Mon·Aug 30, 2021Monday·August 30, 2021

1. 01*

   Photoproduction of $K^{+}\Lambda (1405)\to K^{+}{\pi }^0{\Sigma }^0$ extending to forward angles and low momentum transfer

   G. Scheluchin🇩🇪 · T.C. Jude🇩🇪 · S. Alef🇩🇪 · P. Bauer🇩🇪 · D. Bayadilov🇩🇪 · R. Beck🇩🇪 · A. Braghieri🇮🇹 · P.L. Cole🇺🇸 · R. Di Salvo🇮🇹 · D. Elsner🇩🇪 · A. Fantini🇮🇹 · O. Freyermuth🇩🇪 and 23 other authors

   $K^{+}\Lambda (1405)$ photoproduction has been studied at the BGOOD experiment via the all neutral decay, $\Lambda (1405)\to {\Sigma }^0{\pi }^0$. The unique BGOOD experimental setup allows both the cross section and $\Lambda (1405)$ invariant mass distribution (line shape) to be measured over a broad $K^{+}$ polar angle range, extending to extreme forward $K^{+}$ angles unattainable at previous experiments. Evidence is provided for the role of a triangle singularity driven by the $N^{\ast }(2030)$ resonance, which appears to contribute significantly to $K^{+}\Lambda (1405)$ photoproduction. This is observed in both the angular distributions and the integrated cross section which was determined with unprecedented energy resolution. The measured line shape is also in agreement with the previous results of CLAS and ANKE, and is consistent with two poles derived in $\chi$PT based models.

   nucl-exPLB(2022)·33 citations
2. 02*

   Dynamical model of $\varphi$ meson photoproduction on the nucleon and ${}^{4}He$

   Sang-Ho Kim🇰🇷 · T.-S. H. Lee🇺🇸 · Seung-il Nam🇰🇷 · Yongseok Oh🇰🇷

   We investigate $\varphi$ meson photoproduction on the nucleon and the \nuclide[4]{He} targets within a dynamical model approach based on a Hamiltonian which describes the production mechanisms by the Pomeron-exchange, meson-exchanges, $\varphi$ radiations, and nucleon resonance excitations mechanisms. The final $\varphi N$ interactions are included being described by the gluon-exchange, direct $\varphi N$ couplings, and the box-diagrams arising from the couplings with $\pi N$, $\rho N$, $K\Lambda$, and $K\Sigma$ channels. The parameters of the Hamiltonian are determined by the experimental data of $\gamma p\to \varphi p$ from the CLAS Collaboration. The resulting Hamiltonian is then used to predict the coherent $\varphi$-meson production on the \nuclide[4]{He} targets by using the distorted-wave impulse approximation. For the proton target, the final $\varphi N$ rescattering effects, as required by the unitarity condition, are found to be very weak, which supports the earlier calculations in the literature. For the \nuclide[4]{He} targets, the predicted differential cross sections are in good agreement with the data obtained by the LEPS Collaboration. The role of each mechanism in this reaction is discussed and predictions for a wide range of scattering angles are presented, which can be tested in future experiments.

   ↳ nucl-thhep-phnucl-exPRC(2021)·19 citations
3. 03*

   Super- and hyper-deformation in ${}^{60}$Zn, ${}^{62}$Zn, and ${}^{64}$Ge at high spins

   Kenichi Yoshida🇯🇵

   Background: The observation of the superdeformed (SD) bands in ${}^{60,62}$Zn indicates that the particle number 30 is a magic particle number, where two and four neutron single-particles are considered to be promoted to the intruder $1g_{9/2}$ shell. However, the SD-yrast band in ${}^{62}$Zn is assigned negative parity. Purpose: I investigate various SD configurations in the rapidly rotating ${}^{60,62}$Zn and ${}^{64}$Ge, and attempt elucidating the different roles of the energy gaps at particle numbers 30 and 32. Method: I employ a nuclear energy-density functional (EDF) method: the configuration-constrained cranked Skyrme-Kohn-Sham approach is used to describe the rotational bands near the yrast line. Results: The negative-parity SD bands appear higher in energy than the positive-parity SD-yrast band in ${}^{60}$Zn by about 4 MeV, which is indicative of the SD doubly-magic nucleus. However, the energy gap in ${}^{64}$Ge is smaller $\sim 2\text{-}3$ MeV, though the quadrupole deformation of the SD states in ${}^{64}$Ge is greater than that of ${}^{60}$Zn. The present calculation predicts the occurrence of the hyperdeformed state in ${}^{60}$Zn and ${}^{64}$Ge at a high rotational frequency $\sim 2.0$ MeV$/\hslash$ due to the occupation of the $h_{11/2}$ shell. Conclusions: An SD-shell gap at particle number 30 and 32 appears at different deformations and the energy gap at particle number 32 is low, which make the SD structures of ${}^{62}$Zn unique, where the negative-parity SD states appear lower in energy than the positive-parity one.

   ↳ nucl-thnucl-exPRC(2022)·4 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.