Proton form factor effects in hydrogenic atoms
Daza, F. Garcia; Kelkar, N. G.; Nowakowski, M.
2011-10-21
The proton structure corrections to the hyperfine splittings in electronic and muonic hydrogen are evaluated using the Breit potential with electromagnetic form factors. In contrast to other methods, the Breit equation with q{sup 2} dependent form factors is just an extension of the standard Breit equation which gives the hyperfine splitting Hamiltonian. Precise QED corrections are comparable to the structure corrections which therefore need to be evaluated ab initio.
Proton Form Factor Measurements at Jefferson Lab
Charles Perdrisat; Vina Punjabi
2004-09-27
In two experiments at Jefferson Lab in Hall A, the first one in 1998 and the second in 2000, the ratio of the electromagnetic form factors of the proton was obtained by measuring P{sub t} and P{sub ell}, the transverse and longitudinal recoil proton polarization components, respectively, in {rvec e}p {yields} e{rvec p}; the ratio G{sub E{sub p}}/G{sub M{sub p}} is proportional to P{sub t}/P{sub {ell}}. Simultaneous measurement of P{sub t} and P{sub {ell}} provides good control of the systematic uncertainty. The first measurement of G{sub E{sub p}}/G{sub M{sub p}} ratio was made to Q{sup 2} = 3.5 GeV{sup 2} and the second measurement to Q{sup 2} = 5.6 GeV{sup 2}. The results from these two experiments indicate that the ratio scales like 1/Q{sup 2}, in stark contrast with cross section data analyzed by the Rosenbluth separation method which gives a constant value for this ratio. The incompatibility of the recoil polarization results with most of the Rosenbluth separation results appears now well established above Q{sup 2} of about 3 GeV{sup 2}. The consensus at the present time is that the interference of the two-photon exchange with the Born term, which had been deemed negligible until recently, might explain the discrepancy between the results of the two techniques; the possibility that the discrepancy is due to incomplete radiative correction has also been recently discussed.
The Proton Form Factor Ratio Measurements at Jefferson Lab
Punjabi, Vina A.; Perdrisat, Charles F.
2014-03-01
The ratio of the proton form factors, G{sub Ep}/G{sub Mp}, has been measured from Q{sup 2} of 0.5 GeV{sup 2} to 8.5 GeV{sup 2}, at the Jefferson Laboratory, using the polarization transfer method. This ratio is extracted directly from the measured ratio of the transverse and longitudinal polarization components of the recoiling proton in elastic electron-proton scattering. The discovery that the proton form factor ratio measured in these experiments decreases approximately linearly with four-momentum transfer, Q{sup 2}, for values above ~1 GeV{sup 2}, is one of the most significant results to come out of JLab. These results have had a large impact on progress in hadronic physics; and have required a significant rethinking of nucleon structure. The increasingly common use of the double-polarization technique to measure the nucleon form factors, in the last 15 years, has resulted in a dramatic improvement of the quality of all four nucleon electromagnetic form factors, G{sub Ep}, G{sub Mp}, G{sub En} and G{sub Mn}. There is an approved experiment at JLab, GEP(V), to continue the ratio measurements to 12 GeV{sup 2}. A dedicated experimental setup, the Super Bigbite Spectrometer (SBS), will be built for this purpose. It will be equipped with a focal plane polarimeter to measure the polarization of the recoil protons. The scattered electrons will be detected in an electromagnetic calorimeter. In this presentation, I will review the status of the proton elastic electromagnetic form factors and discuss a number of theoretical approaches to describe nucleon form factors.
The proton form factor ratio results from Jefferson Lab
Vina Punjabi
2012-09-01
The ratio of the proton form factors, GE p/GMp, has been measured extensively, from Q2 of 0.5 GeV2 to 8.5 GeV2, at the Jefferson Laboratory, using the polarization transfer method. This ratio is extracted directly from the measured ratio of the transverse and longitudinal polarization components of the recoiling proton in elastic electron-proton scattering. The polarization transfer results are of unprecedented high precision and accuracy, due in large part to the small systematic uncertainties associated with the experimental technique. There is an approved experiment at JLab, GEP(5), to continue the ratio measurements to 12 GeV2. A dedicated experimental setup, the Super Bigbite Spectrometer (SBS), will be built for this purpose. It will be equipped with a focal plane polarimeter to measure the polarization of the recoil protons. The scattered electrons will be detected in an electromagnetic calorimeter. In this presentation, I will review the status of the proton elastic electromagnetic form factors and discuss a number of theoretical approaches to describe nucleon form factors.
Reanalysis of Rosenbluth measurements of the proton form factors
NASA Astrophysics Data System (ADS)
Gramolin, A. V.; Nikolenko, D. M.
2016-05-01
We present a reanalysis of the data from Stanford Linear Accelerator Center (SLAC) experiments E140 [R. C. Walker et al., Phys. Rev. D 49, 5671 (1994), 10.1103/PhysRevD.49.5671] and NE11 [L. Andivahis et al., Phys. Rev. D 50, 5491 (1994), 10.1103/PhysRevD.50.5491] on elastic electron-proton scattering. This work is motivated by recent progress in calculating the corresponding radiative corrections and by the apparent discrepancy between the Rosenbluth and polarization transfer measurements of the proton electromagnetic form factors. New, corrected values for the scattering cross sections are presented, as well as a new form factor fit in the Q2 range from 1 to 8.83 GeV2. We also provide a complete set of revised formulas to account for radiative corrections in single-arm measurements of unpolarized elastic electron-proton scattering.
Proton Form Factors Measurements in the Time-Like Region
Anulli, F.; /Frascati
2007-10-22
I present an overview of the measurement of the proton form factors in the time-like region. BABAR has recently measured with great accuracy the e{sup +}e{sup -} {yields} p{bar p} reaction from production threshold up to an energy of {approx} 4.5 GeV, finding evidence for a ratio of the electric to magnetic form factor greater than unity, contrary to expectation. In agreement with previous measurements, BABAR confirmed the steep rise of the magnetic form factor close to the p{bar p} mass threshold, suggesting the possible presence of an under-threshold N{bar N} vector state. These and other open questions related to the nucleon form factors both in the time-like and space-like region, wait for more data with different experimental techniques to be possibly solved.
Helicity non-conserving form factor of the proton
Voutier, E.; Furget, C.; Knox, S.
1994-04-01
The study of the hadron structure in the high Q{sup 2} range contributes to the understanding of the mechanisms responsible for the confinement of quarks and gluons. Among the numerous experimental candidates sensitive to these mechanisms, the helicity non-conserving form factor of the proton is a privileged observable since it is controlled by non-perturbative effects. The authors investigate here the feasibility of high Q{sup 2} measurements of this form factor by means of the recoil polarization method in the context of the CEBAF 8 GeV facility. For that purpose, they discuss the development of a high energy proton polarimeter, based on the H({rvec p},pp) elastic scattering, to be placed at the focal plane of a new hadron spectrometer. It is shown that this experimental method significantly improves the knowledge of the helicity non-conserving form factor of the proton up to 10 GeV{sup 2}/c{sup 2}.
The Mainz high-precision proton form factor measurement
NASA Astrophysics Data System (ADS)
Bernauer, Jan
2011-04-01
Form factors offer a direct approach to fundamental properties of the nucleons like the radius and charge distribution. Renewed interest was stirred up by the 5 sigma discrepancy between a recent determination of the proton radius from the Lamb shift in muonic hydrogen and preceding electron scattering results. The low-q shape of the form factors might also contain a direct signal of a pion cloud around the nucleus and is a strong test of hadron models. In my talk, I will discuss the electron scattering experiment performed with the 3-spectrometer-facility of the A1 collaboration at MAMI in Mainz, Germany. The data set covers the Q2-range from 0.004 to 1 (GeV / c) 2 and includes about 1400 separate cross section measurements, spanning the range of scattering angles from below 20° to above 120° at six beam energies between 180 and 855 MeV, with statistical uncertainties below 0.4%. The 3-spectrometer-setup allowed for a simultaneous monitoring of the luminosity and overlapping and redundant measurements of the cross section to achieve stringent control over systematic uncertainties. Beam stabilization systems and redundant current measurements further limit systematic effects. The measured cross sections were analyzed with the standard Rosenbluth separation technique and by employing direct fits of a large set of form factor models. The high redundancy of the data set allowed us to extract the form factors up to 0.6 (GeV / c) 2 with very small uncertainties and to give a new, precise value for the proton radius from electron scattering. From the form factors, the charge distribution and Zemach moments were calculated. The latter constitute important input for the theoretical corrections of the muonic Lamb shift experiment. However, the revised values can not explain the discrepancy. Further possible explanations include higher order QED-corrections, vacuum effects or even physics beyond the standard model.
Proton Form Factor Measurements Using Polarization Method: Beyond Born Approximation
Pentchev, Lubomir
2008-10-13
Significant theoretical and experimental efforts have been made over the past 7 years aiming to explain the discrepancy between the proton form factor ratio data obtained at JLab using the polarization method and the previous Rosenbluth measurements. Preliminary results from the first high precision polarization experiment dedicated to study effects beyond Born approximation will be presented. The ratio of the transferred polarization components and, separately, the longitudinal polarization in ep elastic scattering have been measured at a fixed Q{sup 2} of 2.5 GeV{sup 2} over a wide kinematic range. The two quantities impose constraints on the real part of the ep elastic amplitudes.
Electric and magnetic form factors of the proton
NASA Astrophysics Data System (ADS)
Bernauer, J. Â. C.; Distler, M. Â. O.; Friedrich, J.; Walcher, Th.; Achenbach, P.; Ayerbe Gayoso, C.; Böhm, R.; Bosnar, D.; Debenjak, L.; Doria, L.; Esser, A.; Fonvieille, H.; Gómez Rodríguez de la Paz, M.; Friedrich, J. Â. M.; Makek, M.; Merkel, H.; Middleton, D. Â. G.; Müller, U.; Nungesser, L.; Pochodzalla, J.; Potokar, M.; Sánchez Majos, S.; Schlimme, B. Â. S.; Širca, S.; Weinriefer, M.; A1 Collaboration
2014-07-01
This paper describes a precise measurement of electron scattering off the proton at momentum transfers of 0.003≲Q2≲1 GeV2. The average point-to-point error of the cross sections in this experiment is ˜0.37%. These data are used for a coherent new analysis together with all world data of unpolarized and polarized electron scattering from the very smallest to the highest momentum transfers so far measured. The extracted electric and magnetic form factors provide new insight into their exact shape, deviating from the classical dipole form, and of structure on top of this gross shape. The data reaching very low Q2 values are used for a new determination of the electric and magnetic radii. An empirical determination of the two-photon-exchange correction is presented. The implications of this correction on the radii and the question of a directly visible signal of the pion cloud are addressed.
Resolving the Proton Form Factor Problem with Positron-Proton Scattering
NASA Astrophysics Data System (ADS)
Weinstein, Lawrence
2012-10-01
The proton electromagnetic form factors are essential pieces of our knowledge of nucleon structure. However, Rosenbluth separation measurements of the proton electric form factor, GE(Q^2), differ from polarization transfer measurements by a factor of three at Q^2 = 5.6 (GeV/c)^2. This discrepancy must be resolved. One possible resolution is to include the contribution of hard two-photon exchange (TPE) contributions. These contributions are very difficult to calculate. However, we can directly determine the TPE effect by measuring the ratio of the positron-proton to electron-proton elastic scattering cross sections, R=σ(e^+p)/σ(e^-p), because the TPE amplitude has the same sign as the e^+p born amplitude and the opposite sign as the e^-p born amplitude. We have measured R over a wide range of momentum transfer, 0.2 <=Q^2 <=2 GeV^2, and virtual photon polarization, 0.1 <=ɛ<=0.9, using a mixed identical beam of electrons and positrons in Hall B at Jefferson Lab. This talk will describe the experimental techniques used to produce this beam, the analysis techniques to identify elastic scattering events, and some preliminary results.
Measurement of the Neutral Weak Form Factors of the Proton
Deur, Alexandre; Fleck, Andre; Saha, Arunava; Gasparian, Ashot; Frois, Bernard; Wojtsekhowski, Bogdan; Vlahovic, Branislav; Perdrisat, Charles; Cavata, Christian; Jutier, Christophe; De Jager, Cornelis; Neyret, Damien; Dale, Daniel; Armstrong, David; Lhuillier, David; Prout, David; Margaziotis, Demetrius; Kim, Donghee; Burtin, Etienne; Chudakov, Eugene; Hersman, F.; Garibaldi, Franco; Marie, Frederic; Miller, Greg; Rutledge, Gary; Gerstner, George; Petratos, Gerassimos; Quemener, Gilles; Cates, Gordon; Thompson, J.; Martino, Jacques; Gomez, Javier; Jorda, Jean-Paul; Hansen, Jens-Ole; Chen, Jian-Ping; Jardillier, Johann; Calarco, John; LeRose, John; Price, John; Gao, Juncai; McIntyre, Justin; McCormick, Kathy; Fissum, Kevin; Kramer, Kevin; Aniol, Konrad; Kumar, Krishna; Wijesooriya, Krishni; Ewell, Lars; Todor, Luminita; Spradlin, Marcus; Jones, Mark; Leuschner, Mark; Epstein, Martin; Baylac, Maud; Holtrop, Maurik; Finn, Michael; Kuss, Michael; Kim, Min; Falletto, Nicolas; Liyanage, Nilanga; Glamazdin, Oleksandr; Rutt, Paul; Souder, Paul; Ulmer, Paul; Mastromarino, Peter; Djawotho, Pibero; Wilson, Richard; Suleiman, Riad; Holmes, Richard; Madey, Richard; Lourie, Robert; Michaels, Robert; Pomatsalyuk, Roman; Gilman, Ronald; Incerti, Sebastien; Escoffier, Stephanie; Pussieux, Thierry; Humensky, Thomas; Gorbenko, Viktor; Punjabi, Vina; Kahl, William; Meziani, Zein-Eddine
1999-02-01
We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from the proton. The kinematic point [(Theta_{lab}) = 12.3r and (Q^{2}) = 0.48 (GeV/c)^{2}] is chosen to provide sensitivity, at a level that is of theoretical interest, to the strange electric form factor G^{s}_{E}. The result, A = - 14.5 + or - 2.2 ppm, is consistent with the electroweak standard model and no additional contributions from strange quarks. In particular, the measurement implies G^{s}_{E} + 0.39G^{s}_{M} = 0.023 + or - 0.034(stat) + or - 0.022(syst) + or - 0.026(delta-G^{n}_{E}), where the last uncertainty arises from the estimated uncertainty in the neutron electric form factor.
Measurement of the neutral weak form factors of the proton
Aniol, K.A.; Epstein, M.B.; Margaziotis, D.J.; Deur, A.; Spradlin, M.; Wilson, R.; Garibaldi, F.; Chen, J.; Chudakov, E.; de Jager, C.W.; Deur, A.; Gomez, J.; Hansen, O.; Kuss, M.; LeRose, J.; Michaels, R.; Price, J.S.; Rutt, P.M.; Saha, A.; Wojtsekhowski, B.; Madey, R.; Petratos, G.G.; Prout, D.; Suleiman, R.; Dale, D.; Glamazdin, A.; Gorbenko, V.; Pomatsalyuk, R.; Kim, D.H.; Kim, M.S.; Ewell, L.; Fissum, K.; Gao, J.; Liyanage, N.; Calarco, J.; Hersman, F.; Holtrop, M.; Leuschner, M.; Punjabi, V.; Vlahovic, B.; Jutier, C.; McCormick, K.; Todor, L.; Ulmer, P.E.; Cates, G.D.; Humensky, B.; Kumar, K.S.; Mastromarino, P.; Miller, G.W.; Spradlin, M.; Fleck, A.; Gilman, R.; McIntyre, J.; and others
1999-02-01
We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from the proton. The kinematic point [{l_angle}{theta}{sub lab }{r_angle}=12.3{degree} and {l_angle}Q{sup 2}{r_angle}=0.48 (GeV /c){sup 2} ] is chosen to provide sensitivity, at a level that is of theoretical interest, to the strange electric form factor G{sup s}{sub E} . The result, A={minus}14.5{plus_minus}2.2 ppm , is consistent with the electroweak standard model and no additional contributions from strange quarks. In particular, the measurement implies G{sup s}{sub E}+0.39G{sup s}{sub M}=0.023 {plus_minus}0.034(stat){plus_minus}0.022( syst){plus_minus}0.026({delta}G{sup n}{sub E}) , where the last uncertainty arises from the estimated uncertainty in the neutron electric form factor. {copyright} {ital 1999} {ital The American Physical Society}
Proton form factors and two-photon exchange in elastic electron-proton scattering
Nikolenko, D. M.; Arrington, J.; Barkov, L. M.; Vries, H. de; Gauzshtein, V. V.; Golovin, R. A.; Gramolin, A. V.; Dmitriev, V. F.; Zhilich, V. N.; Zevakov, S. A.; Kaminsky, V. V.; Lazarenko, B. A.; Mishnev, S. I.; Muchnoi, N. Yu.; Neufeld, V. V.; Rachek, I. A.; Sadykov, R. Sh.; Stibunov, V. N.; Toporkov, D. K.; Holt, R. J.; and others
2015-05-15
Proton electromagnetic form factors are among the most important sources of information about the internal structure of the proton. Two different methods for measuring these form factors, the method proposed by Rosenbluth and the polarization-transfer method, yield contradictory results. It is assumed that this contradiction can be removed upon taking into account the hard part of the contribution of two-photon exchange to the cross section for elastic electron-proton scattering. This contribution can measured experimentally via a precision comparison of the cross sections for the elastic scattering of positrons and electrons on protons. Such a measurement, performed at the VEPP-3 storage ring in Novosibirsk at the beam energies of 1.6 and 1.0 GeV for positron (electron) scattering angles in the ranges of θ{sub e} = 15°–25° and 55°–75° in the first case and in the range of θ{sub e} = 65°–105° in the second case is described in the present article. Preliminary results of this experiment and their comparison with theoretical predictions are described.
New results on strange form factors of the proton
Richard Holmes
2000-12-12
At the Thomas Jefferson National Accelerator Facility, we have studied the elastic scattering of polarized electrons from hydrogen. The resulting parity-violating electroweak asymmetry is sensitive to the contributions of strange quarks to the nucleon form factors at a level that is of theoretical interest. Using events at a laboratory scattering angle of 12.3{sup o} and (Q{sup 2})=0.477 GeV/c, we measure the linear combination of strange form factors (G{sup n}{sub E}) + 0.39G{sup E}{sub M}/(G{sup py}{sub M}/mu{sub p}) = 0.091+/-0.054+/-0.039, where the first error is the quadratic sum of our systematic and statistical errors and the second error is due to uncertainty in nucleon form factors.
Theoretical and Experimental Review on Proton Form Factors
NASA Astrophysics Data System (ADS)
Baldini Ferroli, Rinaldo; Pacetti, Simone
2014-12-01
During the last three lustra nucleon form factors experiments have lived a golden age, full of interesting results, that likely will continue and culminate when new data will come from BESIII, SND, CMD3 and PANDA, in the time-like region and, Jefferson Lab and A1 in the space-like region. On the other hand, from theoretical point of view, mainly concerning the possibility of descriptions in all kinematical regions, no great breakthrough has been made.
Andrew Puckett
2009-12-01
Electromagnetic form factors are fundamental properties of the nucleon that describe the effect of its internal quark structure on the cross section and spin observables in elastic lepton-nucleon scattering. Double-polarization experiments have become the preferred technique to measure the proton and neutron electric form factors at high momentum transfers. The recently completed GEp-III experiment at the Thomas Jefferson National Accelerator Facility used the recoil polarization method to extend the knowledge of the proton electromagnetic form factor ratio GpE/GpM to Q2 = 8.5 GeV2. In this paper we present the preliminary results of the experiment.
Proton electromagnetic form factors: present status and future perspectives at PANDA
NASA Astrophysics Data System (ADS)
Tomasi-Gustafsson, E.
2015-05-01
Data and models on electromagnetic proton form factors are reviewed, highlighting the contribution foreseen by the PANDA collaboration. Electromagnetic hadron form factors contain essential information on the internal structure of hadrons. Precise and surprising data have been obtained at electron accelerators, applying the polarization method in electron-proton elastic scattering. At electron-positron colliders, using initial state radiation, BABAR measured proton time-like form factors in a wide time-like kinematical region and the BESIII collaboration will measure very precisely proton and neutron form factors in the threshold region. In the next future an antiproton beam with momentum up to 15 GeV/c will be available at FAIR (Darmstadt). Measurements of the reaction p̅ + p → e+ + e- by the PANDA collaboration will contribute to the individual determination of electric and magnetic form factors in the time-like region of momentum transfer squared, as well as to their first determination in the unphysical region (below the kinematical threshold), through the reaction p̅ + p → e+ + e- + π0. From the discussion on feasibility studies at PANDA, we focus on the consequences of such measurements in view of an unified description of form factors in the full kinematical region. We present models which have the necessary analytical requirements and apply to the data in the whole kinematical region.
Pion and proton form factors in the regge description of electroproduction p( e, e' π +) n
NASA Astrophysics Data System (ADS)
Choi, Tae Keun; Kong, Kook Jin; Yu, Byung Geel
2015-10-01
Electroproduction of π + above the resonance region is analyzed in the Regge model for π + ρ exchanges. The importance of the roles of the pion and the proton form factors in the process is discussed in comparison with the existing models of Kaskulov and Mosel and of Vrancx and Ryckebusch. The present model with a proton form factor of a simple dipole-type is shown to yield a better description of DESY and JLab data over those models for the high Q 2 and - t region up to 5 GeV2.
New Precision Limit on the Strange Vector Form Factors of the Proton
NASA Astrophysics Data System (ADS)
Ahmed, Z.; Allada, K.; Aniol, K. A.; Armstrong, D. S.; Arrington, J.; Baturin, P.; Bellini, V.; Benesch, J.; Beminiwattha, R.; Benmokhtar, F.; Canan, M.; Camsonne, A.; Cates, G. D.; Chen, J.-P.; Chudakov, E.; Cisbani, E.; Dalton, M. M.; de Jager, C. W.; de Leo, R.; Deconinck, W.; Decowski, P.; Deng, X.; Deur, A.; Dutta, C.; Franklin, G. B.; Friend, M.; Frullani, S.; Garibaldi, F.; Giusa, A.; Glamazdin, A.; Golge, S.; Grimm, K.; Hansen, O.; Higinbotham, D. W.; Holmes, R.; Holmstrom, T.; Huang, J.; Huang, M.; Hyde, C. E.; Jen, C. M.; Jin, G.; Jones, D.; Kang, H.; King, P.; Kowalski, S.; Kumar, K. S.; Lee, J. H.; Lerose, J. J.; Liyanage, N.; Long, E.; McNulty, D.; Margaziotis, D.; Meddi, F.; Meekins, D. G.; Mercado, L.; Meziani, Z.-E.; Michaels, R.; Muñoz-Camacho, C.; Mihovilovic, M.; Muangma, N.; Myers, K. E.; Nanda, S.; Narayan, A.; Nelyubin, V.; Nuruzzaman; Oh, Y.; Pan, K.; Parno, D.; Paschke, K. D.; Phillips, S. K.; Qian, X.; Qiang, Y.; Quinn, B.; Rakhman, A.; Reimer, P. E.; Rider, K.; Riordan, S.; Roche, J.; Rubin, J.; Russo, G.; Saenboonruang, K.; Saha, A.; Sawatzky, B.; Silwal, R.; Sirca, S.; Souder, P. A.; Sperduto, M.; Subedi, R.; Suleiman, R.; Sulkosky, V.; Sutera, C. M.; Tobias, W. A.; Urciuoli, G. M.; Waidyawansa, B.; Wang, D.; Wexler, J.; Wilson, R.; Wojtsekhowski, B.; Zhan, X.; Yan, X.; Yao, H.; Ye, L.; Zhao, B.; Zheng, X.
2012-03-01
The parity-violating cross-section asymmetry in the elastic scattering of polarized electrons from unpolarized protons has been measured at a four-momentum transfer squared Q2=0.624GeV2 and beam energy Eb=3.48GeV to be APV=-23.80±0.78(stat)±0.36(syst) parts per million. This result is consistent with zero contribution of strange quarks to the combination of electric and magnetic form factors GEs+0.517GMs=0.003±0.010(stat)±0.004(syst)±0.009(ff), where the third error is due to the limits of precision on the electromagnetic form factors and radiative corrections. With this measurement, the world data on strange contributions to nucleon form factors are seen to be consistent with zero and not more than a few percent of the proton form factors.
The Proton Coulomb Form Factor from Polarized Inclusive e-p Scattering
Chris Harris
2001-08-01
The proton form factors provide information on the fundamental properties of the proton and provide a test for models based on QCD. In 1998 at Jefferson Lab (JLAB) in Newport News, VA, experiment E93026 measured the inclusive e-p scattering cross section from a polarized ammonia (15NH3) target at a four momentum transfer squared of Q2 = 0.5 (GeV/c)2. Longitudinally polarized electrons were scattered from the polarized target and the scattered electron was detected. Data has been analyzed to obtain the asymmetry from elastically scattered electrons from hydrogen in 15NH3. The asymmetry, Ap, has been used to determine the proton elastic form factor GEp. The result is consistent with the dipole model and data from previous experiments. However, due to the choice of kinematics, the uncertainty in the measurement is large.
High Precision Measurement of the Proton Elastic Form Factor Ratio at Low Q2
Xiaohui Zhan
2009-12-01
A high precision measurement of the proton elastic form factor ratio µpGEp/GMp in the range Q2 = 0.3–0.7 GeV2/c2 was performed using recoil polarimetry in Jefferson Lab Hall A. In this low Q2 range, previous data from LEDEX [5] along with many fits and calculations [2, 3, 4] indicate substantial deviations of the ratio from unity. In this new measurement, with 80% polarized electron beam for 24 days, we are able to achieve <1% statistical uncertainty. Preliminary results are a few percent lower than expected from previous world data and fits, indicating a smaller GEp at this region. Beyond the intrinsic interest in nucleon structure, the improved form factor measurements also have implications for DVCS, determinations of the proton Zemach radius and strangeness form factors through parity violation experiments.
High-Precision Determination of the Electric and Magnetic Form Factors of the Proton
Bernauer, J. C.; Achenbach, P.; Ayerbe Gayoso, C.; Boehm, R.; Distler, M. O.; Doria, L.; Esser, A.; Friedrich, J.; Gomez Rodriguez de la Paz, M.; Merkel, H.; Middleton, D. G.; Mueller, U.; Nungesser, L.; Pochodzalla, J.; Sanchez Majos, S.; Schlimme, B. S.; Walcher, Th.; Weinriefer, M.; Bosnar, D.; Makek, M.
2010-12-10
New precise results of a measurement of the elastic electron-proton scattering cross section performed at the Mainz Microtron MAMI are presented. About 1400 cross sections were measured with negative four-momentum transfers squared up to Q{sup 2}=1 (GeV/c){sup 2} with statistical errors below 0.2%. The electric and magnetic form factors of the proton were extracted by fits of a large variety of form factor models directly to the cross sections. The form factors show some features at the scale of the pion cloud. The charge and magnetic radii are determined to be
High-precision determination of the electric and magnetic form factors of the proton.
Bernauer, J C; Achenbach, P; Ayerbe Gayoso, C; Böhm, R; Bosnar, D; Debenjak, L; Distler, M O; Doria, L; Esser, A; Fonvieille, H; Friedrich, J M; Friedrich, J; Gómez Rodríguez de la Paz, M; Makek, M; Merkel, H; Middleton, D G; Müller, U; Nungesser, L; Pochodzalla, J; Potokar, M; Sánchez Majos, S; Schlimme, B S; Sirca, S; Walcher, Th; Weinriefer, M
2010-12-10
New precise results of a measurement of the elastic electron-proton scattering cross section performed at the Mainz Microtron MAMI are presented. About 1400 cross sections were measured with negative four-momentum transfers squared up to Q² = 1 (GeV/c)² with statistical errors below 0.2%. The electric and magnetic form factors of the proton were extracted by fits of a large variety of form factor models directly to the cross sections. The form factors show some features at the scale of the pion cloud. The charge and magnetic radii are determined to be
Global analysis of proton elastic form factor data with two-photon exchange corrections
J. Arrington; W. Melnitchouk; J. A. Tjon
2007-09-01
We use the world's data on elastic electron-proton scattering and calculations of two-photon exchange effects to extract corrected values of the proton's electric and magnetic form factors over the full Q^2 range of the existing data. Our analysis combines the corrected Rosenbluth cross section and polarization transfer data, and is the first extraction of G_Ep and G_Mp including explicit two-photon exchange corrections and their associated uncertainties. In addition, we examine the angular dependence of the corrected cross sections, and discuss the possible nonlinearities of the cross section as a function of epsilon.
Towards a Resolution of the Proton Form Factor Problem: New Electron and Positron Scattering Data
NASA Astrophysics Data System (ADS)
Adikaram, D.; Rimal, D.; Weinstein, L. B.; Raue, B.; Khetarpal, P.; Bennett, R. P.; Arrington, J.; Brooks, W. K.; Adhikari, K. P.; Afanasev, A. V.; Amaryan, M. J.; Anderson, M. D.; Anefalos Pereira, S.; Avakian, H.; Ball, J.; Battaglieri, M.; Bedlinskiy, I.; Biselli, A. S.; Bono, J.; Boiarinov, S.; Briscoe, W. J.; Burkert, V. D.; Carman, D. S.; Careccia, S.; Celentano, A.; Chandavar, S.; Charles, G.; Colaneri, L.; Cole, P. L.; Contalbrigo, M.; Crede, V.; D'Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Dodge, G. E.; Dupre, R.; Egiyan, H.; El Alaoui, A.; El Fassi, L.; Elouadrhiri, L.; Eugenio, P.; Fedotov, G.; Fegan, S.; Filippi, A.; Fleming, J. A.; Fradi, A.; Garillon, B.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Goetz, J. T.; Gohn, W.; Golovatch, E.; Gothe, R. W.; Griffioen, K. A.; Guegan, B.; Guidal, M.; Guo, L.; Hafidi, K.; Hakobyan, H.; Hanretty, C.; Harrison, N.; Hattawy, M.; Hicks, K.; Holtrop, M.; Hughes, S. M.; Hyde, C. E.; Ilieva, Y.; Ireland, D. G.; Ishkhanov, B. S.; Jenkins, D.; Jiang, H.; Jo, H. S.; Joo, K.; Joosten, S.; Kalantarians, N.; Keller, D.; Khandaker, M.; Kim, A.; Kim, W.; Klein, A.; Klein, F. J.; Koirala, S.; Kubarovsky, V.; Kuhn, S. E.; Livingston, K.; Lu, H. Y.; MacGregor, I. J. D.; Markov, N.; Mattione, P.; Mayer, M.; McKinnon, B.; Mestayer, M. D.; Meyer, C. A.; Mirazita, M.; Mokeev, V.; Montgomery, R. A.; Moody, C. I.; Moutarde, H.; Movsisyan, A.; Camacho, C. Munoz; Nadel-Turonski, P.; Niccolai, S.; Niculescu, G.; Osipenko, M.; Ostrovidov, A. I.; Park, K.; Pasyuk, E.; Peña, C.; Pisano, S.; Pogorelko, O.; Price, J. W.; Procureur, S.; Prok, Y.; Protopopescu, D.; Puckett, A. J. R.; Ripani, M.; Rizzo, A.; Rosner, G.; Rossi, P.; Roy, P.; Sabatié, F.; Salgado, C.; Schott, D.; Schumacher, R. A.; Seder, E.; Sharabian, Y. G.; Simonyan, A.; Skorodumina, I.; Smith, E. S.; Smith, G. D.; Sober, D. I.; Sokhan, D.; Sparveris, N.; Stepanyan, S.; Stoler, P.; Strauch, S.; Sytnik, V.; Taiuti, M.; Tian, Ye; Trivedi, A.; Ungaro, M.; Voskanyan, H.; Voutier, E.; Walford, N. K.; Watts, D. P.; Wei, X.; Wood, M. H.; Zachariou, N.; Zana, L.; Zhang, J.; Zhao, Z. W.; Zonta, I.; CLAS Collaboration
2015-02-01
There is a significant discrepancy between the values of the proton electric form factor, GEp, extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of GEp from the unpolarized electron-proton cross sections. We determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections using a simultaneous, tertiary electron-positron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual photon polarization (ɛ ) and momentum transfer (Q2) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing ɛ at Q2=1.45 GeV2 . This measurement is consistent with the size of the form factor discrepancy at Q2≈1.75 GeV2 and with hadronic calculations including nucleon and Δ intermediate states, which have been shown to resolve the discrepancy up to 2 - 3 GeV2 .
