Simultaneous production of lepton pairs in ultraperipheral relativistic heavy ion collisions

NASA Astrophysics Data System (ADS)

Kurban, E.; Güçlü, M. C.

2017-10-01

We calculate the total cross sections and probabilities of electromagnetic productions of electron, muon, and tauon pairs simultaneously. At the CERN Large Hadron Collider (LHC), the available electromagnetic energy is sufficient to produce all kinds of leptons coherently. The masses of muons and tauons are large, so their Compton wavelengths are small enough to interact with the colliding nuclei. Therefore, the realistic nuclear form factors are included in the calculations of electromagnetic pair productions. The cross section calculations show that, at LHC energies, the probabilities of simultaneous productions of all kinds of leptons are increased significantly compared to energies available at the BNL Relativistic Heavy Ion Collider (RHIC) . Experimentally, observing this simultaneous production can give us important information about strong QED.

Behavioral effects of neurofeedback in adolescents with ADHD: a randomized controlled trial.

PubMed

Bink, Marleen; van Nieuwenhuizen, Chijs; Popma, Arne; Bongers, Ilja L; van Boxtel, Geert J M

2015-09-01

Neurofeedback has been proposed as a potentially effective intervention for reducing Attention Deficit Hyperactivity Disorder (ADHD) symptoms. However, it remains unclear whether neurofeedback is of additional value to treatment as usual (TAU) for adolescents with clinical ADHD symptoms. Using a multicenter parallel-randomized controlled trial design, adolescents with ADHD symptoms were randomized to receive either a combination of TAU and neurofeedback (NFB + TAU, n = 45) or TAU-only (n = 26). Randomization was computer generated and stratified for age group (ages 12 through 16, 16 through 20, 20 through 24). Neurofeedback treatment consisted of approximately 37 sessions of theta/sensorimotor rhythm (SMR)-training on the vertex (Cz). Primary behavioral outcome measures included the ADHD-rating scale, Youth Self Report, and Child Behavior Checklist all assessed pre- and post-intervention. Behavioral problems decreased equally for both groups with medium to large effect sizes, range of partial η2 = 0.08-0.31, p < 0.05. Hence, the combination of NFB + TAU was not more effective than TAU-only on the behavioral outcome measures. In addition, reported adverse effects were similar for both groups. On behavioral outcome measures, the combination of neurofeedback and TAU was as effective as TAU-only for adolescents with ADHD symptoms. Considering the absence of additional behavioral effects in the current study, in combination with the limited knowledge of specific treatment effects, it is questionable whether theta/SMR neurofeedback for adolescents with ADHD and comorbid disorders in clinical practice should be used. Further research is warranted to investigate possible working mechanisms and (long-term) specific treatment effects of neurofeedback.

Analysis of the Decay Tauon Going to Rho Particle Neutrino

NASA Astrophysics Data System (ADS)

Bougerolle, Stephen Edward

An analysis of the decay tau^ {+/-}torho^{+/- }nu_{tau} has been undertaken in the OPAL experiment at CERN, in Geneva, Switzerland. From the 1990 experimental run of the LEP particle accelerator, a sample of 3310 e^+ e^-totau^+tau ^- events was selected, with an estimated contamination of 1.9%. Requirements were applied to select a subsample of tau^{+/- }torho^{+/-}nu _tau decays, resulting in 650 decays being found. From studies with simulated data, the non -rho contamination in this sample was estimated to be approximately 22%, and the rho selection efficiency to be approximately 33%. The Branching fraction for the decay is measured to be B(tau^{+/-}to rho^{+/-}nu_{ tau}) = 0.234+/- 0.009(stat.) +/- _sp{0.009}{0.010} (syst.). The mean tau polarisation at the peak of the Z^0 resonance is measured to be P_tau= -0.17+/- 0.10(stat.) +/- 0.08(syst.). From the tau polarisation we extract a measurement of the electroweak mixing sin^2 theta_{W}=0.225 +/- 0.015. The tau polarisation asymmetry at the peak of the Z^0 resonance is also measured, A_sp{FB }{Pol}=-0.09+/- 0.13+/- 0.05. From the polarisation measurement, v_tau /a_tau=0.09+/- 0.06, and from the polarisation asymmetry v_{e }/a_{e}=0.06+/- 0.10. Combined with previous LEP measurements of the tau polarisation, the electroweak mixing is found to be sin^2 theta_{W}=0.2308+/- 0.0042. Combined with measurements from other experiments, one obtains sin ^2 theta_{W }=0.2303+/- 0.0013.

