Thu·Jun 6, 2019Thursday·June 6, 2019

1. 01*

   Symmetry energy constraints from GW170817 and laboratory experiments

   M.B. Tsang🇺🇸 · W.G. Lynch🇺🇸 · P. Danielewicz🇺🇸 · C.Y. Tsang🇺🇸

   The LIGO-Virgo collaboration detection of the binary neutron-star merger event, GW170817, has expanded efforts to understand the Equation of State (EoS) of nuclear matter. These measurements provide new constraints on the overall pressure, but do not elucidate its origins, by not distinguishing the contribution to the pressure from symmetry energy which governs much of the internal structure of a neutron star. By combining the neutron star EoS extracted from the GW170817 event and the EoS of symmetric matter from nucleus-nucleus collision experiments, we extract the symmetry pressure, which is the difference in pressure between neutron and nuclear matter over the density region from 1.2${\rho }_0$ to $4.5{\rho }_0$. While the uncertainties in the symmetry pressure are large, they can be reduced with new experimental and astrophysical results.

   nucl-exnucl-thPLB(2019)·59 citations
2. 02*

   Near-threshold ${\eta }^{\prime }$ meson production in ${\pi }^{-}A$ reactions

   E.Ya.Paryev🇷🇺

   We study the inclusive near-threshold production of ${\eta }^{\prime }$ mesons in ${\pi }^{-}$ meson-nucleus reactions on the basis of the first-collision model relying on the nuclear spectral function and including incoherent processes of ${\eta }^{\prime }$ production in ${\pi }^{-}$ meson--proton collisions. The model accounts for the absorption of initial ${\pi }^{-}$ and final ${\eta }^{\prime }$ mesons, the binding of intranuclear protons and their Fermi motion, as well as the effect of the scalar ${\eta }^{\prime }$--nucleus potential (or the in-medium shift of the ${\eta }^{\prime }$ meson mass) on these processes. We calculate the differential and total cross sections for ${\eta }^{\prime }$ production off carbon and tungsten nuclei at laboratory angles of 0${}^{\circ }$--10${}^{\circ }$ and 10${}^{\circ }$--45${}^{\circ }$ by ${\pi }^{-}$ mesons with momentum of 1.7 GeV/c, which is close to the threshold momentum for ${\eta }^{\prime }$ creation on a free target proton at rest. We show that the calculated ${\eta }^{\prime }$ production cross sections are larger than those, studied earlier in the ${\eta }^{\prime }$ photoproduction reactions, by about two orders of magnitude. We also demonstrate that the high absolute values of the present differential and total ${\eta }^{\prime }$ production cross sections in the momentum ranges of 0.2--0.3 GeV/c and 0.1--0.6 GeV/c, respectively, possess a high sensitivity to changes in the in-medium shift of the ${\eta }^{\prime }$ mass. This offers the possibility of evaluating the above shift at these momenta from the respective data, which could be taken in future experiments at the GSI pion beam facility or at J-PARC.

   ↳ nucl-thnucl-exNPA(2019)·2 citations
3. 03*

   The early life of millisecond magnetars

   D I Jones🇺🇸

   Some neutron stars may be born spinning fast and with strong magnetic fields---the so-called \emph{millisecond magnetars}. It is important to understand how a star's magnetic axis moves with respect to the spin axis in the star's early life, as this effects both electromagnetic and gravitational wave emission. Previous studies have highlighted the importance of viscous dissipation within the star in this process. We advance this program by additionally considering the effect of the electromagnetic torque. We find an interesting interplay between the viscous dissipation, which makes the magnetic axis orthogonalise with respect to the spin, verses magnetic torques that tend to make the magnetic axis align with the spin axis. We present some results, and highlight areas where our model needs to be made more realistic.

   ↳ astro-ph.HEastro-ph.SRnucl-exnucl-thAIP Conf.Proc.(2019)·0 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.