Fri·Feb 11, 2022Friday·February 11, 2022

1. 01*

   Coherent photoproduction of the neutral pion and eta meson on the deuteron at incident energies below 1.15 GeV

   T. Ishikawa🇯🇵 · A. Fix🇷🇺 · H. Fujimura🇯🇵 · H. Fukasawa🇯🇵 · R. Hashimoto🇯🇵 · Q. He🇯🇵 · Y. Honda🇯🇵 · T. Iwata🇯🇵 · S. Kaida🇯🇵 · J. Kasagi🇯🇵 · A. Kawano🇯🇵 · S. Kuwasaki🇯🇵 and 26 other authors

   Coherent photoproduction of the neutral pion and eta meson on the deuteron, $\gamma d${$\to$}${\pi }^0\eta d$, has been experimentally studied at incident photon energies ranging from the reaction threshold to 1.15 GeV. The total cross section demonstrates a rapid rise below 1 GeV. The data are underestimated by the existing theoretical calculations based on quasi-free ${\pi }^0\eta$ photoproduction on the nucleon followed by deuteron coalescence. At the same time, the data are rather well reproduced by the calculations taking into account the final-state interaction. We have also measured for the first time the differential cross sections: the ${\pi }^0\eta$ invariant-mass distribution $d\sigma /d{M}_{\pi \eta }$, the ${\pi }^{0}d$ invariant-mass distribution $d\sigma /d{M}_{\pi d}$, the $\eta d$ invariant-mass distribution $d\sigma /d{M}_{\eta d}$, and the distribution over the deuteron emission angle $d\sigma /d{\Omega }_d$ in the overall center-of-mass frame. The measured cross section $d\sigma /d{\Omega }_d$ does not exhibit strongly backward-peaking behavior predicted by the calculations. At all incident energies, an increase in $d\sigma /d{M}_{\eta d}$ near the $\eta d$ threshold is observed, which indicates a bound or virtual $\eta d$ state resulting from a strong attraction between $\eta$ and a deuteron. The possibilities of using coherent ${\pi }^0\eta$ photoproduction on a nucleus to study the $\eta$-nuclear interaction are also discussed.

   nucl-exhep-exnucl-thPRC(2022)·12 citations
2. 02*

   Experimental study of the relative probability of high-spin isomeric states population in ($\alpha$,n)-reactions

   T. V. Chuvilskaya

   Results of the investigations of the yield of high-spin and low-spin isomers in reactions ${}^{41}$K($\alpha$,n)${}^{44}$Sc, ${}^{86}$Sr ($\alpha$,n)${}^{89}$Zr, ${}^{112}$Sn($\alpha$,n)${}^{115}$Te, and ${}^{134}$Ba($\alpha$,n)${}^{137}$Ce in the energy range of the alpha particles 15 $÷$ 31 MeV based on off-beam measurements of induced activity of members of the isomeric pair are presented. The anomalous behavior of the isomeric cross-section ratios for the first of these reactions is confirmed. Uniquely large isomeric cross-section ratios for the second and third ones are obtained. The features of the fourth reaction, which are promising for its application in fundamental research, are revealed. Quality of the description of this dynamics by popular computer codes is analyzed.

   nucl-ex0 citations
3. 03*

   Light Baryon Spectroscopy

   Annika Thiel🇩🇪 · Farah Afzal🇩🇪 · Yannick Wunderlich🇩🇪

   This review treats the advances in Light Baryon Spectroscopy of the last two decades, which were mainly obtained by measuring meson-production reactions at photon facilities all over the world. We provide a consistent compendium of experimental results, as well as a review of the theoretical methods of amplitude analysis used to analyze the data. The most significant datasets are presented in detail and are listed in combination with a full set of the relevant references. In addition, a brief summary of spin-formalisms, which are ubiquitous in Light Baryon Spectroscopy, as well as a review on complete experiments, are provided. The synthesis of the reviewed knowledge is presented in a full interpretation of the new results on the Light Baryon Spectrum.

   nucl-exnucl-thPPNP(2022)·84 citations
4. 04*

   New Opportunities in Femto-to-Nanometer Scale with High-Intensity Lasers

   Changbo Fu🇨🇳 · Guoqiang Zhang🇨🇳 · Yugang Ma🇨🇳

   On the scale of nanometer to femtometer, there have several puzzles, including neutron lifetime, proton charge radius, and deep Dirac level, etc. With the development of high-intensity laser technologies, lasers today can induce extremely strong electromagnetic (EM) fields. Electrons in deep shells of atoms, as well as the atomic nucleus themself, can be affected by the laser EM fields. This may provide a new experimental platform for studies the physical processes on the femto-to-nanometer scale, where atomic physics and nuclear physics coexist. In this paper, we review possible new opportunities for studying the puzzles on femto-to-nanometer scale with high-intensity lasers.

   nucl-exphysics.plasm-phMatter Radiat.Extremes(2022)·12 citations
5. 05*

   Beta decay of halo nuclei

   Karsten Riisager🇩🇰

   Beta decay is a well-established and efficient probe of nuclear structure and provides important information also for halo nuclei. Detailed decay studies of near-dripline nuclei are challenging, but are now feasible due to the technical progress during the last decades in isotope production as well as detection capabilities. The halo structure can change the dynamics of the decay process, most noticably when decays proceed directly to continuum states as seems to be the case in beta-delayed deuteron emission, a process only observed until now for the halo nuclei ${}^6$He and ${}^{11}$Li. The pronounced clustering in halo states also leaves an imprint on the decay patterns, although the isospin symmetry remains important; in several cases the isobaric analogue states of halo states have also been established. Beta-delayed particle emission channels can be expected to dominate the decays of heavier halo nuclei, if not in terms of branching ratio than certainly in terms of beta strength. A remaining challenge is to find experimental as well as theoretical tools to study the multi-neutron final states that appear for most neutron dripline nuclei.

