Mon·Sep 16, 2024Monday·September 16, 2024

1. 01*

   Measurement of the nucleon spin structure functions for 0.01<$Q^2$<1 GeV${}^2$ using CLAS

   A. Deur · S.E. Kuhn · M. Ripani · X. Zheng · A.G. Acar · P. Achenbach · K.P. Adhikari · J. S. Alvarado · M.J. Amaryan · W. R. Armstrong · H. Atac · H. Avakian and 138 other authors

   The spin structure functions of the proton and the deuteron were measured during the EG4 experiment at Jefferson Lab in 2006. Data were collected for longitudinally polarized electron scattering off longitudinally polarized NH${}_3$ and ND${}_3$ targets, for $Q^2$ values as small as 0.012 and 0.02 GeV${}^2$, respectively, using the CEBAF Large Acceptance Spectrometer (CLAS). This is the archival paper of the EG4 experiment that summaries the previously reported results of the polarized structure functions $g_1$, $A_1{F}_1$, and their moments ${\overline{\Gamma }}_1$, ${\overline{\gamma }}_0$, and ${\overline{I}}_{TT}$, for both the proton and the deuteron. In addition, we report on new results on the neutron $g_1$ extracted by combining proton and deuteron data and correcting for Fermi smearing, and on the neutron moments ${\overline{\Gamma }}_1$, ${\overline{\gamma }}_0$, and ${\overline{I}}_{TT}$ formed directly from those of the proton and the deuteron. Our data are in good agreement with the Gerasimov-Drell-Hearn sum rule for the proton, deuteron, and neutron. Furthermore, the isovector combination was formed for $g_1$ and the Bjorken integral ${\overline{\Gamma }}_1^{p-n}$, and compared to available theoretical predictions. All of our results provide for the first time extensive tests of spin observable predictions from chiral effective field theory ($\chi$EFT) in a $Q^2$ range commensurate with the pion mass. They motivate further improvement in $\chi$EFT calculations from other approaches such as the lattice gauge method.

   nucl-exPRC(2025)·8 citations
2. 02*

   Optical model potentials for deuteron scattering off ${}^{24}$Mg, ${}^{28}$Si, ${}^{58}$Ni, ${}^{90}$Zr, ${}^{116}$Sn, and ${}^{208}$Pb at $\sim$100 MeV/nucleon

   D. Patel🇮🇳 · D.C. Cuong · K.B. Howard · U. Garg🇺🇸 · Dao T. Khoa · H. Akimune · G.P.A. Berg🇺🇸 · M. Fujiwara🇯🇵 · M.N. Harakeh🇳🇱 · M. Itoh · C. Iwamoto🇯🇵 · T. Kawabata🇯🇵 and 4 other authors

   Angular distributions of the elastic and inelastic deuteron-nucleus scattering off ${}^{24}$Mg, ${}^{28}$Si, ${}^{58}$Ni, ${}^{90}$Zr, ${}^{116}$Sn, and ${}^{208}$Pb have been measured at a beam energy of 98 MeV/nucleon, with the goal of constraining the deuteron optical potential in this kinematical regime, and to extract the reduced transition probabilities for the ground-state transitions to low-lying excited states of these nuclei. Two potential models were used in the analysis of the measured $(d,d)$ and $(d,d^{\prime })$ data within the optical model and the distorted-wave Born approximation: the phenomenological optical model potential associated with the collective model of nuclear scattering, and the semi-microscopic double-folding model of the deuteron-nucleus potential based on a realistic density-dependent M3Y interaction. The deuteron optical potential and inelastic $(d,d^{\prime })$ scattering form factors were calculated using these two potential models, allowing for a direct comparison between the potential models as well as the validation of the deduced $E\lambda$ transition rates.

   nucl-exnucl-thPRC(2024)·0 citations
3. 03*

   Resonance suppression during the hadronic stage from the FAIR to the intermediate RHIC energy regime

   Amine Chabane🇩🇪 · Lisa Engel🇩🇪 · Tom Reichert🇩🇪 · Jan Steinheimer🇩🇪 · Marcus Bleicher🇩🇪

   The energy and centrality dependence of the kaon resonance ratio $(K^{\ast 0}+\text{Bar}{K}^{\ast 0})/(K^{+}+K^{-})$ is explored in the RHIC-BES and CBM-FAIR energy regime. To this aim, the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model is employed to simulate reconstructable $K^{\ast }$ resonances in Au+Au and p+p collisions from $\sqrt{s_{\text{NN}}}=3-39$ GeV. We obtain a good description of the resonance yields and mean transverse momenta over the whole investigated energy range. The decrease of the $K^{\ast }/K$ ratio, with increasing centrality is in line with the available experimental data. We also observe the experimenatlly measured increase in $⟨p_{\text{T}}⟩$ with increasing centrality which is interpreted as a lower reconstruction probability of low-$p_{\text{T}}$ $K^{\ast }$ due to the $p_{\text{T}}$ dependent absorption of the decay daughter hadrons. We conclude that the observed suppression of reconstructable $K^{\ast }$ resonances provides a strong sign of an extended hadronic rescattering stage at all investigated energies. Its duration increases from peripheral to central reactions as expected. Following a method, suggested by the STAR experiment, the "duration" of the hadronic stage is extracted using the $K^{\ast }/K$ ratios at chemical and kinetic freeze-out. The resulting lifetimes are in good agreement with the experimental data, but much shorter than the actual lifetime of the hadronic phase in the transport simulation. This indicates that the experimental method to estimate the life time of the hadronic stage is too simplified.

   ↳ hep-phnucl-exnucl-thPRC(2025)·6 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.