Tue·Aug 13, 2019Tuesday·August 13, 2019

1. 01*

   Bulk Properties of the System Formed in Au+Au Collisions at $\sqrt{s_{\mathrm{NN}}}$ = 14.5 GeV

   STAR Collaboration: J. Adam🇺🇸 · L. Adamczyk🇵🇱 · J. R. Adams🇺🇸 · J. K. Adkins🇺🇸 · G. Agakishiev🇷🇺 · M. M. Aggarwal🇮🇳 · Z. Ahammed🇮🇳 · I. Alekseev🇷🇺 · D. M. Anderson🇺🇸 · R. Aoyama🇯🇵 · A. Aparin🇷🇺 · E. C. Aschenauer🇺🇸 and 336 other authors

   We report systematic measurements of bulk properties of the system created in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 14.5 GeV recorded by the STAR detector at the Relativistic Heavy Ion Collider (RHIC).The transverse momentum spectra of ${\pi }^{\pm }$, $K^{\pm }$ and $p(\bar{p})$ are studied at mid-rapidity ($|y|<0.1$) for nine centrality intervals. The centrality, transverse momentum ($p_T$),and pseudorapidity ($\eta$) dependence of inclusive charged particle elliptic flow ($v_2$), and rapidity-odd charged particles directed flow ($v_1$) results near mid-rapidity are also presented. These measurements are compared with the published results from Au+Au collisions at other energies, and from Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV. The results at $\sqrt{s_{\mathrm{NN}}}$ = 14.5 GeV show similar behavior as established at other energies and fit well in the energy dependence trend. These results are important as the 14.5 GeV energy fills the gap in ${\mu }_B$, which is of the order of 100 MeV,between $\sqrt{s_{\mathrm{NN}}}$ =11.5 and 19.6 GeV. Comparisons of the data with UrQMD and AMPT models show poor agreement in general.

   nucl-exhep-exhep-phPRC(2020)·73 citations
2. 02*

   Constraints for stellar electron-capture rates on ${}^{86}$Kr via the ${}^{86}$Kr($t$,${}^3$He$+\gamma$)${}^{86}$Br reaction and the implications for core-collapse supernovae

   R. Titus🇺🇸 · E.M. Ney · R.G.T. Zegers🇺🇸 · D. Bazin🇺🇸 · J. Belarge · P.C. Bender🇨🇦 · B.A. Brown🇺🇸 · C.M. Campbell🇺🇸 · B. Elman · J. Engel🇺🇸 · A. Gade🇺🇸 · B. Gao and 11 other authors

   In the late stages of stellar core-collapse, prior to core bounce, electron captures on medium-heavy nuclei drive deleptonization and simulations require the use of accurate reaction rates. Nuclei with neutron number near $N=50$, just above atomic number $Z=28$, play an important role, but rates used in astrophysical simulations rely primarily on a relatively simple single-state approximation. In order to improve the accuracy of astrophysical simulations, experimental data are needed to test the electron-capture rates and to guide the development of better theoretical models. This work presents the results of the ${}^{86}$Kr($t$,${}^3$He+$\gamma$) experiment at the NSCL, from which an upper limit for the Gamow-Teller strength up to an excitation energy in ${}^{86}$Br of 5 MeV is extracted. The derived upper limit for the electron-capture rate on ${}^{86}$Kr indicates that the rate estimated through the single-state approximation is too high and that rates based on Gamow-Teller strengths estimated in shell-model and QRPA calculations are more accurate. The QRPA calculations tested in this manner were used for estimating the electron capture rates for 78 isotopes near $N=50$ and above $Z=28$. The impact of using these new electron-capture rates in simulations of supernovae instead of the rates based on the single-state approximation is investigated, indicating a significant reduction in the deleptonization that affects multi-messenger signals, such as the emission of neutrinos and gravitational waves.

   nucl-exastro-ph.HEastro-ph.SRnucl-thPRC(2019)·18 citations
3. 03*

   Resolving the 11B(p, ${\alpha }_0$) Cross Section Discrepancies between 0.5 and 3.5 MeV

   Michael Munch · Oliver Sølund Kirsebom · Jacobus Andreas Swartz🇩🇰 · Hans Otto Uldall Fynbo🇩🇰

   The reaction 11B(p, 3$\alpha$) is relevant for fields as diverse as material science, nuclear structure, nuclear astrophysics, and fusion science. However, for the channel proceeding via the ground state of 8Be, the available cross-section data shows large discrepancies of both normalization and energy scale. The present paper reports on a measurement of the 11B(p, ${\alpha }_0$) cross section using an array of modern large area segmented silicon detectors and low beam current on an enriched thin target with the aim of resolving the discrepancies amongst previous measurements.

