Fri·May 19, 2023Friday·May 19, 2023

1. 01*

   Understanding radioactive ion beam production at ISAC through yield measurements and simulations

   Peter Kunz🇨🇦 · Jens Lassen🇨🇦 · Corina Andreoiu · Fatima H. Garcia🇺🇸 · Hua Yang🇨🇳 · Valery Radchenko🇨🇦

   The high-intensity proton beam of the TRIUMF 500 MeV cyclotron offers unique opportunities to produce rare isotopes by irradiating a variety of targets. In particular, the ISAC (Isotope Separation and ACceleration) facility provides the infrastructure to deliver customized rare ion beams for fundamental research in nuclear physics, astrophysics, material science, and nuclear medicine. A continuous effort is made to develop new radioactive ion beams (RIB) and improve their intensity or purity, properties that depend strongly on the type of target, operating conditions, the ion source, and beam transport efficiency. Yield data and theoretical production rates based on FLUKA and Geant4 simulations are collected in the TRIUMF Isotope Database, providing a valuable resource for RIB development and experiment planning. This paper introduces the newly upgraded TRIUMF Isotope Database and presents examples on how it's resources can be used to plan experiments and understand the origin of certain RIB. In particular we discuss the collection of 155Tb which is an important component of medical isotope research at TRIUMF.

   ↳ physics.acc-phnucl-exNucl.Instrum.Meth.B(2023)·1 citation
2. 02*

   Bottomonium production in pp and heavy-ion collisions

   Taesoo Song🇩🇪 · Joerg Aichelin🇫🇷 · Jiaxing Zhao🇫🇷 · Pol Bernard Gossiaux🇫🇷 · Elena Bratkovskaya🇩🇪

   We study bottomonium $b\bar{b}$ production in pp collisions as well as in heavy-ion collisions, using a quantal density matrix approach. The initial bottom (anti)quarks are provided by the PYTHIA event generator. We solve the Schrödinger equation for the $b\bar{b}$ pair, identifying the potential with the free energy, calculated with lattice QCD, to obtain the temperature dependent $b\bar{b}$ density matrix as well as the dissociation temperature. The formation of bottomonium is given by projection of the bottomonium density matrix onto the density matrix of the system. With this approach we describe the rapidity and transverse momentum distribution of the ${\rm Y}$(nS) in pp collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV extending a similar calculation for the charmonium states \cite{Song:2017phm}. We employ the Remler formalism to study the $b\bar{b}$ production in heavy ion collisions in which the heavy quarks scatter elastically with partons from the quark gluon plasma (QGP). The elastic scattering of heavy (anti)quark in QGP is realized by the dynamical quasi-particle model (DQPM) and the expanding QGP is modeled by PHSD. We find that a reduction to 10 \% of the scattering cross section for a (anti)bottom quark with a QGP parton reproduces the experimental data. This suggests that due to color neutrality the scattering cross section of the small $b\bar{b}$ system with a parton is considerably smaller than twice the bottom-parton scattering cross section.

   ↳ nucl-thhep-phnucl-exPRC(2023)·29 citations
3. 03*

   Hyperon global polarization in heavy-ion collisions at NICA energies. Feed-down effects and the role of ${\Sigma }^0$ hyperons

   V. Voronyuk (JINR, Dubna)🇷🇺 · E.E. Kolomeitsev (Matej Bel Univ., Slovakia, JINR, Dubna)🇷🇺 · N.S. Tsegelnik (JINR, Dubna)🇷🇺

   Global polarization of hyperons induced by the local vorticity of the medium created in heavy-ion collisions at energies 2.3\,GeV$\le \sqrt{s_{NN}}\le$11.5 GeV is calculated in the parton-hadron-string dynamic (PHSD) model. The separation of spectator nucleons and the fluidization of the generated particle distributions are performed. The polarization of all anti-hyperon species is found significantly larger than that of hyperons. The $\overline{\Xi }$ hyperons are found to be polarized as strong as $\overline{\Lambda }$s but $\Xi$ hyperons have weaker polarization compared to $\Lambda$s. The $\Omega$ and $\overline{\Omega }$ polarizations show the strongest dependence on the collision energy. Despite the strong polarization of the produced $\Lambda$s and $\overline{\Lambda }$s induced by the vortical flows in the medium, the observed polarization signal is significantly depleted because of the feed down from weak and electromagnetic decays of heavier hyperons. Particularly strong suppression is found to be due to electromagnetic decays of ${\Sigma }^0$ hyperons, which multiplicities obtained in the transport are poorly constrained both from the microscopic input of the ${\Sigma }^0$ production reactions and from the experimental data. The final $\Lambda (\overline{\Lambda })$ polarization signal strongly depends on the ${\Sigma }^0$ multiplicity generated in the model. With all these effects we can reproduce the measured global $\Lambda$ polarization in collisions at $\sqrt{s_{NN}}=7.7$ and $11.5$ GeV and the global $\overline{\Lambda }$ polarization at 11.5 GeV. For energies $<3$ GeV, the calculated $\Lambda$ polarization is smaller than the observed one. The polarization of $\Xi (\overline{\Xi })$ hyperons is calculated. The signal of $\Xi (\overline{\Xi })$ polarization is argued to be insensitive to feed-down effects and be a more direct probe of the degree of the vorticity in the system.

   ↳ nucl-thnucl-exPRC(2025)·8 citations
4. 04*

   Production of $p$-nuclei from $r$-process seeds: the $\nu r$-process

   Zewei Xiong🇩🇪 · Gabriel Martínez-Pinedo🇩🇪 · Oliver Just🇩🇪 · Andre Sieverding🇺🇸

   We present a new nucleosynthesis process that may take place on neutron-rich ejecta experiencing an intensive neutrino flux. The nucleosynthesis proceeds similarly to the standard $r$-process, a sequence of neutron-captures and beta-decays, however with charged-current neutrino absorption reactions on nuclei operating much faster than beta-decays. Once neutron capture reactions freeze-out the produced $r$-process neutron-rich nuclei undergo a fast conversion of neutrons into protons and are pushed even beyond the $\beta$-stability line producing the neutron-deficient $p$-nuclei. This scenario, which we denote as the $\nu r$-process, provides an alternative channel for the production of $p$-nuclei and the short-lived nucleus ${}^{92}$Nb. We discuss the necessary conditions posed on the astrophysical site for the $\nu r$-process to be realized in nature. While these conditions are not fulfilled by current neutrino-hydrodynamic models of $r$-process sites, future models, including more complex physics and a larger variety of outflow conditions, may achieve the necessary conditions in some regions of the ejecta.

   ↳ astro-ph.HEnucl-exnucl-thPRL(2024)·14 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.