Mon·Dec 28, 2020Monday·December 28, 2020

1. 01*

   Global polarization of $\Xi$ and $\Omega$ hyperons in Au+Au collisions at $\sqrt{s_{{}_{NN}}}$ = 200 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🇺🇸 · A. Aparin🇷🇺 · E. C. Aschenauer🇺🇸 · M. U. Ashraf🇨🇳 and 358 other authors

   Global polarization of $\Xi$ and $\Omega$ hyperons has been measured for the first time in Au+Au collisions at $\sqrt{s_{{}_{NN}}}$ = 200 GeV. The measurements of the ${\Xi }^{-}$ and ${\bar{\Xi }}^{+}$ hyperon polarization have been performed by two independent methods, via analysis of the angular distribution of the daughter particles in the parity violating weak decay $\Xi \to \Lambda +\pi$, as well as by measuring the polarization of the daughter $\Lambda$-hyperon, polarized via polarization transfer from its parent. The polarization, obtained by combining the results from the two methods and averaged over ${\Xi }^{-}$ and ${\bar{\Xi }}^{+}$, is measured to be $⟨P_{\Xi }⟩=0.47\pm 0.10(stat.)\pm 0.23(syst.)\%$ for the collision centrality 20\%-80\%. The $⟨P_{\Xi }⟩$ is found to be slightly larger than the inclusive $\Lambda$ polarization and in reasonable agreement with a multi-phase transport model (AMPT). The $⟨P_{\Xi }⟩$ is found to follow the centrality dependence of the vorticity predicted in the model, increasing toward more peripheral collisions. The global polarization of $\Omega$, $⟨P_{\Omega }⟩=1.11\pm 0.87(stat.)\pm 1.97(syst.)\%$ was obtained by measuring the polarization of daughter $\Lambda$ in the decay $\Omega \to \Lambda +K$, assuming the polarization transfer factor $C_{\Omega \Lambda }=1$.

   nucl-exPRL(2021)·153 citations
2. 02*

   Fission fragments intrinsic spins and their correlations

   A. Bulgac🇺🇸 · I. Abdurrahman🇺🇸 · S. Jin🇨🇳 · K. Godbey🇺🇸 · N. Schunck🇺🇸 · I. Stetcu🇺🇸

   The intrinsic spins and their correlations are the least understood characteristics of fission fragments from both theoretical and experimental points of view. In many nuclear reactions the emerging fragments are typically excited and acquire an intrinsic excitation energy and an intrinsic spin depending on the type of the reactions and interaction mechanism. Both the intrinsic excitation energies and the fragments intrinsic spins and parities are controlled by the interaction mechanism and conservations laws, which lead to their correlations and determines the character of their de-excitation mechanism. We outline here a framework for the theoretical extraction of the intrinsic spin distributions of the fragments and their correlations within the fully microscopic real-time density functional theory formalism and illustrate it on the example of induced fission of ${}^{236}$U and ${}^{240}$Pu, using two nuclear energy density functionals. These fission fragment intrinsic spin distributions display new qualitative features previously not discussed in literature. Within this fully microscopic framework we extract for the first time the intrinsic spin distributions of fission fragments of ${}^{236}$U and ${}^{240}$Pu as well as the correlations of their intrinsic spins, which have been debated in literature for more than six decades with no definite conclusions so far.

   ↳ nucl-thnucl-exPRL(2021)·67 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.