Thu·May 30, 2019Thursday·May 30, 2019

1. 01*

   The Double Spin Asymmetry of Nitrogen in Elastic and Quasielastic Kinematics from a Solid Ammonia Dynamically Polarized Target

   Moshe Friedman🇺🇸 · Jessica Campbell · Donal Day🇺🇸 · Douglas W. Higinbotham🇺🇸 · Adam Sarty🇨🇦 · Guy Ron🇮🇱

   Solid ammonia (NH${}_3$) is commonly used as a dynamically polarized proton target for electron and muon scattering cross-section asymmetry measurements. As spin 1${}^{+}$ particles, the ${}^{14}$N nuclei in the target are also polarized and contribute a non-trivial asymmetry background that should be addressed. We describe here a method to extract the nitrogen contribution to the asymmetry, and report the cross-section asymmetries of electron-nitrogen scattering at beam energies of $E=1.7$ GeV and $E=2.2$ GeV, and momentum transfer of $Q^2=0.023-0.080$ GeV${}^2$.

   nucl-exNucl.Instrum.Meth.A(2019)·0 citations
2. 02*

   Masses of neutron-rich ${}^{52-54}$Sc and ${}^{54,56}$Ti nuclides: The $N=32$ subshell closure in scandium

   X. Xu🇨🇳 · M. Wang🇨🇳 · K. Blaum🇩🇪 · J. D. Holt🇨🇦 · Yu. A. Litvinov🇩🇪 · A. Schwenk🇩🇪 · J. Simonis🇩🇪 · S. R. Stroberg🇨🇦 · Y. H. Zhang🇨🇳 · H. S. Xu🇨🇳 · P. Shuai🇨🇳 · X. L. Tu🇨🇳 and 27 other authors

   Isochronous mass spectrometry has been applied in the storage ring CSRe to measure the masses of the neutron-rich ${}^{52-54}$Sc and ${}^{54,56}$Ti nuclei. The new mass excess values $ME$(${}^{52}$Sc) $=$ $-40525(65)$ keV, $ME$(${}^{53}$Sc) $=$ $-38910(80)$ keV, and $ME$(${}^{54}$Sc) $=$ $-34485(360)$ keV, deviate from the Atomic Mass Evaluation 2012 by 2.3$\sigma$, 2.8$\sigma$, and 1.7$\sigma$, respectively. These large deviations significantly change the systematics of the two-neutron separation energies of scandium isotopes. The empirical shell gap extracted from our new experimental results shows a significant subshell closure at $N=32$ in scandium, with a similar magnitude as in calcium. Moreover, we present $ab$ $initio$ calculations using the valence-space in-medium similarity renormalization group based on two- and three-nucleon interactions from chiral effective field theory. The theoretical results confirm the existence of a substantial $N=32$ shell gap in Sc and Ca with a decreasing trend towards lighter isotones, thus providing a consistent picture of the evolution of the $N=32$ magic number from the $pf$ into the $sd$ shell.

   nucl-exPRC(2019)·40 citations
3. 03*

   New physics via pion capture and simple nuclear reactions

   Chien-Yi Chen🇨🇦 · David McKeen🇨🇦 · Maxim Pospelov🇨🇦

   Light, beyond-the-standard-model particles $X$ in the 1-100 MeV mass range can be produced in nuclear and hadronic reactions but would have to decay electromagnetically. We show that simple and well-understood low-energy hadronic processes can be used as a tool to study $X$ production and decay. In particular, the pion capture process ${\pi }^{-}p\to Xn\to e^{+}{e}^{-}n$ can be used in a new experimental setup to search for anomalies in the angular distribution of the electron-positron pair, which could signal the appearance of dark photons, axion-like particles and other exotic states. This process can be used to decisively test the hypothesis of a new particle produced in the ${}^7\mathrm{Li}+p$ reaction. We also discuss a variety of other theoretically clean hadronic processes, such as $p+\mathrm{D}(\mathrm{T})$ fusion, as a promising source of $X$ particles.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2019)·8 citations
4. 04*

   Sensitivity of D meson azimuthal anisotropies to system size and nuclear structure

   Roland Katz🇫🇷 · Caio A. G. Prado🇨🇳 · Jacquelyn Noronha-Hostler🇺🇸 · Jorge Noronha🇧🇷 · Alexandre A. P. Suaide🇧🇷 · Marcelo G. Munhoz🇧🇷

   Recent experimental data at the Large Hadron Collider (LHC) confirmed that the soft sector azimuthal anisotropies in central XeXe collisions are sensitive to deformations in the wave function of the Xenon nucleus. Additionally, the CMS experiment found that D meson flow is slightly suppressed compared to other particle species when considering quark number scaling in small systems of pPb compared to PbPb. In this talk we used the D and B Mesons Modular (DAB-MOD) code coupled to Trento+v-USPhydro to calculate the $R_{AA}$ and $v_n$'s of D mesons using different energy loss models and Langevin techniques. Comparing D mesons $R_{AA}$ and $v_n$ in PbPb to XeXe collisions it is found that in central collisions D meson azimuthal anisotropies are sensitive to details in the nuclear structure wave function of Xenon. Additionally, we find that in mid-central collisions the smaller system size of XeXe suppresses D meson flow.

   ↳ nucl-thhep-phnucl-exPoS(2020)·0 citations
5. 05*

   Towards Understanding Astrophysical Effects of Nuclear Symmetry Energy

   Bao-An Li🇺🇸 · Plamen G. Krastev🇺🇸 · De-Hua Wen🇨🇳 · Nai-Bo Zhang🇨🇳

   Determining the Equation of State (EOS) of dense neutron-rich nuclear matter is a shared goal of both nuclear physics and astrophysics. Except possible phase transitions, the density dependence of nuclear symmetry \esym is the most uncertain part of the EOS of neutron-rich nucleonic matter especially at supra-saturation densities. Much progresses have been made in recent years in predicting the symmetry energy and understanding why it is still very uncertain using various microscopic nuclear many-body theories and phenomenological models. Simultaneously, significant progresses have also been made in probing the symmetry energy in both terrestrial nuclear laboratories and astrophysical observatories. In light of the GW170817 event as well as ongoing or planned nuclear experiments and astrophysical observations probing the EOS of dense neutron-rich matter, we review recent progresses and identify new challenges to the best knowledge we have on several selected topics critical for understanding astrophysical effects of the nuclear symmetry energy.

   ↳ nucl-thastro-ph.HEgr-qcnucl-exEPJA(2019)·218 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.