particles of the partonic medium. We investigate the electric conductivity of a hot plasma of quarks and gluons, solving the relativistic Boltzmann equation. In order to extract this transport coefficient, we employ the Green-Kubo formalism and, independently, a method motivated by the classical definition of electric conductivity. To this end we evaluate the static electric diffusion current upon the influence of an electric field. Both methods give identical results. For the first time, we obtain numerically the Drude electric conductivity formula for an ultrarelativistic gas of quarks and gluons employing constant isotropic binary cross sections. Furthermore, we extract the electric conductivity for a system of massless quarks and gluons including screened binary and inelastic, radiative 2 ↔3 perturbative QCD scattering. Comparing with recent lattice results, we find an agreement in the temperature dependence of the conductivity.