Towards a Resolution of the Proton Form Factor Problem: New Electron and Positron Scattering Data
Adikaram, D.; Rimal, D.; Weinstein, L. B.; Raue, B.; Khetarpal, P.; Bennett, R. P.; Arrington, J.; Brooks, W. K.; Adhikari, K. P.; Afanasev, A. V.; Dupre, R.; El Alaoui, A.; El Fassi, L.; Hafidi, K.; Moody, C. I.
2015-02-10
There is a significant discrepancy between the values of the proton electric form factor, G(E)(p), extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of G(E)(p). from the unpolarized electron-proton cross sections. We determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections using a simultaneous, tertiary electron-positron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual photon polarization (epsilon) and momentum transfer (Q(2)) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing epsilon at Q(2) = 1.45 GeV2. This measurement is consistent with the size of the form factor discrepancy at Q(2) approximate to 1.75 GeV2 and with hadronic calculations including nucleon and Delta intermediate states, which have been shown to resolve the discrepancy up to 2-3 GeV2.
Towards a resolution of the proton form factor problem: new electron and positron scattering data.
Adikaram, D; Rimal, D; Weinstein, L B; Raue, B; Khetarpal, P; Bennett, R P; Arrington, J; Brooks, W K; Adhikari, K P; Afanasev, A V; Amaryan, M J; Anderson, M D; Anefalos Pereira, S; Avakian, H; Ball, J; Battaglieri, M; Bedlinskiy, I; Biselli, A S; Bono, J; Boiarinov, S; Briscoe, W J; Burkert, V D; Carman, D S; Careccia, S; Celentano, A; Chandavar, S; Charles, G; Colaneri, L; Cole, P L; Contalbrigo, M; Crede, V; D'Angelo, A; Dashyan, N; De Vita, R; De Sanctis, E; Deur, A; Djalali, C; Dodge, G E; Dupre, R; Egiyan, H; El Alaoui, A; El Fassi, L; Elouadrhiri, L; Eugenio, P; Fedotov, G; Fegan, S; Filippi, A; Fleming, J A; Fradi, A; Garillon, B; Gilfoyle, G P; Giovanetti, K L; Girod, F X; Goetz, J T; Gohn, W; Golovatch, E; Gothe, R W; Griffioen, K A; Guegan, B; Guidal, M; Guo, L; Hafidi, K; Hakobyan, H; Hanretty, C; Harrison, N; Hattawy, M; Hicks, K; Holtrop, M; Hughes, S M; Hyde, C E; Ilieva, Y; Ireland, D G; Ishkhanov, B S; Jenkins, D; Jiang, H; Jo, H S; Joo, K; Joosten, S; Kalantarians, N; Keller, D; Khandaker, M; Kim, A; Kim, W; Klein, A; Klein, F J; Koirala, S; Kubarovsky, V; Kuhn, S E; Livingston, K; Lu, H Y; MacGregor, I J D; Markov, N; Mattione, P; Mayer, M; McKinnon, B; Mestayer, M D; Meyer, C A; Mirazita, M; Mokeev, V; Montgomery, R A; Moody, C I; Moutarde, H; Movsisyan, A; Camacho, C Munoz; Nadel-Turonski, P; Niccolai, S; Niculescu, G; Osipenko, M; Ostrovidov, A I; Park, K; Pasyuk, E; Peña, C; Pisano, S; Pogorelko, O; Price, J W; Procureur, S; Prok, Y; Protopopescu, D; Puckett, A J R; Ripani, M; Rizzo, A; Rosner, G; Rossi, P; Roy, P; Sabatié, F; Salgado, C; Schott, D; Schumacher, R A; Seder, E; Sharabian, Y G; Simonyan, A; Skorodumina, I; Smith, E S; Smith, G D; Sober, D I; Sokhan, D; Sparveris, N; Stepanyan, S; Stoler, P; Strauch, S; Sytnik, V; Taiuti, M; Tian, Ye; Trivedi, A; Ungaro, M; Voskanyan, H; Voutier, E; Walford, N K; Watts, D P; Wei, X; Wood, M H; Zachariou, N; Zana, L; Zhang, J; Zhao, Z W; Zonta, I
2015-02-13
There is a significant discrepancy between the values of the proton electric form factor, G(E)(p), extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of G(E)(p) from the unpolarized electron-proton cross sections. We determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections using a simultaneous, tertiary electron-positron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual photon polarization (ϵ) and momentum transfer (Q(2)) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing ϵ at Q(2)=1.45 GeV(2). This measurement is consistent with the size of the form factor discrepancy at Q(2)≈1.75 GeV(2) and with hadronic calculations including nucleon and Δ intermediate states, which have been shown to resolve the discrepancy up to 2-3 GeV(2). PMID:25723209
Towards a Resolution of the Proton Form Factor Problem: New Electron and Positron Scattering Data
Adikaram, D.; Rimal, D.; Weinstein, L. B.; Raue, B.; Khetarpal, P.; Bennett, R.; Arrington, J.; Brooks, W.; Adhikari, K.; Afanasev, A.; Amaryan, M.; Anderson, M.; Anefalos Pereira, S.; Avakian, H.; Ball, J.; Battaglieri, M.; Bedlinskiy, I.; Biselli, A.; Bono, J.; Boiarinov, S.; Briscoe, W.; Burkert, V.; Carman, D.; Careccia, S.; Celentano, A.; Chandavar, S.; Charles, G.; Colaneri, L.; Cole, P.; Contalbrigo, M.; Crede, V.; D'Angelo, A.; Dashyan, N.; De Vita, R.; De Sanctis, E.; Deur, A.; Djalali, C.; Dodge, G.; Dupre, R.; Egiyan, H.; El Alaoui, A.; El Fassi, L.; Elouadrhiri, L.; Eugenio, P.; Fedotov, G.; Fegan, S.; Filippi, A.; Fleming, J.; Fradi, A.; Garillon, B.; Gilfoyle, G.; Giovanetti, K.; Girod, F.; Goetz, J.; Gohn, W.; Golovatch, E.; Gothe, R.; Griffioen, K.; Guegan, B.; Guidal, M.; Guo, L.; Hafidi, K.; Hakobyan, H.; Hanretty, C.; Harrison, N.; Hattawy, M.; Hicks, K.; Holtrop, M.; Hughes, S.; Hyde, C. E.; Ilieva, Y.; Ireland, D.; Ishkhanov, B.; Jenkins, D.; Jiang, H.; Jo, H.; Joo, K.; Joosten, S.; Kalantarians, N.; Keller, D.; Khandaker, M.; Kim, A.; Kim, W.; Klein, A.; Klein, F.; Koirala, S.; Kubarovsky, V.; Kuhn, S.; Livingston, K.; Lu, H.; MacGregor, I.; Markov, N.; Mattione, P.; Mayer, M.; McKinnon, B.; Mestayer, M.; Meyer, C.; Mirazita, M.; Mokeev, V.; Montgomery, R.; Moody, C.; Moutarde, H.; Movsisyan, A.; Camacho, C. Munoz; Nadel-Turonski, P.; Niccolai, S.; Niculescu, G.; Osipenko, M.; Ostrovidov, A.; Park, K.; Pasyuk, E.; Pisano, S.; Pogorelko, O.; Price, J.; Procureur, S.; Prok, Y.; Protopopescu, D.; Puckett, A.; Ripani, M.; Rizzo, A.; Rosner, G.; Rossi, P.; Roy, P.; Sabati, F.; Salgado, C.; Schott, D.; Schumacher, R.; Seder, E.; Sharabian, Y.; Simonyan, A.; Skorodumina, I.; Smith, E.; Smith, G.; Sober, D.; Sokhan, D.; Sparveris, N.; Stepanyan, S.; Stoler, P.; Strauch, S.; Sytnik, V.; Taiuti, M.; Tian, Ye; Trivedi, A.; Ungaro, M.; Voskanyan, H.; Voutier, E.; Walford, N.; Watts, D.; Wei, X.; Wood, M.; Zachariou, N.; Zana, L.; Zhang, J.; Zhao, Z.; Zonta, I.
2015-02-10
There is a significant discrepancy between the values of the proton electric form factor, GpE, extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of GpE from the unpolarized electron-proton cross sections. We determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections using a simultaneous, tertiary electron-positron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual photon polarization (epsilon) and momentum transfer (Q2) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing ε at Q2=1.45 GeV2. This measurement is consistent with the size of the form factor discrepancy at Q2≈1.75 GeV2 and with hadronic calculations including nucleon and Delta intermediate states, which have been shown to resolve the discrepancy up to 2-3 GeV2.
Towards a Resolution of the Proton Form Factor Problem: New Electron and Positron Scattering Data
Adikaram, D.; Rimal, D.; Weinstein, L. B.; Raue, B.; Khetarpal, P.; Bennett, R.; Arrington, J.; Brooks, W.; Adhikari, K.; Afanasev, A.; et al
2015-02-10
There is a significant discrepancy between the values of the proton electric form factor, GpE, extracted using unpolarized and polarized electron scattering. Calculations predict that small two-photon exchange (TPE) contributions can significantly affect the extraction of GpE from the unpolarized electron-proton cross sections. We determined the TPE contribution by measuring the ratio of positron-proton to electron-proton elastic scattering cross sections using a simultaneous, tertiary electron-positron beam incident on a liquid hydrogen target and detecting the scattered particles in the Jefferson Lab CLAS detector. This novel technique allowed us to cover a wide range in virtual photon polarization (epsilon) and momentummore » transfer (Q2) simultaneously, as well as to cancel luminosity-related systematic errors. The cross section ratio increases with decreasing ε at Q2=1.45 GeV2. This measurement is consistent with the size of the form factor discrepancy at Q2≈1.75 GeV2 and with hadronic calculations including nucleon and Delta intermediate states, which have been shown to resolve the discrepancy up to 2-3 GeV2.« less
New Precision Limit on the Strange Vector Form Factors of the Proton
Ahmed, Z.; Allada, K.; Aniol, K. A.; Armstrong, D. S.; Arrington, J.; Baturin, P.; Bellini, V.; Benesch, J.; Beminiwattha, R.; Benmokhtar, F.; Canan, M.; Camsonne, A.; Cates, G. D.; Chen, J. -P.; Chudakov, E.; Cisbani, E.; Dalton, M. M.; de Jager, C. W.; De Leo, R.; Deconinck, W.; Decowski, P.; Deng, X.; Deur, A.; Dutta, C.; Franklin, G. B.; Friend, M.; Frullani, S.; Garibaldi, F.; Giusa, A.; Glamazdin, A.; Golge, S.; Grimm, K.; Hansen, O.; Higinbotham, D. W.; Holmes, R.; Holmstrom, T.; Huang, J.; Huang, M.; Hyde, C. E.; Jen, C. M.; Jin, G.; Jones, D.; Kang, H.; King, P.; Kowalski, S.; Kumar, K. S.; Lee, J. H.; LeRose, J. J.; Liyanage, N.; Long, E.; McNulty, D.; Margaziotis, D.; Meddi, F.; Meekins, D. G.; Mercado, L.; Meziani, Z. -E.; Michaels, R.; Muñoz-Camacho, C.; Mihovilovic, M.; Muangma, N.; Myers, K. E.; Nanda, S.; Narayan, A.; Nelyubin, V.; Nuruzzaman, None; Oh, Y.; Pan, K.; Parno, D.; Paschke, K. D.; Phillips, S. K.; Qian, X.; Qiang, Y.; Quinn, B.; Rakhman, A.; Reimer, P. E.; Rider, K.; Riordan, S.; Roche, J.; Rubin, J.; Russo, G.; Saenboonruang, K.; Saha, A.; Sawatzky, B.; Silwal, R.; Sirca, S.; Souder, P. A.; Sperduto, M.; Subedi, R.; Suleiman, R.; Sulkosky, V.; Sutera, C. M.; Tobias, W. A.; Urciuoli, G. M.; Waidyawansa, B.; Wang, D.; Wexler, J.; Wilson, R.; Wojtsekhowski, B.; Zhan, X.; Yan, X.; Yao, H.; Ye, L.; Zhao, B.; Zheng, X.
2012-03-01
The parity-violating cross-section asymmetry in the elastic scattering of polarized electrons from unpolarized protons has been measured at a four-momentum transfer squared Q^{2} = 0.624 GeV^{2} and beam energy E_{b} = 3.48 GeV to be A_{PV} = -23.80 ± 0.78 (stat) ± 0.36 (syst) parts per million. This result is consistent with zero contribution of strange quarks to the combination of electric and magnetic form factors G_{E}^{s} + 0.517 G_{M}^{s} = 0.003 ± 0.010 (stat) ± 0.004 (syst) ± 0.009 (ff), where the third error is due to the limits of precision on the electromagnetic form factors and radiative corrections. With this measurement, the world data on strange contributions to nucleon form factors are seen to be consistent with zero and not more than a few percent of the proton form factors.
New Precision Limit on the Strange Vector Form Factors of the Proton
Ahmed, Z.; Allada, K.; Aniol, K. A.; Armstrong, D. S.; Arrington, J.; Baturin, P.; Bellini, V.; Benesch, J.; Beminiwattha, R.; Benmokhtar, F.; et al
2012-03-01
The parity-violating cross-section asymmetry in the elastic scattering of polarized electrons from unpolarized protons has been measured at a four-momentum transfer squared Q2 = 0.624 GeV2 and beam energy Eb = 3.48 GeV to be APV = -23.80 ± 0.78 (stat) ± 0.36 (syst) parts per million. This result is consistent with zero contribution of strange quarks to the combination of electric and magnetic form factors GEs + 0.517 GMs = 0.003 ± 0.010 (stat) ± 0.004 (syst) ± 0.009 (ff), where the third error is due to the limits of precision on the electromagnetic form factors and radiative corrections.more » With this measurement, the world data on strange contributions to nucleon form factors are seen to be consistent with zero and not more than a few percent of the proton form factors.« less
New precision limit on the strange vector form factors of the proton.
Ahmed, Z; Allada, K; Aniol, K A; Armstrong, D S; Arrington, J; Baturin, P; Bellini, V; Benesch, J; Beminiwattha, R; Benmokhtar, F; Canan, M; Camsonne, A; Cates, G D; Chen, J-P; Chudakov, E; Cisbani, E; Dalton, M M; de Jager, C W; De Leo, R; Deconinck, W; Decowski, P; Deng, X; Deur, A; Dutta, C; Franklin, G B; Friend, M; Frullani, S; Garibaldi, F; Giusa, A; Glamazdin, A; Golge, S; Grimm, K; Hansen, O; Higinbotham, D W; Holmes, R; Holmstrom, T; Huang, J; Huang, M; Hyde, C E; Jen, C M; Jin, G; Jones, D; Kang, H; King, P; Kowalski, S; Kumar, K S; Lee, J H; LeRose, J J; Liyanage, N; Long, E; McNulty, D; Margaziotis, D; Meddi, F; Meekins, D G; Mercado, L; Meziani, Z-E; Michaels, R; Muñoz-Camacho, C; Mihovilovic, M; Muangma, N; Myers, K E; Nanda, S; Narayan, A; Nelyubin, V; Nuruzzaman; Oh, Y; Pan, K; Parno, D; Paschke, K D; Phillips, S K; Qian, X; Qiang, Y; Quinn, B; Rakhman, A; Reimer, P E; Rider, K; Riordan, S; Roche, J; Rubin, J; Russo, G; Saenboonruang, K; Saha, A; Sawatzky, B; Silwal, R; Sirca, S; Souder, P A; Sperduto, M; Subedi, R; Suleiman, R; Sulkosky, V; Sutera, C M; Tobias, W A; Urciuoli, G M; Waidyawansa, B; Wang, D; Wexler, J; Wilson, R; Wojtsekhowski, B; Zhan, X; Yan, X; Yao, H; Ye, L; Zhao, B; Zheng, X
2012-03-01
The parity-violating cross-section asymmetry in the elastic scattering of polarized electrons from unpolarized protons has been measured at a four-momentum transfer squared Q2 = 0.624 GeV2 and beam energy E(b) = 3.48 GeV to be A(PV) = -23.80 ± 0.78(stat) ± 0.36(syst) parts per million. This result is consistent with zero contribution of strange quarks to the combination of electric and magnetic form factors G(E)(s) + 0.517G(M)(s) = 0.003 ± 0.010(stat) ± 0.004(syst) ± 0.009(ff), where the third error is due to the limits of precision on the electromagnetic form factors and radiative corrections. With this measurement, the world data on strange contributions to nucleon form factors are seen to be consistent with zero and not more than a few percent of the proton form factors. PMID:22468841
Feasibility studies on time-like proton electromagnetic form factors at PANDA-FAIR
NASA Astrophysics Data System (ADS)
Zimmermann, Iris; Dbeyssi, Alaa; Khaneft, Dmitry
2016-05-01
This contribution reports on the latest status of the feasibility studies for the measurement of time-like proton electromagnetic form factors (FF's) at the PANDA experiment [1] at FAIR (Germany). Electromagnetic FF's are fundamental quantities parameterizing the electric and magnetic structure of hadrons. In the time-like region proton FF's can be accessed experimentally through the annihilation processes p ¯p → l+l- (l = e, μ), assuming that the interaction takes place through the exchange of one virtual photon. Due to the low luminosity available at colliders in the past, an individual determination of the time-like electric and magnetic proton FF's was not feasible. The statistical precision, at which the proton FF's will be determined at PANDA, is estimated for both signal processes p ¯p → l+l- (l = e, μ) using the PandaRoot software, which encompasses full detector simulation and event reconstruction. The signal identification and suppression of the main background process (p ¯p → π+π-) is studied. Different methods have been used to generate and analyze the processes of interest. The results from the different analyses show that time-like electromagnetic FF's can be measured at PANDA with unprecedented statistical accuracy.
Phenomenological analysis of near-threshold periodic modulations of the proton timelike form factor
NASA Astrophysics Data System (ADS)
Bianconi, A.; Tomasi-Gustafsson, E.
2016-03-01
We have recently highlighted the presence of a periodically oscillating 10% modulation in the BABAR Collaboration data on the proton timelike form factors, expressing the deviations from the pointlike behavior of the proton-antiproton electromagnetic current in the reaction e++e-→p ¯+p . Here we deepen our previous data analysis and confirm that in the case of several standard parametrizations it is possible to write the form factor in the form F0+Fosc , where F0 is a parametrization expressing the long-range trend of the form factor (for q2 ranging from the p ¯p threshold to 36 GeV2), and Fosc is a function of the form exp(-B p )cos(C p ) , where p is the relative momentum of the final p ¯p pair. Error bars allow for a clean identification of the main features of this modulation for q2<10 GeV2 . Assuming this oscillatory modulation to be an effect of final-state interactions between the forming proton and the antiproton, we propose a phenomenological model based on a double-layer imaginary optical potential. This potential is flux absorbing when the distance between the proton and antiproton centers of mass is ≳1.7 - 1.8 fm and flux generating when it is ≲1.7 - 1.8 fm. The main features of the oscillations may be reproduced with some freedom in the potential parameters, but the transition between the two layers must be sudden (0-0.2 fm) to get the correct oscillation period. The flux-absorbing part of the p ¯p interaction is well known in the phenomenology of small-energy antiproton interactions and is due to the annihilation of p ¯p pairs into multimeson states. We interpret the flux-creating part of the potential as due to the creation of a 1 /q -ranged state when the virtual photon decays into a set of current quarks and antiquarks. This short-lived compact state may be expressed as a sum of several hadronic states including the ones with large mass Qn≫q , that may exist for a time t ˜1 /(Qn-q ) . The decay of these large-mass states leads to an
NASA Astrophysics Data System (ADS)
Rimal, Dipak
The electromagnetic form factors are the most fundamental observables that encode information about the internal structure of the nucleon. The electric (GE) and the magnetic ( GM) form factors contain information about the spatial distribution of the charge and magnetization inside the nucleon. A significant discrepancy exists between the Rosenbluth and the polarization transfer measurements of the electromagnetic form factors of the proton. One possible explanation for the discrepancy is the contributions of two-photon exchange (TPE) effects. Theoretical calculations estimating the magnitude of the TPE effect are highly model dependent, and limited experimental evidence for such effects exists. Experimentally, the TPE effect can be measured by comparing the ratio of positron-proton elastic scattering cross section to that of the electron-proton [R = sigma(e +p)/sigma(e+p)]. The ratio R was measured over a wide range of kinematics, utilizing a 5.6 GeV primary electron beam produced by the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab. This dissertation explored dependence of R on kinematic variables such as squared four-momentum transfer (Q2) and the virtual photon polarization parameter (epsilon). A mixed electron-positron beam was produced from the primary electron beam in experimental Hall B. The mixed beam was scattered from a liquid hydrogen (LH2) target. Both the scattered lepton and the recoil proton were detected by the CEBAF Large Acceptance Spectrometer (CLAS). The elastic events were then identified by using elastic scattering kinematics. This work extracted the Q2 dependence of R at high epsilon(epsilon > 0.8) and the $epsilon dependence of R at approx 0.85 GeV2. In these kinematics, our data confirm the validity of the hadronic calculations of the TPE effect by Blunden, Melnitchouk, and Tjon. This hadronic TPE effect, with additional corrections contributed by higher excitations of the intermediate state nucleon, largely
Measurements of the electromagnetic form factor of the Proton at Jlab
Vina Punjabi; Charles Perdrisat
2003-04-01
The ratio of the proton's elastic electromagnetic form factors G{sub E{sub p}}/G{sub M{sub p}} was obtained by measuring P{sub t} and P{sub {ell}}, the transverse and longitudinal recoil proton polarization, respectively. For the elastic reaction {rvec e}p {yields} e{rvec p}, G{sub E{sub p}}/G{sub M{sub p}} is proportional to P{sub t}/P{sub {ell}}. The simultaneous measurement of P{sub t} and P{sub {ell}} in a polarimeter reduces systematic uncertainties. The results for the ratio G{sub E{sub p}}/G{sub M{sub p}} measured in Hall A so far show a systematic decrease with increasing Q{sup 2}, indicating for the first time a definite difference in the distribution of charge and magnetization in the proton. Together these experiments cover the Q{sub 2}- range of 0.5 to 5.6 GeV{sup 2}. A new experiment is currently being prepared, to extend the Q{sup 2}-range to 9 GeV{sup 2} in Hall C.
Proton Magnetic Form Factor from Existing Elastic e-p Cross Section Data
NASA Astrophysics Data System (ADS)
Ou, Longwu; Christy, Eric; Gilad, Shalev; Keppel, Cynthia; Schmookler, Barak; Wojtsekhowski, Bogdan
2015-04-01
The proton magnetic form factor GMp, in addition to being an important benchmark for all cross section measurements in hadron physics, provides critical information on proton structure. Extraction of GMp from e-p cross section data is complicated by two-photon exchange (TPE) effects, where available calculations still have large theoretical uncertainties. Studies of TPE contributions to e-p scattering have observed no nonlinear effects in Rosenbluth separations. Recent theoretical investigations show that the TPE correction goes to 0 when ɛ approaches 1, where ɛ is the virtual photon polarization parameter. In this talk, existing e-p elastic cross section data are reanalyzed by extrapolating the reduced cross section for ɛ approaching 1. Existing polarization transfer data, which is supposed to be relatively immune to TPE effects, are used to produce a ratio of electric and magnetic form factors. The extrapolated reduced cross section and polarization transfer ratio are then used to calculate GEp and GMp at different Q2 values.
Low Q^2 measurements of the proton form factor ratio $mu_p G_E / G_M$
Ron, G; Zhan, X; Lee, B; Allada, K; Armstrong, W; Arrington, J; Beck, A; Benmokhtar, F; Berman, B L; Boeglin, W; Brash, E; Camsonne, A; Calarco, J; Chen, J P; Choi, S; Chudakov, E; Coman, L; Craver, B; Cusanno, F; Dumas, J; Dutta, C; Feuerbach, R; Freyberger, A; Frullani, S; Garibaldi, F; Gilman, R; Hansen, O; Higinbotham, D W; Holmstrom, T; Hyde, C E; Ibrahim, H; Ilieva, Y; de Jager, C W; Jiang, X; Jones, M; Kelleher, A; Khrosinkova, E; Kuchina, E; Kumbartzki, G; LeRose, J J; Lindgren, R; Markowitz, P; May-Tal Beck, S; McCullough, E; Meziane, M; Meziani, Z -E; Michaels, R; Moffit, B; Norum, B E; Oh, Y; Olson, M; Paolone, M; Paschke, K; Perdrisat, C F; Piasetzky, E; Potokar, M; Pomatsalyuk, R; Pomerantz, I; Puckett, A; Punjabi, V; Qian, X; Qiang, Y; Ransome, R; Reyhan, M
2011-11-01
We present an updated extraction of the proton electromagnetic form factor ratio, {mu}{sub p}G{sub E}/G{sub M}, at low Q{sup 2}. The form factors are sensitive to the spatial distribution of the proton, and precise measurements can be used to constrain models of the proton. An improved selection of the elastic events and reduced background contributions yielded a small systematic reduction in the ratio {mu}{sub p}G{sub E}/G{sub M} compared to the original analysis.
Strange magnetic form factor of the proton at $Q^2 = 0.23$ GeV$^2$
Wang, Ping; Leinweber, Derek; Thomas, Anthony; Young, Ross
2009-06-01
We determine the $u$ and $d$ quark contributions to the proton magnetic form factor at finite momentum transfer by applying chiral corrections to quenched lattice data. Heavy baryon chiral perturbation theory is applied at next to leading order in the quenched, and full QCD cases for the valence sector using finite range regularization. Under the assumption of charge symmetry these values can be combined with the experimental values of the proton and neutron magnetic form factors to deduce a relatively accurate value for the strange magnetic form factor at $Q^2=0.23$ GeV$^2$, namely $G_M^s=-0.034 \\pm 0.021$ $\\mu_N$.
Recoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio to Q^2 = 8.5 GeV^2
Puckett, A J.R.; Jones, M K; Luo, W; Meziane, M; Pentchev, L; Perdrisat, C F; Punjabi, V; Wesselmann, F R; Ahmidouch, A; Albayrak, I; Aniol, K A; Arrington, J; Asaturyan, A; Baghdasaryan, H; Benmokhtar, F; Bertozzi, W; Bimbot, L; Bosted, P; Boeglin, W; Butuceanu, C; Carter, P; Chernenko, S; Christy, E; Commisso, M; Cornejo, J C; Covrig, S; Danagoulian, S; Daniel, A; Davidenko, A; Day, D; Dhamija, S; Dutta, D; Ent, R; Frullani, S; Fenker, H; Frlez, E; Garibaldi, F; Gaskell, D; Gilad, S; Gilman, R; Goncharenko, Y; Hafidi, K; Hamilton, D; Higinbotham, D W; Hinton, W; Horn, T; Hu, B; Huang, J; Huber, G M; Jensen, E; Keppel, C; Khandaker, M; King, P; Kirillov, D; Kohl, M; Kravtsov, V; Kumbartzki, G; Li, Y; Mamyan, V; Margaziotis, D J; Marsh, A; Matulenko, Y; Maxwell, J; Mbianda, G; Meekins, D; Melnik, Y; Miller, J; Mkrtchyan, A; Mkrtchyan, H; Moffit, B; Moreno, O; Mulholland, J; Narayan, A; Nedev, S; Nuruzzaman,; Piasetzky, E; Pierce, W; Piskunov, N M; Prok, Y; Ransome, R D; Razin, D S; Reimer, P; Reinhold, J; Rondon, O; Shabestari, M; Shahinyan, A; Shestermanov, K; Sirca, S; Sitnik, I; Smykov, L; Smith, G; Solovyev, L; Solvingnon, P; Subedi, R; Tomasi-Gustafsson, E; Vasiliev, A; Veilleux, M; Wojtsekhowski, B B; Wood, S; Ye, Z; Zanevsky, Y; Zhang, X; Zhang, Y; Zheng, X; Zhu, L
2010-06-01
Among the most fundamental observables of nucleon structure, electromagnetic form factors are a crucial benchmark for modern calculations describing the strong interaction dynamics of the nucleon’s quark constituents; indeed, recent proton data have attracted intense theoretical interest. In this Letter, we report new measurements of the proton electromagnetic form factor ratio using the recoil polarization method, at momentum transfers Q2=5.2, 6.7, and 8.5 GeV2. By extending the range of Q2 for which GEp is accurately determined by more than 50%, these measurements will provide significant constraints on models of nucleon structure in the nonperturbative regime.
The Proton Elastic Form Factor Ratio mu(p) G**p(E)/G**p(M) at Low Momentum Transfer
G. Ron; J. Glister; B. Lee; K. Allada; W. Armstrong; J. Arrington; A. Beck; F. Benmokhtar; B.L. Berman; W. Boeglin; E. Brash; A. Camsonne; J. Calarco; J. P. Chen; Seonho Choi; E. Chudakov; L. Coman; B. Craver; F. Cusanno; J. Dumas; C. Dutta; R. Feuerbach; A. Freyberger; S. Frullani; F. Garibaldi; R. Gilman; O. Hansen; D. W. Higinbotham; T. Holmstrom; C.E. Hyde; H. Ibrahim; Y. Ilieva; C. W. de Jager; X. Jiang; M. K. Jones; A. Kelleher; E. Khrosinkova; E. Kuchina; G. Kumbartzki; J. J. LeRose; R. Lindgren; P. Markowitz; S. May-Tal Beck; E. McCullough; D. Meekins; M. Meziane; Z.-E. Meziani; R. Michaels; B. Moffit; B.E. Norum; Y. Oh; M. Olson; M. Paolone; K. Paschke; C. F. Perdrisat; E. Piasetzky; M. Potokar; R. Pomatsalyuk; I. Pomerantz; A. Puckett; V. Punjabi; X. Qian; Y. Qiang; R. Ransome; M. Reyhan; J. Roche; Y. Rousseau; A. Saha; A.J. Sarty; B. Sawatzky; E. Schulte; M. Shabestari; A. Shahinyan; R. Shneor; S. ˇ Sirca; K. Slifer; P. Solvignon; J. Song; R. Sparks; R. Subedi; S. Strauch; G. M. Urciuoli; K. Wang; B. Wojtsekhowski; X. Yan; H. Yao; X. Zhan; X. Zhu
2007-11-01
High precision measurements of the proton elastic form factor ratio have been made at four-momentum transfers, Q^2, between 0.2 and 0.5 GeV^2. The new data, while consistent with previous results, clearly show a ratio less than unity and significant differences from the central values of several recent phenomenological fits. By combining the new form-factor ratio data with an existing cross-section measurement, one finds that in this Q^2 range the deviation from unity is primarily due to GEp being smaller than the dipole parameterization.
High Precision Measurement of the Proton Elastic Form Factor Ratio at Low Q^{2}
Zhan, Xiaohui
2010-01-01
Experiment E08-007 measured the proton elastic form factor ratio μ_{p}G_{E}/G_{M} in the range of Q^{2} = 0.3-0.7(GeV/c)^{2} by recoil polarimetry. Data were taken in 2008 at the Thomas Jefferson National Accelerator Facility in Virginia, USA. A 1.2 GeV polarized electron beam was scattered off a cryogenic hydrogen target. The recoil proton was detected in the left HRS in coincidence with the elasticly scattered electrons tagged by the BigBite spectrometer. The proton polarization was measured by the focal plane polarimeter (FPP). In this low Q^{2} region, previous measurement from Jefferson Lab Hall A (LEDEX) along with various fits and calculations indicate substantial deviations of the ratio from unity. For this new measurement, the proposed statistical uncertainty (< 1%) was achieved. These new results are a few percent lower than expected from previous world data and fits, which indicate a smaller G_{Ep} at this region. Beyond the intrinsic interest in nucleon structure, the new results also have implications in determining the proton Zemach radius and the strangeness form factors from parity violation experiments.
