Mon·Mar 29, 2021Monday·March 29, 2021

1. 01*

   Proton-${}^3\mathrm{He}$ elastic scattering at intermediate energies

   A. Watanabe🇯🇵 · S. Nakai🇯🇵 · Y. Wada🇯🇵 · K. Sekiguchi🇯🇵 · A. Deltuva🇱🇹 · T. Akieda🇯🇵 · D. Etoh🇯🇵 · M. Inoue🇯🇵 · Y. Inoue🇯🇵 · K. Kawahara🇯🇵 · H. Kon🇯🇵 · K. Miki🇯🇵 and 33 other authors

   We present a precise measurement of the cross section, proton and ${}^3\mathrm{He}$ analyzing powers, and spin correlation coefficient $C_{y,y}$ for $p$-${}^3\mathrm{He}$ elastic scattering near 65 MeV, and a comparison with rigorous four-nucleon scattering calculations based on realistic nuclear potentials and a model with $\Delta$-isobar excitation. Clear discrepancies are seen in some of the measured observables in the regime around the cross section minimum. Theoretical predictions using scaling relations between the calculated cross section and the ${}^3\mathrm{He}$ binding energy are not successful in reproducing the data. Large sensitivity to the $NN$ potentials and rather small $\Delta$-isobar effects in the calculated cross section are noticed as different features from those in the deuteron-proton elastic scattering. The results obtained above indicate that $p$-${}^3\mathrm{He}$ scattering at intermediate energies is an excellent tool to explore nuclear interactions not accessible by three-nucleon scattering.

   nucl-exnucl-thPRC(2021)·12 citations
2. 02*

   Constraints on the initial state of PbPb collisions via measurements of Z boson yields and azimuthal anisotropy at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV

   CMS Collaboration

   The CMS experiment at the LHC has measured the differential cross sections of Z bosons decaying to pairs of leptons, as functions of transverse momentum and rapidity, in lead-lead collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The measured Z boson elliptic azimuthal anisotropy coefficient is compatible with zero, showing that Z bosons do not experience significant final-state interactions in the medium produced in the collision. Yields of Z bosons are compared to Glauber model predictions and are found to deviate from these expectations in peripheral collisions, indicating the presence of initial collision geometry and centrality selection effects. The precision of the measurement allows, for the first time, for a data-driven determination of the nucleon-nucleon integrated luminosity as a function of lead-lead centrality, thereby eliminating the need for its estimation based on a Glauber model.

   ↳ hep-exnucl-exPRL(2021)·44 citations
3. 03*

   Effect of magnetic field on jet transport coefficient $\hat{q}$

   Debjani Banerjee🇮🇳 · Prottoy Das🇮🇳 · Souvik Paul🇮🇳 · Abhi Modak🇮🇳 · Ankita Budhraja🇮🇳 · Sabyasachi Ghosh🇮🇳 · Sidharth K. Prasad🇮🇳

   We report the estimation of jet transport coefficient, $\hat{q}$ for quark- and gluon-initiated jets using a simple quasi-particle model in absence and presence of magnetic field. This model introduces a temperature and magnetic field-dependent degeneracy factor of partons, which is tuned by fitting the entropy density of lattice quantum chromodynamics data. At a finite magnetic field, $\hat{q}$ for quark jets splits into parallel and perpendicular components whose magnetic field dependence comes from two sources: the field-dependent degeneracy factor and the phase space part guided from the shear viscosity to entropy density ratio. Due to the electrically neutral nature of gluons, the estimation of $\hat{q}$ for gluon jets is affected only by the field-dependent degeneracy factor. In presence of a finite magnetic field, we find a significant enhancement in $\hat{q}$ for both quark- and gluon-initiated jets at low temperature, which gradually decreases towards high temperature. We compare the obtained results with the earlier calculations based on the anti-de Sitter/conformal field theory correspondence, and a qualitatively similar trend is observed. The change in $\hat{q}$ in presence of magnetic field is, however, quantitatively different for quark- and gluon-initiated jets. This is an interesting observation which can be explored experimentally to verify the effect of magnetic field on $\hat{q}$.

   ↳ hep-phhep-exnucl-exnucl-thPramana(2023)·7 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.