Nuclear Theory·nucl-th

Thursday·September 7, 2023

9 papers—5 primary·4 cross-listed

01
Nuclear Equation of State and many-body phase-space correlations in the Constrained Molecular Dynamics
Massimo Papa
Many-body correlations characterizing the Constrained Molecular Dynamics (CoMD)are analyzed in the case of finite and zero range effective microscopic interactions. The study begins by analyzing the case of infinite nuclear matter at zero temperature. A comparison with the predictions in the mean-field(MF) limit corresponding to different effective masses, highlights non-negligible differences regarding the produced Equation of State (EoS). A procedure is illustrated to determine the necessary corrections of the effective interaction parameters in the CoMD model so to reproduce the chosen EoS. The specific model calculations, the general feature of the discussed correlations gives a wider meaning to the resulting differences, which are in fact strongly related both to the Pauli principle constraint and to the localization effects related to wave-packets dynamics. Moving on to finite systems, preliminary results are shown in relation to the reaction mechanisms in the $^{64} N i +^{48} C a$ system described by the CoMD model. Therefore, the topic covered illustrates the effects produced by the correlations of the CoMD dynamics on the EoS and on some observables commonly studied in heavy ion collisions.
nucl-thNPA(2024)·5 citations
02
Effect of Backing on Neutron Spectra for Low Energy Quasi-Mono-energetic p+ $^{7}$ Li Reaction
H. Kumawat
$MO$ nte-carlo $N$ ucleon transport $C$ ode (MONC) for nucleon transport is extended for below 20MeV proton transport using ENDF and EXFOR data base. It is used to simulate p+ $^{7}$ Li reaction upto 20MeV proton energies and produced neutron spectra are reported here. The simulated results are compared with calculated values from other available codes like PINO, EPEN, SimLiT and experimental data. The spectra reported here can be used to get the neutron cross-section for the quasi-mono-energetic neutron reaction and will help to subtract the low energy contribution. The neutron spectra also useful as this reaction is used for accelerator based Boron Neutron Capture Therapy. The backing materials are used to fully stop the proton beam hence contribution from the neutrons from backing materials is estimated. It is found that Tantalum is good backing material below $\sim$ 8 MeV and Carbon is better at higher energies.
nucl-thnucl-exNucl.Sci.Eng.(2025)·2 citations
03
Production of doubly charmed hadron $Ξ_{cc}^{++}$ and $T_{cc}^{+}$ in relativistic heavy ion collisions
Baoyi Chen🇨🇳 · Meimei Yang🇨🇳 · Ge Chen🇬🇧 · Jiaxing Zhao🇫🇷 · Xiao-hai Liu🇨🇳
Heavy ion collisions provide a unique opportunity for studying the properties of exotic hadrons with two charm quarks. The production of $T_{cc}^{+}$ is significantly enhanced in nuclear collisions compared to proton-proton collisions due to the creation of multiple charm pairs. In this study, we employ the Langevin equation in combination with the Instantaneous Coalescence Model (LICM) to investigate the production of $T_{cc}^{+}$ and $Ξ_{cc}^{++}$ which consists of two charm quarks. We consider $T_{cc}^{+}$ as molecular states composed of $D$ and $D^{*}$ mesons. The Langevin equation is used to calculate the energy loss of charm quarks and $D$ mesons in the hot medium. The hadronization process, where charm quarks transform into each $D$ state as constituents of $T_{cc}^{+}$ production, is described using the coalescence model. The coalescence probability between $D$ and $D^{*}$ is determined by the Wigner function, which encodes the information of the $T_{cc}^{+}$ wave function. Our results show that the $T_{cc}^{+}$ production varies by approximately one order of magnitude when different widths in the Wigner function, representing distinct binding energies of $T_{cc}^{+}$ , are considered. This variation offers valuable insights into the nature of $T_{cc}^{+}$ through the analysis of its wave function. The $Ξ_{cc}^{++}$ is treated as a hadronic state produced at the hadronization of the deconfined matter. Its production is also calculated as a comparison with the molecular state $T_{cc}^{+}$ .
nucl-thhep-phPRC(2024)·6 citations
04
Polarization of Thermal Dilepton Radiation
Florian Seck🇩🇪 · Bengt Friman🇩🇪 · Tetyana Galatyuk🇩🇪 · Hendrik van Hees🇩🇪 · Ralf Rapp🇺🇸 · Enrico Speranza🇺🇸 · Jochen Wambach🇩🇪
The invariant mass spectra of dileptons radiated from the fireballs formed in high-energy heavy-ion collisions have been successfully used to investigate the properties of hot and dense QCD matter. Using a realistic model for the in-medium electromagnetic spectral function, we predict polarization observables and compare them to experiment. This allows, for the first time, independent tests of the longitudinal and transverse components of the virtual photon's selfenergy. While the low- and high-mass regions exhibit the expected limits of transverse and unpolarized photons, respectively, baryon-driven medium effects in the $ρ$ -meson mass region create a marked longitudinal polarization that transits into a largely unpolarized emission from the quark-gluon plasma, thus providing a sensitive test of microscopic emission processes in QCD matter. Applications to available data from the HADES and NA60 experiments at SIS and SPS energies, respectively, are consistent with our predictions and set the stage for quantitative polarization studies at FAIR and collider energies.
nucl-thPLB(2025)·15 citations
05
Complex scaling in finite volume
Hang Yu · Nuwan Yapa · Sebastian König
Quantum resonances, i.e., metastable states with a finite lifetime, play an important role in nuclear physics and other domains. Describing this phenomenon theoretically is generally a challenging task. In this work, we combine two established techniques to address this challenge. Complex scaling makes it possible to calculate resonances with bound-state-like methods. Finite-volume simulations exploit the fact that the infinite-volume properties of quantum systems are encoded in how discrete energy levels change as one varies the size of the volume. We apply complex scaling to systems in finite periodic boxes and derive the volume dependence of states in this scenario, demonstrating with explicit examples how one can use these relations to infer infinite-volume resonance energies and lifetimes.
nucl-thPRC(2024)·9 citations

Affiliations

first authorsco-authorsvia INSPIRE

Nuclear Equation of State and many-body phase-space correlations in the Constrained Molecular Dynamics

Effect of Backing on Neutron Spectra for Low Energy Quasi-Mono-energetic p+7Li Reaction

Production of doubly charmed hadron Ξcc++​ and Tcc+​ in relativistic heavy ion collisions

Polarization of Thermal Dilepton Radiation

Complex scaling in finite volume

Affiliations

Effect of Backing on Neutron Spectra for Low Energy Quasi-Mono-energetic p+ $^{7}$ Li Reaction

Production of doubly charmed hadron $Ξ_{cc}^{++}$ and $T_{cc}^{+}$ in relativistic heavy ion collisions