High-precision measurement of the proton elastic form factor ratio μpGE/GM at low Q2
Zhan, X.; Allada, K.; Armstrong, D. S.; Arrington, J.; Bertozzi, W.; Boeglin, W.; Chen, J. -P.; Chirapatpimol, K.; Choi, S.; Chudakov, E.; et al
2011-10-06
Here, we report a new high precision measurement of the proton elastic form factor ratio μpGE/GM for the four-momentum transfer squared Q2 = 0.3-0.7 (GeV/c)2. The measurement was performed at Jefferson Lab (JLab) in Hall A using recoil polarimetry. With the achieved ~1% total uncertainty, the new data clearly show that the deviation of the ratio μpGE/GM from unity observed in previous polarization measurements at high Q2 continues down to the lowest Q2 value of this measurement. The updated global fit that includes the new results yields in this Q2 range an electric (magnetic) form factor ~2% smaller (~1% larger)more » than the previous global fit. We obtain new extractions of the proton electric and magnetic radii, which are (rE2)1/2 = 0.875 ± 0.010 fm and (rM2)1/2 = 0.867 ± 0.020 fm. Moreover, the charge radius is consistent with other recent extractions based on the electron-proton interaction, including the atomic hydrogen Lamb shift measruements, which suggests a missing correction in the comparison of measurements of the proton charge radius using electron probes and the recent extraction from the muonic hydrogen Lamb shift.« less
Konrad Aniol; David Armstrong; Todd Averett; Maud Baylac; Etienne Burtin; John Calarco; Gordon Cates; Christian Cavata; Zhengwei Chai; C. Chang; Jian-Ping Chen; Eugene Chudakov; Evaristo Cisbani; Marius Coman; Daniel Dale; Alexandre Deur; Pibero Djawotho; Martin Epstein; Stephanie Escoffier; Lars Ewell; Nicolas Falletto; John Finn; A. Fleck; Bernard Frois; Salvatore Frullani; Juncai Gao; Franco Garibaldi; Ashot Gasparian; G. M. Gerstner; Ronald Gilman; Oleksandr Glamazdin; Javier Gomez; Viktor Gorbenko; Jens-ole Hansen; F. Hersman; Douglas Higinbotham; Richard Holmes; Maurik Holtrop; Thomas Humensky; Sebastien Incerti; Mauro Iodice; Cornelis De Jager; Johann Jardillier; Xiaodong Jiang; Mark Jones; J. Jorda; Christophe Jutier; W. Kahl; James Kelly; Donghee Kim; M. -J. Kim; Minsuk Kim; Ioannis Kominis; Edgar Kooijman; Kevin Kramer; Krishna Kumar; Michael Kuss; John LeRose; Raffaele De Leo; M. Leuschner; David Lhuillier; Meihua Liang; Nilanga Liyanage; R. Lourie; Richard Madey; Sergey Malov; Demetrius Margaziotis; Frederic Marie; Pete Markowitz; Jacques Martino; Peter Mastromarino; Kathy McCormick; Justin McIntyre; Zein-Eddine Meziani; Robert Michaels; Brian Milbrath; Gerald Miller; Joseph Mitchell; Ludyvine Morand; Damien Neyret; Gerassimos Petratos; Roman Pomatsalyuk; John Price; David Prout; Thierry Pussieux; Gilles Quemener; Ronald Ransome; David Relyea; Yves Roblin; Julie Roche; Gary Rutledge; Paul Rutt; Marat Rvachev; Franck Sabatie; Arunava Saha; Paul Souder; Marcus Spradlin; Steffen Strauch; Riad Suleiman; Jeffrey Templon; T. Teresawa; James Thompson; Raphael Tieulent; Luminita Todor; Baris Tonguc; Paul Ulmer; Guido Urciuoli; Branislav Vlahovic; Krishni Wijesooriya; R. Wilson; Bogdan Wojtsekhowski; Rhett Woo; Wang Xu; Imran Younus; C. Zhang
2001-06-01
We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from the proton. The result is A = -15.05 +- 0.98(stat) {+-} 0.56(syst) ppm at the kinematic point theta{sub lab} = 12.3 degrees and Q{sup 2} = 0.477 (GeV/c){sup 2}. The measurement implies that the value for the strange form factor (G{sub E}{sup s} + 0.392 G{sub M}{sup s})/(G{sub M}{sup p} {mu}{sub p}) = 0.069 +- 0.056 +- 0.039, where the first error is experimental and the second arises from the uncertainties in electromagnetic form factors. This measurement is the first fixed-target parity violation experiment that used either a ''strained'' GaAs photocathode to produce highly polarized electrons or a Compton polarimeter to continuously monitor the electron beam polarization.
Parity-Violating Electron Deuteron Scattering and the Proton's Neutral Weak Axial Vector Form Factor
Ito, Takeyasu; Averett, Todd; Barkhuff, David; Batigne, Guillaume; Beck, Douglas; Beise, Elizabeth; Blake, A.; Breuer, Herbert; Carr, Robert; Clasie, Benjamin; Covrig, Silviu; Danagoulian, Areg; Dodson, George; Dow, Karen; Dutta, Dipangkar; Farkhondeh, Manouchehr; Filippone, Bradley; FRANKLIN, W.; Furget, Christophe; Gao, Haiyan; Gao, Juncai; Gustafsson, Kenneth; Hannelius, Lars; Hasty, R.; Allen, Alice; Herda, M.C.; Jones, CE; King, Paul; Korsch, Wolfgang; Kowalski, Stanley; Kox, Serge; Kramer, Kevin; Lee, P.; Liu, Jinghua; Martin, Jeffery; McKeown, Robert; Mueller, B.; Pitt, Mark; Plaster, Bradley; Quemener, Gilles; Real, Jean-Sebastien; Ritter, J.; Roche, Julie; Savu, V.; Schiavilla, Rocco; Seely, Charles; Spayde, Damon; Suleiman, Riad; Taylor, S.; Tieulent, Raphael; Tipton, Bryan; Tsentalovich, E.; Wells, Steven; Yang, Bin; Yuan, Jing; Yun, Junho; Zwart, Townsend
2004-03-01
We report on a new measurement of the parity-violating asymmetry in quasielastic electron scattering from the deuteron at backward angles at Q2 = 0.038 (GeV/c)2. This quantity provides a determination of the neutral weak axial vector form factor of the nucleon, which can potentially receive large electroweak corrections. The measured asymmetry A = z3.51Â±0.57 (stat)Â±0.58 (syst) ppm is consistent with theoretical predictions. We also report on updated results of the previous experiment at Q2 = 0.091 (GeV/c)2, which are also consistent with theoretical predictions.
Two-photon exchange contribution to proton form factors in the time-like region
Chen, D. Y.; Dong, Y. B.; Zhou, H. Q.
2008-10-15
We estimate the two-photon exchange contribution to the process e{sup +}+e{sup -}{yields}p+p . The two-photon exchange corrections to double spin polarization observables and form factors in the time-like region are calculated. The corrections are found to be small in magnitude but with a strong angular dependence at fixed momentum transfer. These two features are the same as those in the space-like region. In future experiments, the double spin polarization observable P{sub z} deserves to be considered.
NASA Astrophysics Data System (ADS)
Chen, Hong-Yu; Zhou, Hai-Qing
2014-10-01
A new form of two-photon exchange (TPE) effect is studied to explain the discrepancy between unpolarized and polarized experimental data in elastic ep scattering. The mechanism is based on a simple idea that apart from the usual TPE effects from box and crossed-box diagrams, the mesons may also be exchanged in elastic ep scattering by two-photon coupling at loop level. The detailed study shows such contributions to reduced unpolarized cross section (σun) and polarized observables (Pt,Pl) at fixed Q2 are only dependent on proton's electromagnetic form factors GE ,M and a new unknown universal parameter g. After combining this contribution with the usual TPE contributions from box and crossed-box diagrams, the ratio μpGE/GM extracted from the recent precise unpolarized and polarized experimental data can be described consistently.
Crawford, C B; Sindile, A; Akdogan, T; Alarcon, R; Bertozzi, W; Booth, E; Botto, T; Calarco, J; Clasie, B; Degrush, A; Donnelly, T W; Dow, K; Dutta, D; Farkhondeh, M; Fatemi, R; Filoti, O; Franklin, W; Gao, H; Geis, E; Gilad, S; Haeberli, W; Hasell, D; Hersman, W; Holtrop, M; Karpius, P; Kohl, M; Kolster, H; Lee, T; Maschinot, A; Matthews, J; McIlhany, K; Meitanis, N; Milner, R G; Redwine, R P; Seely, J; Shinozaki, A; Sirca, S; Six, E; Smith, T; Tonguc, B; Tschalaer, C; Tsentalovich, E; Turchinetz, W; van den Brand, J F J; van der Laan, J; Wang, F; Wise, T; Xiao, Y; Xu, W; Zhang, C; Zhou, Z; Ziskin, V; Zwart, T
2007-02-01
We report the first precision measurement of the proton electric to magnetic form factor ratio from spin-dependent elastic scattering of longitudinally polarized electrons from a polarized hydrogen internal gas target. The measurement was performed at the MIT-Bates South Hall Ring over a range of four-momentum transfer squared Q2 from 0.15 to 0.65 (GeV/c)(2). Significantly improved results on the proton electric and magnetic form factors are obtained in combination with existing cross-section data on elastic electron-proton scattering in the same Q2 region. PMID:17358849
Recoil polarization measurements of the proton electromagnetic form factor ratio to Q2 = 8.5 GeV2.
Puckett, A J R; Brash, E J; Jones, M K; Luo, W; Meziane, M; Pentchev, L; Perdrisat, C F; Punjabi, V; Wesselmann, F R; Ahmidouch, A; Albayrak, I; Aniol, K A; Arrington, J; Asaturyan, A; Baghdasaryan, H; Benmokhtar, F; Bertozzi, W; Bimbot, L; Bosted, P; Boeglin, W; Butuceanu, C; Carter, P; Chernenko, S; Christy, E; Commisso, M; Cornejo, J C; Covrig, S; Danagoulian, S; Daniel, A; Davidenko, A; Day, D; Dhamija, S; Dutta, D; Ent, R; Frullani, S; Fenker, H; Frlez, E; Garibaldi, F; Gaskell, D; Gilad, S; Gilman, R; Goncharenko, Y; Hafidi, K; Hamilton, D; Higinbotham, D W; Hinton, W; Horn, T; Hu, B; Huang, J; Huber, G M; Jensen, E; Keppel, C; Khandaker, M; King, P; Kirillov, D; Kohl, M; Kravtsov, V; Kumbartzki, G; Li, Y; Mamyan, V; Margaziotis, D J; Marsh, A; Matulenko, Y; Maxwell, J; Mbianda, G; Meekins, D; Melnik, Y; Miller, J; Mkrtchyan, A; Mkrtchyan, H; Moffit, B; Moreno, O; Mulholland, J; Narayan, A; Nedev, S; Nuruzzaman; Piasetzky, E; Pierce, W; Piskunov, N M; Prok, Y; Ransome, R D; Razin, D S; Reimer, P; Reinhold, J; Rondon, O; Shabestari, M; Shahinyan, A; Shestermanov, K; Sirca, S; Sitnik, I; Smykov, L; Smith, G; Solovyev, L; Solvignon, P; Subedi, R; Tomasi-Gustafsson, E; Vasiliev, A; Veilleux, M; Wojtsekhowski, B B; Wood, S; Ye, Z; Zanevsky, Y; Zhang, X; Zhang, Y; Zheng, X; Zhu, L
2010-06-18
Among the most fundamental observables of nucleon structure, electromagnetic form factors are a crucial benchmark for modern calculations describing the strong interaction dynamics of the nucleon's quark constituents; indeed, recent proton data have attracted intense theoretical interest. In this Letter, we report new measurements of the proton electromagnetic form factor ratio using the recoil polarization method, at momentum transfers Q2=5.2, 6.7, and 8.5 GeV2. By extending the range of Q2 for which G(E)(p) is accurately determined by more than 50%, these measurements will provide significant constraints on models of nucleon structure in the nonperturbative regime. PMID:20873943
Measurements of the proton elastic-form-factor ratio mu pG p E/G p M at low momentum transfer.
Ron, G; Glister, J; Lee, B; Allada, K; Armstrong, W; Arrington, J; Beck, A; Benmokhtar, F; Berman, B L; Boeglin, W; Brash, E; Camsonne, A; Calarco, J; Chen, J P; Choi, Seonho; Chudakov, E; Coman, L; Craver, B; Cusanno, F; Dumas, J; Dutta, C; Feuerbach, R; Freyberger, A; Frullani, S; Garibaldi, F; Gilman, R; Hansen, O; Higinbotham, D W; Holmstrom, T; Hyde, C E; Ibrahim, H; Ilieva, Y; de Jager, C W; Jiang, X; Jones, M K; Kang, H; Kelleher, A; Khrosinkova, E; Kuchina, E; Kumbartzki, G; LeRose, J J; Lindgren, R; Markowitz, P; May-Tal Beck, S; McCullough, E; Meekins, D; Meziane, M; Meziani, Z-E; Michaels, R; Moffit, B; Norum, B E; Oh, Y; Olson, M; Paolone, M; Paschke, K; Perdrisat, C F; Piasetzky, E; Potokar, M; Pomatsalyuk, R; Pomerantz, I; Puckett, A; Punjabi, V; Qian, X; Qiang, Y; Ransome, R; Reyhan, M; Roche, J; Rousseau, Y; Saha, A; Sarty, A J; Sawatzky, B; Schulte, E; Shabestari, M; Shahinyan, A; Shneor, R; Sirca, S; Slifer, K; Solvignon, P; Song, J; Sparks, R; Subedi, R; Strauch, S; Urciuoli, G M; Wang, K; Wojtsekhowski, B; Yan, X; Yao, H; Zhan, X; Zhu, X
2007-11-16
High-precision measurements of the proton elastic form-factor ratio, mu pG p E/G p M, have been made at four-momentum transfer, Q2, values between 0.2 and 0.5 GeV2. The new data, while consistent with previous results, clearly show a ratio less than unity and significant differences from the central values of several recent phenomenological fits. By combining the new form-factor ratio data with an existing cross-section measurement, one finds that in this Q2 range the deviation from unity is primarily due to G p E being smaller than expected. PMID:18233135
Nucleon Electromagnetic Form Factors
Kees de Jager
2004-08-01
Although nucleons account for nearly all the visible mass in the universe, they have a complicated structure that is still incompletely understood. The first indication that nucleons have an internal structure, was the measurement of the proton magnetic moment by Frisch and Stern (1933) which revealed a large deviation from the value expected for a point-like Dirac particle. The investigation of the spatial structure of the nucleon, resulting in the first quantitative measurement of the proton charge radius, was initiated by the HEPL (Stanford) experiments in the 1950s, for which Hofstadter was awarded the 1961 Nobel prize. The first indication of a non-zero neutron charge distribution was obtained by scattering thermal neutrons off atomic electrons. The recent revival of its experimental study through the operational implementation of novel instrumentation has instigated a strong theoretical interest. Nucleon electro-magnetic form factors (EMFFs) are optimally studied through the exchange of a virtual photon, in elastic electron-nucleon scattering. The momentum transferred to the nucleon by the virtual photon can be selected to probe different scales of the nucleon, from integral properties such as the charge radius to scaling properties of its internal constituents. Polarization instrumentation, polarized beams and targets, and the measurement of the polarization of the recoiling nucleon have been essential in the accurate separation of the charge and magnetic form factors and in studies of the elusive neutron charge form factor.
Nucleon Electromagnetic Form Factors
Marc Vanderhaeghen; Charles Perdrisat; Vina Punjabi
2007-10-01
There has been much activity in the measurement of the elastic electromagnetic proton and neutron form factors in the last decade, and the quality of the data has greatly improved by performing double polarization experiments, in comparison with previous unpolarized data. Here we review the experimental data base in view of the new results for the proton, and neutron, obtained at JLab, MAMI, and MIT-Bates. The rapid evolution of phenomenological models triggered by these high-precision experiments will be discussed, including the recent progress in the determination of the valence quark generalized parton distributions of the nucleon, as well as the steady rate of improvements made in the lattice QCD calculations.
A Precision Measurement of the Proton Strange-Quark Form Factors at Q2 = 0.624 GeV2
NASA Astrophysics Data System (ADS)
Friend, Megan Lynn
The parity-violating asymmetry of the elastic scattering of highly polarized 3.84 GeV electrons from unpolarized protons at Q2 = 0.624 GeV2 has been measured to high precision. The measurement was carried out by the HAPPEX collaboration in Hall A of Jefferson Lab's Continuous Electron Beam Accelerator Facility. This precision measurement required careful control of any potential systematic effects, as well as a very precise determination of the absolute electron-beam polarization. In order to obtain the required precision on the electron-beam polarization measurement, an upgrade of the Hall A Compton polarimeter, and, in particular, the polarimeter's photon-arm detector and data acquisition system, was completed. A parity-violating asymmetry of APV = --23.80 +/- 0.78(stat) +/- 0.36(syst) ppm was measured. The predicted parity-violating asymmetry in the absence of strange quarks is ANS = --24.062 +/- 0.734 ppm. This allows for the extraction of the linear combination of proton strange-quark form factors GsE + 0.517 GsM = 0.003 +/- 0.010(stat) +/- 0.004(syst) +/- 0.009( ANS), where the third error is due to uncertainties in the nucleon electromagnetic form factors and radiative corrections. This measurement is consistent with zero strange contribution to the proton form factors at Q2 = 0.624 GeV2.
NASA Astrophysics Data System (ADS)
Ledwig, Tim; Silva, Antonio; Kim, Hyun-Chul
2010-09-01
We investigate the form factors of the chiral-odd nucleon matrix element of the tensor current. In particular, we aim at the anomalous tensor magnetic form factors of the nucleon within the framework of the SU(3) and SU(2) chiral quark-soliton model. We consider 1/Nc rotational corrections and linear effects of SU(3) symmetry breaking with the symmetry-conserving quantization employed. We first obtain the results of the anomalous tensor magnetic moments for the up and down quarks: κTu=3.56 and κTd=1.83, respectively. The strange anomalous tensor magnetic moment is yielded to be κTs=0.2˜-0.2, that is compatible with zero. We also calculate the corresponding form factors κTq(Q2) up to a momentum transfer Q2≤1GeV2 at a renormalization scale of 0.36GeV2.
Precision Measurement of the proton neutral weak form factors at Q{sup 2} ~ 0.1 GeV{sup 2}
Kaufman, Lisa
2007-02-01
This thesis reports the HAPPEX measurement of the parity-violating asymmetry for longitudinally polarized electrons elastically scattered from protons in a liquid hydrogen target. The measurement was carried out in Hall A at Thomas Jefferson National Accelerator Facility using a beam energy E = 3 GeV and scattering angle <θ{sub lab}> = 6°. The asymmetry is sensitive to the weak neutral form factors from which we extract the strange quark electric and magnetic form factors (G{sup s}{sub E} and G{sup s}{sub M}) of the proton. The measurement was conducted during two data-taking periods in 2004 and 2005. This thesis describes the methods for controlling the helicity-correlated beam asymmetries and the analysis of the raw asymmetry. The parity-violating asymmetry has been measured to be A{sub PV} = -1.14± 0.24 (stat)±0.06 (syst) ppm at = 0.099 GeV{sup 2} (2004), and A{sub PV} = -1.58±0.12 (stat)±0.04 (syst) ppm at
= 0.109 GeV{sup 2} (2005). The strange quark form factors extracted from the asymmetry are G{sup s}{sub E} + 0.080G{sup s}{sub M} = 0.030 ± 0.025 (stat) ± 0.006 (syst) ± 0.012 (FF) (2004) and G{sup s}{sub E} +0.088G{sup s}{sub M} = 0.007±0.011 (stat)±0.004 (syst)±0.005 (FF) (2005). These results place the most precise constraints on the strange quark form factors and indicate little strange dynamics in the proton.
Baunack, S.; Becker, D.; Gerz, K.; Kumar, K.; Maas, F. E.
2013-11-07
The P2 experiment at the future accelerator facility MESA in Mainz aims for a precise determination of the weak charge of the proton at low momentum transfer. The experimental method is a measurement of the parity violating asymmetry in elastic electron-proton scattering at forward angle. This asymmetry is dominated by the weak charge, but also the proton structure plays a role. Here we consider a back angle measurement, which is more sensitive to the proton structure, and present its possible implications on the main P2 measurement.
Proton elastic form factor ratios to Q{sup 2} = 3.5 GeV{sup 2} by polarization transfer
V. Punjabi; C.F. Perdrisat; et al
2005-01-01
The ratio of the proton elastic electromagnetic form factors, G{sub E{sub p}}/G{sub M{sub p}}, was obtained by measuring P{sub t} and P{sub {ell}}, the transverse and longitudinal recoil proton polarization components, respectively, for the elastic {rvec e}p {yields} e{rvec p} reaction in the four-momentum transfer squared range of 0.5 to 3.5 GeV{sup 2}. In the single-photon exchange approximation, the ratio G{sub E{sub p}}/G{sub M{sub p}} is directly proportional to the ratio P{sub t}/P{sub {ell}}. The simultaneous measurement of P{sub t} and P{sub {ell}} in a polarimeter reduces systematic uncertainties. The results for the ratio G{sub E{sub p}}/G{sub M{sub p}} show a systematic decrease with increasing Q{sup 2}, indicating for the first time a definite difference in the distribution of charge and magnetization in the proton. The data have been re-analyzed and systematic uncertainties have become significantly smaller than previously published results.
Proton elastic form factor ratios to Q{sup 2}=3.5 GeV{sup 2} by polarization transfer
Punjabi, V.; Perdrisat, C.F.; Gerstner, G.; Pentchev, L.; Rutledge, G.; Strauch, S.; Wijesooriya, K.; Aniol, K.A.; Epstein, M.B.; Margaziotis, D.J.; Baker, F.T.; Templon, J.A.; Berthot, J.; Bertin, P.Y.; Besson, A.; Fonvieille, H.; Jaminion, S.; Laveissiere, G.
2005-05-01
The ratio of the proton elastic electromagnetic form factors, G{sub Ep}/G{sub Mp}, was obtained by measuring P{sub t} and P{sub l}, the transverse and longitudinal recoil proton polarization components, respectively, for the elastic e{sup {yields}}p{yields}ep{sup {yields}}reaction in the four-momentum transfer squared range of 0.5 to 3.5 GeV{sup 2}. In the single-photon exchange approximation, G{sub Ep}/G{sub Mp} is directly proportional to P{sub t}/P{sub l}. The simultaneous measurement of P{sub t} and P{sub l} in a polarimeter reduces systematic uncertainties. The results for G{sub Ep}/G{sub Mp} show a systematic decrease with increasing Q{sup 2}, indicating for the first time a definite difference in the distribution of charge and magnetization in the proton. The data have been reanalyzed and their systematic uncertainties have become significantly smaller than those reported previously.
Proton form factor ratio, μ_{p}G_{E}^{P}/G_{M}^{P} from double spin asymmetry
Habarakada Liyanage, Anusha Pushpakumari
2013-08-01
The form factors are fundamental properties of the nucleon representing the effect of its structure on its response to electromagnetic probes such as electrons. They are functions of the four-momentum transfer squared Q^{2} between the electron and the proton. This thesis reports the results of a new measurement of the ratio of the electric and magnetic form factors of the proton up to Q^{2} = 5.66 (GeV/c)^{2} using the double spin asymmetry with a polarized beam and target. Experiment E07-003 (SANE, Spin Asymmetries of the Nucleon Experiment) was carried out in Hall C at Jefferson Lab in 2009 to study the proton spin structure functions with a dynamically polarized ammonia target and longitudinally polarized electron beam. By detecting elastically scattered protons in the High-Momentum Spectrometer (HMS) in coincidence with the electrons in the Big Electron Telescope Array (BETA), elastic measurements were carried out in parallel. The elastic double spin asymmetry allows one to extract the proton electric to magnetic form factor ratio G^{p}_{E}/G^{p}_{M} at high-momentum transfer, Q^{2}= 5.66 (GeV/c)^{2}. In addition to the coincidence data, inclusively scattered electrons from the polarized ammonia target were detected by HMS, which allows to measure the beam-target asymmetry in the elastic region with the target spin nearly perpendicular to the momentum transfer, and to extract G^{p}_{E}/G^{p}_{M} at low Q^{2}= 2.06 (GeV/c)^{2}. This alternative measurement of G^{p}_{E}/G^{p}_{M} has verified and confirmed the dramatic discrepancy at high Q^{2} between the Rosenbluth and the recoil-polarization-transfer iv method with a different measurement technique and systematic uncertainties uncorrelated to those of the recoil-polarization measurements. The measurement of the form factor ratio at Q^{2} = 2
Final analysis of proton form factor ratio data at Q2 = 4.0, 4.8, and 5.6 GeV2
Puckett, A. J. R.; Brash, E. J.; Gayou, O.; Jones, M. K.; Pentchev, L.; Perdrisat, C. F.; Punjabi, V.; Aniol, K. A.; Averett, T.; Benmokhtar, F.; et al
2012-04-11
Recently published measurements of the proton electromagnetic form factor ratio R = μp GEp/GMp at momentum transfers Q2 up to 8.5 GeV2 in Jefferson Lab Hall C deviate from the linear trend of previous measurements in Jefferson Lab Hall A, favoring a slower rate of decrease of R with Q2. While statistically compatible in the region of overlap with Hall A, the Hall C data hint at a systematic difference between the two experiments. This possibility was investigated in a reanalysis of the Hall A data. We find that the original analysis underestimated the background in the selection of elasticmore » events. The application of an additional cut to further suppress the background increases the results for R, improving the consistency between Halls A and C.« less
Frederic D. R. Bonnet; Robert G. Edwards; George T. Fleming; Randal Lewis; David Richards
2003-07-22
We have started a program to compute the electromagnetic form factors of mesons. We discuss the techniques used to compute the pion form factor and present preliminary results computed with domain wall valence fermions on MILC asqtad lattices, as well as Wilson fermions on quenched lattices. These methods can easily be extended to rho-to-gamma-pi transition form factors.
Nucleon Form Factors Using Spin Degrees of Freedom
Mark Jones
2002-04-01
An overview of recent measurements of the neutron and proton electromagnetic form factors from double polarization experiments. Spin observables are sensitive to the product of nucleon form factor which allows access to the small nucleon electric form factors.
The Form Factors of the Nucleons
Perdrisat, Charles F.
2013-11-01
There has been much activity in the measurement of the elastic electromagnetic proton and neutron form factors in the last decade, and the quality of the data has been greatly improved by performing double-polarization experiments, in comparison with with pre-vious unpolarized cross section data. Here we will review the experimental data base in view of the new results for the proton and the neutron, obtained at MIT-Bates, JLab and MAMI. The rapid evolution of phenomenological models triggered by these high- precision experiments will be discussed. In particular, the possibility that the proton is non-spherical in its ground state, and that the transverse charge density are model in- dependently defined in the infinite momentum frame. Likewise, flavor decomposition of the nucleon form factors into dressed u and d quark form factors, may give information about the quark-diquark structure of the nucleon. The current proton radius "crisis" will also be discussed.
Electromagnetic nucleon form factors
Bender, A.; Roberts, C.D.; Frank, M.R.
1995-08-01
The Dyson-Schwinger equation framework is employed to obtain expressions for the electromagnetic nucleon form factor. In generalized impulse approximation the form factor depends on the dressed quark propagator, the dressed quark-photon vertex, which is crucial to ensuring current conservation, and the nucleon Faddeev amplitude. The approach manifestly incorporates the large space-like-q{sup 2} renormalization group properties of QCD and allows a realistic extrapolation to small space-like-q{sup 2}. This extrapolation allows one to relate experimental data to the form of the quark-quark interaction at small space-like-q{sup 2}, which is presently unknown. The approach provides a means of unifying, within a single framework, the treatment of the perturbative and nonperturbative regimes of QCD. The wealth of experimental nucleon form factor data, over a large range of q{sup 2}, ensures that this application will provide an excellent environment to test, improve and extend our approach.
Nucleon Form Factors from Generalized Parton Distributions
M. Guidal; Maxim Polyakov; Anatoly Radyushkin; Marc Vanderhaeghen
2004-10-01
We discuss the links between Generalized Parton Distributions (GPDs) and elastic nucleon form factors. These links, in the form of sum rules, represent powerful constraints on parametrizations of GPDs. A Regge parametrization for GPDs at small momentum transfer, is extended to the large momentum transfer region and it is found to describe the basic features of proton and neutron electromagnetic form factor data. This parametrization is used to estimate the quark contribution to the nucleon spin.
Inelastic Scattering Form Factors
Energy Science and Technology Software Center (ESTSC)
1992-01-01
ATHENA-IV computes form factors for inelastic scattering calculations, using single-particle wave functions that are eigenstates of motion in either a Woods-Saxon potential well or a harmonic oscillator well. Two-body forces of Gauss, Coulomb, Yukawa, and a sum of cut-off Yukawa radial dependences are available.
Nucleon Form Factors - A Jefferson Lab Perspective
John Arrington, Kees de Jager, Charles F. Perdrisat
2011-06-01
The charge and magnetization distributions of the proton and neutron are encoded in their elastic electromagnetic form factors, which can be measured in elastic electron--nucleon scattering. By measuring the form factors, we probe the spatial distribution of the proton charge and magnetization, providing the most direct connection to the spatial distribution of quarks inside the proton. For decades, the form factors were probed through measurements of unpolarized elastic electron scattering, but by the 1980s, progress slowed dramatically due to the intrinsic limitations of the unpolarized measurements. Early measurements at several laboratories demonstrated the feasibility and power of measurements using polarization degrees of freedom to probe the spatial structure of the nucleon. A program of polarization measurements at Jefferson Lab led to a renaissance in the field of study, and significant new insight into the structure of matter.
Olivier Gayou
2002-04-01
In this thesis, we present the results of the experiment E99-007, which measured the ratio of the electric to magnetic form factors of the proton to the four momentum transfer square Q{sup 2} = 5.6 GeV{sup 2}, by recoil polarimetry. Data were taken in 2000 at the Thomas Jefferson National Accelerator Facility in Virginia, USA. A 4.6 GeV polarized electron beam was scattered off a cryogenic hydrogen target. The polarization of the recoil proton was measured in the Focal Plane Polarimeter, located after one of the two High Resolution Spectrometers in the hall. The ratio of the transverse to longitudinal components of the recoil proton polarization is proportional to the ratio of the form factors. Elastic events were selected by detecting the scattered electron in a large acceptance lead-glass calorimeter. The main result of this experiment is the linear decrease of the form factor ratio with increasing Q{sup 2}, corresponding to different spatial distributions of the electric charge and the magnetization. Numerous theoretical calculations show that relativistic effects, such as mixing of spin states due to Lorentz boosts, are important to account for the observed data in this critical intermediate kinematic region.
Electromagnetic pion form factor
Roberts, C.D.
1995-08-01
A phenomenological Dyson-Schwinger/Bethe-Salpeter equation approach to QCD, formalized in terms of a QCD-based model field theory, the Global Color-symmetry Model (GCM), was used to calculate the generalized impulse approximation contribution to the electromagnetic pion form factor at space-like q{sup 2} on the domain [0,10] GeV{sup 2}. In effective field theories this form factor is sometimes understood as simply being due to Vector Meson Dominance (VMD) but this does not allow for a simple connection with QCD where the VMD contribution is of higher order than that of the quark core. In the GCM the pion is treated as a composite bound state of a confined quark and antiquark interacting via the exchange of colored vector-bosons. A direct study of the quark core contribution is made, using a quark propagator that manifests the large space-like-q{sup 2} properties of QCD, parameterizes the infrared behavior and incorporates confinement. It is shown that the few parameters which characterize the infrared form of the quark propagator may be chosen so as to yield excellent agreement with the available data. In doing this one directly relates experimental observables to properties of QCD at small space-like-q{sup 2}. The incorporation of confinement eliminates endpoint and pinch singularities in the calculation of F{sub {pi}}(q{sup 2}). With asymptotic freedom manifest in the dressed quark propagator the calculation yields q{sup 4}F{sub {pi}}(q{sup 2}) = constant, up to [q{sup 2}]- corrections, for space-like-q{sup 2} {approx_gt} 35 GeV{sup 2}, which indicates that soft, nonperturbative contributions dominate the form factor at presently accessible q{sup 2}. This means that the often-used factorization Ansatz fails in this exclusive process. A paper describing this work was submitted for publication. In addition, these results formed the basis for an invited presentation at a workshop on chiral dynamics and will be published in the proceedings.
D. Day
2007-03-01
The nucleon form factors are still the subject of active investigation even after an experimental effort spanning 50 years. This is because they are of critical importance to our understanding of the electromagnetic properties of nuclei and provide a unique testing ground for QCD motivated models of nucleon structure. Progress in polarized beams, polarized targets and recoil polarimetry have allowed an important and precise set of data to be collected over the last decade. I will review the experimental status of elastic electron scattering from the nucleon along with an outlook for future progress.
Ryong Ji, C.; Pang, A.; Szczepaniak, A.
1994-04-01
It is pointed out that the correct criterion to define the legal PQCD contribution to the exclusive processes in the lightcone perturbative expansion should be based on the large off-shellness of the lightcone energy in the intermediate states. In the lightcone perturbative QCD calculation of the pion form factor, the authors find that the legal PQCD contribution defined by the lightcone energy cut saturates in the smaller Q{sup 2} region compared to that defined by the gluon four-momentum square cut. This is due to the contribution by the highly off-energy-shell gluons in the end point regions of the phase space, indicating that the gluon four-momentum-square cut may have cut too much to define the legal PQCD.
