Wed·Mar 25, 2015Wednesday·March 25, 2015

1. 01*

   Hadronic "flow" in p--Pb collisions at the Large Hadron Collider?

   You Zhou🇩🇰 · Xiangrong Zhu🇨🇳 · Pengfei Li🇨🇳 · Huichao Song🇨🇳

   Using the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model, we investigate azimuthal correlations in p--Pb collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=5.02$ TeV. Comparison with the experimental data shows that UrQMD can not reproduce the multiplicity dependence of 2- and 4-particle cumulants, especially the transition from positive to negative values of $c_2\{4\}$ in high multiplicity events, which has been taken as experimental evidence of collectivity in p--Pb collisions. Meanwhile, UrQMD can not qualitatively describe the differential elliptic flow, $v_2(p_{\mathrm{T}})$, of all charged hadrons at various multiplicity classes. These discrepancies show that the simulated hadronic p--Pb systems can not generate enough collective flow as observed in experiment, the associated hadron emissions are largely influenced by non-flow effects. However, the characteristic $v_2(p_{\mathrm{T}})$ mass-ordering of pions, kaons and protons is observed in UrQMD, which is the consequence of hadronic interactions and not necessarily associated with strong fluid-like expansions.

   ↳ nucl-thnucl-exPRC(2015)·65 citations
2. 02*

   Comments on the radial distribution of charged particles in a magnetic field

   H. Backe

   Magnetic guiding fields in combination with energy dispersive semiconductor detectors have been employed already more than 50 years ago for in-beam internal conversion electron spectroscopy. Even then it was recognized that efficiency modulations may appear as function of the electron energy, arising when electrons hit a baffle or miss the sensitive area of the detector. Current high precision beta decay experiments of polarized neutrons with conceptional similar experimental devices resulted in a detailed study of the point spread function (PSF). The latter describes the radial probability distribution of mono-energetic electrons at the detector plane. Singularities occur as function of the radial detector coordinate which have been investigated and discussed by Sjue at al. (Rev. Scient. Instr. 86, 023102 (2015)), and Dubbers (arXiv:1501.05131v1 [physics.ins-det]). In this comment a rather precise numerical representation of the PSF is presented and compared with approximations in the mentioned papers.

   ↳ physics.ins-detnucl-exRev.Sci.Instrum.(2015)·3 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.