Thu·Sep 26, 2019Thursday·September 26, 2019

1. 01*

   Simultaneous measurement of beta-delayed proton and gamma emission of ${}^{26}$P for ${}^{25}$Al($p,\gamma$)${}^{26}$Si reaction rate

   P. F. Liang · L. J. Sun🇺🇸 · J. Lee🇰🇷 · S. Q. Hou🇺🇸 · X. X. Xu🇨🇳 · C. J. Lin🇨🇳 · C. X. Yuan🇨🇳 · J. J. He🇺🇸 · Z. H. Li🇨🇳 · J. S. Wang🇨🇳 · D. X. Wang · H. Y. Wu🇨🇳 and 44 other authors

   $\beta$ decay of ${}^{26}$P was used to populate the astrophysically important $E_x=$5929.4(8) keV $J^{\pi }=3{}^{+}$ state of ${}^{26}$Si. Both $\beta$-delayed proton at 418(8) keV and gamma ray at 1742(2) keV emitted from this state were measured simultaneously for the first time with corresponding absolute intensities of 11.1(12)\% and 0.59(44)\%, respectively. Besides, shell model calculations with weakly bound effects were performed to investigate the decay properties of other resonant states and a spin-parity of $4^{+}$ rather than $0^{+}$ was favored for the $E_x=$5945.9(40) keV state. Combining the experimental results and theoretical calculations, ${}^{25}$Al($p,\gamma$)${}^{26}$Si reaction rate in explosive hydrogen burning environments was calculated and compared with previous studies.

   nucl-exPRC(2020)·18 citations
2. 02*

   Recent progress on hypernuclei

   Avraham Gal🇮🇱

   Some of last year's progress made in hypernuclear physics is reviewed as follows: (i) resolving the ${}_{\Lambda }^5$He overbinding problem in single-$\Lambda$ hypernuclei [1]; (ii) arguing that the onset of binding double-$\Lambda$ hypernuclei is most likely at $A$=5, with the neutral systems ${}_{\Lambda \Lambda }^3$n and ${}_{\Lambda \Lambda }^4$n unbound by a large margin [2]; and (iii) revising the calculated value of the loosely bound ${}_{\Lambda }^3$H lifetime to a level of $\sim$20% shorter than the free $\Lambda$ lifetime [3], given recent claims from relativistic heavy ion experiments that $\tau {(}_{\Lambda }^3$H) is shorter than ${\tau }_{\Lambda }$ by as much as $\approx$(30$\pm$8)%. Also discussed briefly in this context is the lifetime expected for the questionable ${}_{\Lambda }^3$n hypernucleus.

   ↳ nucl-thhep-phnucl-exJ.Phys.Conf.Ser.(2020)·3 citations
3. 03*

   The mean transverse momentum of ultracentral heavy-ion collisions: A new probe of hydrodynamics

   Fernando G. Gardim🇧🇷 · Giuliano Giacalone🇫🇷 · Jean-Yves Ollitrault🇫🇷

   We predict that the mean transverse momentum of charged hadrons $⟨p_t⟩$ rises as a function of the charged-particle multiplicity in ultracentral nucleus-nucleus collisions. We explain that this phenomenon has a simple physical origin and represents an unambiguous prediction of the hydrodynamic framework of heavy-ion collisions. We argue that the relative increase of $⟨p_t⟩$ is proportional to the speed of sound squared $c_s^2$ of the quark-gluon plasma. Based on the value of $c_s^2$ from lattice QCD, we expect $⟨p_t⟩$ to increase by approximately $18$ MeV between 1\% and 0.001\% centrality in Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV.

   ↳ nucl-thhep-phnucl-exPLB(2020)·64 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.