Thu·Oct 25, 2018Thursday·October 25, 2018

1. 01*

   How different is the core of ${}^{25}$F from ${}^{24}$O${}_{g.s.}$?

   T. L. Tang🇯🇵 · T. Uesaka🇯🇵 · S. Kawase🇯🇵 · D. Beaumel🇫🇷 · M. Dozono🇯🇵 · T. Fujii🇯🇵 · N. Fukuda🇯🇵 · T. Fukunaga🇯🇵 · A. Galindo-Uribarri🇺🇸 · S. H. Hwang🇰🇷 · N. Inabe🇯🇵 · D. Kameda🇯🇵 and 35 other authors

   The neutron-shell structure of ${}^{25}$F was studied using quasi-free (p,2p) knockout reaction at 270A MeV in inverse kinematics. The sum of spectroscopic factors of $\pi$0d${}_{5/2}$ orbital is found to be $1.0\pm 0.3$. However, the spectroscopic factor for the ground-state to ground-state transition (${}^{25}$F, ${}^{24}$O${}_{g.s.}$) is only $0.36\pm 0.13$, and ${}^{24}$O excited states are produced from the 0d${}_{5/2}$ proton knockout. The result shows that the ${}^{24}$O core of ${}^{25}$F nucleus significantly differs from a free ${}^{24}$O nucleus, and the core consists of 35% ${}^{24}$O${}_{g.s}$. and 65% excited ${}^{24}$O.

   nucl-exnucl-thPRL(2020)·22 citations
2. 02*

   Measurements of Dielectron Production in Au$+$Au Collisions at $\sqrt{s_{NN}}$= 27, 39, and 62.4 GeV from the STAR Experiment

   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🇷🇺 · D. Arkhipkin🇺🇸 and 345 other authors

   We report systematic measurements of dielectron ($e^{\pm }{e}^{\pm }$) invariant-mass $M_{ee}$ spectra at mid-rapidity in Au+Au collisions at $\sqrt{s_{NN}}$ = 27, 39, and 62.4 GeV taken with the STAR detector at the Relativistic Heavy Ion Collider. For all energies studied, a significant excess yield of dielectrons is observed in the low-mass region (0.40$<M_{ee}<0.75$ MeV/$c^2$) compared to hadronic cocktail simulations at freeze-out. Models that include an in-medium broadening of the $\rho$-meson spectral function consistently describe the observed excess. In addition, we report acceptance-corrected dielectron-excess spectra for Au+Au collisions at mid-rapidity ($\left|y_{ee}\right|$ $<$ 1) in the 0$-$80% centrality bin for each collision energy. The integrated excess yields for $0.4<M_{ee}<0.75\text{GeV}/c^2$, normalized by the charged particle multiplicity at mid-rapidity, are compared with previously published measurements for Au+Au at $\sqrt{s_{NN}}$ = 19.6 and 200 GeV. The normalized excess yields in the low-mass region show no significant collision energy dependence. The data, however, are consistent with model calculations that demonstrate a modest energy dependence.

   nucl-ex30 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.