Issam A. Qattan
2005-12-01
Due to the inconsistency in the results of the mupGEp/GMp ratio of the proton, as extracted from the Rosenbluth and recoil polarization techniques, high precision measurements of the e-p elastic scattering cross sections were made at Q{sup 2} = 2.64, 3.20, and 4.10 GeV{sup 2}. Protons were detected, in contrast to previous measurements where the scattered electrons were detected, which dramatically decreased-dependent systematic uncertainties and corrections. A single spectrometer measured the scattered protons of interest while simultaneous measurements at Q{sup 2} = 0.5 GeV{sup 2} were carried out using another spectrometer which served as a luminosity monitor in order to remove any uncertainties due to beam charge and target density fluctuations. The absolute uncertainty in the measured cross sections is {approx}3% for both spectrometers and with relative uncertainties, random and slope, below 1% for the higher Q{sup 2} protons, and below 1% random and 6% slope for the monitor spectrometer. The extracted electric and magnetic form factors were determined to 4%-7% for GEp and 1.5% for GMp. The ratio mupGEp/GMp was determined to 4%-7% and showed mupGEp/GMp {approx} 1.0. The results of this work are in agreement with the previous Rosenbluth data and inconsistent with high-Q{sup 2} recoil polarization results, implying a systematic difference between the two techniques.
Survey of nucleon electromagnetic form factors
Perdrisat, Charles F.; Punjabi, Vina A.
2011-09-20
There has been much activity in the measurement of the elastic electromagnetic proton and neutron form factors in the last decade, and the quality of the data has been greatly improved by performing double polarization experiments, in compar- ison with previous unpolarized data. Here we review the experimental data base in view of the new results for the proton, and neutron, obtained at MIT-Bates, MAMI, and JLab. The rapid evolution of phenomenological models triggered by these high-precision experiments will be discussed.
Nucleon form factor studies at Jlab
Giusa, A; Mammoliti, F; Russo, G; Sperduto, M L; Sutera, C M; Cisbani, E; Garibaldi, F; Urciuoli, G M; Capogni, M; Cates, G D; de Jager, K; Wojtsekhowski, B
2011-08-01
The ratio of the electromagnetic proton elastic form factors, GpE/GpM, has been measured at Jefferson Lab up to View the MathML source, by using the CEBAF 6 GeV electron beam, and revealing an unexpected and challenging physical behaviour. The 2014 scheduled 12 GeV upgrade will allow the measurement of GpE/GpM up to View the MathML source, by taking advantage of the new large-acceptance forward spectrometer Super BigBite (SBS) in Hall A. Measurements of neutron form factors in the region around 10 (GeV/c)2, where quark confinement plays an important role, are expected to show the behaviour already observed in the proton case.
Elastic form factors at higher CEBAF energies
Petratos, G.G.
1994-04-01
The prospects for elastic scattering from few body systems with higher beam energies at CEBAF is presented. The deuteron and{sup 3}He elastic structure functions A(Q{sup 2}) can be measured at sufficiently high momentum transfers to study the transition between the conventional meson-nucleon and the constituent quark-gluon descriptions. Possible improvements in the proton magnetic form factor data are also presented.
Hadronic form factors in kaon photoproduction
Syukurilla, L. Mart, T.
2014-09-25
We have revisited the effect of hadronic form factors in kaon photoproduction process by utilizing an isobaric model developed for kaon photoproduction off the proton. The model is able to reproduce the available experimental data nicely as well as to reveal the origin of the second peak in the total cross section, which was the main source of confusion for decades. Different from our previous study, in the present work we explore the possibility of using different hadronic form factors in each of the KΛN vertices. The use of different hadronic form factors, e.g. dipole, Gaussian, and generalized dipole, has been found to produce a more flexible isobar model, which can provide a significant improvement in the model.
Final analysis of proton form factor ratio data at Q^{2} = 4.0, 4.8, and 5.6 GeV^{2}
Puckett, A. J. R.; Brash, E. J.; Gayou, O.; Jones, M. K.; Pentchev, L.; Perdrisat, C. F.; Punjabi, V.; Aniol, K. A.; Averett, T.; Benmokhtar, F.; Bertozzi, W.; Bimbot, L.; Calarco, J. R.; Cavata, C.; Chai, Z.; Chang, C. -C.; Chang, T.; Chen, J. P.; Chudakov, E.; De Leo, R.; Dieterich, S.; Endres, R.; Epstein, M. B.; Escoffier, S.; Fissum, K. G.; Fonvieille, H.; Frullani, S.; Gao, J.; Garibaldi, F.; Gilad, S.; Gilman, R.; Glamazdin, A.; Glashausser, C.; Gomez, J.; Hansen, J. -O.; Higinbotham, D.; Huber, G. M.; Iodice, M.; de Jager, C. W.; Jiang, X.; Khandaker, M.; Kozlov, S.; Kramer, K. M.; Kumbartzki, G.; LeRose, J. J.; Lhuillier, D.; Lindgren, R. A.; Liyanage, N.; Lolos, G. J.; Margaziotis, D. J.; Marie, F.; Markowitz, P.; McCormick, K.; Michaels, R.; Milbrath, B. D.; Nanda, S. K.; Neyret, D.; Piskunov, N. M.; Ransome, R. D.; Raue, B. A.; Roché, R.; Rvachev, M.; Salgado, C.; Sirca, S.; Sitnik, I.; Strauch, S.; Todor, L.; Tomasi-Gustafsson, E.; Urciuoli, G. M.; Voskanyan, H.; Wijesooriya, K.; Wojtsekhowski, B. B.; Zheng, X.; Zhu, L.
2012-04-11
Recently published measurements of the proton electromagnetic form factor ratio R = μ_{p} G_{E}^{p}/G_{M}^{p} at momentum transfers Q^{2} up to 8.5 GeV^{2} in Jefferson Lab Hall C deviate from the linear trend of previous measurements in Jefferson Lab Hall A, favoring a slower rate of decrease of R with Q^{2}. While statistically compatible in the region of overlap with Hall A, the Hall C data hint at a systematic difference between the two experiments. This possibility was investigated in a reanalysis of the Hall A data. We find that the original analysis underestimated the background in the selection of elastic events. The application of an additional cut to further suppress the background increases the results for R, improving the consistency between Halls A and C.
The Dirac form factor predicts the Pauli form factor in the Endpoint Model
NASA Astrophysics Data System (ADS)
Dagaonkar, Sumeet K.; Jain, Pankaj; Ralston, John P.
2016-07-01
We compute the momentum-transfer dependence of the proton Pauli form factor F2 in the Endpoint overlap Model. We find the model correctly reproduces the scaling of the ratio of F2 with the Dirac form factor F1 observed at the Jefferson Laboratory. The calculation uses the leading-power, leading-twist Dirac structure of the quark light-cone wave function and the same endpoint dependence previously determined from the Dirac form factor F1. There are no parameters and no adjustable functions in the Endpoint Model's prediction for the scaling behavior of F2. The model's predicted momentum dependence of the ratio F2(Q2)/F1(Q2) is quite insensitive to the endpoint wave function, which explains why the observed ratio scales like 1 / Q down to rather low momentum transfers. We also fit the magnitude of this ratio by adjusting the parameters of the wave function. The Endpoint Model appears to be the only comprehensive model consistent with all form factor information as well as reproducing fixed-angle proton-proton scattering at large momentum transfer. Any one of the processes is capable of predicting the others.
The structure of the nucleon: Elastic electromagnetic form factors
Punjabi, V.; Perdrisat, C. F.; Jones, M. K.; Brash, E. J.; Carlson, C. E.
2015-07-10
Precise proton and neutron form factor measurements at Jefferson Lab, using spin observables, have recently made a significant contribution to the unraveling of the internal structure of the nucleon. Accurate experimental measurements of the nucleon form factors are a test-bed for understanding how the nucleon's static properties and dynamical behavior emerge from QCD, the theory of the strong interactions between quarks. There has been enormous theoretical progress, since the publication of the Jefferson Lab proton form factor ratio data, aiming at reevaluating the picture of the nucleon. We will review the experimental and theoretical developments in this field and discuss the outlook for the future.
Protonated Forms of Monoclinic Zirconia: A Theoretical Study
Mantz, Yves A.; Gemmen, Randall S.
2010-05-06
In various materials applications of zirconia, protonated forms of monoclinic zirconia may be formed, motivating their study within the framework of density-functional theory. Using the HCTH/120 exchange-correlation functional, the equations of state of yttria and of the three low-pressure zirconia polymorphs are computed, to verify our approach. Next, the favored charge state of a hydrogen atom in monoclinic zirconia is shown to be positive for all Fermilevel energies in the band gap, by the computation of defect formation energies.This result is consistent with a single previous theoretical prediction at midgap as well as muonium spectroscopy experiments. For the formally positively (+1e) charged system of a proton in monoclinic zirconia (with a homogeneous neutralizing background charge densityimplicitly included), modeled using up to a 3 x 3 x 3 arrangement of unit cells, different stable and metastable structures are identified. They are similar to those structures previously proposed for the neutral system of hydrogen-doedmonoclinic zirconia, at a similar level of theory. As predicted using the HCTH/120 functional, the lowest energy structure of the proton bonded to one of the two available oxygen atom types, O1, is favored by 0.39 eV compared to that of the proton bonded to O2. The rate of proton transfer between O1 ions is slower than that for hydrogen-dopedmonoclinic zirconia, whose transition-state structures may be lowered in energy by the extra electron.
Agúndez, M.; Cernicharo, J.; de Vicente, P.; Marcelino, N.; Roueff, E.; Fuente, A.; Gerin, M.; Guélin, M.; Albo, C.; Barcia, A.; Barbas, L.; Bolaño, R.; Colomer, F.; Diez, M. C.; Gallego, J. D.; Gómez-González, J.; López-Fernández, I.; López-Fernández, J. A.; López-Pérez, J. A.; Malo, I.; Serna, J. M.; Tercero, F.
2015-01-01
Cyanogen (NCCN) is the simplest member of the series of dicyanopolyynes. It has been hypothesized that this family of molecules can be important constituents of interstellar and circumstellar media, although the lack of a permanent electric dipole moment prevents its detection through radioastronomical techniques. Here we present the first solid evidence of the presence of cyanogen in interstellar clouds through the detection of its protonated form toward the cold dark clouds TMC-1 and L483. Protonated cyanogen (NCCNH+) has been identified through the J = 5 – 4 and J = 10 – 9 rotational transitions using the 40m radiotelescope of Yebes and the IRAM 30m telescope. We derive beam averaged column densities for NCCNH+ of (8.6 ± 4.4) × 1010 cm−2 in TMC-1 and (3.9 ± 1.8) × 1010 cm−2 in L483, which translate to fairly low fractional abundances relative to H2, in the range (1-10) × 10−12. The chemistry of protonated molecules in dark clouds is discussed, and it is found that, in general terms, the abundance ratio between the protonated and non protonated forms of a molecule increases with increasing proton affinity. Our chemical model predicts an abundance ratio NCCNH+/NCCN of ~ 10−4, which implies that the abundance of cyanogen in dark clouds could be as high as (1-10) × 10−8 relative to H2, i.e., comparable to that of other abundant nitriles such as HCN, HNC, and HC3N. PMID:26543239
Nucleon and Elastic and Transition Form Factors
NASA Astrophysics Data System (ADS)
Segovia, Jorge; Cloët, Ian C.; Roberts, Craig D.; Schmidt, Sebastian M.
2014-12-01
We present a unified study of nucleon and elastic and transition form factors, and compare predictions made using a framework built upon a Faddeev equation kernel and interaction vertices that possess QCD-like momentum dependence with results obtained using a symmetry-preserving treatment of a vector vector contact-interaction. The comparison emphasises that experiments are sensitive to the momentum dependence of the running couplings and masses in the strong interaction sector of the Standard Model and highlights that the key to describing hadron properties is a veracious expression of dynamical chiral symmetry breaking in the bound-state problem. Amongst the results we describe, the following are of particular interest: possesses a zero at Q 2 = 9.5 GeV2; any change in the interaction which shifts a zero in the proton ratio to larger Q 2 relocates a zero in to smaller Q 2; there is likely a value of momentum transfer above which ; and the presence of strong diquark correlations within the nucleon is sufficient to understand empirical extractions of the flavour-separated form factors. Regarding the -baryon, we find that, inter alia: the electric monopole form factor exhibits a zero; the electric quadrupole form factor is negative, large in magnitude, and sensitive to the nature and strength of correlations in the Faddeev amplitude; and the magnetic octupole form factor is negative so long as rest-frame P- and D-wave correlations are included. In connection with the transition, the momentum-dependence of the magnetic transition form factor, , matches that of once the momentum transfer is high enough to pierce the meson-cloud; and the electric quadrupole ratio is a keen measure of diquark and orbital angular momentum correlations, the zero in which is obscured by meson-cloud effects on the domain currently accessible to experiment. Importantly, within each framework, identical propagators and vertices are sufficient to describe all properties discussed herein. Our
Valencia, Diego; Whiting, Gareth T; Bulo, Rosa E; Weckhuysen, Bert M
2016-01-21
In an earlier work, protonated thiophene-based oligomers were identified inside ZSM-5 zeolites. The novel compounds exhibited π-π* absorption wavelengths deep within the visible region, earmarking them for possible use as chromophores in a variety of applications. In this computational study, we determine the factors that cause such low-energy transitions, and describe the electronic structure of these remarkable compounds. DFT calculations of conjugated thiophene-based oligomers with up to five monomer units reveal that the main absorption band of each protonated oligomer is strongly red-shifted compared to the unprotonated form. This effect is counterintuitive, since protonation is expected to diminish aromaticity, and thereby increase the HOMO-LUMO gap. We find that upon protonation the π-electrons remain delocalized over the entire π-conjugated molecule, but the positive charge is localized predominantly on the protonated side of the molecule. A possible explanation for this ground-state charge localization is the participation of the C-H bond in the π-system of the protonated ring, locally providing aromatic stabilization for the positive charge. The addition of the proton stabilizes all electronic orbitals, but due to the ground state π-electron distribution away from the added nucleus, the HOMO is stabilized less than the LUMO. The main absorption peak upon protonation corresponds to the charge transfer excitation involving the frontier orbitals, and the small band gap explains the observed red shift. Analogue calculations on thiophene within a ZSM-5 zeolite cluster model confirm the same trends upon protonation as observed in the non-interacting compounds. Understanding the electronic structure of these compounds is very relevant to correlate UV-Vis bands with acidic strength and possibly environment in zeolites and to improve their performance in catalytic and energy related applications. PMID:26685895
Flavor decomposition of the nucleon electromagnetic form factors at low Q2
NASA Astrophysics Data System (ADS)
Qattan, I. A.; Arrington, J.; Alsaad, A.
2015-06-01
Background: The spatial distribution of charge and magnetization within the proton is encoded in the elastic form factors. These have been precisely measured in elastic electron scattering, and the combination of proton and neutron form factors allows for the separation of the up- and down-quark contributions. Purpose: In this work, we extract the proton and neutron form factors from worldwide data with an emphasis on precise new data covering the low-momentum region, which is sensitive to the large-scale structure of the nucleon. From these, we separate the up- and down-quark contributions to the proton form factors. Method: We combine cross section and polarization measurements of elastic electron-proton scattering to separate the proton form factors and two-photon exchange (TPE) contributions. We combine the proton form factors with parametrization of the neutron form factor data and uncertainties to separate the up- and down-quark contributions to the proton's charge and magnetic form factors. Results: The extracted TPE corrections are compared to previous phenomenological extractions, TPE calculations, and direct measurements from the comparison of electron and positron scattering. The flavor-separated form factors are extracted and compared to models of the nucleon structure. Conclusions: With the inclusion of the precise new data, the extracted TPE contributions show a clear change of sign at low Q2, which is necessary to explain the high-Q2 form factor discrepancy while being consistent with the known Q2→0 limit. We find that the new Mainz data yield a significantly different result for the proton magnetic form factor and its flavor-separated contributions. We also observe that the rms radius of both the up- and down-quark distributions are smaller than the rms charge radius of the proton.
Dru Renner
2012-04-01
Precision computation of hadronic physics with lattice QCD is becoming feasible. The last decade has seen precent-level calculations of many simple properties of mesons, and the last few years have seen calculations of baryon masses, including the nucleon mass, accurate to a few percent. As computational power increases and algorithms advance, the precise calculation of a variety of more demanding hadronic properties will become realistic. With this in mind, I discuss the current lattice QCD calculations of generalized parton distributions with an emphasis on the prospects for well-controlled calculations for these observables as well. I will do this by way of several examples: the pion and nucleon form factors and moments of the nucleon parton and generalized-parton distributions.
Electric Form Factor of the Neutron
Feuerbach, Robert
2007-10-13
Recent polarization-based precision measurements of the nucleons' elastic electric form factors have led to surprising results. The measurement of the ratio of the proton's electromagnetic form factors, $\\mu_p G_E^p/G_M^p$, was found to drop nearly linearly with $Q^2$ out to at least $5 \\mathrm{GeV}^2$, inconsistent with the older Rosenbluth-type experiments. A recent measurement of $G_E^n$, the neutron's electric form-factor saw $G_E^n$ does not fall off as quickly as commonly expected up to $Q^2 \\approx 1.5 \\mathrm{GeV}^2$. Extending this study, a precision measurement of $G_E^n$ up to $Q^2=3.5 \\mathrm{GeV}^2$ was completed in Hall A at Jefferson Lab. The ratio $G_E^n/G_M^n$ was measured through the beam-target asymmetry $A_\\perp$ of electrons quasi-elastically scattered off polarized neutrons in the reaction ${}^{3}\\overrightarrow{He}(\\overrightarrow{e},e' n)$. The experiment took full advantage of the electron beam, recent target developments, as well as two detectors new to Jefferson Lab. The measurement used the accelerator's 100\\% duty-cycle high-polarization (typically 84\\%) electron beam and a new, hybrid optically-pumped polarized ${}^{3}\\overrightarrow{He}$ target which achieved in-beam polarizations in excess of 50\\%. A medium acceptance (80msr) open-geometry magnetic spectrometer (BigBite) detected the scattered electron, while a geometrically matched neutron detector observed the struck neutron. Preliminary results from this measurement will be discussed and compared to modern calculations of $G_E^n$.
Measuring Form Factors and Structure Functions with CLAS
G.P. Gilfoyle
2007-09-10
The physics program at the Thomas Jefferson National Accelerator Facility includes a strong effort to measure form factors and structure functions to probe the structure of hadronic matter, reveal the nature of confinement, and develop an understanding of atomic nuclei using quark-gluon degrees of freedom. The CLAS detector is a large acceptance device occupying one of the end stations. We discuss here two programs that use CLAS; measuring the magnetic form factor of the neutron and the virtual photon asymmetry of the proton. The form factor has been measured with unprecedented kinematic coverage and precision up to Q2=4.7 GeV2 and is consistent within 5%-10% of the dipole parameterization. The proton virtual photon asymmetry has been measured across a wide range in Bjorken x. The data exceed the SU(6)-symmetric quark prediction and show evidence of a smooth approach to the scaling limit prescribed by perturbative QCD.
The structure of the nucleon: Elastic electromagnetic form factors
Punjabi, V.; Perdrisat, C. F.; Jones, M. K.; Brash, E. J.; Carlson, C. E.
2015-07-10
Precise proton and neutron form factor measurements at Jefferson Lab, using spin observables, have recently made a significant contribution to the unraveling of the internal structure of the nucleon. Accurate experimental measurements of the nucleon form factors are a test-bed for understanding how the nucleon's static properties and dynamical behavior emerge from QCD, the theory of the strong interactions between quarks. There has been enormous theoretical progress, since the publication of the Jefferson Lab proton form factor ratio data, aiming at reevaluating the picture of the nucleon. We will review the experimental and theoretical developments in this field and discussmore » the outlook for the future.« less
Transition Form Factor from CLAS
Park, Kijun
2009-01-01
The excitation of nucleon resonances in electromagnetic interaction has long been studied. The study of resonances helps us to understand the long- and short- range structures of the nucleon and its excited states in terms of quark confinement. While the existing data of the low-lying resonances are consistent with the well-studied SU(6) circle times operator O(3) constituent quark model classification, many open questions still remain. Exclusive electro-production is one of the best ways to investigate nucleon resonances. The exclusive electro-production process View the MathML source was measured in the photon virtuality range Q2 = 1.7 â 4.5 GeV2 and the invariant mass range for the n?+ system of W = 1.15 â 1.7 GeV using the CEBAF Large Acceptance Spectrometer. For the first time, these kinematics are probed in exclusive ?+ production from protons with nearly full coverage in the azimuthal and polar angles of the n?+ center-of-mass system. The n?+ channel has particular sensitivity t
Analytic parametrization for nuclear form factors
Atkin, G.; Dumbrajs, O.
1982-08-01
A new analytic parametrization of the nuclear form factor is developed using a factorization theorem. We show that the nuclear form factor can be represented in terms of its real zeros and its asymptotic behavior. The parametrization is applied to nuclear form factor data of /sup 3/He and /sup 4/He. Our results suggest that further diffraction minima can be expected at higher momentum transfer where experiments have not yet been made.
Charge density distributions and charge form factors of the N=82 and N=126 isotonic nuclei
Wang Zaijun; Fan Ying; Ren Zhongzhou
2006-01-15
Charge form factors for N=82 and N=126 isotonic nuclei are calculated with the relativistic eikonal approximation, in which the charge density distributions are from the relativistic mean-field theory. The variations of charge form factors with proton number are discussed in detail. It is found that the most sensitive parts of the charge form factors are those around the minimums and maximums. For an increasing proton number, the charge form factors near the extrema have an upward shift. As the protons increase and occupy a new shell, the minimums and maximums of the charge form factors could also have a significant inward shift. The results can be useful for the study of behaviors of valence-proton wave functions for such nuclei as can be considered as a core plus proton(s), and thus the proton-halo phenomenon. In addition, the results can also be useful for future electron-unstable nucleus scattering experiments and provide tests of the reliability of the relativistic mean-field theory for the unstable nuclei.
Mkrtchyan, Arthur
2012-05-31
Among the fundamental observables of nucleon structure, electromagnetic form factors are a crucial benchmark for modern calculations describing the strong interaction dynamics of the nucleon's quark constituents. Electromagnetic probes are traditionally preferered to the hadronic beams. The electromagnetic interaction is a powerful tool for investigating the nucleon structure since it is well understood and it reveals observables that can be directly interpreted in terms of the current carried by the quarks. Elastic scattering leads to the form factors that describe the spatial charge and current distributions inside the nucleon. The reaction mechanism is assumed to be one photon exchange, the electromagnetic interaction is exactly calculable in QED, and one can safely extract the information on the hadronic vertex. The most important feature of early measurements of proton form factor ratio G_{E}^{p}/G_{M}^{p} with recoil polarization technique at Q^{2} up to 5.6 (GeV/c)^{2} is the sharp decline of the ratio with Q^{2} increases, indicating that G_{E}^{p} falls much faster than G_{M}^{p}. This contradicts to data obtained by Rosenbluth separation method. An intriguing question was whether G_{E}^{p} will continue to decrease or become constant when Q^{2} increases. New set of measurements of proton form factor ratio G_{E}^{p}/G_{M}^{p} at Q^{2} = 2.5, 5.2, 6.7 and 8.5 (GeV/c)^{2} have been conducted at JLab Hall C using ~85% longitudinally polarized electron elastic scattering from unpolarized hydrogen target. Recoil protons were detected in the HMS magnetic spectrometer with the standard detector package, combined with newly installed trigger scintillators and Focal Plane Polarimeter. The BigCal electromagnetic calorimeter (1744 channel) have been used for electron detection. Data obtained in this
On form factors of boundary changing operators
NASA Astrophysics Data System (ADS)
Bajnok, Z.; Hollo, L.
2016-04-01
We develop a form factor bootstrap program to determine the matrix elements of local, boundary condition changing operators. We propose axioms for these form factors and determine their solutions in the free boson and Lee-Yang models. The sudden change in the boundary condition, caused by an operator insertion, can be interpreted as a local quench and the form factors provide the overlap of any state before the quench with any outgoing state after the quench.
Physical and biological factors determining the effective proton range
Grün, Rebecca; Friedrich, Thomas; Krämer, Michael; Scholz, Michael; Zink, Klemens; Durante, Marco; Engenhart-Cabillic, Rita
2013-11-15
Purpose: Proton radiotherapy is rapidly becoming a standard treatment option for cancer. However, even though experimental data show an increase of the relative biological effectiveness (RBE) with depth, particularly at the distal end of the treatment field, a generic RBE of 1.1 is currently used in proton radiotherapy. This discrepancy might affect the effective penetration depth of the proton beam and thus the dose to the surrounding tissue and organs at risk. The purpose of this study was thus to analyze the impact of a tissue and dose dependent RBE of protons on the effective range of the proton beam in comparison to the range based on a generic RBE of 1.1.Methods: Factors influencing the biologically effective proton range were systematically analyzed by means of treatment planning studies using the Local Effect Model (LEM IV) and the treatment planning software TRiP98. Special emphasis was put on the comparison of passive and active range modulation techniques.Results: Beam energy, tissue type, and dose level significantly affected the biological extension of the treatment field at the distal edge. Up to 4 mm increased penetration depth as compared to the depth based on a constant RBE of 1.1. The extension of the biologically effective range strongly depends on the initial proton energy used for the most distal layer of the field and correlates with the width of the distal penumbra. Thus, the range extension, in general, was more pronounced for passive as compared to active range modulation systems, whereas the maximum RBE was higher for active systems.Conclusions: The analysis showed that the physical characteristics of the proton beam in terms of the width of the distal penumbra have a great impact on the RBE gradient and thus also the biologically effective penetration depth of the beam.
Flavor Decomposition of the Elastic Nucleon Electromagnetic Form Factors
NASA Astrophysics Data System (ADS)
Cates, G. D.; de Jager, C. W.; Riordan, S.; Wojtsekhowski, B.
2011-06-01
The u- and d-quark contributions to the elastic nucleon electromagnetic form factors have been determined by using experimental data on GEn, GMn, GEp, and GMp. Such a flavor separation of the form factors became possible up to negative four-momentum transfer squared Q2=3.4GeV2 with recent data on GEn from Hall A at Jefferson Lab. For Q2 above 1GeV2, for both the u and the d quark, the ratio of the Pauli and Dirac form factors, F2/F1, was found to be almost constant in sharp contrast to the behavior of F2/F1 for the proton as a whole. Also, again for Q2>1GeV2, both F2d and F1d are roughly proportional to 1/Q4, whereas the dropoff of F2u and F1u is more gradual.
Isomers and conformational barriers of gas phase nicotine, nornicotine and their protonated forms
Yoshida, Tomoki; Farone, William A.; Xantheas, Sotiris S.
2014-07-17
We report extensive conformational searches of the neutral nicotine, nornicotine and their protonated analogs that are based on ab-initio second order Møller-Plesset perturbation (MP2) electronic structure calculations. Initial searches were performed with the 6-31G(d,p) and the energetics of the most important structures were further refined from geometry optimizations with the aug-cc-pVTZ basis set. Based on the calculated free energies at T=298 K for the gas phase molecules, neutral nicotine has two dominant trans conformers, whereas neutral nornicotine is a mixture of several conformers. For nicotine, the protonation on both the pyridine and the pyrrolidine sites is energetically competitive, whereas nornicotine prefers protonation on the pyridine nitrogen. The protonated form of nicotine is mainly a mixture of two pyridine-protonated trans conformers and two pyrrolidine-protonated trans conformers, whereas the protonated form of nornicotine is a mixture of four pyridine-protonated trans conformers. Nornicotine is conformationally more flexible than nicotine, however it is less protonated at the biologically important pyrrolidine nitrogen site. The lowest energy isomers for each case were found to interconvert via low (< 6 kcal/mol) rotational barriers around the pyridine-pyrrolidine bond.
Form factor and boundary contribution of amplitude
NASA Astrophysics Data System (ADS)
Huang, Rijun; Jin, Qingjun; Feng, Bo
2016-06-01
The boundary contribution of an amplitude in the BCFW recursion relation can be considered as a form factor involving boundary operator and unshifted particles. At the tree-level, we show that by suitable construction of Lagrangian, one can relate the leading order term of boundary operators to some composite operators of mathcal{N} = 4 superYang-Mills theory, then the computation of form factors is translated to the computation of amplitudes. We compute the form factors of these composite operators through the computation of corresponding double trace amplitudes.
Measurements of the elastic electromagnetic form factor ratio {mu}pGEp/GMp via polarization transfer
Olivier Gayou; Oleksandr Glamazdin; Andrei Afanasev; Arunava Saha; Brendan Fox; Bogdan Wojtsekhowski; C. Chang; Cathleen Jones; Charles Glashausser; Charles Perdrisat; D. Crovelli; Daniel Simon; David Meekins; Demetrius Margaziotis; Dipangkar Dutta; Edgar Kooijman; Elaine Schulte; Edward Brash; Edward Kinney; Eugene Chudakov; Feng Xiong; Franco Garibaldi; Garth Huber; Gerfried Kumbartzki; Guido Urciuoli; Haiyan Gao; Jordan Hovdebo; James Kelly; Javier Gomez; Jens-Ole Hansen; Jian-Ping Chen; John Calarco; John LeRose; Joseph Mitchell; Juncai Gao; Konrad Aniol; Kamal Benslama; Kathy McCormick; Cornelis De Jager; Cornelis de Jager; Kevin Fissum; Krishni Wijesooriya; Louis Bimbot; Ludyvine Morand; Luminita Todor; Moskov Amarian; Marat Rvachev; Mark Jones; Martin Epstein; Meihua Liang; Michael Kuss; Nilanga Liyanage; Adam Sarty; Paul Ulmer; Pete Markowitz; Peter Bosted; R. Holt; Riad Suleiman; Richard Lindgren; Rikki Roche; Robert Michaels; Roman Pomatsalyuk; Ronald Gilman; Ronald Ransome; Stephen Becher; Scott Dumalski; Salvatore Frullani; Seonho Choi; Sergey Malov; Sonja Dieterich; Steffen Strauch; Steve Churchwell; Ting Chang; Viktor Gorbenko; Vina Punjabi; Wang Xu; Xiangdong Ji; Zein-Eddine Meziani; Zhengwei Chai
2001-09-01
We present measurements of the ratio of the proton elastic electromagnetic form factors, {mu}pGEp/GMp. The Jefferson Lab Hall A Focal Plane Polarimeter was used to determine the longitudinal and transverse components of the recoil proton polarization in ep elastic scattering; the ratio of these polarization components is proportional to the ratio of the two form factors. These data reproduce the observation of Jones et al. [Phys. Rev. Lett. 84, 1398 (2000)], that the form factor ratio decreases significantly from unity above Q2 = 1 GeV2.
Processes forming and sustaining Saturn's proton radiation belts
NASA Astrophysics Data System (ADS)
Kollmann, P.; Roussos, E.; Paranicas, C.; Krupp, N.; Haggerty, D. K.
2013-01-01
Saturn's proton radiation belts extend over the orbits of several moons that split this region of intense radiation into several distinct belts. Understanding their distribution requires to understand how their particles are created and evolve. High-energy protons are thought to be dominantly produced by cosmic ray albedo neutron decay (CRAND). The source of the lower energies and the role of other effects such as charge exchange with the gas originating from Enceladus is still an open question. There is also no certainty so far if the belts exist independently from each other and the rest of the magnetosphere or if and how particles are exchanged between these regions. We approach these problems by using measurements acquired by the MIMI/LEMMS instrument onboard the Cassini spacecraft. Protons in the range from 500 keV to 40 MeV are considered. Their intensities are averaged over 7 years of the mission and converted to phase space densities at constant first and second adiabatic invariant. We reproduce the resulting radial profiles with a numerical model that includes radial diffusion, losses from moons and interactions with gas, and a phenomenological source. Our results show that the dominating effects away from the moon sweeping corridors are diffusion and the source, while interactions with gas are secondary. Based on a GEANT4 simulation of the interaction of cosmic rays with Saturn's rings, we conclude that secondary particles produced within the rings can only account for the high-energy part of the source. A comparison with the equivalent processes within Earth's atmosphere shows that Saturn's atmosphere can contribute to the production of the lower energies and might be even dominating at the higher energies. Other possibilities to supply the belts and exchange particles between them, as diffusion and injections from outside the belts, or stripping of ENAs, can be excluded.
Nucleon and Δ electromagnetic form factors
NASA Astrophysics Data System (ADS)
Bartoš, Erik; Dubnička, Stanislav; Dubničková, Anna-Zuzana
2015-11-01
The unitary and analytic model for nucleons works very well. The model for spin 1 2+ baryons can predict static parameters for Λ, Σ+, Σ0, Σ-, Ξ, Ξ-. We prepared the scheme how to construct the model also for Δ nucleon resonance. It was used to describe transition form factor GM∗ and the experimentally measured ratio RSM with the help of relations for magnetic dipole transition and charge quadrupole form factors.
