Thu·Feb 8, 2024Thursday·February 8, 2024

1. 01*

   Nucleon Spin Sum Rules and Spin Polarizabilities at low $Q^2$

   A. Deur🇺🇸

   We report on recently published experimental studies on spin sum rules, namely the generalized Gerasimov-Drell-Hearn, Bjorken, Burkhardt-Cottingham, Schwinger, and generalized spin polarizability sum rules. The data were taken at Jefferson Lab in Halls A and B by experiments E97-110 and EG4, respectively. They covered the very low $Q^2$ domain, down to $Q^2$$\simeq$0.02 GeV${}^2$, where Chiral Effective Field Theory ($\chi$EFT) predictions should be valid. While some of the obervables agree with the state-of-the-art $\chi$EFT predictions, others are in tensions, including the Longitudinal-Transverse interference polarizability ${\delta }_{\mathrm{LT}}^n(Q^2)$ for which $\chi$EFT prediction was expected to be robust. This suggests that $\chi$EFT does not yet consistently describes nucleon spin observables, even in the very low $Q^2$ domain covered by the experiments.

   nucl-exhep-exPoS(2024)·0 citations
2. 02*

   Interpretation of AMS-02 beryllium isotope fluxes using data-driven production cross sections

   Meng-Jie Zhao🇨🇳 · Xiao-Jun Bi🇨🇳 · Kun Fang🇨🇳 · Peng-Fei Yin🇨🇳

   The Be isotopic measurements preliminarily reported by the AMS-02 Collaboration have reached an unprecedented energy of 12 GeV/$n$. As secondary cosmic rays (CRs), the Be isotopes include both stable and unstable species, which are crucial for constraining the propagation parameters of Galactic CRs. However, uncertainties in their production cross sections can skew the interpretation of the CR data, especially when cross-section measurements are of significantly lower quality than CR measurements. In this work, we consider the uncertainties of the cross sections to interpret the Be isotopic data by adopting a cross-section parametrization that fully utilizes the available experimental data. Owing to the high-quality measurements of the ${}^7$Be production cross section, we innovatively employ ${}^7$Be instead of ${}^9$Be to constrain propagation parameters. Notably, the diffusion halo thickness is constrained to $5.67\pm 0.76$~kpc, representing a moderate value compared to previous analogous works. Combining the well-constrained CR propagation model and the precise CR measurements of ${}^9$Be, we conversely constrain the major production cross section of ${}^9$Be and find that it ought to be remarkably lower than previously thought. Our analysis also questions the reliability of certain cross sections measured by some experiments, potentially marking the first time CR data has been used to identify dubious nucleon production cross sections. The method presented in this work holds promise for analyzing upcoming isotopic data from other nuclei.

   ↳ astro-ph.HEhep-phnucl-exPRD(2024)·8 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.