Lepton flavor violation with displaced vertices

NASA Astrophysics Data System (ADS)

Heeck, Julian; Rodejohann, Werner

2018-01-01

If light new physics with lepton-flavor-violating couplings exists, the prime discovery channel might not be ℓ →ℓ‧ γ but rather ℓ →ℓ‧ X, where the new boson X could be an axion, majoron, familon or Z‧ gauge boson. The most conservative bound then comes from ℓ →ℓ‧ + inv , but if the on-shell X can decay back into leptons or photons, displaced-vertex searches could give much better limits. We show that only a narrow region in parameter space allows for displaced vertices in muon decays, μ → eX , X → γγ , ee, whereas tauon decays can have much more interesting signatures.

Astrophysical signatures of leptonium

NASA Astrophysics Data System (ADS)

Ellis, Simon C.; Bland-Hawthorn, Joss

2018-01-01

More than 1043 positrons annihilate every second in the centre of our Galaxy yet, despite four decades of observations, their origin is still unknown. Many candidates have been proposed, such as supernovae and low mass X-ray binaries. However, these models are difficult to reconcile with the distribution of positrons, which are highly concentrated in the Galactic bulge, and therefore require specific propagation of the positrons through the interstellar medium. Alternative sources include dark matter decay, or the supermassive black hole, both of which would have a naturally high bulge-to-disc ratio. The chief difficulty in reconciling models with the observations is the intrinsically poor angular resolution of gamma-ray observations, which cannot resolve point sources. Essentially all of the positrons annihilate via the formation of positronium. This gives rise to the possibility of observing recombination lines of positronium emitted before the atom annihilates. These emission lines would be in the UV and the NIR, giving an increase in angular resolution of a factor of 104 compared to gamma ray observations, and allowing the discrimination between point sources and truly diffuse emission. Analogously to the formation of positronium, it is possible to form atoms of true muonium and true tauonium. Since muons and tauons are intrinsically unstable, the formation of such leptonium atoms will be localised to their places of origin. Thus observations of true muonium or true tauonium can provide another way to distinguish between truly diffuse sources such as dark matter decay, and an unresolved distribution of point sources. Contribution to the Topical Issue "Low Energy Positron and Electron Interactions", edited by James Sullivan, Ron White, Michael Bromley, Ilya Fabrikant and David Cassidy.

Internet-based attentional bias modification training as add-on to regular treatment in alcohol and cannabis dependent outpatients: a study protocol of a randomized control trial.

PubMed

Heitmann, Janika; van Hemel-Ruiter, Madelon E; Vermeulen, Karin M; Ostafin, Brian D; MacLeod, Colin; Wiers, Reinout W; DeFuentes-Merillas, Laura; Fledderus, Martine; Markus, Wiebren; de Jong, Peter J

2017-05-23

The automatic tendency to attend to and focus on substance-related cues in the environment (attentional bias), has been found to contribute to the persistence of addiction. Attentional bias modification (ABM) interventions might, therefore, contribute to treatment outcome and the reduction of relapse rates. Based on some promising research findings, we designed a study to test the clinical relevance of ABM as an add-on component of regular intervention for alcohol and cannabis patients. The current protocol describes a study which will investigate the effectiveness and cost-effectiveness of a newly developed home-delivered, multi-session, internet-based ABM (iABM) intervention as an add-on to treatment as usual (TAU). TAU consists of cognitive behavioural therapy-based treatment according to the Dutch guidelines for the treatment of addiction. Participants (N = 213) will be outpatients from specialized addiction care institutions diagnosed with alcohol or cannabis dependency who will be randomly assigned to one of three conditions: TAU + iABM; TAU + placebo condition; TAU-only. Primary outcome measures are substance use, craving, and rates of relapse. Changes in attentional bias will be measured to investigate whether changes in primary outcome measures can be attributed to the modification of attentional bias. Indices of cost-effectiveness and secondary physical and psychological complaints (depression, anxiety, and stress) are assessed as secondary outcome measures. This randomized control trial will be the first to investigate whether a home-delivered, multi-session iABM intervention is (cost-) effective in reducing relapse rates in alcohol and cannabis dependency as an add-on to TAU, compared with an active and a waiting list control group. If proven effective, this ABM intervention could be easily implemented as a home-delivered component of current TAU. Netherlands Trial Register, NTR5497 , registered on 18th September 2015.