NASA Astrophysics Data System (ADS)
Morita, T.; Kugland, N. L.; Wan, W.; Crowston, R.; Drake, R. P.; Fiuza, F.; Gregori, G.; Huntington, C.; Ishikawa, T.; Koenig, M.; Kuranz, C.; Levy, M. C.; Martinez, D.; Meinecke, J.; Miniati, F.; Murphy, C. D.; Pelka, A.; Plechaty, C.; Presura, R.; Quirós, N.; Remington, B. A.; Reville, B.; Ross, J. S.; Ryutov, D. D.; Sakawa, Y.; Steele, L.; Takabe, H.; Yamaura, Y.; Woolsey, N.; Park, H.-S.
2016-03-01
We report the measurements of electrostatic field structures associated with an electrostatic shock formed in laser-produced counter-streaming plasmas with proton imaging. The thickness of the electrostatic structure is estimated from proton images with different proton kinetic energies from 4.7 MeV to 10.7 MeV. The width of the transition region is characterized by electron scale length in the laser-produced plasma, suggesting that the field structure is formed due to a collisionless electrostatic shock.
Electromagnetic Form Factors of Hadrons in Quantum Field Theories
Dominguez, C. A.
2008-10-13
In this talk, recent results are presented of calculations of electromagnetic form factors of hadrons in the framework of two quantum field theories (QFT), (a) Dual-Large N{sub c} QCD (Dual-QCD{sub {infinity}}) for the pion, proton, and {delta}(1236), and (b) the Kroll-Lee-Zumino (KLZ) fully renormalizable Abelian QFT for the pion form factor. Both theories provide a QFT platform to improve on naive (tree-level) Vector Meson Dominance (VMD). Dual-QCD{sub {infinity}} provides a tree-level improvement by incorporating an infinite number of zero-width resonances, which can be subsequently shifted from the real axis to account for the time-like behaviour of the form factors. The renormalizable KLZ model provides a QFT improvement of VMD in the framework of perturbation theory. Due to the relative mildness of the {rho}{pi}{pi} coupling, and the size of loop suppression factors, the perturbative expansion is well defined in spite of this being a strong coupling theory. Both approaches lead to considerable improvements of VMD predictions for electromagnetic form factors, in excellent agreement with data.
Magnetic form factors of the trinucleons
Schiavilla, R; Pandharipande, V R; Riska, Dan-Olof
1989-11-01
The magnetic form factors of ^{3}H and ^{3}He are calculated with the Monte Carlo method from variational ground-state wave functions obtained for the Argonne and Urbana two- and three-nucleon interactions. The electromagnetic current operator contains one- and two-body terms that are constructed so as to satisfy the continuity equation with the two-nucleon potential in the Hamiltonian. The results obtained with the Argonne two-nucleon interaction are in overall agreement with the empirical values. It appears that the remaining theoretical uncertainty, in the calculation of these form factors from a given interaction model, is dominated by that in the electromagnetic form factors of the nucleon. It is found that the isovector magnetic form factors are rather sensitive to the details of the isospin-dependent tensor force, and they are much better reproduced with the Argonne than the Urbana potential. The isoscalar magnetic form factors appear to be sensitive to the spin-orbit interactions, and are better reproduced with the Urbana potential. The Argonne potential has a stronger τ1∙τ2 tensor force, while the Urbana one has a shorter-range spin-orbit interaction.
Electroweak form factors of the Δ (1232 ) resonance
NASA Astrophysics Data System (ADS)
Graczyk, Krzysztof M.; Żmuda, Jakub; Sobczyk, Jan T.
2014-11-01
Nucleon →Δ (1232 ) transition electroweak form factors are discussed in a single pion production model with nonresonant background terms originating from a chiral perturbation theory. Fits to electron-proton scattering F2 as well as neutrino scattering bubble chamber experimental data are performed. Both ν -proton and ν -neutron channel data are discussed in a unified statistical model. A new parametrization of the N →Δ (1232 ) vector form factors is proposed. In the case of model with deuteron nuclear effects fit to neutrino scattering data gives the axial mass MA Δ=0.85-0.08+0.09 GeV and C5A(0 )=1.10-0.14+0.15 in accordance with the Goldberger-Treiman relation. However, the consistency is spoiled when the deuteron effects are omitted; i.e., in this case the fit gives the axial mass MA Δ=0.8 1-0.09+0.09 GeV and C5A(0 )=0.9 3-0.13+0.13 .
Charm form factors in hadronic interactions
Bracco, M. E.; Navarra, F. S.; Nielsen, M.; Chiapparini, M.
2010-12-28
We calculate the form factors and the coupling constants in vertices with charm mesons, such as {rho}D*D*, in the framework of QCD sum rules. We first discuss the applications of these form factors in heavy ion collisions and in B decays. We then present an introduction to the method of QCD sum rules and describe how to work with the three-point function. We give special attention to the procedure employed to extrapolate results obtained in the deep euclidean region to the poles of the particles, located in the time-like region. Finally we present a table of ready-to-use parametrizations of all the form factors, which are relevant for the processes mentioned in the introduction. We also give the coupling constants.
Precision comparison of the g-factor of the proton and anti-proton
NASA Astrophysics Data System (ADS)
Disciacca, Jack
2013-05-01
We report the first measurement of the antiproton magnetic moment using a single antiproton. The magnetic moment in nuclear magnetons is μp /μN = - 2 . 792845 +/- 0 . 000012 , a 4.4 parts per million (ppm) measurement. This represents a factor of 680 improvement in precision over previous work using exotic atom spectroscopy, which has achieved a 3000 ppm precision and remained essentially unchanged in the past 20 years., Our measurement allows for an improved comparison of the proton and antiproton magnetic moments, yielding a result consistent with the prediction of charge, parity and time reversal symmetry. Following a proof of principle, 2.5 ppm measurement of the proton magnetic moment, the experiment was moved to CERN for the antiproton experiment. Initial work focused on catching, cooling and trapping a single antiproton from the 5 MeV beam at CERN's Antiproton Decelerator. Following this work, we undertook a magnetic moment measurement. The spin and cyclotron frequency are measured to determine the g-factor, g / 2 =fs /fc . Prospects for further improvement should be possible with single spin flip detection, similar to what was used to measure the electron magnetic moment - currently the most precisely measured property of a fundamental particle. The new antiproton magnetic moment measurement is likely a first step towards improved precision by an additional factor of 103 or 104 improvement, with a precision at the part per billion level.,, A. Kreissl, et al., Z. Phys. C: Part. Fields 37, 557 (1988).
Electromagnetic charged and neutral kaon form factors
Roberts, C.D.; Burden, C.J.; Thomson, M.J.
1995-08-01
The electromagnetic form factor of the charged and neutral kaon is calculated using the approach applied in the successful study of the pion form factor, described above. The charged kaon form factor will be measured in forthcoming experiments at CEBAF. Our calculation involves the dressed strange quark propagator, to which F{sub {pi}}(q{sup 2}) is not sensitive, and hence it provides us with constraints on the strange-quark sector of QCD. Our preliminary results are encouraging. We find that the strange and up/down quark propagators are not too different, once the change in the current-quark-mass is accounted for. However, the difference that remains is important since it allows {l_angle}{bar s}s{r_angle}<{l_angle}{bar u}u{r_angle}. This calculation is the first to yield a value of f{sub K}/f{sub {pi}} that is in good agreement with experiment and also yields r{sub K+}/r{sub {pi}} in good agreement with experiment. Our calculated charged kaon form factor provides a prediction that will be tested in the forthcoming CEBAF experiments. Our studies also show that K{sup 0} has a negative charge radius, as is to be expected. Our calculated value will be compared with that measured in K{sub s}{sup 0} regeneration from electrons.
Meson-photon transition form factors
Balakireva, Irina; Lucha, Wolfgang; Melikhov, Dmitri
2012-10-23
We present the results of our recent analysis of the meson-photon transition form factors F{sub P{gamma}}(Q{sup 2}) for the pseudoscalar mesons P {pi}{sup 0},{eta},{eta} Prime ,{eta}{sub c}, using the local-duality version of QCD sum rules.
Form Factors and Radii of Light Nuclei
Sick, Ingo
2015-09-15
We discuss the determination of electromagnetic form factors from the world data on electron–nucleus scattering for nuclei Z ≤ 3, with particular emphasis on the derivation of the moments required for comparison with measurements from electronic/muonic atoms and isotope shifts.
Form Factors and Radii of Light Nuclei
NASA Astrophysics Data System (ADS)
Sick, Ingo
2015-09-01
We discuss the determination of electromagnetic form factors from the world data on electron-nucleus scattering for nuclei Z ≤ 3, with particular emphasis on the derivation of the moments required for comparison with measurements from electronic/muonic atoms and isotope shifts.
Form factor effects in the direct detection of isospin-violating dark matter
Zheng, Hao; Zhang, Zhen; Chen, Lie-Wen E-mail: malkuth@sjtu.edu.cn
2014-08-01
Isospin-violating dark matter (IVDM) provides a possible mechanism to ameliorate the tension among recent direct detection experiments. For IVDM, we demonstrate that the results of direct detection experiments based on neutron-rich target nuclei may depend strongly on the density dependence of the symmetry energy which is presently largely unknown and controls the neutron skin thickness that reflects the relative difference of neutron and proton form factors in the neutron-rich nuclei. In particular, using the neutron and proton form factors obtained from Skyrme-Hartree-Fock calculations by varying the symmetry energy within the uncertainty region set by the latest model-independent measurement of the neutron skin thickness of {sup 208}Pb from PREX experiment at JLab, we find that, for IVDM with neutron-to-proton coupling ratio fixed to f{sub n}/f{sub p}=-0.7, the form factor effect may enhance the sensitivity of Xe-based detectors (e.g., XENON100 and LUX) to the DM-proton cross section by a factor of 3 in the DM mass region constrained by CMDS-II(Si) and even by more than an order of magnitude for heavy DM with mass larger than 80 GeV, compared with the results using the empirical Helm form factor. Our results further indicate that the form factor effect can significantly modify the recoil spectrum of Xe-based detectors for heavy IVDM with f{sub n}/f{sub p}=-0.7.
Energy-dependent dipole form factor in a QCD-inspired model
NASA Astrophysics Data System (ADS)
Bahia, C. A. S.; Broilo, M.; Luna, E. G. S.
2016-04-01
We consider the effect of an energy-dependent dipole form factor in the high-energy behavior of the forward amplitude. The connection between the semihard parton-level dynamics and the hadron-hadron scattering is established by an eikonal QCD-based model. Our results for the proton-proton (pp) and antiproton-proton (¯pp) total cross sections, σpp,\\bar{pp}tot(s), obtained using the CTEQ6L1 parton distribution function, are consistent with the recent data from the TOTEM experiment.
Experimental validation of beam quality correction factors for proton beams
NASA Astrophysics Data System (ADS)
Gomà, Carles; Hofstetter-Boillat, Bénédicte; Safai, Sairos; Vörös, Sándor
2015-04-01
This paper presents a method to experimentally validate the beam quality correction factors (kQ) tabulated in IAEA TRS-398 for proton beams and to determine the kQ of non-tabulated ionization chambers (based on the already tabulated values). The method is based exclusively on ionometry and it consists in comparing the reading of two ionization chambers under the same reference conditions in a proton beam quality Q and a reference beam quality 60Co. This allows one to experimentally determine the ratio between the kQ of the two ionization chambers. In this work, 7 different ionization chamber models were irradiated under the IAEA TRS-398 reference conditions for 60Co beams and proton beams. For the latter, the reference conditions for both modulated beams (spread-out Bragg peak field) and monoenergetic beams (pseudo-monoenergetic field) were studied. For monoenergetic beams, it was found that the experimental kQ values obtained for plane-parallel chambers are consistent with the values tabulated in IAEA TRS-398; whereas the kQ values obtained for cylindrical chambers are not consistent—being higher than the tabulated values. These results support the suggestion (of previous publications) that the IAEA TRS-398 reference conditions for monoenergetic proton beams should be revised so that the effective point of measurement of cylindrical ionization chambers is taken into account when positioning the reference point of the chamber at the reference depth. For modulated proton beams, the tabulated kQ values of all the ionization chambers studied in this work were found to be consistent with each other—except for the IBA FC65-G, whose experimental kQ value was found to be 0.6% lower than the tabulated one. The kQ of the PTW Advanced Markus chamber, which is not tabulated in IAEA TRS-398, was found to be 0.997 ± 0.042 (k = 2), based on the tabulated value of the PTW Markus chamber.
Unified description of kaon electroweak form factors
A. Afanasev; W. Buck
1996-06-01
A calculation of the semileptonic decays of the kaon (K{sub l3}) is presented. The results are direct predictions of a covariant model of the pion and kaon introduced earlier by Ito, Buck, Gross. The weak form factors for K{sub l3} are predicted with absolutely no parameter adjustments of the model. The authors obtained for the form factor parameters: f{sub {minus}}(q{sup 2}=m{sub l}{sup 2})/f{sub +}(q{sup 2}=m{sub l}{sup 2})={minus}0.28 and {lambda}{sub +}= 0.028, both within experimental error bars. Connections of this approach to heavy quark symmetry will also be discussed.
Heavy to light baryon transition form factors
Guo, X. |; Huang, T. |; Li, Z.
1996-05-01
Recently, Stech found form factor relations for heavy to light transitions based on two simple dynamical assumptions for a spectator particle. In this paper we generalize his approach to the case of baryons and find that for {Lambda}{sub {ital Q}}{r_arrow}{Lambda} ({ital Q}={ital b} or {ital c}) only one independent form factor remains in the limit {ital m}{sub {ital Q}}{r_arrow}{infinity}. Furthermore, combining with the model of Guo and Kroll we determine both of the two form factors for {Lambda}{sub {ital Q}}{r_arrow}{Lambda} in the heavy quark limit. The results are applied to {Lambda}{sub {ital b}}{r_arrow}{Lambda}+{ital J}/{psi} which is not clarified both theoretically and experimentally. It is found that the branching ratio of {Lambda}{sub {ital b}}{r_arrow}{Lambda}+{ital J}/{psi} is of order 10{sup {minus}5}. {copyright} {ital 1996 The American Physical Society.}
Yamashita, Ken-Ichi; Sakata, Naoya; Ogawa, Takuji
2016-09-01
Direct structural evidence of the presence and location of the attached proton in the protonated form of rare earth bis(porphyrinato) double-decker complexes is obtained from an X-ray diffraction study of single crystals for a series of protonated forms of bis(tetraphenylporphyrinato) complexes [M(III)(tpp)(tppH)] (M = Tb, Y, Sm, Nd, and La). When CHCl3 is used as a solvent for crystallization of the complexes, their nondisordered molecular structures are obtained and the attached proton is identified on one of the eight nitrogen atoms. Use of other solvents affords another type of crystal, in which the position of the proton is disordered and thus the molecular structure is averaged. La complex also affords the disordered average structure even when CHCl3 is used for crystallization. A variable-temperature diffraction study for the Tb complex reveals that the dynamics of the proton in the nondisordered crystal is restricted. PMID:27541189
Longitudinal electron scattering form factors for 54,56Fe
NASA Astrophysics Data System (ADS)
Salman, A. D.; Kadhim, D. R.
2014-09-01
In this paper, inelastic longitudinal electron scattering form factors for C2 transition have been studied in 54Fe and 56Fe with the aid of shell model calculations. The GX1 effective interaction for the fp-shell is used with the nucleon-nucleon realistic interaction Michigan three-range Yukawa and Modified surface delta interaction as a two-body interactions. The core polarization effects is taken into account through the first-order perturbation theory with the effective charge, which is taken to the proton and the neutron. The effective charge along with the core effects up to 6 ℏw enhanced the calculation very well and improving good agreement with the experimental data.
Pion form factor from a contact interaction
Gutierrez-Guerrero, L. X.; Bashir, A.; Cloeet, I. C.; Roberts, C. D.
2010-06-15
In a Poincare-covariant vector-boson-exchange theory, the pion possesses components of pseudovector origin, which materially influence its observable properties. For a range of such quantities, we explore the consequences of a momentum-independent interaction, regularized in a symmetry-preserving manner. The contact interaction, while capable of describing pion static properties, produces a form factor whose evolution for Q{sup 2}>0.17 GeV{sup 2} disagrees markedly with experiment and whose asymptotic power-law behavior conflicts strongly with perturbative QCD.
Pion form factor from a contact interaction.
Gutierrez-Guerrero, L. X.; Bashir, A.; Cloet, I. C.; Roberts, C. D.
2010-01-01
In a Poincare-covariant vector-boson-exchange theory, the pion possesses components of pseudovector origin, which materially influence its observable properties. For a range of such quantities, we explore the consequences of a momentum-independent interaction, regularized in a symmetry-preserving manner. The contact interaction, while capable of describing pion static properties, produces a form factor whose evolution for Q{sup 2} > 0.17 GeV{sup 2} disagrees markedly with experiment and whose asymptotic power-law behavior conflicts strongly with perturbative QCD.
Electromagnetic Transition Form Factors of Nucleon Resonances
Burkert, Volker D.
2008-10-13
Recent measurements of nucleon resonance transition form factors with CLAS at Jefferson Lab are discussed. The new data resolve a long-standing puzzle of the nature of the Roper resonance, and confirm the assertion of the symmetric constituent quark model of the Roper as the first radial excitation of the nucleon. The data on high Q{sup 2} n{pi}{sup +} production confirm the slow fall off of the S{sub 11}(1535) transition form factor with Q{sup 2}, and better constrain the branching ratios {beta}{sub N{pi}} = 0.50 and {beta}{sub N{eta}} = 0.45. For the first time, the longitudinal transition amplitude to the S{sub 11}(1535) was extracted from the n{pi}{sup +} data. Also, new results on the transition amplitudes for the D{sub 13}(1520) resonance are presented showing a rapid transition from helicity 3/2 dominance seen at the real photon point to helicty 1/2 dominance at higher Q{sup 2}.
Helium Compton Form Factor Measurements at CLAS
Voutier, Eric J.-M.
2013-07-01
The distribution of the parton content of nuclei, as encoded via the generalized parton distributions (GPDs), can be accessed via the deeply virtual Compton scattering (DVCS) process contributing to the cross section for leptoproduction of real photons. Similarly to the scattering of light by a material, DVCS provides information about the dynamics and the spatial structure of hadrons. The sensitivity of this process to the lepton beam polarization allows to single-out the DVCS amplitude in terms of Compton form factors that contain GPDs information. The beam spin asymmetry of the $^4$He($\\vec {\\mathrm e}$,e$' \\gamma ^4$He) process was measured in the experimental Hall B of the Jefferson Laboratory to extract the real and imaginary parts of the twist-2 Compton form factor of the $^4$He nucleus. The experimental results reported here demonstrate the relevance of this method for such a goal, and suggest the dominance of the Bethe-Heitler amplitude to the unpolarized process in the kinematic range explored by the experiment.
... nucleus is surrounded by electrons. In proton therapy, beams of fast-moving protons are used to destroy ... atoms to release proton, neutron, and helium ion beams. In this highly specialized form of radiosurgery , proton ...
Is the proton electromagnetic form factor modified in nuclei?
Morgenstern, J; Meziani, Zein-eddine
2003-06-01
Guided by the recent experimental confirmation of the validity of the Effective Momentum Approximation (EMA) in quasi-elastic scattering off nuclei, we have re-examined the extraction of the Longitudinal and Transverse Response Functions in medium-weight and heavy nuclei. In the EMA we have performed a Rosenbluth separation of the available world data on 40Ca, 48Ca, 56Fe and 208Pb. We find that the Longitudinal Response Function for these nuclei is quenched and that the Coulomb sum is not saturated, at odds with recent claims in the literature.
Chiral corrections to hyperon vector form factors
NASA Astrophysics Data System (ADS)
Anderson, Jeffrey; Luty, Markus A.
1993-06-01
We show that the leading chiral corrections to the ΔS=1 f1 vector form factors of hyperons are O(ms) and O(m3/2s), and are expected to be ~20-30 % by dimensional analysis. This is consistent with the Ademollo-Gatto theorem. We compute the O(ms) corrections and a subset of the O(m3/2s) corrections using an effective Lagrangian in which the baryons are treated as heavy particles. All of these corrections are surprisingly small, ~5% combining them, we obtain ~5-10 % corrections. The pattern of corrections is very different from that predicted by quark models.
Elastic and Transition Form Factors in DSEs
NASA Astrophysics Data System (ADS)
Segovia, Jorge
2016-06-01
A symmetry preserving framework for the study of continuum quantum chromodynamics (QCD) is obtained from a truncated solution of the QCD equations of motion or QCD's Dyson-Schwinger equations (DSEs). A nonperturbative solution of the DSEs enables the study of, e.g., hadrons as composites of dressed-quarks and dressed-gluons, the phenomena of confinement and dynamical chiral symmetry breaking, and therefrom an articulation of any connection between them. It is within this context that we present a unified study of Nucleon, Delta and Roper elastic and transition form factors, and compare predictions made using a framework built upon a Faddeev equation kernel and interaction vertices that possess QCD-like momentum dependence with results obtained using a symmetry-preserving treatment of a vector ⊗ vector contact-interaction.
Nucleon Transition Form Factors and New Perspectives
Gothe, R W
2007-10-01
The status of the electro-excitation program to study baryon resonances at Jefferson Lab will be exemplified by the most recent results on resonance parameters and transition form factors in single and double-pion production. These results demonstrate that the separation of resonance and background contributions and therefore the extraction of the electro-coupling amplitudes of resonances become easier and cleaner at higher four-momentum transfers (Q2). Furthermore, the double-pion in comparison to the single-pion channel shows a higher sensitivity to higher excited resonances and a distinctly different Q2 dependence of the background amplitudes. The combined analysis of the single- and double-pion data reduces model dependent uncertainties significantly, which allows us to extract the resonant electrocoupling amplitudes with an unprecedented quality.
Role of diquark correlations and the pion cloud in nucleon elastic form factors
NASA Astrophysics Data System (ADS)
Cloët, Ian C.; Bentz, Wolfgang; Thomas, Anthony W.
2014-10-01
Electromagnetic form factors of the nucleon in the spacelike region are investigated within the framework of a covariant and confining Nambu-Jona-Lasinio model. The bound-state amplitude of the nucleon is obtained as the solution of a relativistic Faddeev equation, where diquark correlations appear naturally as a consequence of the strong coupling in the color 3¯ qq channel. Pion degrees of freedom are included as a perturbation to the "quark-core" contribution obtained using the Poincaré covariant Faddeev amplitude. While no model parameters are fit to form-factor data, excellent agreement is obtained with the empirical nucleon form factors (including the magnetic moments and radii) where pion loop corrections play a critical role for Q2≲1GeV2. Using charge symmetry, the nucleon form factors can be expressed as proton quark sector form factors. The latter are studied in detail, leading, for example, to the conclusion that the d-quark sector of the Dirac form factor is much softer than the u-quark sector, a consequence of the dominance of scalar diquark correlations in the proton wave function. On the other hand, for the proton quark sector Pauli form factors we find that the effect of the pion cloud and axial-vector diquark correlations overcomes the effect of scalar diquark dominance, leading to a larger d-quark anomalous magnetic moment and a form factor in the u-quark sector that is slightly softer than in the d-quark sector.
Alpha-helical hydrophobic polypeptides form proton-selective channels in lipid bilayers
NASA Technical Reports Server (NTRS)
Oliver, A. E.; Deamer, D. W.
1994-01-01
Proton translocation is important in membrane-mediated processes such as ATP-dependent proton pumps, ATP synthesis, bacteriorhodopsin, and cytochrome oxidase function. The fundamental mechanism, however, is poorly understood. To test the theoretical possibility that bundles of hydrophobic alpha-helices could provide a low energy pathway for ion translocation through the lipid bilayer, polyamino acids were incorporated into extruded liposomes and planar lipid membranes, and proton translocation was measured. Liposomes with incorporated long-chain poly-L-alanine or poly-L-leucine were found to have proton permeability coefficients 5 to 7 times greater than control liposomes, whereas short-chain polyamino acids had relatively little effect. Potassium permeability was not increased markedly by any of the polyamino acids tested. Analytical thin layer chromatography measurements of lipid content and a fluorescamine assay for amino acids showed that there were approximately 135 polyleucine or 65 polyalanine molecules associated with each liposome. Fourier transform infrared spectroscopy indicated that a major fraction of the long-chain hydrophobic peptides existed in an alpha-helical conformation. Single-channel recording in both 0.1 N HCl and 0.1 M KCl was also used to determine whether proton-conducting channels formed in planar lipid membranes (phosphatidylcholine/phosphatidylethanolamine, 1:1). Poly-L-leucine and poly-L-alanine in HCl caused a 10- to 30-fold increase in frequency of conductive events compared to that seen in KCl or by the other polyamino acids in either solution. This finding correlates well with the liposome observations in which these two polyamino acids caused the largest increase in membrane proton permeability but had little effect on potassium permeability. Poly-L-leucine was considerably more conductive than poly-L-alanine due primarily to larger event amplitudes and, to a lesser extent, a higher event frequency. Poly-L-leucine caused two
Baryon Transition Form Factors at JLab: Status and Outlook
Ralf Gothe
2009-12-01
The measurements of exclusive single-meson and double-pion electro-production cross sections off the proton to study nucleon resonances will be extended to higher momentum transfers with the CLAS12 detector and the energy upgraded CEBAF beam. Based on new theoretical developments to extract and interpret the electromagnetic transition form factors and on the experience gained from the most recent results, the newly formed collaboration of experimentalists and theorists shall enable us to provide unprecedented high-precision data, high-quality analyses, and state-of-the-art model and QCD based calculations in a Q domain up to 10 GeV{sup 2}. For the first time nucleon resonance structures will be studied at still unexplored distance scales, where the dressed quark contributions are the dominating degrees of freedom and their strong interaction is responsible for the ground and excited nucleon state formation. These studies also open up a promising opportunity to understand the origin of more than 98% of the nucleon mass that is created by strong fields predominantly at these distance scales by dressing the current quarks.
Nucleon Structure and hyperon form factors from lattice QCD
Lin, Huey-Wen
2007-06-11
In this work, I report the latest lattice QCD calculations of nucleon and hyperon structure from chiral fermions in 2+1-flavor dynamical simulations. All calculations are done with a chirally symmetric fermion action, domain-wall fermions, for valence quarks. I begin with the latest lattice results on the nucleon structure, focusing on results from RBC/UKQCD using 2+1-flavor chiral fermion actions. We find the chiral-extrapolated axial coupling constant at physical pion mass point to be 1.23(5), consistant with experimental value. The renormalization constants for the structure functions are obtained from RI/MOM-scheme non-perturbative renormalization. We find first moments of the polarized and unpolarized nucleon structure functions at zero transfer momentum to be 0.133(13) and 0.203(23) respectively, using continuum chiral extrapolation. These are consistent with the experimental values, unlike previous calculations which have been 50% larger. We also have a prediction for the transversity, which we find to be 0.56(4). The twist-3 matrix element is consistent with zero which agrees with the prediction of the Wandzura-Wilczek relation. In the second half of this work, I report an indirect dynamical estimation of the strangeness proton magnetic moments using mixed actions. With the analysis of hyperon form factors and using charge symmetry, the strangeness of proton is found to be -0.066(26), consistent with the Adelaide-JLab Collaboration's result. The hyperon Sigma and Xi axial coupling constants are also performed for the first time in a lattice calculation, g_SigmaSigma = 0.441(14) and g_XiXi = -0.277(11).
Nucleon Structure and Hyperon Form Factors from Lattice QCD.
Lin,H.W.
2007-06-11
In this work, I report the latest lattice QCD calculations of nucleon and hyperon structure from chiral fermions in 2+1-flavor dynamical simulations. All calculations are done with a chirally symmetric fermion action, domain-wall fermions, for valence quarks. I begin with the latest lattice results on the nucleon structure, focusing on results from RBC/UKQCD using 2+1-flavor chiral fermion actions. We find the chiral-extrapolated axial coupling constant at physical pion mass point. to be 1.23(5), consistent with experimental value. The renormalization constants for the structure functions are obtained from RI/MOM-scheme non-perturbative renormalization. We find first moments of the polarized and unpolarized nucleon structure functions at zero transfer momentum to be 0.133(13) and 0.203(23) respectively, using continuum chiral extrapolation. These are consistent with the experimental values, unlike previous calculations which have been 50% larger. We also have a prediction for the transversity, which we find to be 0.56(4). The twist-3 matrix element is consistent with zero which agrees with the prediction of the Wandzura-Wilczek relation. In the second half of this work, I report an indirect dynamical estimation of the strangeness proton magnetic moments using mixed actions. With the analysis of hyperon form factors and using charge symmetry, the strangeness of proton is found to be -0.066(2G), consistent with the Adelaide-JLab Collaboration's result. The hyperon {Sigma} and {Xi} axial coupling constants are also performed for the first time in a lattice calculation, g{sub {Sigma}{Sigma}} = 0.441(14) and g{sub {Xi}{Xi}} = -0.277(11).
Optimized perturbation theory: the pion form factor
Gupta, R.
1981-10-01
The order ..cap alpha../sup 2//sub s/(Q/sup 2/) corrections to the pion form-factor F/sub ..pi../(Q/sup 2/) are calculated using perturbative QCD and dimensional regularization. The result is compared in the MS and MOM subtraction schemes and plotted as a function of Q/sup 2//Q/sup 2/ where Q is the subtraction point. There is a large dependence on the scheme, the definition of the running coupling constant ..cap alpha../sub s/(Q/sup 2/) and the subtraction point Q. We find it best to invert the ..beta..-function equation for the definition of ..cap alpha../sub s/ rather than make an expansion in powers of log(Q/sup 2//..lambda../sup 2/). We study two methods to optimize the result with respect to Q: Stevenson's prescription and putting the 0(..cap alpha../sup 2//sub s/) term to zero. Both methods give almost the same value for Q/sup 2/F/sub ..pi../ and this value is scheme independent.
Fluorescence characteristics of protonated form of 6-hydroxyquinoline in Nafion® film
NASA Astrophysics Data System (ADS)
Mehata, M. S.; Joshi, H. C.; Tripathi, H. B.
2003-02-01
Fluorescence characteristics of 6-hydroxyquinoline (6-HQ) have been studied at room temperature in Nafion® film by steady state and nano-second time-resolved fluorescence spectroscopy. The fluorescence spectrum exhibits single emission band corresponding to the protonated form of 6-HQ in this matrix. However, the decay fits with two or three exponential functions depending on the emission wavelength monitored. At blue edge of the emission, the decay fits to three-exponential function, whereas at longer wavelengths, the decay fits to bi-exponential function. Two tentative mechanisms have been proposed to explain the experimental data, viz. a closely lying charge transfer state (CT) or an excited state proton transfer (ESPT) process. The photophysical parameters appear to be sensitive to the change in microstructure due to swelling of the membrane by the solvents.
Neutron-Proton Asymmetry Dependence of Spectroscopic Factors in Ar Isotopes
Lee, Jenny; Tsang, Betty; Shapira, Dan
2010-01-01
Spectroscopic factors have been extracted for proton-rich 34Ar and neutron-rich 46Ar using the (p, d) neutron transfer reaction. The experimental results show little reduction of the ground state neutron spectroscopic factor of the proton-rich nucleus 34Ar compared to that of 46Ar. The results suggest that correlations, which generally reduce such spectroscopic factors, do not depend strongly on the neutron-proton asymmetry of the nucleus in this isotopic region as was reported in knockout reactions. The present results are consistent with results from systematic studies of transfer reactions but inconsistent with the trends observed in knockout reaction measurements.
Neutron-Proton Asymmetry Dependence of Spectroscopic Factors in Ar Isotopes
NASA Astrophysics Data System (ADS)
Lee, Jenny; Tsang, M. B.; Bazin, D.; Coupland, D.; Henzl, V.; Henzlova, D.; Kilburn, M.; Lynch, W. G.; Rogers, A. M.; Sanetullaev, A.; Signoracci, A.; Sun, Z. Y.; Youngs, M.; Chae, K. Y.; Charity, R. J.; Cheung, H. K.; Famiano, M.; Hudan, S.; O'Malley, P.; Peters, W. A.; Schmitt, K.; Shapira, D.; Sobotka, L. G.
2010-03-01
Spectroscopic factors have been extracted for proton-rich Ar34 and neutron-rich Ar46 using the (p, d) neutron transfer reaction. The experimental results show little reduction of the ground state neutron spectroscopic factor of the proton-rich nucleus Ar34 compared to that of Ar46. The results suggest that correlations, which generally reduce such spectroscopic factors, do not depend strongly on the neutron-proton asymmetry of the nucleus in this isotopic region as was reported in knockout reactions. The present results are consistent with results from systematic studies of transfer reactions but inconsistent with the trends observed in knockout reaction measurements.
