Mon·Jul 22, 2024Monday·July 22, 2024

1. 01*

   First simultaneous measurement of the gamma-ray and neutron emission probabilities in inverse kinematics at a heavy-ion storage ring

   M. Sguazzin🇫🇷 · B. Jurado🇫🇷 · J. Pibernat🇫🇷 · J. A. Swartz🇫🇷 · M. Grieser🇩🇪 · J. Glorius🇩🇪 · Yu. A. Litvinov🇩🇪 · C. Berthelot🇫🇷 · B. Włoch🇫🇷 · J. Adamczewski-Musch🇩🇪 · P. Alfaurt🇫🇷 · P. Ascher🇫🇷 and 41 other authors

   The probabilities for gamma-ray and particle emission as a function of the excitation energy of a decaying nucleus are valuable observables for constraining the ingredients of the models that describe the de-excitation of nuclei near the particle emission threshold. These models are essential in nuclear astrophysics and applications. In this work, we have for the first time simultaneously measured the gamma-ray and neutron emission probabilities of 208Pb. The measurement was performed in inverse kinematics at the Experimental Storage Ring (ESR) of the GSI/FAIR facility, where a 208Pb beam interacted through the 208Pb(p,p') reaction with a hydrogen gas jet target. Instead of detecting the gamma-rays and neutrons emitted by 208Pb, we detected the heavy beam-like residues produced after gamma and neutron emission. These heavy residues were fully separated by a dipole magnet of the ESR and were detected with outstanding efficiencies. The comparison of the measured probabilities with model calculations has allowed us to test and select different descriptions of the gamma-ray strength function and the nuclear level density available in the literature.

   nucl-exPRC(2025)·4 citations
2. 02*

   Investigating event-shape methods in the search for the chiral magnetic effect in relativistic heavy ion collisions

   Han-Sheng Li🇺🇸 · Yicheng Feng🇺🇸 · Fuqiang Wang🇺🇸

   The Chiral Magnetic Effect (CME) is a phenomenon in which electric charge is separated by a strong magnetic field from local domains of chirality imbalance and parity violation in quantum chromodynamics (QCD). The CME-sensitive observable, charge-dependent three-point azimuthal correlator $\Delta \gamma$, is contaminated by a major physics background proportional to the particle's elliptic flow anisotropy $v_2$. Event-shape engineering (ESE) binning events in dynamical fluctuations of $v_2$ and event-shape selection (ESS) binning events in statistical fluctuations of $v_2$ are two methods to search for the CME by projecting $\Delta \gamma$ to the measured anisotropy $v_2=0$ intercept. We conduct a systematic study of these two methods using physics models as well as toy model simulations. It is observed that the ESE method fulfills the general premise of measuring the CME but is statistically hungry. It is found that the intercept from the ESS method depends on the details of the event content, such as the mixtures of background-contributing sources, because of statistical fluctuations of intertwining variables used in the method, and is thus not practically useful or clean to measure the CME.

   ↳ physics.data-annucl-exnucl-thPRC(2025)·7 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.