   nucl-exEPJA(2020)·8 citations
4. 04*

   Puzzling Radii of Calcium Isotopes: ${}^{40}\mathrm{Ca}{\to }^{44}\mathrm{Ca}{\to }^{48}\mathrm{Ca}{\to }^{52}\mathrm{Ca}$, and Duality in the Structure of ${}_{14}^{42}{\mathrm{Si}}_{28}$ and ${}_{20}^{48}{\mathrm{Ca}}_{28}$

   Syed Afsar Abbas🇮🇳 · Anisul Ain Usmani🇮🇳 · Usuf Rahaman🇮🇳 · Mohammad Ikram

   In this paper we study the issue of the puzzle of the radii of calcium isotopes. Despite an excess of eight neutrons, strangely ${}^{48}\mathrm{Ca}$ exhibits essentially the same charge radius as ${}^{40}\mathrm{Ca}$ does. A fundamental microscopic description of this is still lacking. Also strange is a peak in charge radius of calcium at N = 24. The ${}^{52}\mathrm{Ca}$ (N = 32) nucleus, well known to be doubly magical, amazingly has recently been found to have a very large charge radius. Also amazing is the property of ${}_{14}^{42}{\mathrm{Si}}_{28}$ which simultaneously appears to be both magical/spherical and strongly deformed as well. We use a Quantum Chromodynamics based model, which treats triton as elementary entity to make up ${}_{14}^{42}{\mathrm{Si}}_{28}$. We show here how this QCD based model is able to provide a consistent physical understanding of simultaneity of magicity/sphericity and strong deformation of a single nucleus. This brings in an essential duality in the structure of ${}_{14}^{42}{\mathrm{Si}}_{28}$ and subsequently also that of ${}_{20}^{48}{\mathrm{Ca}}_{28}$ We also provide consistent understanding of the puzzling radii of calcium isotopes. We predict that the radius of ${}^{54}\mathrm{Ca}$ should be even bigger than that of ${}^{52}\mathrm{Ca}$; and also that the radius of ${}^{60}\mathrm{Ca}$ should be the same as that of ${}^{40}\mathrm{Ca}$. In addition we also show wherefrom arises the neutron E2 effective charge of $\frac{1}{2}$.

   ↳ nucl-thnucl-ex0 citations
5. 05*

   Event multiplicity, transverse momentum and energy dependence of charged particle production, and system thermodynamics in $pp$ collisions at the Large Hadron Collider

   Rutuparna Rath🇮🇳 · Arvind Khuntia🇵🇱 · Raghunath Sahoo🇮🇳 · Jean Cleymans🇿🇦

   In the present work, we study the recent collision energy and multiplicity dependence of the charged particle transverse momentum spectra as measured by the ALICE collaboration in $pp$ collisions at $\sqrt{s}$ = 5.02 and 13 TeV using the non-extensive Tsallis distribution and the Boltzmann-Gibbs Blast Wave (BGBW) model. A thermodynamically consistent form of the Tsallis distribution is used to extract the kinetic freeze-out parameters from the transverse momentum spectra of charged particles at mid-rapidity. In addition, a comprehensive study of fitting range dependence of transverse momentum spectra on the freeze-out parameters is done using Tsallis statistics. The applicability of BGBW model is verified by fitting the transverse momentum spectra of the bulk part ($\sim 2.5\mathrm{GeV}/c$)for both 5.02 and 13 TeV energies and also in different multiplicity classes. The radial flow, $<\beta >$ is almost independent of collision energy and multiplicity whereas the behavior of kinetic freeze-out temperature significantly depends on multiplicity classes. It is found that the Tsallis distribution generally leads to a better description for the complete transverse momentum spectra whereas the BGBW model explains the bulk part of the system.

   ↳ hep-phhep-exnucl-exnucl-thJ.Phys.G(2020)·32 citations
6. 06*

   Light particle and quark chemical potentials from negatively to positively charged particle yield ratios corrected by removing strong and weak decays

   Hai-Ling Lao🇨🇳 · Ya-Qin Gao🇨🇳 · Fu-Hu Liu🇨🇳

   The yield ratios of negatively to positively charged pions (${\pi }^{-}/{\pi }^{+}$), negatively to positively charged kaons ($K^{-}/K^{+}$), and anti-protons to protons ($\bar{p}/p$) produced in mid-rapidity interval in central gold-gold (Au-Au) collisions, central lead-lead (Pb-Pb) collisions, and inelastic (INEL) or non-single-diffractive (NSD) proton-proton ($pp$) collisions, as well as in forward rapidity region in INEL $pp$ collisions are analyzed in the present work. Over an energy range from a few GeV to above 10 TeV, the chemical potentials of light flavor particles (pion, kaon, and proton) and quarks (up, down, and strange quarks) are extracted from the mentioned yield ratios in which the contributions of strong decay from high-mass resonance and weak decay from heavy flavor hadrons are removed. Most energy dependent chemical potentials show the maximum at about 4 GeV, while the energy dependent yield ratios do not show such an extremum.

   ↳ hep-phhep-exnucl-exnucl-thAdv.High Energy Phys.(2020)·4 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.