Calculation of neutral weak nucleon form factors with the AdS/QCD correspondence
NASA Astrophysics Data System (ADS)
Lohmann, Mark
The AdS/QCD (Anti-de Sitter/Quantum Chromodynamics) is a mathematical formalism applied to a theory based on the original AdS/CFT (Anti-de Sitter/ Conformal Field Theory) correspondence. The aim is to describe properties of the strong force in an essentially non-perturbative way. AdS/QCD theories break the conformal symmetry of the AdS metric (a sacrifice) to arrive at a boundary theory which is QCD-like (a payoff). This correspondence has been used to calculate well-known quantities in nucleon spectra and structure like Regge trajectories, form factors, and many others within an error of less than 20% from experiment. This is impressive considering that ordinary perturbation theory in QCD applied to the strongly interacting domain usually obtains an error of about 30%. In this thesis, the AdS/QCD correspondence method of light-front holography established by Brodsky and de Teramond is used in an attempt to calculate the Dirac and Pauli neutral weak form factors, FZ1 (Q2) and FZ2 (Q 2) respectively, for both the proton and the neutron. With this approach, we were able to determine the neutral weak Dirac form factor for both nucleons and the Pauli form factor for the proton, while the method did not succeed at determining the neutral weak Pauli form factor for the neutron. With these we were also able to extract the proton's strange electric and magnetic form factor, which addresses important questions in nucleon sub-structure that are currently being investigated through experiments at the Thomas Jefferson National Accelerator Facility.
Nucleon form factors to next-to-leading order with light-cone sum rules
Passek-Kumericki, K.; Peters, G.
2008-08-01
We have calculated the leading-twist next-to-leading order (NLO), i.e., O({alpha}{sub s}), correction to the light-cone sum rules prediction for the electromagnetic form factors of the nucleon. We have used the Ioffe nucleon interpolation current and worked in M{sub N}=0 approximation, with M{sub N} being the mass of the nucleon. In this approximation, only the Pauli form factor F{sub 2} receives a correction and the calculated correction is quite sizable (ca. 60%). The numerical results for the proton form factors show the improved agreement with the experimental data. We also discuss the problems encountered when going away from M{sub N}=0 approximation at NLO, as well as gauge invariance of the perturbative results. This work presents the first step towards the NLO accuracy in the light-cone sum rules for baryon form factors.
Proton tissue dose for the blood forming organ in human geometry: Isotropic radiation
NASA Technical Reports Server (NTRS)
Khandelwal, G. S.; Wilson, J. W.
1974-01-01
A computer program is described which calculates doses averaged within five major segments of the blood forming organ in the human body taking into account selfshielding of the detailed body geometry and nuclear star effects for proton radiation of arbitrary energy spectrum (energy less than 1 GeV) and isotropic angular distribution. The dose calculation includes the first term of an asymptotic series expansion of transport theory which is known to converge rapidly for most points in the human body. The result is always a conservative estimate of dose and is given as physical dose (rad) and dose equivalent (rem).
Structure of olefin-imidacloprid and gas-phase fragmentation chemistry of its protonated form.
Fusetto, Roberto; White, Jonathan M; Hutton, Craig A; O'Hair, Richard A J
2016-02-01
One of the major insect metabolites of the widely used neonicotinoid insecticide imidacloprid, 1 (1-[(6-chloro-3-pyridinyl)methyl]-N-nitro-1H-imidazol-2-amine), is the olefin 2. To better understand how the structure of olefin 2 relates to the gas-phase fragmentation of its protonated form, 2H(+), X-ray crystallography, tandem mass spectrometry experiments and DFT calculations were carried out. Olefin 2 was found to be in a tautomeric form where the proton is on the N(1) position of the imidazole ring and forms a hydrogen bond to one of the oxygen atoms of the coplanar nitroamine group. Under conditions of low-energy collision-induced dissociation (CID) in a linear ion trap, 2H(+), formed via electrospray ionization (ESI), fragments via a major loss of water, together with minor competing losses of HNO2 and NO2•.This contrasts with 1H+, which mainly undergoes bond homolysis via NO2• loss. Thus, installation of the double bond in 2 plays a key role in facilitating the loss of water. DFT calculations, carried out using the B3LYP/6-311G++(d,p) level of theory, revealed that loss of water was energetically more favourable compared to HNO2 and NO2• loss. Three multistep, energetically accessible mechanisms were identified for loss of water from 2H(+), and these have the following barriers: (I) direct proton transfer from N(5) of the pyridine to O(1) on the NO2 group (119 kJ mol(-1)); (II) rotation of the N(2)-N(4) bond (117 kJ mol(-1)); (III) 1,3-intramolecular proton transfer between the two oxygen atoms of the NO2 group (145 kJ mol(-1)). Given that the lowest barrier for the losses of HNO2 and NO2• is 156 kJ mol(-1), it is likely that all three water loss mechanisms occur concurrently. PMID:26726997
Benmensour, Mohamed Ali; Djennane-Bousmaha, Sema; Boucekkine, Abdou
2014-07-01
A theoretical study of the sulfur cumulenes SCnS (n = 3-8), CnS ( n = 1-8) and of their protonated forms (SCnS)H(+) and (CnS)H(+) that might exist in the interstellar environment, has been carried out by means of the standard B3LYP/6-311G** method. The geometries and relative energies of singlet and triplet states according to the number of carbons have been computed. Like neutral species, we have found that the ground state of the most stable protonated forms (SC(CH)Cn-2S)(+) and ((HC)Cn-1S)(+), alternates between a triplet state for the even series and a singlet state for the odd series. We provided the data needed to simulate infrared and microwave spectra (vibration frequencies, dipole moments, and rotational constants) for each protonated species (SCnS)H(+) and (CnS)H(+) and for each neutral CnS species. The computing of dissociation energies of the most stable protonated forms (SC(CH)Cn-2S)(+) (n = 3-8) has shown that the lowest values are obtained for the dissociation of compounds with an even number of carbons, in their triplet state, which produce the observed fragments CS and C3S. The dissociation of even protonated forms requires less energy than for the odd protonated forms. PMID:24935110
Neutrons in proton pencil beam scanning: parameterization of energy, quality factors and RBE.
Schneider, Uwe; Hälg, Roger A; Baiocco, Giorgio; Lomax, Tony
2016-08-21
The biological effectiveness of neutrons produced during proton therapy in inducing cancer is unknown, but potentially large. In particular, since neutron biological effectiveness is energy dependent, it is necessary to estimate, besides the dose, also the energy spectra, in order to obtain quantities which could be a measure of the biological effectiveness and test current models and new approaches against epidemiological studies on cancer induction after proton therapy. For patients treated with proton pencil beam scanning, this work aims to predict the spatially localized neutron energies, the effective quality factor, the weighting factor according to ICRP, and two RBE values, the first obtained from the saturation corrected dose mean lineal energy and the second from DSB cluster induction. A proton pencil beam was Monte Carlo simulated using GEANT. Based on the simulated neutron spectra for three different proton beam energies a parameterization of energy, quality factors and RBE was calculated. The pencil beam algorithm used for treatment planning at PSI has been extended using the developed parameterizations in order to calculate the spatially localized neutron energy, quality factors and RBE for each treated patient. The parameterization represents the simple quantification of neutron energy in two energy bins and the quality factors and RBE with a satisfying precision up to 85 cm away from the proton pencil beam when compared to the results based on 3D Monte Carlo simulations. The root mean square error of the energy estimate between Monte Carlo simulation based results and the parameterization is 3.9%. For the quality factors and RBE estimates it is smaller than 0.9%. The model was successfully integrated into the PSI treatment planning system. It was found that the parameterizations for neutron energy, quality factors and RBE were independent of proton energy in the investigated energy range of interest for proton therapy. The pencil beam algorithm has
Neutrons in proton pencil beam scanning: parameterization of energy, quality factors and RBE
NASA Astrophysics Data System (ADS)
Schneider, Uwe; Hälg, Roger A.; Baiocco, Giorgio; Lomax, Tony
2016-08-01
The biological effectiveness of neutrons produced during proton therapy in inducing cancer is unknown, but potentially large. In particular, since neutron biological effectiveness is energy dependent, it is necessary to estimate, besides the dose, also the energy spectra, in order to obtain quantities which could be a measure of the biological effectiveness and test current models and new approaches against epidemiological studies on cancer induction after proton therapy. For patients treated with proton pencil beam scanning, this work aims to predict the spatially localized neutron energies, the effective quality factor, the weighting factor according to ICRP, and two RBE values, the first obtained from the saturation corrected dose mean lineal energy and the second from DSB cluster induction. A proton pencil beam was Monte Carlo simulated using GEANT. Based on the simulated neutron spectra for three different proton beam energies a parameterization of energy, quality factors and RBE was calculated. The pencil beam algorithm used for treatment planning at PSI has been extended using the developed parameterizations in order to calculate the spatially localized neutron energy, quality factors and RBE for each treated patient. The parameterization represents the simple quantification of neutron energy in two energy bins and the quality factors and RBE with a satisfying precision up to 85 cm away from the proton pencil beam when compared to the results based on 3D Monte Carlo simulations. The root mean square error of the energy estimate between Monte Carlo simulation based results and the parameterization is 3.9%. For the quality factors and RBE estimates it is smaller than 0.9%. The model was successfully integrated into the PSI treatment planning system. It was found that the parameterizations for neutron energy, quality factors and RBE were independent of proton energy in the investigated energy range of interest for proton therapy. The pencil beam algorithm has
Virtuality Distributions and Pion Transition Form Factor
Radyushkin, Anatoly V.
2015-03-01
Using the example of hard exclusive transition process γ*γ → π0 at the handbag level, we outline basics of a new approach to transverse momentum dependence in hard processes. In coordinate representation, matrix elements of operators (in the simplest case, bilocal O(0,z)) describing a hadron with momentum p, are functions of (pz) and z2 parametrized through virtuality distribution amplitudes (VDA) Φ(x, σ), with x being Fourier-conjugate to (pz) and σ Laplace-conjugate to z2. For intervals with z+=0, we introduce the transverse momentum distribution amplitude (TMDA) Ψ(x, k_perp), and write it in terms of VDA Φ(x,σ). We propose models for softmore » VDAs/TMDAs, and use them for comparison of handbag results with experimental (BaBar and BELLE) data. We also discuss the generation of hard tails of TMDAs from initially soft forms.« less
Virtuality Distributions and Pion Transition Form Factor
NASA Astrophysics Data System (ADS)
Radyushkin, A. V.
2015-02-01
Using the example of hard exclusive transition process γ*γ → π0 at the handbag level, we outline basics of a new approach to transverse momentum dependence in hard processes. In coordinate representation, matrix elements of operators (in the simplest case, bilocal 𝒪(0, z)) describing a hadron with momentum p, are functions of (pz) and z2 parametrized through virtuality distribution amplitudes (VDA) Φ(x, σ), with x being Fourier-conjugate to (pz) and σ Laplace-conjugate to z2. For intervals with z+ = 0, we introduce the transverse momentum distribution amplitude (TMDA) Ψ(x, k⊥), and write it in terms of VDA Φ(x, σ). We propose models for soft VDAs/TMDAs, and use them for comparison of handbag results with experimental (BaBar and BELLE) data. We also discuss the generation of hard tails of TMDAs from initially soft forms.
Molecular mobility of imidazoles in molten state as a key factor to enhance proton conductivity
NASA Astrophysics Data System (ADS)
Jarumaneeroj, Chatchai; Tashiro, Kohji; Chirachanchai, Suwabun
2014-03-01
A systematic study on alkyl urocanates related to the proton conductivity performances to clarify the role of molecular mobility and hydrogen bond in proton transfer is carried out. Depending on the methylene units, the melting (Tm) and degradation temperatures (Td) change remarkably. When methylene unit is four, C4U shows the lowest melting point (as low as 46 °C) and this suggests the favorable molecular mobility in the molten state. The short hydrogen bond distance and the short T1 relaxation time lead to a scheme of proton conductivity of C4U to be under a regular imidazole arrangement with highly active alkyl chain molecular motion. When C4U is in molten state, the proton transfer is under vehicle mechanism clarified by Volgel-Tammann-Fulcher (VTF) equation. By applying C4U as a proton conductive additive in a sulfonated poly(ether ether ketone) (SPEEK) membrane without any acid dopants, the proton conductivity in the heating process up to 170 °C continuously increases to be ∼104 times higher than that of the neat SPEEK. The present work not only demonstrates the thermal mobility as a key factor to govern the proton conductivity but also proposes the effective proton transfer of heterocyclic compounds based on the molten state.
Virtuality Distributions and Pion Transition Form Factor
Radyushkin, Anatoly V.
2015-03-01
Using the example of hard exclusive transition process γ*γ → π^{0} at the handbag level, we outline basics of a new approach to transverse momentum dependence in hard processes. In coordinate representation, matrix elements of operators (in the simplest case, bilocal O(0,z)) describing a hadron with momentum p, are functions of (pz) and z^{2} parametrized through virtuality distribution amplitudes (VDA) Φ(x, σ), with x being Fourier-conjugate to (pz) and σ Laplace-conjugate to z^{2}. For intervals with z^{+}=0, we introduce the transverse momentum distribution amplitude (TMDA) Ψ(x, k_perp), and write it in terms of VDA Φ(x,σ). We propose models for soft VDAs/TMDAs, and use them for comparison of handbag results with experimental (BaBar and BELLE) data. We also discuss the generation of hard tails of TMDAs from initially soft forms.
Factor Structure of the Personality Research Form-E: A Maximum Likelihood Analysis.
ERIC Educational Resources Information Center
Fowler, Patrick C.
1985-01-01
Presents a five-factor, structural model of the Personality Research Form-E for 140 university undergraduates. All factors demonstrated an excellent level of similarity to those previously reported for other forms of the PRF, as well as to the conceptual scheme developed by Jackson (1974). (Author/JAC)
Studies of Nucleon Form Factors with 12 GeV CEBAF and SuperBigBite
Hansen, Jens-Ole
2012-04-01
The elastic electromagnetic form factors are among the most fundamental quantities that describe the ground-state structure of the proton and neutron. Precision data of the form factors over a wide kinematical range provide a powerful test of current theories of hadron structure. A number of experiments aiming to measure the electric and magnetic elastic form factors of the neutron, G{sub E}{sup n} and G{sub M}{sup n}, and proton, G{sub E}{sup p}, at very high momentum transfer, up to the range of Q{sup 2} = 10-14 (GeV/c){sup 2}, are planned to be carried out with the future 11 GeV electron beam of the upgraded CEBAF at Jefferson Lab. These experiments will determine the nucleon form factors with unprecedented precision to Q{sup 2}-values up to three times higher than those of existing data. We review the approved proposals and the conceptual design of a new spectrometer, SuperBigBite, that will be used in these and other future experiments at Jefferson Lab.
Conformal symmetry and pion form factor: Space- and timelike region
Choi, Ho-Meoyng; Ji, Chueng-Ryong
2008-06-01
We extend a recent analysis of the pion electromagnetic form factor constrained by the conformal symmetry to explore the timelike region. We show explicitly that the timelike form factor obtained by the analytic continuation of the spacelike form factor correctly satisfies the dispersion relation. Our results indicate that the quark spin and dynamical mass effects are crucial to yield the realistic features of the vector meson dominance phenomena.
HERMES impact for the access of Compton form factors
NASA Astrophysics Data System (ADS)
Kumerički, K.; Müller, D.; Murray, M.
2014-07-01
We utilize the DVCS asymmetry measurements of the HERMES collaboration for access to Compton form factors in the deeply virtual regime and to generalized parton distributions. In particular, the (almost) complete measurement of DVCS observables allows us to map various asymmetries into the space of Compton form factors, where we still rely in this analysis on dominance of twist-two associated Compton form factors. We compare this one-to-one map with local Compton form factor fits and a model dependent global fit.
Analytical evaluation of atomic form factors: Application to Rayleigh scattering
Safari, L.; Santos, J. P.; Amaro, P.; Jänkälä, K.; Fratini, F.
2015-05-15
Atomic form factors are widely used for the characterization of targets and specimens, from crystallography to biology. By using recent mathematical results, here we derive an analytical expression for the atomic form factor within the independent particle model constructed from nonrelativistic screened hydrogenic wave functions. The range of validity of this analytical expression is checked by comparing the analytically obtained form factors with the ones obtained within the Hartee-Fock method. As an example, we apply our analytical expression for the atomic form factor to evaluate the differential cross section for Rayleigh scattering off neutral atoms.
Schnier, P D; Gross, D S; Williams, E R
1995-11-01
A relatively simple model for calculation of the energetics of gas-phase proton transfer reactions and the maximum charge state of multiply protonated ions formed by electrospray ionization is presented. This model is based on estimates of the intrinsic proton transfer reactivity of sites of protonation and point charge Coulomb interactions. From this model, apparent gas-phase basicities (GB(app)) of multiply protonated ions are calculated. Comparison of this value to the gas-phase basicity of the solvent from which an ion is formed enables a maximum charge state to be calculated. For 13 commonly electrosprayed proteins, our calculated maximum charge states are within an average of 6% of the experimental values reported in the literature. This indicates that the maximum charge state for proteins is determined by their gas-phase reactivity. Similar results are observed for peptides with many basic residues. For peptides with few basic residues, we find that the maximum charge state is better correlated to the charge state in solution. For low charge state ions, we find that the most basic sites Arg, Lys, and His are preferentially protonated. A significant fraction of the less basic residues Pro, Trp, and Gln are protonated in high charge state ions. The calculated GB(app) of individual protonation sites varies dramatically in the high charge state ions. From these values, we calculate a reduced cross section for proton transfer reactivity that is significantly lower than the Langevin collision frequency when the GB(app) of the ion is approximately equal to the GB of the neutral base. PMID:24214055
Nucleon Form Factors experiments with 12 GeV CEBAF
Wojtsekhowski, B.
2008-10-13
A number of precision form factor experiments at high momentum transfer will be performed with the 11 GeV electron beam of CEBAF. We review the approved proposals and the conceptual schemes of several new suggestions. Form factor data will serve as a major input for the construction of a tomographic image of the nucleon.
Form factors in SU(3)-invariant integrable models
NASA Astrophysics Data System (ADS)
Belliard, S.; Pakuliak, S.; Ragoucy, E.; Slavnov, N. A.
2013-04-01
We study SU(3)-invariant integrable models solvable by a nested algebraic Bethe ansatz. We obtain determinant representations for form factors of diagonal entries of the monodromy matrix. This representation can be used for the calculation of form factors and correlation functions of the XXX SU(3)-invariant Heisenberg chain.
X-Ray Form Factor, Attenuation and Scattering Tables
National Institute of Standards and Technology Data Gateway
SRD 66 X-Ray Form Factor, Attenuation and Scattering Tables (Web, free access) This database collects tables and graphs of the form factors, the photoabsorption cross section, and the total attenuation coefficient for any element (Z <= 92).
Factors Influencing Students' Achievement in Form 5 Islamic Studies Subject
ERIC Educational Resources Information Center
bin Che Noh, Mohd Aderi; Omar, Noraini binti; bin Kasan, Hasnan
2013-01-01
This study is aimed at analyzing the factors influencing the achievements of students in the subject of Islamic Studies for Form 5 SPM (KBSM) in schools in the area of Samarahan, Sarawak. The factors analysed is attitude and interest. This is a survey based study and data was compiled from the survey forms which had the topic "Factors…
Orthopositronium decay form factors and two-photon correlations
Adkins, Gregory S.; Droz, Daniel R.; Rastawicki, Dominik; Fell, Richard N.
2010-04-15
We give results for the orthopositronium decay form factors through one-loop order. We use the form factors to calculate momentum correlations of the final-state photons
Relativistic quark model for the Omega- electromagnetic form factors
G. Ramalho, K. Tsushima, Franz Gross
2009-08-01
We compute the Omega- electromagnetic form factors and the decuplet baryon magnetic moments using a quark model application of the Covariant Spectator Theory. Our predictions for the Omega- electromagnetic form factors can be tested in the future by lattice QCD simulations at the physical strange quark mass.
In-flight calibration of NOAA POES proton detectors—Derivation of the MEPED correction factors
NASA Astrophysics Data System (ADS)
Sandanger, Marit Irene; Ødegaard, Linn-Kristine Glesnes; Nesse Tyssøy, Hilde; Stadsnes, Johan; Søraas, Finn; Oksavik, Kjellmar; Aarsnes, Kjell
2015-11-01
The MEPED instruments on board the NOAA POES and MetOp satellites have been continuously measuring energetic particles in the magnetosphere since 1978. However, degradation of the proton detectors over time leads to an increase in the energy thresholds of the instrument and imposes great challenges to studies of long-term variability in the near-Earth space environment as well as a general quantification of the proton fluxes. By comparing monthly mean accumulated integral flux from a new and an old satellite at the same magnetic local time (MLT) and time period, we estimate the change in energy thresholds. The first 12 monthly energy spectra of the new satellite are used as a reference, and the derived monthly correction factors over a year for an old satellite show a small spread, indicating a robust calibration procedure. The method enables us to determine for the first time the correction factors also for the highest-energy channels of the proton detector. In addition, we make use of the newest satellite in orbit (MetOp-01) to find correction factors for 2013 for the NOAA 17 and MetOp-02 satellites. Without taking into account the level of degradation, the proton data from one satellite cannot be used quantitatively for more than 2 to 3 years after launch. As the electron detectors are vulnerable to contamination from energetic protons, the corrected proton measurements will be of value for electron flux measurements too. Thus, the correction factors ensure the correctness of both the proton and electron measurements.
NASA Astrophysics Data System (ADS)
Nymmik, Rikho; Pervaia, Taisia
2016-07-01
Experimental data on the fluxes of protons of solar energetic particles (SEP) are analyzed. It is known that above energies of 2-45 MeV (averaging 27-30 MeV), the proton spectra are a power-law function of the energy (at relativistic energies - from the momentum) of the particles. At lower energies, the spectra become harder, with the high-energy part of the spectra forming the "knee". This report is devoted to the determination of the parameters of the SEP spectra, having the form of a "double power-law shape", to ascertain the reliability of the parameters of the approximations of the experimental data.
Proton beam shaped by "particle lens" formed by laser-driven hot electrons
NASA Astrophysics Data System (ADS)
Zhai, S. H.; Shen, B. F.; Wang, W. P.; Zhang, H.; He, S. K.; Lu, F.; Zhang, F. Q.; Deng, Z. G.; Dong, K. G.; Wang, S. Y.; Zhou, K. N.; Xie, N.; Wang, X. D.; Zhang, L. G.; Huang, S.; Liu, H. J.; Zhao, Z. Q.; Gu, Y. Q.; Zhang, B. H.; Xu, Z. Z.
2016-05-01
Two-dimensional tailoring of a proton beam is realized by a "particle lens" in our experiment. A large quantity of electrons, generated by an intense femtosecond laser irradiating a polymer target, produces an electric field strong enough to change the trajectory and distribution of energetic protons flying through the electron area. The experiment shows that a strip pattern of the proton beam appears when hot electrons initially converge inside the plastic plate. Then the shape of the proton beam changes to a "fountain-like" pattern when these hot electrons diffuse after propagating a distance.
ERIC Educational Resources Information Center
bin Pet, Mokhtar; Sihes, Ahmad Johari Hj
2015-01-01
This study aims to examine the external factors of form six teachers who can influence thinking domain form six teachers in their teaching. This study was conducted using a quantitative approach using questionnaires. A total of 300 form six teacher schools in Johor were chosen as respondents. The findings were obtained as student background…
Roaming form factors for the tricritical to critical Ising flow
NASA Astrophysics Data System (ADS)
Horváth, D. X.; Dorey, P. E.; Takács, G.
2016-07-01
We study the massless flows described by the staircase model introduced by Al.B. Zamolodchikov through the analytic continuation of the sinh-Gordon S-matrix, focusing on the renormalisation group flow from the tricritical to the critical Ising model. We show that the properly defined roaming limits of certain sinh-Gordon form factors are identical to the form factors of the order and disorder operators for the massless flow. As a by-product, we also construct form factors for a semi-local field in the sinh-Gordon model, which can be associated with the twist field in the ultraviolet limiting free massless bosonic theory.
Low-energy expansion of meson form factors
NASA Astrophysics Data System (ADS)
Gasser, J.; Leutwyler, H.
We calculate the corrections to various low-energy theorems concerning the behaviour of the pseudoscalar meson form factors near t=0. In particular we discuss (i) the Ademollo-Gatto theorem, (ii) Sirlin's relation between the Kl3 form factor ƒ +Kπ (t) and the electromagnetic form factors, (iii) the Callan-Treiman relation, and (iv) the Dashen-Weinstein relation, which connects the slope λ0 of ƒ 0Kπ (t) with the ratio FK/ Fπ. Furthermore, we point out a remarkable isospin breaking effect which is clearly visible in the experimental rates of the decays K +→ π0e +ν, K 0→ π-e +ν.
Longitudinal vector form factors in weak decays of nuclei
Šimkovic, F.; Kovalenko, S.; Krivoruchenko, M. I.
2015-10-28
The longitudinal form factors of the weak vector current of particles with spin J = 1/2 and isospin I = 1/2 are determined by the mass difference and the charge radii of members of the isotopic doublets. The most promising reactions to measure these form factors are the reactions with large momentum transfers involving the spin-1/2 isotopic doublets with a maximum mass splitting. Numerical estimates of longitudinal form factors are given for nucleons and eight nuclear spin-1/2 isotopic doublets.
Exploring strange nucleon form factors on the lattice
NASA Astrophysics Data System (ADS)
Babich, Ronald; Brower, Richard C.; Clark, Michael A.; Fleming, George T.; Osborn, James C.; Rebbi, Claudio; Schaich, David
2012-03-01
We discuss techniques for evaluating sea quark contributions to hadronic form factors on the lattice and apply these to an exploratory calculation of the strange electromagnetic, axial, and scalar form factors of the nucleon. We employ the Wilson gauge and fermion actions on an anisotropic 243×64 lattice, probing a range of momentum transfer with Q2<1GeV2. The strange electric and magnetic form factors, GEs(Q2) and GMs(Q2), are found to be small and consistent with zero within the statistics of our calculation. The lattice data favor a small negative value for the strange axial form factor GAs(Q2) and exhibit a strong signal for the bare strange scalar matrix element ⟨N|s¯s|N⟩0. We discuss the unique systematic uncertainties affecting the latter quantity relative to the continuum, as well as prospects for improving future determinations with Wilson-like fermions.
Personality Research Form: Factor Structure and Response Style Involvement
ERIC Educational Resources Information Center
Stricker, Lawrence J.
1974-01-01
Explores factor structure of the Personality Research Form (PRF) and examines the inventory's relations with response styles. In general, the PRF content scales correlate moderately with each other and with measures of acquiescence, social desirability, and defensiveness response biases. (Author)
Normalization Of Thermal-Radiation Form-Factor Matrix
NASA Technical Reports Server (NTRS)
Tsuyuki, Glenn T.
1994-01-01
Report describes algorithm that adjusts form-factor matrix in TRASYS computer program, which calculates intraspacecraft radiative interchange among various surfaces and environmental heat loading from sources such as sun.
Hadronic Form Factors in Asymptotically Free Field Theories
DOE R&D Accomplishments Database
Gross, D. J.; Treiman, S. B.
1974-01-01
The breakdown of Bjorken scaling in asymptotically free gauge theories of the strong interactions is explored for its implications on the large q{sup 2} behavior of nucleon form factors. Duality arguments of Bloom and Gilman suggest a connection between the form factors and the threshold properties of the deep inelastic structure functions. The latter are addressed directly in an analysis of asymptotically free theories; and through the duality connection we are then led to statements about the form factors. For very large q{sup 2} the form factors are predicted to fall faster than any inverse power of q{sup 2}. For the more modest range of q{sup 2} reached in existing experiments the agreement with data is fairly good, though this may well be fortuitous. Extrapolations beyond this range are presented.
Vector Meson Form Factors and Wave Functions from Holographic QCD
Hovhannes Grigoryan; Anatoly Radyushkin
2007-10-10
Based on the holographic dual model of QCD, we study 2- and 3-point functions of vector currents and derive form factors as well as wave functions for the vector mesons. As a result, generalized vector-meson dominance representation for form factors is obtained with a very specific VMD pattern. The calculated electric radius of the rho-meson is shown to be in a good agreement with predictions from lattice QCD.
From quarks and gluons to baryon form factors
Eichmann, Gernot
2012-01-01
I briefly summarize recent results for nucleon and Δ(1232) electromagnetic, axial and transition form factors in the Dyson–Schwinger approach. The calculation of the current diagrams from the quark–gluon level enables a transparent discussion of common features such as: the implications of dynamical chiral symmetry breaking and quark orbital angular momentum, the timelike structure of the form factors, and their interpretation in terms of missing pion-cloud effects. PMID:26766879
In-medium modified energy-momentum tensor form factors
NASA Astrophysics Data System (ADS)
Jung, Ju-Hyun; Yakhshiev, Ulugbek; Kim, Hyun-Chul
2014-04-01
In this talk, we report a recent investigation on the energy-momentum tensor form factors of the nucleon in nuclear medium, based on the framework of the in-medium modified chiral soliton model. The model was constructed by taking into account the influence of the surrounding environment to the mesonic sector (π-, ρ- and ω-meson properties). We briefly discuss the results of the energy-momentum tensor form factors.
Breather boundary form factors in sine-Gordon theory
NASA Astrophysics Data System (ADS)
Lencsés, M.; Takács, G.
2011-11-01
A previously conjectured set of exact form factors of boundary exponential operators in the sinh-Gordon model is tested against numerical results from boundary truncated conformal space approach in boundary sine-Gordon theory, related by analytic continuation to sinh-Gordon model. We find that the numerical data strongly support the validity of the form factors themselves; however, we also report a discrepancy in the case of diagonal matrix elements, which remains unresolved for the time being.
Deuteron form factor measurements at low momentum transfers
NASA Astrophysics Data System (ADS)
Schlimme, B. S.; Achenbach, P.; Beričič, J.; Böhm, R.; Bosnar, D.; Correa, L.; Distler, M. O.; Esser, A.; Fonvieille, H.; Friščić, I.; Griffioen, K. A.; Huan, Y.; Kegel, S.; Kohl, Y.; Merkel, H.; Mihovilovič, M.; Müller, J.; Müller, U.; Pochodzalla, J.; Schoth, M.; Schulz, F.; Sfienti, C.; Širca, S.; Štajner, S.; Thiel, M.; Weber, A.
2016-03-01
A precise measurement of the elastic electron-deuteron scattering cross section at four-momentum transfers of 0.24 fm-1 ≤ Q ≤ 2.7 fm-1 has been performed at the Mainz Microtron. In this paper we describe the utilized experimental setup and the necessary analysis procedure to precisely determine the deuteron charge form factor from these data. Finally, the deuteron charge radius rd can be extracted from an extrapolation of that form factor to Q2 = 0.
On Gravitational Form Factors and Transverse Spin Sum Rule
NASA Astrophysics Data System (ADS)
Chakrabarti, D.; Mondal, C.; Mukherjee, A.
2016-06-01
Using the light front wave functions of the scalar quark-diquark model for nucleon predicted by the soft-wall AdS/QCD, we calculate the flavor dependent gravitational form factors. We evaluate the matrix element of Pauli-Lubanski operator in this model and show that the intrinsic spin sum rule involves the higher twist form factor {bar{C}}. The longitudinal momentum densities in the transverse impact parameter space are also discussed for both unpolarized and transversely polarized nucleons.
Charm and bottom hadronic form factors with QCD sum rules
Bracco, M. E.; Rodrigues, B. O.; Cerqueira, A. Jr.
2013-03-25
We present a brief review of some calculations of form factors and coupling constants in vertices with charm and bottom mesons in the framework of QCD sum rules. We first discuss the motivation for this work, describing possible applications of these form factors to charm and bottom decays processes. We first make a summarize of the QCD sum rules method. We give special attention to the uncertainties of the method introducing by the intrinsic variation of the parameters. Finally we conclude.
Online Soil Science Lesson 3: Soil Forming Factors
Technology Transfer Automated Retrieval System (TEKTRAN)
This lesson explores the five major factors of soil formation, namely: 1) climate; 2) organisms; 3) time; 4) topography; and 5) parent material and their influence in forming soil. The distinction between active and passive factors, moisture and temperature regimes, organism and topographic influen...
The roles of STOP1-like transcription factors in aluminum and proton tolerance
Fan, Wei; Lou, He Qiang; Yang, Jian Li; Zheng, Shao Jian
2016-01-01
ABSTRACT Aluminum (Al) and proton (H+) are 2 coexisting rhizotoxicities limiting plant growth in acid soils. Sensitive to Proton Rhizotoxicity (STOP) 1-like zinc finger transcription factors play important roles in regulating expression of downstream genes involved in tolerance mechanism of either stress. In this mini-review, we summarized recent advances in characterizing STOP1-like proteins with respect to plant Al and H+ tolerance. The possible involvement of structure-function of STOP1-like proteins in differential regulation of Al and H+ tolerance are discussed. In addition, we also direct research in this area to protein phosphorylation. PMID:26689896
The roles of STOP1-like transcription factors in aluminum and proton tolerance.
