Wed·Aug 3, 2016Wednesday·August 3, 2016

1. 01*

   Nuclear Data for Astrophysical Modeling

   Boris Pritychenko🇺🇸

   Nuclear physics has been playing an important role in modern astrophysics and cosmology. Since the early 1950's it has been successfully applied for the interpretation and prediction of astrophysical phenomena. Nuclear physics models helped to explain the observed elemental and isotopic abundances and star evolution and provided valuable insights on the Big Bang theory. Today, the variety of elements observed in stellar surfaces, solar system and cosmic rays, and isotope abundances are calculated and compared with the observed values. Consequently, the overall success of the modeling critically depends on the quality of underlying nuclear data that helps to bring physics of macro and micro scales together. To broaden the scope of traditional nuclear astrophysics activities and produce additional complementary information, I will investigate applicability of the U.S. Nuclear Data Program (USNDP) databases for astrophysical applications. EXFOR (Experimental Nuclear Reaction Data) and ENDF (Evaluated Nuclear Data File) libraries have large astrophysics potential; the former library contains experimental data sets while the latter library includes evaluated neutron cross sections. ENSDF (Evaluated Nuclear Structure Data File) database is a primary depository of nuclear structure and decay rates information. The decay rates are essential in stellar nucleosynthesis calculations, and these rates are evaluated using nuclear structure codes. The structure evaluation codes are pure mathematical procedures that can be applied to diverse data samples. A brief review of astrophysical nuclear data needs has been presented. Several opportunities and the corresponding computer tools have been identified. Further work will include extensive analysis of nuclear databases and computer procedures for astrophysical calculations.

   ↳ astro-ph.IMnucl-ex0 citations
2. 02*

   Contrasting Freezeouts in Large Versus Small Systems

   Sandeep Chatterjee🇮🇳 · Ajay Kumar Dash🇮🇳 · Bedangadas Mohanty🇮🇳

   We study the data on mean hadron yields and contrast the chemical freezeout conditions in p+p, p+Pb and Pb+Pb at the Large Hadron Collider (LHC) energies. We study several schemes for freezeout that mainly differ in the way strangeness is treated: i. strangeness freezes out along with the non-strange hadrons in complete equilibrium (1CFO), ii. strangeness freezes out along with non-strange hadrons with an additional parameter ${\gamma }_S$ accounting for non-equilibrium production of strangeness (1CFO+${\gamma }_S$), and iii. strangeness freezes out earlier than non-strange hadrons and in thermal equilibrium (2CFO). A comparison of the chisquares of the fits indicate a dependence of the freezeout scheme on the system size. The minimum bias p+p and different centralities of p+Pb and peripheral Pb+Pb data prefer 1CFO$+{\gamma }_S$ with ${\gamma }_S$ approaching unity as we go from p+p to central p+Pb and peripheral Pb+Pb. On the other hand, the mid-central to central Pb+Pb data prefer 2CFO over 1CFO+${\gamma }_S$. Such system size dependence of freezeout scheme could be an indication of the additional interaction in Pb+Pb over p+Pb and p+p.

   ↳ nucl-thhep-exhep-lathep-ph+1J.Phys.G(2017)·27 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.