Thu·Mar 14, 2024Thursday·March 14, 2024

1. 01*

   First identification of a doublet wobbling excitation mode in ${}^{105}$Pd

   A. Karmakar · P. Datta🇺🇸 · N. Rather · S. Pal🇨🇦 · R. Palit🇩🇪 · A. Goswami🇮🇳 · G.H. Bhat🇮🇳 · J. A. Sheikh🇮🇳 · S. Jehangir🇮🇳 · S. Chattopadhyay🇮🇳 · S. Frauendorf

   An experimental investigation of ${}^{105}$Pd has revealed, for the first time, the existence of two wobbling bands, both having one phonon configuration and originating from excitation which is the wobbling from the yrast band with the $h_{11/2}$ quasineutron fully aligned with the short axis, and from an excited band with the same quasineutron but with less alignment along the short axis. These observations have been drawn from the measured ratios of the inter-band and intra-band gamma transition rates. Model calculations based on the triaxial projected shell model (TPSM) approach have been performed and are found to be in good agreement with the experimental energies and relative transition probabilities. The analysis of the TPSM results provides an insight into the nature of the observed structures at a microscopic level.

   nucl-exnucl-thPRC(2025)·7 citations
2. 02*

   Gluonic gravitational form factors of the proton

   Zein-Eddine Meziani🇺🇸

   The gravitational form factors (GFFs) are a fundamental and elegant way to describe the structure of nucleons and nuclei. Their Fourier transform allows a description of the spatial distribution of the mass, angular momentum, pressure, and shear force densities for both quarks and gluons in the nucleon. While previous investigations predominantly focused on the proton electromagnetic form factors (EMFFs) leading to the charge and magnetization distributions determination, the current emphasis has shifted towards expanding our understanding of the gravitational form factors of quarks and gluons where little is known. In particular, more recently, the proton {\it gluonic} GFFs have been the target of an intensive investigation at Jefferson Lab. This endeavor, is not without its challenges, particularly in navigating the complexities associated with the near-threshold region. Nevertheless, it provides a bedrock for future nucleon and nuclei gluonic structure studies at the future EIC. In this talk, I will focus on the recent results of $J/\psi$ photoproduction near-threshold on the proton at Jefferson Lab to determine, in particular, the elusive {\it gluonic} gravitational form factors. We discuss the caveats of their extraction in the threshold region and mention the complementary measurements of ${\rm Y}$ at the EIC critical to access the trace anomaly and gain insight into the origin of the nucleon mass.

   nucl-exPoS(2024)·6 citations
3. 03*

   Nucleon charge and magnetisation distributions: flavour separation and zeroes

   Zhao-Qian Yao🇨🇳 · Daniele Binosi🇮🇹 · Zhu-Fang Cu · Craig D. Roberts🇨🇳

   A symmetry-preserving truncation of the quantum field equations describing hadron properties is used to deliver parameter-free predictions for all nucleon elastic electromagnetic form factors and their flavour separation to large values of momentum transfer, $Q^2$. The proton electric form factor, $G_E^p$, possesses a zero, whereas that of the neutron, $G_E^n$, does not. The difference owes to the behaviour of the Pauli form factor of the proton's singly-represented valence $d$-quark. Consequently, $G_E^n>G_E^p$ on a material large-$Q^2$ domain. These predictions can be tested in modern experiments.

   ↳ hep-phhep-exhep-latnucl-ex+1Fund.Res.(2026)·23 citations
4. 04*

   Suppression of diffraction in deep-inelastic scattering on nuclei and dynamical mechanism of leading twist nuclear shadowing

   V. Guzey (Jyvaskyla U. and Helsinki Inst. of Phys.)🇫🇮 · M. Strikman (Penn State U.)🇺🇸

   Using the leading twist approach (LTA) to nuclear shadowing, we calculate the ratios of diffractive and usual parton distributions for a heavy nucleus (Pb) and the proton, $R_{A/p}=(f_{i/A}^{D(3)}/f_{i/A})/(f_{i/p}^{D(3)}/f_{i/p})$, for coherent and summed (coherent plus quasi-elastic) nuclear deep-inelastic scattering. We find that $R_{A/p}\approx 0.5-1$ for quarks as well as for the ratio of the diffractive and total cross sections $[(d{\sigma }_{\mathrm{diff}}/d{M}_X^2)/{\sigma }_{\mathrm{tot}}{]}_{eA}/[(d{\sigma }_{\mathrm{diff}}/d{M}_X^2)/{\sigma }_{\mathrm{tot}}{]}_{ep}$ and $R_{A/p}\approx 0.5-1.3$ for gluons in a broad range of $x$, including the kinematics of the Electron-Ion Collider, which reaffirms the difference from the nuclear enhancement of $R_{A/p}$ predicted in the gluon saturation framework. We demonstrate that the magnitude of $R_{A/p}$ is controlled by the cross section of the interaction of hadronic fluctuations of the virtual photon with target nucleons, which explains an enhancement of $R_{A/p}$ in the color dipole model and its suppression in LTA. We argue that the black disk limit corresponds to $R_{A/p}=1$ and $R_{A/p}^{\mathrm{coh}}=0.86$ for the summed and coherent scattering, respectively. Relying on an intuitive definition of the saturation scale, we show that the ratio of the saturation scales of a heavy nucleus and proton $Q_{sA}^2(b)/Q_{sp}^2(b)\approx 1$ at small impact parameters $b$ due to the strong leading twist nuclear shadowing and diluteness of the nuclear density.

   ↳ hep-phhep-exnucl-exJHEP(2024)·4 citations
5. 05*

   Opportunities and open questions in modern $\beta$ decay

   Leendert Hayen🇫🇷

   For well over half a century, precision studies of neutron and nuclear $\beta$ decays have been at the forefront of searches for exotic electroweak physics. Recent advances in nuclear ab initio theory and the widespread use of effective field theories means that its modern understanding is going through a transitional phase. This has been propelled by current tensions in the global data set leading to renewed scrutiny of its theoretical ingredients. In parallel, a host of novel techniques and methods are being investigated that are able to sidestep many traditional systematic uncertainties and require a diverse palette of skills and collaboration with material science and condensed matter physics. We highlight the current opportunities and open questions with the aim of facilitating the transition to a more modern understanding of $\beta$ decay.

   ↳ nucl-thnucl-exAnn.Rev.Nucl.Part.Sci.(2024)·18 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.