Fan, Wei; Lou, He Qiang; Yang, Jian Li; Zheng, Shao Jian
2016-02-01
Aluminum (Al) and proton (H(+)) are 2 coexisting rhizotoxicities limiting plant growth in acid soils. Sensitive to Proton Rhizotoxicity (STOP) 1-like zinc finger transcription factors play important roles in regulating expression of downstream genes involved in tolerance mechanism of either stress. In this mini-review, we summarized recent advances in characterizing STOP1-like proteins with respect to plant Al and H(+) tolerance. The possible involvement of structure-function of STOP1-like proteins in differential regulation of Al and H(+) tolerance are discussed. In addition, we also direct research in this area to protein phosphorylation. PMID:26689896
High-precision calculation of the strange nucleon electromagnetic form factors
Green, Jeremy; Meinel, Stefan; Engelhardt, Michael G.; Krieg, Stefan; Laeuchli, Jesse; Negele, John W.; Orginos, Kostas; Pochinsky, Andrew; Syritsyn, Sergey
2015-08-26
We report a direct lattice QCD calculation of the strange nucleon electromagnetic form factors G^{s}_{E} and G^{s}_{M} in the kinematic range 0 ≤ Q^{2} ≤ 1.2GeV^{2}. For the first time, both G^{s}_{E} and G^{s}_{M} are shown to be nonzero with high significance. This work uses closer-to-physical lattice parameters than previous calculations, and achieves an unprecented statistical precision by implementing a recently proposed variance reduction technique called hierarchical probing. We perform model-independent fits of the form factor shapes using the z-expansion and determine the strange electric and magnetic radii and magnetic moment. As a result, we compare our results to parity-violating electron-proton scattering data and to other theoretical studies.
Electroweak single pion production and form factors of the Δ(1232) resonance
NASA Astrophysics Data System (ADS)
Żmuda, Jakub; Graczyk, Krzysztof M.
2015-10-01
We extend and review our analysis of the nucleon → Δ(1232) transition electroweak form factors from Ref. [1]. New fit of the Δ(1232) vector form factors to electron-proton scattering F2 structure function is introduced as well, leading to results different from the popular parametrization of Ref. [2]. A clear model dependence of the extracted parameters emerges. Fit to neutrino scattering data is performed in all available isospin channels. The resulting axial mass is MA Δ=0.85-0.08+0.09(GeV) and C5A(0 )=1.10-0.14+0.15 . The latter value is in accordance with Goldberger-Treiman relation as long as the deuteron effects are included.
Electromagnetic structure of the proton within the CP-violation hypothesis
Krutov, A. F. Kudinov, M. Yu.
2013-11-15
The so-called non-Rosenbluth behavior of the proton electromagnetic form factors can be explained within the hypothesis of CP violation in electromagnetic processes involving composite systems of strongly interacting particles. It is shown that this hypothesis leads to the appearance of an additional, anapole, form factor of the proton. The proton electromagnetic form factors, including the anapole form factor, are estimated on the basis of experimental data on elastic electron-proton scattering.
Solis, Brian H.; Maher, Andrew G.; Dogutan, Dilek K.; Nocera, Daniel G.; Hammes-Schiffer, Sharon
2016-01-01
The development of more effective energy conversion processes is critical for global energy sustainability. The design of molecular electrocatalysts for the hydrogen evolution reaction is an important component of these efforts. Proton-coupled electron transfer (PCET) reactions, in which electron transfer is coupled to proton transfer, play an important role in these processes and can be enhanced by incorporating proton relays into the molecular electrocatalysts. Herein nickel porphyrin electrocatalysts with and without an internal proton relay are investigated to elucidate the hydrogen evolution mechanisms and thereby enable the design of more effective catalysts. Density functional theory calculations indicate that electrochemical reduction leads to dearomatization of the porphyrin conjugated system, thereby favoring protonation at the meso carbon of the porphyrin ring to produce a phlorin intermediate. A key step in the proposed mechanisms is a thermodynamically favorable PCET reaction composed of intramolecular electron transfer from the nickel to the porphyrin and proton transfer from a carboxylic acid hanging group or an external acid to the meso carbon of the porphyrin. The C–H bond of the active phlorin acts similarly to the more traditional metal-hydride by reacting with acid to produce H2. Support for the theoretically predicted mechanism is provided by the agreement between simulated and experimental cyclic voltammograms in weak and strong acid and by the detection of a phlorin intermediate through spectroelectrochemical measurements. These results suggest that phlorin species have the potential to perform unique chemistry that could prove useful in designing more effective electrocatalysts. PMID:26655344
Measurements of the Helium Form Factors at JLab
Khrosinkova, Elena
2007-10-26
An experiment to measure elastic electron scattering off {sup 3}He and {sup 4}He at large momentum transfers is presented. The experiment was carried out in the Hall A Facility of Jefferson Lab. Elastic electron scattering off {sup 3}He was measured at forward and backward electron scattering angles to extract the isotope's charge and magnetic form factors. The charge form factor of {sup 4}He will be extracted from forward-angle electron scattering angle measurements. The data are expected to significantly extend and improve the existing measurements of the three- and four-body form factors. The results will be crucial for the establishment of a canonical standard model for the few-body nuclear systems and for testing predictions of quark dimensional scaling and hybrid nucleon-quark models.
Nucleon to delta electromagnetic transition form factors in lattice QCD
Alexandrou, C.; Koutsou, G.; Neff, H.; Negele, J. W.; Schroers, W.; Tsapalis, A.
2008-04-15
The electromagnetic nucleon to {delta} transition form factors are evaluated using two degenerate flavors of dynamical Wilson fermions and using dynamical sea staggered fermions with domain-wall valence quarks. The two subdominant quadrupole form factors are evaluated for the first time in full QCD to sufficient accuracy to exclude a zero value, which is taken as a signal for deformation in the nucleon-{delta} system. For the Coulomb quadrupole form factor the unquenched results begin to deviate from the quenched results at low q{sup 2} indicating that dynamical lattice results are closer to experiment. This can be taken as a first confirmation of the expected importance of pion cloud contributions on this quantity.
Master integrals for the four-loop Sudakov form factor
NASA Astrophysics Data System (ADS)
Boels, Rutger H.; Kniehl, Bernd A.; Yang, Gang
2016-01-01
The light-like cusp anomalous dimension is a universal function in the analysis of infrared divergences. In maximally (N = 4) supersymmetric Yang-Mills theory (SYM) in the planar limit, it is known, in principle, to all loop orders. The non-planar corrections are not known in any theory, with the first appearing at the four-loop order. The simplest quantity which contains this correction is the four-loop two-point form factor of the stress tensor multiplet. This form factor was largely obtained in integrand form in a previous work for N = 4 SYM, up to a free parameter. In this work, a reduction of the appearing integrals obtained by solving integration-by-parts (IBP) identities using a modified version of Reduze is reported. The form factor is shown to be independent of the remaining parameter at integrand level due to an intricate pattern of cancellations after IBP reduction. Moreover, two of the integral topologies vanish after reduction. The appearing master integrals are cross-checked using independent algebraic-geometry techniques explored in the Mint package. The latter results provide the basis of master integrals applicable to generic form factors, including those in Quantum Chromodynamics. Discrepancies between explicitly solving the IBP relations and the MINT approach are highlighted. Remaining bottlenecks to completing the computation of the four-loop non-planar cusp anomalous dimension in N = 4 SYM and beyond are identified.
The B → K* form factors on the lattice
NASA Astrophysics Data System (ADS)
Agadjanov, Andria; Bernard, Véronique; Meißner, Ulf-G.; Rusetsky, Akaki
2016-09-01
The extraction of the B →K* transition form factors from lattice data is studied, applying non-relativistic effective field theory in a finite volume. The possible mixing of πK and ηK states is taken into account. The two-channel analogue of the Lellouch-Lüscher formula is reproduced. Due to the resonance nature of the K*, an equation is derived, which allows to determine the form factors at the pole position in a process-independent manner. The infinitely-narrow width approximation of the results is discussed.
Form factor of pNIPAM microgels in overpacked states
Gasser, U.; Hyatt, J. S.; Lietor-Santos, J.-J.; Fernandez-Nieves, A.; Herman, E. S.; Lyon, L. A.
2014-07-21
We study the form factor of thermoresponsive microgels based on poly(N-isopropylacrylamide) at high generalized volume fractions, ζ, where the particles must shrink or interpenetrate to fit into the available space. Small-angle neutron scattering with contrast matching techniques is used to determine the particle form factor. We find that the particle size is constant up to a volume fraction roughly between random close packing and space filling. Beyond this point, the particle size decreases with increasing particle concentration; this decrease is found to occur with little interpenetration. Noteworthily, the suspensions remain liquid-like for ζ larger than 1, emphasizing the importance of particle softness in determining suspension behavior.
Electromagnetic form factors of the Δ with D-waves
Ramalho, Gilberto T.F.; Pena, Maria Teresa; Gross, Franz L.
2010-06-01
The electromagnetic form factors of the Δ baryon are evaluated within the framework of a covariant spectator quark model, where S and D-states are included in the Δ wave function. We predict all the four Δ multipole form factors: the electric charge G_{E0}, the magnetic dipole G_{M1}, the electric quadrupole G_{E2} and the magnetic octupole G_{M3}. We compare our predictions with other theoretical calculations. Our results are compatible with the available experimental data and recent lattice QCD data.
Pion electromagnetic form factor in the Covariant Spectator Theory
Biernat, Elmar P.; Gross, Franz L.; Pena, Teresa; Stadler, Alfred
2014-01-01
The pion electromagnetic form factor at spacelike momentum transfer is calculated in relativistic impulse approximation using the Covariant Spectator Theory. The same dressed quark mass function and the equation for the pion bound-state vertex function as discussed in the companion paper are used for the calculation, together with a dressed quark current that satisfies the Ward-Takahashi identity. The results obtained for the pion form factor are in agreement with experimental data, they exhibit the typical monopole behavior at high momentum transfer and they satisfy some remarkable scaling relations.
Pseudo-scalar form factors at three loops in QCD
NASA Astrophysics Data System (ADS)
Ahmed, Taushif; Gehrmann, Thomas; Mathews, Prakash; Rana, Narayan; Ravindran, V.
2015-11-01
The coupling of a pseudo-scalar Higgs boson to gluons is mediated through a heavy quark loop. In the limit of large quark mass, it is described by an effective Lagrangian that only admits light degrees of freedom. In this effective theory, we compute the three-loop massless QCD corrections to the form factor that describes the coupling of a pseudo-scalar Higgs boson to gluons. Due to the axial anomaly, the pseudo-scalar operator for the gluonic field strength mixes with the divergence of the axial vector current. Working in dimensional regularization and using the 't Hooft-Veltman prescription for the axial vector current, we compute the three-loop pseudo-scalar form factors for massless quarks and gluons. Using the universal infrared factorization properties, we independently derive the three-loop operator mixing and finite operator renormalisation from the renormalisation group equation for the form factors, thereby confirming recent results in the operator product expansion. The finite part of the three-loop form factor is an important ingredient to the precise prediction of the pseudo-scalar Higgs boson production cross section at hadron colliders. We discuss potential applications and derive the hard matching coefficient in soft-collinear effective theory.
Pion Electromagnetic Form Factor in Virtuality Distribution Formalism
Radyushkin, Anatoly V.
2016-01-01
We discuss two applications of the {\\it Virtuality Distribution Amplitudes} (VDA) formalism developed in our recent papers. We start with an overview of the main properties of the pion distribution amplitude emphasizing the quantitative measures of its width, and possibility to access them through the pion transition form factor studies. We formulate the basic concepts of the VDA approach and introduce the pion {\\it transverse momentum distribution amplitude} (TMDA) which plays, in a covariant Lagrangian formulation, a role similar to that of the pion wave function in the 3-dimensional Hamiltonian light-front approach. We propose simple factorized models for soft TMDAs, and use them to describe existing data on the pion transition form factor, thus fixing the scale determining the size of the transverse-momentum effects. Finally, we apply the VDA approach to the one-gluon exchange contribution for the pion electromagnetic form factor. We observe a very late $Q^2 \\gtrsim 20$ GeV$^2$ onset of transition to the asymptotic pQCD predictions and show that in the $Q^2 \\lesssim 10$ GeV$^2$ region there is essentially no sensitivity to the shape of the pion distribution amplitude. Furthermore, the magnitude of the one-gluon exchange contribution in this region is estimated to be an order of magnitude below the Jefferson Lab data, thus leaving the Feynman mechanism as the only one relevant to the pion electromagnetic form factor behavior for accessible $Q^2$.
NASA Technical Reports Server (NTRS)
Lee, Timothy J.; Rice, Julia E.
1992-01-01
The equilibrium structures, harmonic vibrational frequencies, IR intensities, and relative energetics of HNO3 and its protonated form H2NO3+ were investigated using double-zeta plus polarization and triple-zeta plus polarization basis sets in conjunction with high-level ab initio methods. The latter include second-order Moller-Plesset perturbation theory, the single and double excitation coupled cluster (CCSD) methods, a perturbational estimate of the effects of connected triple excitations (CCSD(T)), and the self-consistent field. To determine accurate energy differences CCSD(T) energies were computed using large atomic natural orbital basis sets. Four different isomers of H2NO3+ were considered. The lowest energy form of protonated nitric acid was found to correspond to a complex between H2O and NO2+, which is consistent with earlier theoretical and experimental studies.
Dirac and Pauli form factors based on consideration of the gluon effect in light-cone wave functions
NASA Astrophysics Data System (ADS)
Shojaei, Mohammad Reza; Nikkhoo, Negin Sattary
2015-11-01
We discuss Dirac and Pauli form factors based on a generalized parton distribution framework in the range of high momentum transfers of t < 30 GeV2 and calculate the electromagnetic form factors, GE and GM, for the proton. In previous work, Gaussian parameterization has been used in wave functions for calculating electromagnetic form factors at intermediate-high momentum transfers of 1 GeV2 < t < 10 GeV2; in this paper, by considering an improved Gaussian ansatz, we not only calculate the electromagnetic form factors at moderately high momentum transfers t but also can calculate these quantities at high momentum transfers, achieving reasonable agreement with experimental data and other previous work.
SU-E-T-577: Obliquity Factor and Surface Dose in Proton Beam Therapy
Das, I; Andersen, A; Coutinho, L
2015-06-15
Purpose: The advantage of lower skin dose in proton beam may be diminished creating radiation related sequalae usually seen with photon and electron beams. This study evaluates the surface dose as a complex function of beam parameters but more importantly the effect of beam angle. Methods: Surface dose in proton beam depends on the beam energy, source to surface distance, the air gap between snout and surface, field size, material thickness in front of surface, atomic number of the medium, beam angle and type of nozzle (ie double scattering, (DS), uniform scanning (US) or pencil beam scanning (PBS). Obliquity factor (OF) is defined as ratio of surface dose in 0° to beam angle Θ. Measurements were made in water phantom at various beam angles using very small microdiamond that has shown favorable beam characteristics for high, medium and low proton energy. Depth dose measurements were performed in the central axis of the beam in each respective gantry angle. Results: It is observed that surface dose is energy dependent but more predominantly on the SOBP. It is found that as SSD increases, surface dose decreases. In general, SSD, and air gap has limited impact in clinical proton range. High energy has higher surface dose and so the beam angle. The OF rises with beam angle. Compared to OF of 1.0 at 0° beam angle, the value is 1.5, 1.6, 1,7 for small, medium and large range respectively for 60 degree angle. Conclusion: It is advised that just like range and SOBP, surface dose should be clearly understood and a method to reduce the surface dose should be employed. Obliquity factor is a critical parameter that should be accounted in proton beam therapy and a perpendicular beam should be used to reduce surface dose.
The Modern description of semileptonic meson form factors
Hill, Richard J.
2006-06-01
I describe recent advances in our understanding of the hadronic form factors governing semileptonic meson transitions. The resulting framework provides a systematic approach to the experimental data, as a means of extracting precision observables, testing nonperturbative field theory methods, and probing a poorly understood limit of QCD.
Delta-Isobar magnetic form factor in QCD
Belyaev, Vladimir
1993-01-01
We consider the QCD sum rules approach for Delta-isobar magnetic form factor in the infra-red region $0
Measurement of the pion form factor at higher energies
Mack, D.J.
1994-04-01
One of the strongest arguments for increasing the nominal CEBAF beam energy to equal or exceed 6 GeV is that one would be able to make quality high Q{sup 2} measurements of the charged pion form factor.
JLAB Measurements of the Deuteron Electric and Magnetic Form Factors
Gerassimos G. Petratos
2000-12-12
Large-momentum transfer JLab measurements of the deuteron electric and magnetic form factors are reported. The data are compared to theoretical models based on the relativistic impulse approximation with the inclusion of meson-exchange currents, and to predictions of quark-dimensional scaling and perturbative QCD.
Personality Research Form: Factor Structure and Response Style Involvement.
ERIC Educational Resources Information Center
Stricker, Lawrence J.
The aims of this study were (1) to explore the factor structure of the Personality Research Form (PRF) and (2) to examine the inventory's relations with response styles. In general the PRF content scales correlated moderately with each other and with measures of acquiesence, social desirability, and defensiveness response Biases. Six oblique…
Factor Content of the Hill Interaction Matrix--Form B
ERIC Educational Resources Information Center
Drummond, Robert J.; McIntire, Walter G.
1976-01-01
Investigates the construct validity of the Hill Interaction Matrix--Form B, a 64-item instrument designed to assess preferred modes of interaction in group settings. A factor analysis was performed by using 134 subjects. Results indicate that the items and the conceptual format are appropriate. (Author)
The Super Bigbite Project: A Study of Nucleon Form Factors
Jager, Kees de
2010-06-01
A proposed set of instrumentation, collectively referred to as the Super Bigbite project, is presented. Used in three different con figurations it will allow measurements of three nucleon electromagnetic form factors GEn, GEp, and GMn with unprecedented precision to Q2-values up to three times higher than existing data.
Nucleon form factors program with SBS at JLAB
Wojtsekhowski, Bogdan B.
2014-12-01
The physics of the nucleon form factors is the basic part of the Jefferson Laboratory program. We review the achievements of the 6-GeV era and the program with the 12- GeV beam with the SBS spectrometer in Hall A, with a focus on the nucleon ground state properties.
Santopinto, E.; Vassallo, A.; Giannini, M. M.; De Sanctis, M.
2010-12-15
The ratio R{sub p} between the electric and magnetic proton form factors has been recently measured at Jefferson Lab up to Q{sup 2}=8.5 GeV{sup 2}. We have extended the calculation of the nucleon form factors with the hypercentral constituent quark model and compared them with the data on R{sub p} and on the Q{sup 2} behavior of the ratio Q{sup 2}F{sub 2}/F{sub 1}. In both cases, the theoretical curves agree with the experimental points.
NASA Astrophysics Data System (ADS)
Mishra, Alok; Srivastava, Sunil Kumar; Swati, D.
2013-09-01
The structure-activity relationship of the anticoagulant drug warfarin were studied by studying two enantiomeric forms (S-form and R-form) of warfarin and its protonated as well as deprotonated structures in aqueous media using density functional theory (DFT). Theoretically computed Raman and IR spectra of all the computed structures were compared and their specific vibrational spectroscopic signatures were discussed. The percentage contributions of individual normal modes of warfarin, which provides direct evidence of the different molecular activity due to change in relative atomic position of atoms in molecule, were investigated through potential energy distribution (PED). The optimized energy and molecular electrostatic potential (MEP) maps show that the S-form of the drug molecules warfarin is energetically more stable than R-form and provides higher docking opportunity for the molecular binding with the receptors in the bio-systems.
SU-E-T-595: Output Factor Calculation for a Uniform Scanning Proton Therapy System
Hecksel, D; Stauffer, N; DeFillippo, G; Edwards, J; Pankuch, M
2015-06-15
Purpose: To develop an analytical model that predicts dose output factors for patient treatment fields in a uniform scanning proton therapy system. Methods: A model to predict output factors for patient specific treatment fields was produced based on the methods developed by Kooy et al. (2003). The Kooy model predicts the output factor based on the ratio of the entrance dose under calibration conditions to that for a given range and modulation corrected for the inverse square effect. Field specific output factors were plotted as a function of a single parameter r, where r = (Range-Modulation)/Modulation. The model targeted user range 1 sub-span 3 through user range 2 sup-span 2 of the IBA uniform scanning proton therapy system. The data set included points measured using the 10 cm and 18 cm snout sizes to eliminate stem effects on the monitor unit chambers. The data was fit using equation 15 from Kooy et al. (2003), and the resulting model was tested against measurements that were not included in the original data set. Results: For the range and sub span investigated, 120 data points were tested against the model prediction. The model predicted the output factor within 2% for 96% of the points tested and within 2.5% for 99% of the points tested. All points were within 3% of the predicted values. Conclusion: Monitor units for patient treatment fields with proton ranges that fall within the tested interval can be predicted using a model based on the methods developed at MGH. With further evaluation, it will be possible to model all user ranges and sub-spans of the IBA system. Further testing is also needed to predict output factors using a 25 cm snout which introduces variable scanning pattern sizes and stem effects on the monitor unit chambers.
Electromagnetic form factors and charge densities from hadrons to nuclei
Miller, Gerald A.
2009-10-15
A simple exact covariant model in which a scalar particle {psi} is modeled as a bound state of two different particles is used to elucidate relativistic aspects of electromagnetic form factors F(Q{sup 2}). The model form factor is computed using an exact covariant calculation of the lowest order triangle diagram. The light-front technique of integrating over the minus component of the virtual momentum gives the same result and is the same as the one obtained originally by Gunion et al. [Phys. Rev. D 8, 287 (1973)] by using time-ordered perturbation theory in the infinite-momentum frame. The meaning of the transverse density {rho}(b) is explained by providing a general derivation, using three spatial coordinates, of its relationship with the form factor. This allows us to identify a mean-square transverse size ={integral}d{sup 2}b b{sup 2}{rho}(b)=-4(dF/dQ{sup 2})(Q{sup 2}=0). The quantity is a true measure of hadronic size because of its direct relationship with the transverse density. We show that the rest-frame charge distribution is generally not observable by studying the explicit failure to uphold current conservation. Neutral systems of two charged constituents are shown to obey the conventional lore that the heavier one is generally closer to the transverse origin than the lighter one. It is argued that the negative central charge density of the neutron arises, in pion-cloud models, from pions of high longitudinal momentum that reside at the center. The nonrelativistic limit is defined precisely, and the ratio of the binding energy B to the mass M of the lightest constituent is shown to govern the influence of relativistic effects. It is shown that the exact relativistic formula for F(Q{sup 2}) is the same as the familiar one of the three-dimensional Fourier transform of a square of a wave function for very small values of B/M, but this only occurs for values of B/M less than about 0.001. For masses that mimic the quark-diquark model of
Dirac and Pauli form factors from lattice QCD
Collins, S.; Goeckeler, M.; Nobile, A.; Schaefer, A.; Haegler, Ph.; Horsley, R.; Winter, F.; Zanotti, J. M.; Nakamura, Y.; Pleiter, D.; Rakow, P. E. L.; Schierholz, G.; Schroers, W.; Stueben, H.
2011-10-01
We present a comprehensive analysis of the electromagnetic form factors of the nucleon from a lattice simulation with two flavors of dynamical O(a)-improved Wilson fermions. A key feature of our calculation is that we make use of an extensive ensemble of lattice gauge field configurations with four different lattice spacings, multiple volumes, and pion masses down to m{sub {pi}{approx}1}80 MeV. We find that by employing Kelly-inspired parametrizations for the Q{sup 2} dependence of the form factors, we are able to obtain stable fits over our complete ensemble. Dirac and Pauli radii and the anomalous magnetic moments of the nucleon are extracted and results at light quark masses provide evidence for chiral nonanalytic behavior in these fundamental observables.
Measurement of the gamma gamma* -> pi0 transition form factor
Aubert, B.
2009-06-02
We study the reaction e{sup +}e{sup -} {yields} e{sup +}e{sup -}{pi}{sup 0} in the single tag mode and measure the differential cross section d{sigma}/dQ{sup 2} and the {gamma}{gamma}* {yields} {pi}{sup 0} transition form factor in the mometum transfer range from 4 to 40 GeV{sup 2}. At Q{sup 2} > 10 GeV{sup 2} the measured form factor exceeds the asymptotic limit predicted by perturbative QCD. The analysis is based on 442 fb{sup -1} of integrated luminosity collected at PEP-II with the BABAR detector at e{sup +}e{sup -} center-of-mass energies near 10.6 GeV.
Octet Baryon Electromagnetic Form Factors in a Relativistic Quark Model
Gilberto Ramalho, Kazuo Tsushima
2011-09-01
We study the octet baryon electromagnetic properties by applying the covariant spectator quark model, and provide covariant parametrization that can be used to study baryon electromagnetic reactions. While we use the lattice QCD data in the large pion mass regime (small pion cloud effects) to determine the parameters of the model in the valence quark sector, we use the nucleon physical and octet baryon magnetic moment data to parameterize the pion cloud contributions. The valence quark contributions for the octet baryon electromagnetic form factors are estimated by extrapolating the lattice parametrization in the large pion mass regime to the physical regime. As for the pion cloud contributions, we parameterize them in a covariant, phenomenological manner, combined with SU(3) symmetry. We also discuss the impact of the pion cloud effects on the octet baryon electromagnetic form factors and their radii.
Small form factor full parallax tiled light field display
NASA Astrophysics Data System (ADS)
Alpaslan, Zahir Y.; El-Ghoroury, Hussein S.
2015-03-01
With the recent introduction of Ostendo's Quantum Photonic Imager (QPI) display technology, a very small pixel pitch, emissive display with high brightness and low power consumption became available. We used QPI's to create a high performance light field display tiles with a very small form factor. Using 8 of these QPI light field displays tiled in a 4x2 array we created a tiled full parallax light field display. Each individual light field display tile combines custom designed micro lens array layers with monochrome green QPIs. Each of the light field display tiles can address 1000 x 800 pixels placed under an array of 20 x 16 lenslets with 500 μm diameters. The light field display tiles are placed with small gaps to create a tiled display of approximately 46 mm (W) x 17 mm (H) x 2 mm (D) in mechanical dimensions. The prototype tiled full parallax light field display demonstrates small form factor, high resolution and focus cues.
Bs→Kℓν form factors from lattice QCD
NASA Astrophysics Data System (ADS)
Bouchard, C. M.; Lepage, G. Peter; Monahan, Christopher; Na, Heechang; Shigemitsu, Junko
2014-09-01
We report the first lattice QCD calculation of the form factors for the standard model tree-level decay Bs→K ℓν. In combination with future measurement, this calculation will provide an alternative exclusive semileptonic determination of |Vub|. We compare our results with previous model calculations, make predictions for differential decay rates and branching fractions, and predict the ratio of differential branching fractions between Bs→Kτν and Bs→Kμν. We also present standard model predictions for differential decay rate forward-backward asymmetries and polarization fractions and calculate potentially useful ratios of Bs→K form factors with those of the fictitious Bs→ηs decay. Our lattice simulations utilize nonrelativistic QCD b and highly improved staggered light quarks on a subset of the MILC Collaboration 2+1 asqtad gauge configurations, including two lattice spacings and a range of light quark masses.
Nonlocal form factors for curved-space antisymmetric fields
NASA Astrophysics Data System (ADS)
Netto, Tibério de Paula; Shapiro, Ilya L.
2016-07-01
In a recent paper, Buchbinder, Kirillova, and Pletnev presented formal arguments concerning the quantum equivalence of free massive antisymmetric tensor fields of the second and third rank to the free Proca theory and massive scalar field with minimal coupling to gravity, respectively. We confirm this result using explicit covariant calculations of nonlocal form factors based on the heart-kernel technique and discuss the discontinuity of quantum contributions in the massless limit.
Axial form factor of the nucleon at large momentum transfers
NASA Astrophysics Data System (ADS)
Anikin, I. V.; Braun, V. M.; Offen, N.
2016-08-01
Motivated by the emerging possibilities to study threshold pion electroproduction at large momentum transfers at Jefferson Laboratory following the 12 GeV upgrade, we provide a short theory summary and an estimate of the nucleon axial form factor for large virtualities in the Q2=1 - 10 GeV2 range using next-to-leading-order light-cone sum rules.
Stackable Form-Factor Peripheral Component Interconnect Device and Assembly
NASA Technical Reports Server (NTRS)
Somervill, Kevin M. (Inventor); Ng, Tak-kwong (Inventor); Torres-Pomales, Wilfredo (Inventor); Malekpour, Mahyar R. (Inventor)
2013-01-01
A stackable form-factor Peripheral Component Interconnect (PCI) device can be configured as a host controller or a master/target for use on a PCI assembly. PCI device may comprise a multiple-input switch coupled to a PCI bus, a multiplexor coupled to the switch, and a reconfigurable device coupled to one of the switch and multiplexor. The PCI device is configured to support functionality from power-up, and either control function or add-in card function.
Two-photon exchange corrections to the pion form factor
Peter G. Blunden; Melnitchouk, Wally; Tjon, John A.
2010-01-06
Here, we compute two-photon exchange corrections to the electromagnetic form factor of the pion, taking into account the finite size of the pion. Compared to the soft-photon approximation for the infrared divergent contribution which neglects hadron structure effects, the corrections are found to be ≲ 1% for small Q2 (Q2 < 0.1 GeV2), but increase to several percent for Q2 ≳ 1 GeV2 at extreme backward angles.
The structure of light-front wavefunctions and constraints on hadronic form factors
S. J. Brodsky; J. R. Hiller; D. S. Hwang; V. A. Karmanov
2003-11-17
We study the analytic structure of light-front wave functions (LFWFs) and its consequences for hadron form factors using an explicitly Lorentz-invariant formulation of the front form. The normal to the light front is specified by a general null vector {omega}{sup {mu}}. The LFWFs with definite total angular momentum are eigenstates of a kinematic angular momentum operator and satisfy all Lorentz symmetries. They are analytic functions of the invariant mass squared of the constituents M{sub 0}{sup 2} = ({Sigma} k{sup {mu}}){sup 2} and the light-cone momentum fractions x{sub i} = k{sub i} {center_dot} {omega}/p {center_dot} {omega} multiplied by invariants constructed from the spin matrices, polarization vectors, and {omega}{sup {mu}}. These properties are illustrated using known nonperturbative eigensolutions of the Wick-Cutkosky model. We analyze the LFWFs introduced by Chung and Coester to describe static and low momentum properties of the nucleons. They correspond to the spin-locking of a quark with the spin of its parent nucleon, tog ether with a positive-energy projection constraint. These extra constraints lead to anomalous dependence of form factors on Q rather than Q{sup 2}. In contrast, the dependence of LFWFs on M{sub 0}{sup 2} implies that hadron form factors are analytic functions of Q{sup 2} in agreement with dispersion theory and perturbative QCD. We show that a model incorporating the leading-twist perturbative QCD prediction is consistent with recent data for the ratio of proton Pauli and Dirac form factors.
Strange vector form factors from parity-violating electron scattering
Kent Paschke, Anthony Thomas, Robert Michaels, David Armstrong
2011-06-01
The simplest models might describe the nucleon as 3 light quarks, but this description would be incomplete without inclusion of the sea of glue and qbar q pairs which binds it. Early indications of a particularly large contribution from strange quarks in this sea to the spin and mass of the nucleon motivated an experimental program examining the role of these strange quarks in the nucleon vector form factors. The strangeness form factors can be extracted from the well-studied electromagnetic structure of the nucleon using parity-violation in electron-nuclear scattering to isolate the effect of the weak interaction. With high luminosity and polarization, and a very stable beam due to its superconducting RF cavities, CEBAF at Jefferson Lab is a precision instrument uniquely well suited to the challenge of measurements of the small parity-violating asymmetries. The techniques and results of the two major Jefferson Lab experimental efforts in parity-violation studies, HAPPEX and G0, as well as efforts to describe the strange form factors in QCD, will be reviewed.
Pion transverse charge density from timelike form factor data
Gerald Miller, Mark Strikman, Christian Weiss
2011-01-01
The transverse charge density in the pion can be represented as a dispersion integral of the imaginary part of the pion form factor in the timelike region. This formulation incorporates information from e+e- annihilation experiments and allows one to reconstruct the transverse density much more accurately than from the spacelike pion form factor data alone. We calculate the transverse density using an empirical parametrization of the timelike pion form factor and estimate that it is determined to an accuracy of ~10% at a distance b ~ 0.1 fm, and significantly better at larger distances. The density is found to be close to that obtained from a zero-width rho meson pole over a wide range and shows a pronounced rise at small distances. The resulting two-dimensional image of the fast-moving pion can be interpreted in terms of its partonic structure in QCD. We argue that the singular behavior of the charge density at the center requires a substantial presence of pointlike configurations in the pion's partonic wave function, which can be probed in other high-momentum transfer processes.
