Mon·Dec 16, 2024Monday·December 16, 2024

1. 01*

   Measurements of global and local spin polarization of $\Lambda$ and $\bar{\Lambda }$ in Au+Au collisions from the RHIC Beam Energy Scan

   Q. Hu🇨🇳

   We report the measurements of $\Lambda$ hyperons' global and local spin polarization from second phase of the RHIC Beam Energy Scan (BES-II) in Au+Au collisions at $\sqrt{s_{NN}}$= 7.7--27 GeV. Global polarization measurements of $\bar{\Lambda }$ and $\Lambda$ show no significant differences, offering insights into the late-stage evolution of the magnetic field. The new measurements of the local polarization of $\Lambda$ perpendicular to the reaction plane ($⟨P_{2,y}⟩$) shows a monotonic increase with decreasing collision energy, while the component along the beam direction ($⟨P_{2,z}⟩$) for both $\Lambda$ and $\bar{\Lambda }$ is small in magnitude with no strong energy dependence. The net local polarization observable, $⟨P_{2,y}^{net}⟩=⟨P_{2,y}(\Lambda )⟩-⟨P_{2,y}(\bar{\Lambda })⟩$ and $⟨P_{2,z}^{net}⟩=⟨P_{2,z}(\Lambda )⟩-⟨P_{2,z}(\bar{\Lambda }⟩)$ designed to probe baryonic spin Hall effect, is consistent with zero with large uncertainty.

   nucl-exhep-exEPJ Web Conf.(2025)·2 citations
2. 02*

   Convergence on the Proton Drip-Line in Thulium

   B. Kootte · M.P. Reiter · C. Andreoiu · S. Beck · J. Bergmann · T. Brunner · T. Dickel · K.A. Dietrich · J. Dilling · E. Dunling · J. Flowerdew · L. Graham and 27 other authors

   Direct observation of proton emission for very small Q-values is often unfeasible due to the long partial half-lives of the proton emission channel associated with tunneling through the Coulomb barrier. Therefore, proton emitters with very small decay energies may require the masses of both parent and daughter nuclei in order to establish them as proton unbound. Nuclear mass models have been used to predict the proton drip-line of the thulium (Tm) isotopic chain ($Z=69$), but until now the proton separation energy has not been experimentally tested. Mass measurements were performed using a Multiple Reflection Time-Of-Flight Mass Spectrometer (MR-TOF-MS) at TRIUMF's TITAN facility to conclusively map the limit of proton-bound Tm. The masses of neutron-deficient, ${}^{149}$Tm and ${}^{150}$Tm, combined with measurements of ${}^{149m,g}$Er (which were found to deviate from literature by $\approx$150 keV), provide the first experimental confirmation that ${}^{149}$Tm is the first proton-unbound nuclide in the Tm chain. Our measurements also enable the strength of the $N=82$ neutron shell gap to be determined at the Tm proton drip-line, providing evidence supporting its continued existence.

   nucl-exPRC(2025)·0 citations
3. 03*

   Study of the energy spectrum of alpha particles in an experiment on irradiation of a boron target with a proton beam at the Prometheus accelerator

   A. S. Rusetskii · M. A. Negodaev · A. V. Oginov · V. A. Ryabov K. V. Shpakov · A. E. Shemyakov · I. N. Zavestovskaya

   The energy spectrum of alpha particles from the nuclear reaction p + ${}^{11}$B $\to 3\alpha$ was studied using the beam of the injector of the proton synchrotron of the Prometheus proton therapy complex. The reaction products (alpha particles) were recorded using a CR-39 track detector. The detectors were calibrated using a ${}^{241}$Am radioactive source. It was determined that mainly alpha particles emitted from the boron target have energies from 3 to 5.5 MeV. In this case, a significant part of the alpha particles emitted from the depths of the target have significantly lower energies compared to the calculated ones due to ionization losses. Measuring the energy spectrum of alpha particles from targets containing boron is of great scientific and practical interest for identifying the mechanisms of boron-proton capture therapy and determining the additional contribution to the therapeutic effect of proton irradiation.

   nucl-exphysics.acc-phNucl.Instrum.Meth.B(2025)·0 citations
4. 04*

   Deuteron-${}^3\mathrm{He}$ scattering using nucleon-${}^3\mathrm{He}$ optical potentials fitted to four-body amplitudes

   A. Deltuva🇱🇹 · D. Jurčiukonis🇱🇹

   Deuteron-${}^3\mathrm{He}$ reactions in the 15 to 40 MeV range are studied using a three-body model where the constructed nonlocal optical potentials rely on rigorous nucleon-${}^3\mathrm{He}$ scattering calculations. The differential cross section for the elastic scattering and neutron transfer reaction is predicted quite well up to 90 deg scattering angles. The importance of the Pauli term in complex potentials is demonstrated.

   ↳ nucl-thnucl-exPLB(2025)·0 citations
5. 05*

   Toward a foundation model for heavy-ion collision experiments based on point-cloud diffusion

   Manjunath Omana Kuttan🇩🇪 · Kai Zhou🇩🇪 · Jan Steinheimer🇩🇪 · Horst Stoecker🇩🇪

   A novel point cloud diffusion model for relativistic heavy-ion collisions, capable of ultra-fast generation of complete, event-by-event collision output, is introduced. When trained on UrQMD cascade simulations, the model generates realistic collision event output containing 26 distinct hadron species, as a list of particle momentum vectors along with their particle ID. From solving inverse problems to accelerating model calculations or detector simulations, the model can be a promising general purpose tool for heavy-ion collisions beneficial to both theoretical studies and experimental applications.

   ↳ hep-phhep-exnucl-exnucl-thPRC(2025)·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.