Mon·Aug 19, 2019Monday·August 19, 2019

1. 01*

   Measurement of the 3He Spin-Structure Functions and of Neutron (3He) Spin-Dependent Sum Rules at 0.035<Q^2<0.24 GeV^2

   V. Sulkosky🇺🇸 · J. T. Singh🇺🇸 · C. Peng🇺🇸 · J.-P. Chen🇺🇸 · A. Deur🇺🇸 · S. Abrahamyan🇦🇲 · K. A. Aniol🇺🇸 · D. S. Armstrong🇺🇸 · T. Averett🇺🇸 · S. L. Bailey🇺🇸 · A. Beck🇺🇸 · P. Bertin🇫🇷 and 97 other authors

   The spin-structure functions $g_1$ and $g_2$, and the spin-dependent partial cross-section ${\sigma }_{\mathrm{TT}}$ have been extracted from the polarized cross-sections differences, $\Delta {\sigma }_{\parallel }\left(\nu ,Q^2\right)$ and $\Delta {\sigma }_{\perp }\left(\nu ,Q^2\right)$ measured for the $\overrightarrow{{}^{\text{3}}\text{He}}(\vec{\text{e}},{\text{e}}^{\prime })\text{X}$ reaction, in the E97-110 experiment at Jefferson Lab. Polarized electrons with energies from 1.147 to 4.404 GeV were scattered at angles of 6${}^{\circ }$ and 9${}^{\circ }$ from a longitudinally or transversely polarized ${}^3$He target. The data cover the kinematic regions of the quasi-elastic, resonance production and beyond. From the extracted spin-structure functions, the first moments $\overline{{\Gamma }_1}\left(Q^2\right)$, ${\Gamma }_2\left(Q^2\right)$ and $I_{\mathrm{TT}}\left(Q^2\right)$ are evaluated with high precision for the neutron in the $Q^2$ range from 0.035 to 0.24~GeV${}^2$. The comparison of the data and the chiral effective field theory predictions reveals the importance of proper treatment of the $\Delta$ degree of freedom for spin observables.

   nucl-exhep-exPLB(2020)·31 citations
2. 02*

   One-proton and one-neutron knockout reactions from $N=Z=28$ ${}^{56}$Ni to the $A=55$ mirror pair ${}^{55}$Co and ${}^{55}$Ni

   M. Spieker🇺🇸 · A. Gade🇺🇸 · D. Weisshaar🇺🇸 · B. A. Brown🇺🇸 · J. A. Tostevin🇬🇧 · B. Longfellow🇺🇸 · P. Adrich · D. Bazin🇺🇸 · M. A. Bentley · J. R. Brown🇬🇧 · C. M. Campbell🇺🇸 · C. Aa. Diget and 6 other authors

   We present a high-resolution in-beam $\gamma$-ray spectroscopy study of excited states in the mirror nuclei ${}^{55}$Co and ${}^{55}$Ni following one-nucleon knockout from a projectile beam of ${}^{56}$Ni. The newly determined partial cross sections and the $\gamma$-decay properties of excited states provide a test of state-of-the-art nuclear structure models and probe mirror symmetry in unique ways. A mirror asymmetry for the partial cross sections leading to the two lowest $3/2^{-}$ states in the $A=55$ mirror pair was identified as well as a significant difference in the $E1$ decays from the $1/2_1^{+}$ state to the same two $3/2^{-}$ states. The mirror asymmetry in the partial cross sections cannot be reconciled with the present shell-model picture or small mixing introduced in a two-state model. The observed mirror asymmetry in the $E1$ decay pattern, however, points at stronger mixing between the two lowest $3/2^{-}$ states in ${}^{55}$Co than in its mirror ${}^{55}$Ni.

   nucl-exnucl-thPRC(2019)·13 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.