Mon·May 31, 2021Monday·May 31, 2021

1. 01*

   Peculiar features of missing mass distributions in studies of exclusive reactions

   Iu.A. Skorodumina🇺🇸 · G.V. Fedotov🇷🇺 · R.W. Gothe🇺🇸

   This study examines the influence of the following five factors on missing mass distributions, radiative effects, admixtures from other channels, detector resolution, Fermi smearing, and final state interactions with spectator nucleons. All factors are considered independently of each other. The examination is supported by theoretical calculations and exemplified by distributions of the quantities $M_{X[0]}^2$ and $M_{X[{\pi }^{-}]}^2$ that are produced by the Monte Carlo simulation for the double-pion electroproduction off protons. The study also includes a naive modeling of kinematic effects of final state interactions with spectator nucleons.

   nucl-exphysics.data-an1 citation
2. 02*

   Implications of PREX-2 on the electric dipole polarizability of neutron rich nuclei

   J. Piekarewicz🇺🇸

   The recent announcement by the PREX collaboration of an unanticipated thick neutron skin in 208Pb (Rskin208) has challenged our understanding of neutron rich matter in the vicinity of nuclear saturation density. Whereas earlier constraints indicate that the symmetry energy is relatively soft, the PREX-2 result seems to suggest the opposite. We confront constraints on the symmetry energy obtained from measurements of the electric dipole polarizability against those informed by the PREX-2 measurement of Rskin208 and by the correlations that it entails. Covariant energy density functionals informed by the properties of finite nuclei are used to compute the electric dipole response of 48Ca, 68Ni, 132Sn, and 208Pb. The set of functionals used in this work are consistent with experimental data, yet are flexible enough in that they span a wide range of values of Rskin208. It is found that theoretical predictions of the electric dipole polarizability that are consistent with the PREX-2 measurement systematically overestimate the corresponding values extracted from the direct measurements of the distribution of electric dipole strength. The neutron skin thickness of 208Pb extracted from parity violating electron scattering and the electric dipole polarizability measured in photoabsorption experiments are two of the cleanest experimental tools used to constrain the symmetry energy around nuclear saturation density. However, the recent value of Rskin208 that suggests a fairly stiff symmetry energy stands in stark contrast to the conclusions derived from the electric dipole polarizability. At present, we offer no solution to this dilemma.

   ↳ nucl-thnucl-exPRC(2021)·59 citations
3. 03*

   Hyperon Polarization from the Vortical Fluid in Low Energy Nuclear Collisions

   Yu Guo🇨🇳 · Jinfeng Liao🇺🇸 · Enke Wang🇨🇳 · Hongxi Xing🇨🇳 · Hui Zhang🇨🇳

   In 2017, STAR Collaboration reported the measurements of hyperon global polarization in heavy ion collisions, suggesting the subatomic fireball fluid created in these collisions as the most vortical fluid. There remains the interesting question: at which beam energy the truly most vortical fluid will be located. In this work we perform a systematic study on the beam energy dependence of hyperon global polarization phenomenon, especially in the interesting $\hat{O}(1\sim 10)\mathrm{GeV}$ region. We find a non-monotonic trend, with the global polarization to first increase and then decrease when beam energy is lowered from $27\mathrm{GeV}$ down to $3\mathrm{GeV}$. The maximum polarization signal has been identified around $\sqrt{s_{NN}}=7.7\mathrm{GeV}$, where the heavy ion collisions presumably create the most vortical fluid. Detailed experimental measurements in the $\hat{O}(1\sim 10)\mathrm{GeV}$ beam energy region are expected to test the prediction very soon.

   ↳ nucl-thhep-phnucl-exPRC(2021)·57 citations
4. 04*

   Charge-state distributions of highly charged lead ions at relativistic collision energies

   F. M. Kröger🇩🇪 · G. Weber🇩🇪 · S. Hirlaender🇦🇹 · R. Alemany-Fernandez🇨🇭 · M. W. Krasny🇫🇷 · Th. Stöhlker🇩🇪 · I. Yu. Tolstikhina🇷🇺 · V. P. Shevelko🇷🇺

   Presented is a study of the charge-state evolution of relativistic lead ions passing through a thin aluminum stripper foil. It was motivated by the Gamma Factory project at CERN, where optical laser pulses will be converted into intense gamma-ray beams with energies up to a few hundred MeV via excitation of atomic transitions in few-electron heavy-ions at highly relativistic velocities. In this study all charge-states starting from Pb${}^{54+}$ up to bare ions are considered at kinetic projectile energies of 4.2 and 5.9 GeV/u. To this purpose the BREIT code is employed together with theoretical cross-sections for single-electron loss and capture of the projectile ions. To verify the predicted charge-state evolution, the results are compared to the very few experimental data being available for highly-relativistic lead beams. Reasonable agreement is found, in particular for the yields of Pb${}^{80+}$ and Pb${}^{81+}$ ions that were recently measured using an aluminum stripper foil located in the transfer beam line between the PS and SPS synchrotron accelerators at CERN. The present study lays the groundwork to optimize the yields of charge states of interest for experiments within the scientific program of the future Gamma Factory project.

   ↳ hep-exnucl-exAnnalen Phys.(2022)·6 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.