Mon·Aug 3, 2020Monday·August 3, 2020

1. 01*

   Extraction of beam-spin asymmetries from the hard exclusive ${\pi }^{+}$ channel off protons in a wide range of kinematics

   S. Diehl🇺🇸 · K. Joo🇺🇸 · A. Kim🇺🇸 · H. Avakian🇺🇸 · P. Kroll🇩🇪 · K. Park🇰🇷 · D. Riser🇺🇸 · K. Semenov-Tian-Shansky🇷🇺 · K. Tezgin🇺🇸 · K.P. Adhikari🇺🇸 · S. Adhikari🇺🇸 · M.J. Amaryan🇺🇸 and 126 other authors

   We have measured beam-spin asymmetries to extract the $\sin \varphi$ moment $A_{LU}^{\sin \varphi }$ from the hard exclusive $\vec{e}p\to e^{\prime }n{\pi }^{+}$ reaction above the resonance region, for the first time with nearly full coverage from forward to backward angles in the center-of-mass. The $A_{LU}^{\sin \varphi }$ moment has been measured up to 6.6 GeV${}^2$ in $-t$, covering the kinematic regimes of Generalized Parton Distributions (GPD) and baryon-to-meson Transition Distribution Amplitudes (TDA) at the same time. The experimental results in very forward kinematics demonstrate the sensitivity to chiral-odd and chiral-even GPDs. In very backward kinematics where the TDA framework is applicable, we found $A_{LU}^{\sin \varphi }$ to be negative, while a sign change was observed near 90${}^{\circ }$ in the center-of-mass. The unique results presented in this paper will provide critical constraints to establish reaction mechanisms that can help to further develop the GPD and TDA frameworks.

   nucl-exhep-exhep-phPRL(2020)·23 citations
2. 02*

   Collective 2p-2h intruder states in ${}^{118}$Sn studied via $\beta$-decay of ${}^{118}$In using GRIFFIN

   K. Ortner🇨🇦 · C. Andreoiu🇨🇦 · M. Spieker🇺🇸 · G.C. Ball🇨🇦 · N. Bernier🇨🇦 · H. Bidaman🇨🇦 · V. Bildstein🇨🇦 · M. Bowry🇨🇦 · D.S. Cross🇨🇦 · M.R. Dunlop🇨🇦 · R. Dunlop🇨🇦 · F.H. Garcia🇨🇦 and 16 other authors

   The low-lying structure of semi-magic ${}^{118}$Sn has been investigated through the $\beta$-decay of ${}^{118}$In ($T_{1/2}=4.45$ min) to study shape coexistence via the reduced transition probabilities of states in the 2p-2h proton intruder band. This high-statistics study was carried out at TRIUMF-ISAC with the GRIFFIN spectrometer. In total, 99 transitions have been placed in the level scheme with 43 being newly observed. Three low-lying $\gamma$-ray transitions with energies near 285 keV have been resolved from which the 2${}_{intr.}^{+}\to 0_{intr.}^{+}$ 284.52-keV transition was determined to have half of the previous branching fraction leading to a $B(E2;2_2^{+}\to 0_2^{+})$ of 21(4) W.u. compared to 39(7) W.u. from the previous measurement. Calculations using $sd$ IBM-2 with mixing have also been made to compare the experimental $B(E2)$ values to the theoretical values and to make comparisons to the ${}^{114,116}$Sn isotopes previously studied using the same theoretical model.

   nucl-exPRC(2020)·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.