   nucl-exnucl-th1 citation
6. 06*

   On the possible existence of a soft dipole mode in 8He

   J. Piekarewicz🇺🇸

   With an extreme neutron-to-proton ratio of N/Z=3, 8He provides an ideal laboratory for the study of a variety of exotic phenomena, such as the emergence of a soft dipole mode that is dominated by transitions into the continuum. In this contribution, a covariant density functional theory (DFT) framework is used to compute ground-state properties and the dipole response of 8He. Although 8He is admittedly too light for DFT to be applicable, the great merit of the approach is that the spurious contamination associated with the center-of-mass motion is guaranteed to decouple from the physical response. Given that a strong mixing between the isoscalar and isovector dipole modes is expected for a system with such a large neutron-proton asymmetry as 8He, the narrow structures that emerged at low energies in the isovector dipole response are attributed to the shift of the spurious strength to zero (or near zero) excitation energy. Thus, the theoretical framework implemented here disfavors the emergence of a soft dipole mode in 8He.

   ↳ nucl-thnucl-exPRC(2022)·6 citations
7. 07*

   QCD axial anomaly enhances the $\eta {\eta }^{\prime }$ decay of the hybrid candidate ${\eta }_1(1855)$

   Hua-Xing Chen🇨🇳 · Niu Su🇨🇳 · Shi-Lin Zhu🇨🇳

   We study the hybrid mesons with the exotic quantum number $I^G{J}^{PC}=0^{+}{1}^{-+}$ and investigate their decays into the $\eta {\eta }^{\prime }$, $a_1(1260)\pi$, $f_1(1285)\eta$, $f_1(1420)\eta$, $K^{\ast }(892)\bar{K}$, $K_1(1270)\bar{K}$, and $K_1(1400)\bar{K}$ channels. We find that the QCD axial anomaly enhances the decay width of the $\eta {\eta }^{\prime }$ channel although this mode is strongly suppressed by the small $P$-wave phase space. Our results support the interpretation of the ${\eta }_1(1855)$ recently observed by BESIII as the $\bar{s}sg$ hybrid meson of $I^G{J}^{PC}=0^{+}{1}^{-+}$. The QCD axial anomaly ensures the $\eta {\eta }^{\prime }$ decay mode to be a characteristic signal of the hybrid nature of the ${\eta }_1(1855)$.

   ↳ hep-phhep-exhep-latnucl-ex+1Chin.Phys.Lett.(2022)·55 citations
8. 08*

   Isospin symmetry breaking in the charge radius difference of mirror nuclei

   Tomoya Naito🇯🇵 · Xavier Roca-Maza🇮🇹 · Gianluca Colò🇮🇹 · Haozhao Liang🇯🇵 · Hiroyuki Sagawa🇯🇵

   Isospin symmetry breaking (ISB) effects in the charge radius difference $\Delta R_{\mathrm{ch}}$ of mirror nuclei are studied using the test example of ${}^{48}$Ca and ${}^{48}$Ni. This choice allows for a transparent study of ISB contributions since paring and deformation effects, commonly required for the study of mirror nuclei, can be neglected in this specific pair. The connection of $\Delta R_{\mathrm{ch}}$ with the nuclear Equation of State and the effect of ISB on such a relation are discussed according to an Energy Density Functional approach. We find that nuclear ISB effects may shift the estimated value for the symmetry energy slope parameter $L$ by more than 10 MeV while Coulomb corrections can be neglected. ISB effects on the ground-state energy and charge radii in mirror nuclei have been recently predicted by {\it ab initio} calculations to be relatively small, pointing to a negligible effect for the extraction of information on the nuclear EoS. These contrasting results call for a dedicated theoretical effort to solve this overarching problem that impacts not only the neutron skin thickness or the difference in mass and charge radii of mirror nuclei but also other observables such as the Isobaric Analog State energy.

   ↳ nucl-thnucl-exPRC(2022)·26 citations
9. 09*

   Non-linear Cherenkov Muon Spectrometer Using Multi-Layer Pressurized C3F8 Gas Radiators

   Junghyun Bae🇺🇸 · Stylianos Chatzidakis🇺🇸

   A new Cherenkov muon spectrometer using diversely sized C3F8 gas radiators and nonlinear threshold muon momentum levels was studied using Geant4 simulations. Despite its compact size (<1m3), the performance of the spectrometer was significantly improved over the earlier design (linear and uniform) in two aspects, (i) a stable momentum measurement resolution and (ii) a balanced expected Cherenkov photon yields in all radiators. In addition, CO2 gas radiators are replaced by heavier gas radiators, C3F8, and the sizes of radiators for high momentum levels (low gas pressure) are enlarged to increase the Cherenkov photon yields. Specifically, the absolute momentum resolution, {\sigma}p, for all levels is replaced by the relative momentum resolution, {\sigma}p/p. To demonstrate the functionality of our proposed Cherenkov muon spectrometer, we presented the results of classification rates as a function of muon momentum with various discriminator levels and reconstructed cosmic ray muon spectrum. When the combination of two or more discriminators are used, the average classification rate is 90.08%. In addition, our proposed Cherenkov muon spectrometer successfully reconstructed the cosmic ray muon spectrum and the results show a good agreement with the actual spectrum within 1{\sigma} in most momentum levels.

   ↳ physics.ins-dethep-exnucl-ex0 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.