Meson Transition Form Factors in Light-Front Holographic QCD
Brodsky, Stanley J.; Cao, Fu-Guang; de Teramond, Guy F.; /Costa Rica U.
2011-06-22
We study the photon-to-meson transition form factors (TFFs) F{sub M{gamma}}(Q{sup 2}) for {gamma}{gamma}* {yields} M using light-front holographic methods. The Chern-Simons action, which is a natural form in 5-dimensional anti-de Sitter (AdS) space, leads directly to an expression for the photon-to-pion TFF for a class of confining models. Remarkably, the predicted pion TFF is identical to the leading order QCD result where the distribution amplitude has asymptotic form. The Chern-Simons form is local in AdS space and is thus somewhat limited in its predictability. It only retains the q{bar q} component of the pion wavefunction, and further, it projects out only the asymptotic form of the meson distribution amplitude. It is found that in order to describe simultaneously the decay process {pi}{sup 0} {yields} {gamma}{gamma} and the pion TFF at the asymptotic limit, a probability for the q{bar q} component of the pion wavefunction P{sub q{bar q}} = 0.5 is required; thus giving indication that the contributions from higher Fock states in the pion light-front wavefunction need to be included in the analysis. The probability for the Fock state containing four quarks (anti-quarks) which follows from analyzing the hadron matrix elements, P{sub q{bar q}q{bar q}} {approx} 10%, agrees with the analysis of the pion elastic form factor using light-front holography including higher Fock components in the pion wavefunction. The results for the TFFs for the {eta} and {eta}{prime} mesons are also presented. The rapid growth of the pion TFF exhibited by the BABAR data at high Q{sup 2} is not compatible with the models discussed in this article, whereas the theoretical calculations are in agreement with the experimental data for the {eta} and {eta}{prime} TFFs.
NASA Astrophysics Data System (ADS)
Bedard, Jeremy William
The depletion of fossil fuel resources and the environmental consequences of their use have dictated the development of new sources of energy that are both sustainable and economical. Biomass has emerged as a renewable carbon feedstock that can be used to produce chemicals and fuels traditionally obtained from petroleum. The oxygen content of biomass prohibits its use without modification because oxygenated hydrocarbons are non-volatile and have lower energy content. Chemical processes that eliminate oxygen and keep the carbon backbone intact are required for the development of biomass as a viable chemical feedstock. This dissertation reports on the kinetic and mechanistic studies conducted on high and low temperature catalytic processes for deoxygenation of biomass precursors to produce high-value chemicals and fuels. Low temperature, steady state reaction studies of acetic acid and ethanol were used to identify co-adsorbed acetic acid/ethanol dimers as surface intermediates within specific elementary steps involved in the esterification of acetic acid with ethanol on zeolites. A reaction mechanism involving two dominating surface species, an inactive ethanol dimeric species adsorbed on Bronsted sites inhibiting ester formation and a co-adsorbed complex of acetic acid and ethanol on the active site reacting to produce ethyl acetate, is shown to describe the reaction rate as a function of temperature (323 -- 383 K), acetic acid (0.5 -- 6.0 kPa), and ethanol (5.0 -- 13.0 kPa) partial pressure on proton-form BEA, FER, MFI, and MOR zeolites. Measured differences in rates as a function of zeolite structure and the rigorous interpretation of these differences in terms of esterification rate and equilibrium constants is presented to show that the intrinsic rate constant for the activation of the co-adsorbed complex increases in the order FER < MOR < MFI < BEA. High temperature co-processing of acetic acid, formic acid, or carbon dioxide with methane (CH3COOH/CH4 = 0
Neutron charge radius and the neutron electric form factor
Gentile, T. R.; Crawford, C. B.
2011-05-15
For nearly forty years, the Galster parametrization has been employed to fit existing data for the neutron electric form factor, G{sub E}{sup n}, vs the square of the four-momentum transfer, Q{sup 2}. Typically this parametrization is constrained to be consistent with experimental data for the neutron charge radius. However, we find that the Galster form does not have sufficient freedom to accommodate reasonable values of the radius without constraining or compromising the fit. In addition, the G{sub E}{sup n} data are now at sufficient precision to motivate a two-parameter fit (or three parameters if we include thermal neutron data). Here we present a modified form of a two-dipole parametrization that allows this freedom and fits both G{sub E}{sup n} (including recent data at both low and high four-momentum transfer) and the charge radius well with simple, well-defined parameters. Analysis reveals that the Galster form is essentially a two-parameter approximation to the two-dipole form but becomes degenerate if we try to extend it naturally to three parameters.
Are protons nonidentical fermions?
Mart, T.
2014-09-25
We briefly review the progress of our investigation on the electric (charge) radius of the proton. In order to explain the recently measured proton radius, which is significantly smaller than the standard CODATA value, we assume that the real protons radii are not identical, they are randomly distributed in a certain range. To obtain the measured radius we average the radii and fit both the mean radius and the range. By using an averaged dipole form factor we obtain the charge radius r{sub E} = 0.8333 fm, in accordance with the recent measurement of the Lamb shift in muonic hydrogen.
Cho, Jongmin; Gonzalez-Lepera, Carlos; Manohar, Nivedh; Kerr, Matthew; Krishnan, Sunil; Cho, Sang Hyun
2016-03-21
Some investigators have shown tumor cell killing enhancement in vitro and tumor regression in mice associated with the loading of gold nanoparticles (GNPs) before proton treatments. Several Monte Carlo (MC) investigations have also demonstrated GNP-mediated proton dose enhancement. However, further studies need to be done to quantify the individual physical factors that contribute to the dose enhancement or cell-kill enhancement (or radiosensitization). Thus, the current study investigated the contributions of particle-induced x-ray emission (PIXE), particle-induced gamma-ray emission (PIGE), Auger and secondary electrons, and activation products towards the total dose enhancement. Specifically, GNP-mediated dose enhancement was measured using strips of radiochromic film that were inserted into vials of cylindrical GNPs, i.e. gold nanorods (GNRs), dispersed in a saline solution (0.3 mg of GNRs/g or 0.03% of GNRs by weight), as well as vials containing water only, before proton irradiation. MC simulations were also performed with the tool for particle simulation code using the film measurement setup. Additionally, a high-purity germanium detector system was used to measure the photon spectrum originating from activation products created from the interaction of protons and spherical GNPs present in a saline solution (20 mg of GNPs/g or 2% of GNPs by weight). The dose enhancement due to PIXE/PIGE recorded on the films in the GNR-loaded saline solution was less than the experimental uncertainty of the film dosimetry (<2%). MC simulations showed highly localized dose enhancement (up to a factor 17) in the immediate vicinity (<100 nm) of GNRs, compared with hypothetical water nanorods (WNRs), mostly due to GNR-originated Auger/secondary electrons; however, the average dose enhancement over the entire GNR-loaded vial was found to be minimal (0.1%). The dose enhancement due to the activation products from GNPs was minimal (<0.1%) as well. In conclusion, under the currently
NASA Astrophysics Data System (ADS)
Cho, Jongmin; Gonzalez-Lepera, Carlos; Manohar, Nivedh; Kerr, Matthew; Krishnan, Sunil; Cho, Sang Hyun
2016-03-01
Some investigators have shown tumor cell killing enhancement in vitro and tumor regression in mice associated with the loading of gold nanoparticles (GNPs) before proton treatments. Several Monte Carlo (MC) investigations have also demonstrated GNP-mediated proton dose enhancement. However, further studies need to be done to quantify the individual physical factors that contribute to the dose enhancement or cell-kill enhancement (or radiosensitization). Thus, the current study investigated the contributions of particle-induced x-ray emission (PIXE), particle-induced gamma-ray emission (PIGE), Auger and secondary electrons, and activation products towards the total dose enhancement. Specifically, GNP-mediated dose enhancement was measured using strips of radiochromic film that were inserted into vials of cylindrical GNPs, i.e. gold nanorods (GNRs), dispersed in a saline solution (0.3 mg of GNRs/g or 0.03% of GNRs by weight), as well as vials containing water only, before proton irradiation. MC simulations were also performed with the tool for particle simulation code using the film measurement setup. Additionally, a high-purity germanium detector system was used to measure the photon spectrum originating from activation products created from the interaction of protons and spherical GNPs present in a saline solution (20 mg of GNPs/g or 2% of GNPs by weight). The dose enhancement due to PIXE/PIGE recorded on the films in the GNR-loaded saline solution was less than the experimental uncertainty of the film dosimetry (<2%). MC simulations showed highly localized dose enhancement (up to a factor 17) in the immediate vicinity (<100 nm) of GNRs, compared with hypothetical water nanorods (WNRs), mostly due to GNR-originated Auger/secondary electrons; however, the average dose enhancement over the entire GNR-loaded vial was found to be minimal (0.1%). The dose enhancement due to the activation products from GNPs was minimal (<0.1%) as well. In conclusion, under the
Three-Loop Slope of the Dirac Form Factor and the 1S Lamb Shift in Hydrogen
Melnikov, Kirill; Ritbergen, Timo van
2000-02-21
The last unknown contribution to hydrogen energy levels at order m{alpha}{sup 7} , due to the slope of the Dirac form factor at three loops, is evaluated in a closed analytical form. The resulting shift of the hydrogen nS energy level is found to be 3.016/n{sup 3} kHz . Using the QED calculations of the 1S Lamb shift, we extract a precise value of the proton charge radius r{sub p}=0.883{+-}0.014 fm . (c) 2000 The American Physical Society.
Scattering form factors for self-assembled network junctions
NASA Astrophysics Data System (ADS)
Foster, T.; Safran, S. A.; Sottmann, T.; Strey, R.
2007-11-01
The equilibrium microstructures in microemulsions and other self-assembled systems show complex, connected shapes such as symmetric bicontinuous spongelike structures and asymmetric bicontinuous networks formed by cylinders interconnected at junctions. In microemulsions, these cylinder network microstructures may mediate the structural transition from a spherical or globular phase to the bicontinuous microstructure. To understand the structural and statistical properties of such cylinder network microstructures as measured by scattering experiments, models are needed to extract the real-space structure from the scattering data. In this paper, we calculate the scattering functions appropriate for cylinder network microstructures. We focus on such networks that contain a high density of network junctions that connect the cylindrical elements. In this limit, the network microstructure can be regarded as an assembly of randomly oriented, closed packed network junctions (i.e., the cylinder scattering contributions are neglected). Accordingly, the scattering spectrum of the network microstructure can be calculated as the product of the junction number density, the junction form factor, which describes the scattering from the surface of a single junction, and a structure factor, which describes the local correlations of different junctions due to junction interactions (including their excluded volume). This approach is applied to analyze the scattering data from a bicontinuous microemulsion with equal volumes of water and oil. In a second approach, we included the cylinder scattering contribution in the junction form factor by calculating the scattering intensity of Y junctions to which three rods with spherical cross section are attached. The respective theoretical predictions are compared with results of neutron scattering measurements on a water-in-oil microemulsion with a connected microstructure.
CEBAF at higher energies and the kaon electromagnetic form factor
Baker, O.K.
1994-04-01
The electromagnetic production of strangeness, the physics of exciting systems having strangeness degrees of freedom (production of hadrons with one or more strange constituent quarks) using electromagnetic probes (real or virtual photons), is one of the frontier areas of research which will be investigated at the Continuous Electron Beam Accelerator Facility (CEBAF) when it becomes operational. CEBAF is expected to have an important impact upon this field of research using its specialized set of detection instruments and high quality electron beam. This paper focusses upon one aspect of the associated production of strangeness - the determination of the kaon electromagnetic form factor at high squared momentum transfers.
Baryon octet electromagnetic form factors in a confining NJL model
NASA Astrophysics Data System (ADS)
Carrillo-Serrano, Manuel E.; Bentz, Wolfgang; Cloët, Ian C.; Thomas, Anthony W.
2016-08-01
Electromagnetic form factors of the baryon octet are studied using a Nambu-Jona-Lasinio model which utilizes the proper-time regularization scheme to simulate aspects of colour confinement. In addition, the model also incorporates corrections to the dressed quarks from vector meson correlations in the t-channel and the pion cloud. Comparison with recent chiral extrapolations of lattice QCD results shows a remarkable level of consistency. For the charge radii we find the surprising result that rEp < rEΣ+ and | rEn | < | rEΞ0 |, whereas the magnetic radii have a pattern largely consistent with a naive expectation based on the dressed quark masses.
gamma* p ---> Delta form-factors in QCD
V. M. Belyaev; A. V. Radyushkin
1995-05-01
We use local quark-hadron duality to estimate the purely nonperturbative soft contribution to the {gamma}*p {yields} {Delta} form factors. Our results are in agreement with existing experimental data. We predict that the ratio G*{sub E}(Q{sup 2})/G*{sub M}(Q{sup 2}) is small for all accessible Q{sup 2}, in contrast to the perturbative QCD expectations that G*{sub E}(Q{sup 2}) {yields} -G*{sub M}(Q{sup 2}).
Nucleon strangeness form factors and moments of PDF
Doi, Takumi; Deka, Mridupawan; Dong, Shao-Jing; Draper, Terrence; Liu, Keh-Fei; Mankame, Devdatta; Mathur, Nilmani; Streuer, Thomas
2011-10-24
The calculation of the nucleon strangeness form factors from N{sub f} = 2+1 clover fermion lattice QCD is presented. Disconnected insertions are evaluated using the Z(4) stochastic method, along with unbiased subtractions from the hopping parameter expansion. We find that increasing the number of nucleon sources for each configuration improves the signal significantly. We obtain G{sub M}{sup s}(0) = -0.017(25)(07), which is consistent with experimental values, and has an order of magnitude smaller error. Preliminary results for the strangeness contribution to the second moment of the parton distribution function are also presented.
Two-photon exchange corrections to the pion form factor
Peter G. Blunden; Melnitchouk, Wally; Tjon, John A.
2010-01-06
Here, we compute two-photon exchange corrections to the electromagnetic form factor of the pion, taking into account the finite size of the pion. Compared to the soft-photon approximation for the infrared divergent contribution which neglects hadron structure effects, the corrections are found to be ≲ 1% for small Q^{2} (Q^{2} < 0.1 GeV^{2}), but increase to several percent for Q^{2} ≳ 1 GeV^{2} at extreme backward angles.
Minimal form factor digital-image sensor for endoscopic applications
NASA Astrophysics Data System (ADS)
Wäny, Martin; Voltz, Stephan; Gaspar, Fabio; Chen, Lei
2009-02-01
This paper presents a digital image sensor SOC featuring a total chip area (including dicing tolerances) of 0.34mm2 for endoscopic applications. Due to this extremely small form factor the sensor enables integration in endoscopes, guide wires and locater devices of less than 1mm outer diameter. The sensor embeds a pixel matrix of 10'000 pixels with a pitch of 3um x 3um covered with RGB filters in Bayer pattern. The sensor operates fully autonomous, controlled by an on chip ring oscillator and readout state machine, which controls integration AD conversion and data transmission, thus the sensor only requires 4 pin's for power supply and data communication. The sensor provides a frame rate of 40Frames per second over a LVDS serial data link. The endoscopic application requires that the sensor must work without any local power decoupling capacitances at the end of up to 2m cabling and be able to sustain data communication over the same wire length without deteriorating image quality. This has been achieved by implementation of a current mode successive approximation ADC and current steering LVDS data transmission. An band gap circuit with -40dB PSRR at the data frequency was implemented as on chip reference to improve robustness against power supply ringing due to the high series inductance of the long cables. The B&W versions of the sensor provides a conversion gain of 30DN/nJ/cm2 at 550nm with a read noise in dark of 1.2DN when operated at 2m cable. Using the photon transfer method according to EMVA1288 standard the full well capacity was determined to be 18ke-. According to our knowledge the presented work is the currently world smallest fully digital image sensor. The chip was designed along with a aspheric single surface lens to assemble on the chip without increasing the form factor. The extremely small form factor of the resulting camera permit's to provide visualization with much higher than state of the art spatial resolution in sub 1mm endoscopic
Proton Conductive Nanosheets Formed by Alignment of Metallo-Supramolecular Polymers.
Pandey, Rakesh K; Rana, Utpal; Chakraborty, Chanchal; Moriyama, Satoshi; Higuchi, Masayoshi
2016-06-01
Linear Fe(II)-based metallo-supramolecular polymer chains were precisely aligned by the simple replacement of the counteranion with an N,N'-bis(4-benzosulfonic acid)perylene-3,4,9,10-tetracarboxylbisimide (PSA) dianion, which linked the polymer chains strongly. A parallel alignment of the polymer chains promoted by the PSA dianions yielded nanosheets formation. The nanosheets' structure was analyzed with FESEM, HRTEM, UV-vis, and XRD in detail. The nanosheets showed more than 5 times higher proton conductivity than the original polymer due to the smooth ionic conduction through the aligned polymer chains. The complex impedance plot with two semicircles also suggested the presence of grain boundaries in the polymer nanosheets. PMID:27164027
ρ γ*→π (ρ ) transition form factors in the perturbative QCD factorization approach
NASA Astrophysics Data System (ADS)
Zhang, Ya-Lan; Cheng, Shan; Hua, Jun; Xiao, Zhen-Jun
2015-11-01
In this paper, we studied the ρ γ*→π and ρ γ*→ρ transition processes and made the calculations for the ρ π transition form factor Q4Fρ π(Q2) and the ρ -meson electromagnetic form factors, FLL ,LT ,TT(Q2) and F1 ,2 ,3(Q2), by employing the perturbative QCD (PQCD) factorization approach. For the ρ γ*→π transition, we found that the contribution to form factor Q4Fρ π(Q2) from the term proportional to the distribution amplitude combination ϕρT(x1)ϕπP(x2) is absolutely dominant, and the PQCD predictions for both the size and the Q2-dependence of this form factor Q4Fρ π(Q2) agree well with those from the extended anti-de Sitter/QCD models or the light-cone QCD sum rule. For the ρ γ*→ρ transition and in the region of Q2≥3 GeV2 , furthermore, we found that the PQCD predictions for the magnitude and their Q2-dependence of the F1(Q2) and F2(Q2) form factors agree well with those from the QCD sum rule, while the PQCD prediction for F3(Q2) is much larger than the one from the QCD sum rule.
Meson transition form factors in light-front holographic QCD
Brodsky, Stanley J.; Cao Fuguang; de Teramond, Guy F.
2011-10-01
We study the photon-to-meson transition form factors (TFFs) F{sub M}{gamma}(Q{sup 2}) for {gamma}{gamma}{sup *}{yields}M using light-front holographic methods. The Chern-Simons action, which is a natural form in five-dimensional anti-de Sitter (AdS) space, is required to describe the anomalous coupling of mesons to photons using holographic methods and leads directly to an expression for the photon-to-pion TFF for a class of confining models. Remarkably, the predicted pion TFF is identical to the leading order QCD result where the distribution amplitude has asymptotic form. The Chern-Simons form is local in AdS space and is thus somewhat limited in its predictability. It only retains the qq component of the pion wave function, and further, it projects out only the asymptotic form of the meson distribution amplitude. It is found that in order to describe simultaneously the decay process {pi}{sup 0}{yields}{gamma}{gamma} and the pion TFF at the asymptotic limit, a probability for the qq component of the pion wave function P{sub qq}=0.5 is required, thus giving indication that the contributions from higher Fock states in the pion light-front wave function need to be included in the analysis. The probability for the Fock state containing four quarks P{sub qqqq}{approx}10%, which follows from analyzing the hadron matrix elements for a dressed current model, agrees with the analysis of the pion elastic form factor using light-front holography including higher Fock components in the pion wave function. The results for the TFFs for the {eta} and {eta}{sup '} mesons are also presented. The rapid growth of the pion TFF exhibited by the BABAR data at high Q{sup 2} is not compatible with the models discussed in this article, whereas the theoretical calculations are in agreement with the experimental data for the {eta} and {eta}{sup '} TFFs.
Nucleon electromagnetic form factors in two-flavor QCD
NASA Astrophysics Data System (ADS)
Capitani, S.; Della Morte, M.; Djukanovic, D.; von Hippel, G.; Hua, J.; Jäger, B.; Knippschild, B.; Meyer, H. B.; Rae, T. D.; Wittig, H.
2015-09-01
We present results for the nucleon electromagnetic form factors, including the momentum transfer dependence and derived quantities (charge radii and magnetic moment). The analysis is performed using O (a ) improved Wilson fermions in Nf=2 QCD measured on the Coordinated Lattice Simulations ensembles. Particular focus is placed on a systematic evaluation of the influence of excited states in three-point correlation functions, which lead to a biased evaluation, if not accounted for correctly. We argue that the use of summed operator insertions and fit Ansätze including excited states allow us to suppress and control this effect. We employ a novel method to perform joint chiral and continuum extrapolations, by fitting the form factors directly to the expressions of covariant baryonic chiral effective field theory. The final results for the charge radii and magnetic moment from our lattice calculations include, for the first time, a full error budget. We find that our estimates are compatible with experimental results within their overall uncertainties.
Improved semileptonic form factor calculations in lattice QCD
Evans, Richard; Bali, Gunnar; Collins, Sara
2010-11-01
We investigate the computational efficiency of two stochastic based alternatives to the sequential propagator method used in lattice QCD calculations of heavy-light semileptonic form factors. In the first method, we replace the sequential propagator, which couples the calculation of two of the three propagators required for the calculation, with a stochastic propagator so that the calculations of all three propagators are independent. This method is more flexible than the sequential propagator method but introduces stochastic noise. We study the noise to determine when this method becomes competitive with the sequential propagator method, and find that for any practical calculation it is competitive with or superior to the sequential propagator method. We also examine a second stochastic method, the so-called 'one-end trick', concluding it is relatively inefficient in this context. The investigation is carried out on two gauge field ensembles, using the nonperturbatively improved Wilson-Sheikholeslami-Wohlert action with N{sub f}=2 mass-degenerate sea quarks. The two ensembles have similar lattice spacings but different sea-quark masses. We use the first stochastic method to extract O(a)-improved, matched lattice results for the semileptonic form factors on the ensemble with lighter sea quarks, extracting f{sub +}(0).
Small form factor optical fiber connector evaluation for harsh environments
NASA Astrophysics Data System (ADS)
Ott, Melanie N.; Thomes, W. Joe, Jr.; Chuska, Richard F.; Switzer, Robert; Blair, Diana E.
2011-09-01
For the past decade NASA programs have utilized the Diamond AVIM connector for optical fiber assemblies on space flight instrumentation. These connectors have been used in communications, sensing and LIDAR systems where repeatability and high performance are required. Recently Diamond has released a smaller form factor optical fiber connector called the "Mini-AVIM" which although more compact still includes the tight tolerances and the ratcheting feature of the heritage AVIM. NASA Goddard Space Flight Center Photonics Group in the Parts, Packaging and Assembly Technologies Office has been performing evaluations of this connector to determine how it compares to the performance of the AVIM connector and to assess its feasibility for harsh environmental applications. Vibration and thermal testing were performed on the Mini-AVIM with both multi-mode and single-mode optical fiber using insitu optical transmission monitoring. Random vibration testing was performed using typical launch condition profiles for most NASA missions but extended to 35 Grms, which is much higher than most requirements. Thermal testing was performed incrementally up to a range of -55°C to +125°C. The test results include both unjacketed fiber and cabled assembly evaluations. The data presented here indicate that the Mini-AVIM provides a viable option for small form factor applications that require a high performance optical fiber connector.
Astrophysical S factors for radiative proton capture by {sup 3}H and {sup 7}Li nuclei
Dubovichenko, S. B.
2011-03-15
Within the potential cluster model where orbital states are classified according to Young diagrams and isospin, astrophysical S factors are considered for radiative proton capture by {sup 3}H and {sup 7}Li nuclei at energies of up to 1 and 10 keV, respectively. It is shown that the approach used, which takes into account only the E1 transition for the p{sup 3}H capture process, makes it possible to describe well the most recent experimental data at c.m. energies in the range from 50 keV to 5MeV. In the case of proton capture by {sup 7}Li nuclei, an M1 processwas taken into account in addition to the E1 transition, and a general behavior and the magnitude of the experimental S factor could be correctly reproduced owing to this at astrophysical energies, including the region around the resonance at 0.441 MeV (in the laboratory frame).
Galiano, Vicente; Villalaín, José
2016-06-01
Arbidol is a potent broad-spectrum antiviral molecule for the treatment and prophylaxis of many viral infections. Viruses that can be inhibited by arbidol include enveloped and non-enveloped viruses, RNA and DNA viruses, as well as pH-independent and pH-dependent ones. These differences in viral types highlight the broad spectrum of Arb antiviral activity and, therefore, it must affect a common viral critical step. Arbidol incorporates rapidly into biological membranes, and some of its antiviral effects might be related to its capacity to interact with and locate into the membrane. However, no information is available of the molecular basis of its antiviral mechanism/s. We have aimed to locate the protonated (Arp) and unprotonated (Arb) forms of arbidol in a model membrane system. Both Arb and Arp locate in between the hydrocarbon acyl chains of the phospholipids but its specific location and molecular interactions differ from each other. Whereas both Arb and Arp average location in the membrane palisade is a similar one, Arb tends to be perpendicular to the membrane surface, whereas Arp tends to be parallel to it. Furthermore, Arp, in contrast to Arb, seems to interact stronger with POPG than with POPC, implying the existence of a specific interaction between Arp, the protonated from, with negatively charged phospholipids. This data would suggest that the active molecule of arbidol in the membrane is the protonated one, i.e., the positively charged molecule. The broad antiviral activity of arbidol would be defined by the perturbation it exerts on membrane structure and therefore membrane functioning. PMID:26843065
Thin and small form factor cells : simulated behavior.
Clews, Peggy Jane; Pluym, Tammy; Grubbs, Robert K.; Cruz-Campa, Jose Luis; Zubia, David; Young, Ralph Watson; Okandan, Murat; Gupta, Vipin P.; Nielson, Gregory N.; Resnick, Paul James
2010-07-01
Thin and small form factor cells have been researched lately by several research groups around the world due to possible lower assembly costs and reduced material consumption with higher efficiencies. Given the popularity of these devices, it is important to have detailed information about the behavior of these devices. Simulation of fabrication processes and device performance reveals some of the advantages and behavior of solar cells that are thin and small. Three main effects were studied: the effect of surface recombination on the optimum thickness, efficiency, and current density, the effect of contact distance on the efficiency for thin cells, and lastly the effect of surface recombination on the grams per Watt-peak. Results show that high efficiency can be obtained in thin devices if they are well-passivated and the distance between contacts is short. Furthermore, the ratio of grams per Watt-peak is greatly reduced as the device is thinned.
The Pion Charge Form Factor Through Pion Electroproduction
Horn, Tanja
2006-04-01
The goal of Jefferson Lab experiment E01-004 (F?-2) was the measurement of the longitudinal and transverse cross sections via pion electroproduction from hydrogen and deuterium for the purpose of extracting the charged pion form factor using pole dominance. The data were taken at two values of Q2 (1.60 and 2.45 GeV/c)2. In order to attain full coverage in R?, charged pions were detected in parallel kinematics (along the direction of momentum transfer, q), and at Â±3 degrees off the direction of momentum transfer. For each Q2 data were taken for two values of the virtual photon polarization, ?, respectively. All data were taken at a fixed center of mass energy, W=2.22 GeV. The longitudinal and transverse pieces of the cross section were separated using the Rosenbluth separation method.
Deuteron Electromagnetic Form Factors in AdS/QCD
NASA Astrophysics Data System (ADS)
Lyubovitskij, Valery E.; Gutsche, Thomas; Schmidt, Ivan; Vega, Alfredo
2016-07-01
We extend a soft-wall AdS/QCD approach to a description of deuteron properties. Our framework is based an effective action formulated in terms of AdS fields, which are holographically equivalent to the deuteron and photon fields. This action produces the equation of motion for the deuteron wave function and the Q^2-dependent electromagnetic current, which are then used to calculate the deuteron electromagnetic form factors and structure functions in the Euclidean region. We show that the predicted deuteron quantities are expressed through a universal function, which is defined by a single scale parameter κ and which has the correct 1/Q^{10} power scaling at large Q^2.
Finite-lattice form factors in free-fermion models
NASA Astrophysics Data System (ADS)
Iorgov, N.; Lisovyy, O.
2011-04-01
We consider the general {Z}_2 -symmetric free-fermion model on the finite periodic lattice, which includes as special cases the Ising model on the square and triangular lattices and the {Z}_n -symmetric BBS τ(2)-model with n = 2. Translating Kaufman's fermionic approach to diagonalization of Ising-like transfer matrices into the language of Grassmann integrals, we determine the transfer matrix eigenvectors and observe that they coincide with the eigenvectors of a square lattice Ising transfer matrix. This allows us to find exact finite-lattice form factors of spin operators for the statistical model and the associated finite-length quantum chains, of which the most general is equivalent to the XY chain in a transverse field.
Deuteron Electromagnetic Form Factors in AdS/QCD
NASA Astrophysics Data System (ADS)
Lyubovitskij, Valery E.; Gutsche, Thomas; Schmidt, Ivan; Vega, Alfredo
2016-03-01
We extend a soft-wall AdS/QCD approach to a description of deuteron properties. Our framework is based an effective action formulated in terms of AdS fields, which are holographically equivalent to the deuteron and photon fields. This action produces the equation of motion for the deuteron wave function and the Q^2 -dependent electromagnetic current, which are then used to calculate the deuteron electromagnetic form factors and structure functions in the Euclidean region. We show that the predicted deuteron quantities are expressed through a universal function, which is defined by a single scale parameter κ and which has the correct 1/Q^{10} power scaling at large Q^2.
Chiral corrections to the hyperon vector form factors
NASA Astrophysics Data System (ADS)
Villadoro, Giovanni
2006-07-01
We present a complete calculation of the SU(3)-breaking corrections to the hyperon vector form factors up to O(p4) in heavy baryon chiral perturbation theory. Because of the Ademollo-Gatto theorem, at this order the results do not depend on unknown low energy constants and allow to test the convergence of the chiral expansion. We complete and correct previous calculations and find that O(p3) and O(1/M0) corrections are important. We also study the inclusion of the decuplet degrees of freedom, showing that in this case the perturbative expansion is jeopardized. These results raise doubts on the reliability of the chiral expansion for hyperons.
Lattice calculation of composite dark matter form factors
NASA Astrophysics Data System (ADS)
Appelquist, T.; Brower, R. C.; Buchoff, M. I.; Cheng, M.; Cohen, S. D.; Fleming, G. T.; Kiskis, J.; Lin, M. F.; Neil, E. T.; Osborn, J. C.; Rebbi, C.; Schaich, D.; Schroeder, C.; Syritsyn, S.; Voronov, G.; Vranas, P.; Wasem, J.
2013-07-01
Composite dark matter candidates, which can arise from new strongly-coupled sectors, are well-motivated and phenomenologically interesting, particularly in the context of asymmetric generation of the relic density. In this work, we employ lattice calculations to study the electromagnetic form factors of electroweak-neutral dark-matter baryons for a three-color, QCD-like theory with Nf=2 and 6 degenerate fermions in the fundamental representation. We calculate the (connected) charge radius and anomalous magnetic moment, both of which can play a significant role for direct detection of composite dark matter. We find minimal Nf dependence in these quantities. We generate mass-dependent cross sections for dark matter-nucleon interactions and use them in conjunction with experimental results from XENON100, excluding dark matter candidates of this type with masses below 10 TeV.
Griffin, J.E.; MacLachlan, J.A.; Nicholls, G.N.; Qian, Z.B.
1984-08-09
Both the proton and antiproton bunches which will collide in the Tevatron have longitudinal emittance greater than can be accelerated by the main ring from 8 GeV without large loss and emittance growth. We have previously described the technique of combining several smaller bunches at the Tevatron injection energy with little increase in the total emittance and negligible loss. This technique requires adiabatic debunching of several adjacent 53 MHz bunches by smooth reduction of the RF voltage from approx. 1 MV to approx. 100 V. The very low voltage is extremely difficult to attain with a high-Q system designed for megavolt accelerating potential. The counterphasing technique of voltage reduction which we have used in main ring experiments and proposed for the TeV I project is to divide the accelerating cavities into two closely matched groups and to smoothly shift the relative phase of the drive to the two groups by 180 degrees. When the net voltage has been reduced by this means to the lowest practical level, about 10 kV, the final voltage reduction may be performed by turning off the high-Q system and using a low-Q cavity. The voltage induced on the undriven gaps of the high-Q system is low enough not to be a major problem because the total intensity is low. However, the effects are not negligible, and dynamic beam loading compensation is required. This memo proposes that the process described above be simplified somewhat by replacing the counterphasing voltage reduction with a zero-voltage spreading of the bunches for several milliseconds followed by a few hundred microseconds of rotation to minimum energy spread in buckets produced at high voltage.