Fri·Oct 20, 2017Friday·October 20, 2017

1. 01*

   Improved Monte Carlo Glauber predictions at present and future nuclear colliders

   Constantin Loizides (ORNL)🇺🇸 · Jason Kamin (UiC)🇺🇸 · David d'Enterria (CERN)🇨🇭

   We present the results of an improved Monte Carlo Glauber (MCG) model of relevance for collisions involving nuclei at center-of-mass energies of BNL RHIC ($\sqrt{s_{\mathrm{NN}}}=0.2$ TeV), CERN LHC ($\sqrt{s_{\mathrm{NN}}}=2.76$-$8.8$ TeV), and proposed future hadron colliders ($\sqrt{s_{\mathrm{NN}}}\approx 10$-$63$ TeV). The inelastic pp cross sections as a function of $\sqrt{s_{\mathrm{NN}}}$ are obtained from a precise data-driven parametrization that exploits the many available measurements at LHC collision energies. We describe the nuclear transverse profile with two separated 2-parameter Fermi distributions for protons and neutrons to account for their different densities close to the nuclear periphery. Furthermore, we model the nucleon degrees of freedom inside the nucleus through a lattice with a minimum nodal separation, combined with a "recentering and reweighting" procedure, that overcomes some limitations of previous MCG approaches. The nuclear overlap function, number of participant nucleons and binary nucleon-nucleon collisions, participant eccentricity and triangularity, overlap area and average path length are presented in intervals of percentile centrality for lead-lead (PbPb) and proton-lead (pPb) collisions at all collision energies. We demonstrate for collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV that the central values of the Glauber quantities change by up to 7%, in a few bins of reaction centrality, due to the improvements implemented, though typically remain within the previously assigned systematic uncertainties, while their associated uncertainties are generally smaller (mostly below 5%) at all centralities than for earlier calculations. Tables for all quantities versus centrality at present and foreseen collision energies involving Pb nuclei, as well as for collisions of XeXe at $\sqrt{s_{\mathrm{NN}}}=5.44$, and AuAu and CuCu at $\sqrt{s_{\mathrm{NN}}}=0.2$ TeV, are provided.

   nucl-exhep-phPRC(2018)·388 citations
2. 02*

   Study of Light Backgrounds from Relativistic Electrons in Air Light-Guides

   S. Riordan🇺🇸 · Y. X. Zhao🇺🇸 · S. Baunack🇩🇪 · D. Becker🇩🇪 · C. Clarke🇺🇸 · K. Dehmelt🇺🇸 · A. Deshpande🇺🇸 · M. Gericke🇨🇦 · B. Glaser🇩🇪 · K. Imai🇯🇵 · T. Kutz🇺🇸 · F. E. Maas🇩🇪 and 8 other authors

   The MOLLER experiment proposed at the Thomas Jefferson National Accelerator Facility plans a precision low energy determination of the weak mixing angle via the measurement of the parity-violating asymmetry in the scattering of high energy longitudinally polarized electrons from electrons bound in a liquid hydrogen target (Møller scattering). A relative measure of the scattering rate is planned to be obtained by intercepting the Møller scattered electrons with a circular array of thin fused silica tiles attached to air light guides, which facilitate the transport of Cherenkov photons generated within the tiles to photomultiplier tubes (PMTs). The scattered flux will also pass through the light guides of downstream tiles, generating additional Cherenkov as well as scintillation light and is a potential background. In order to estimate the rate of these backgrounds, a gas-filled tube detector was designed and deployed in an electron beam at the MAMI facility at Johannes Gutenberg University, Mainz, Germany. Described in this paper is the design of a detector to measure separately the scintillation and Cherenkov responses of gas mixtures from relativistic electrons, the results of studies of several gas mixtures with comparisons to simulations, and conclusions about the implications for the design of the MOLLER detector apparatus.

   ↳ physics.ins-dethep-exnucl-exNucl.Instrum.Meth.A(2018)·0 citations
3. 03*

   Combining {\gamma}-ray and particle spectroscopy with SONIC@HORUS

   S. G. Pickstone · M. Weinert · M. Färber · F. Heim · E. Hoemann · J. Mayer🇩🇪 · M. Müscher · S. Prill · P. Scholz · M. Spieker🇺🇸 · V. Vielmetter · J. Wilhelmy · A. Zilges🇩🇪

   The particle spectrometer SONIC for particle-$\gamma$ coincidence measurements was commissioned at the Institute for Nuclear Physics in Cologne, Germany. SONIC consists of up to 12 silicon $\Delta E$-$E$ telescopes with a total solid angle coverage of 9%, and will complement HORUS, a $\gamma$-ray spectrometer with 14 HPGe detectors. The combined setup SONIC@HORUS is used to investigate the $\gamma$-decay behaviour of low-spin states up to the neutron separation threshold excited by light-ion inelastic scattering and transfer reactions using beams provided by a 10 MV FN Tandem accelerator. The particle-$\gamma$ coincidence method will be presented using data from a ${}^{92}$Mo(p,p'$\gamma$) experiment. In a ${}^{119}$Sn(d,X) experiment, excellent particle identification has been achieved because of the good energy resolution of the silicon detectors of approximately 20 keV. Due to the non-negligible momentum transfer in the reaction, a Doppler correction of the detected $\gamma$-ray energy has to be performed, using the additional information from measuring the ejectile energy and direction. The high sensitivity of the setup is demonstrated by the results from a ${}^{94}$Mo(p,p'$\gamma$) experiment, where small $\gamma$-decay branching ratios have been deduced.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2017)·9 citations
4. 04*

   Varying the chiral magnetic effect relative to flow in a single nucleus-nucleus collision

   Hao-jie Xu🇨🇳 · Jie Zhao🇺🇸 · Xiaobao Wang🇨🇳 · Hanlin Li🇨🇳 · Zi-Wei Lin🇺🇸 · Caiwan Shen🇨🇳 · Fuqiang Wang🇺🇸

   We propose a novel method to search for the chiral magnetic effect (CME) in heavy ion collisions. We argue that the relative strength of the magnetic field (mainly from spectator protons and responsible for the CME) with respect to the reaction plane and the participant plane is opposite to that of the elliptic flow background arising from the fluctuating participant geometry. This opposite behavior in a single collision system, hence with small systematic uncertainties, can be exploited to extract the possible CME signal from the flow background. The method is applied to the existing data at RHIC, the outcome of which is discussed.

   ↳ nucl-thhep-phnucl-exCPC(2018)·80 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.