Nuclear Theory·nucl-th

Wednesday·September 22, 2021

8 papers—4 primary·4 cross-listed

01
[Submitted on 21 Sept 2021]
$α$ -clustering effect on flows of direct photons in heavy-ion collisions
Chen-Zhong Shi · Yu-Gang Ma
In this work, we reconstruct the $γ$ -photon energy spectrum which is in good agreement with the experimental data of $^{86}$ Kr + $^{12}$ C at $E / A$ = 44 MeV in the framework of our modified EQMD model. The directed flow and elliptic flow of free protons and direct photons have been investigated by taking $α$ -clustering structure of $^{12}$ C into account. Comparing with the free proton, the direct photon flows give a clearer information about early stage of nuclear reaction. Difference of collective flows between different configurations of $^{12}$ C is observed in this work. This indicates that collective flows of direct photons are sensitive to the initial configuration, therefore the $γ$ bremsstrahlung process might be taken as an alternative probe to investigate $α$ -clustering structure in light nucleus from heavy ion collisions at Fermi-energy region.
Comments:
10 pages, 9 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2109.09938 [pdf]
Nucl.Sci.Tech.(2021)·48 citations
02
[Submitted on 21 Sept 2021]
Lambda polarization in $^{108}$ Ag + $^{108}$ Ag and $^{197}$ Au + $^{197}$ Au collisions around a few GeV
Xian-Gai Deng🇨🇳 · Xu-Guang Huang🇨🇳 · Yu-Gang Ma🇨🇳
Within the framework of Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model, we extract the global spin polarization of $Λ$ hyperon in $^{108}$ Ag + $^{108}$ Ag and $^{197}$ Au + $^{197}$ Au collisions at $s_{NN} = 2.42 - 62.4$ GeV. We use two different approaches to calculate the $Λ$ polarization $P_{y}$ : approach I is based on equilibrium assumption so that $P_{y}$ is determined by thermal vorticity and approach II assumes a proportional relation between $P_{y}$ and the system's angular momentum in $Λ$ 's rest frame. We find that both approaches can describe the experimental data at low energies around a few GeV but only approach I describes well also higher-energy data. This suggests that at higher energies the relativistic effect plays an important role. After taking into such effect properly, the relativity-improved approach II can describe the higher-energy data as well.
Comments:
V3: 6 pages, 5 figures. Published version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2109.09956 [pdf]
PLB(2022)·48 citations
03
[Submitted on 21 Sept 2021]
Persistence of cluster structure in the ground state of $^{11}$ B
Naoyuki Itagaki · Tomoya Naito · Yuichi Hirata
The persistence of $α + α + t$ cluster configuration in the ground state of $^{11}$ B is discussed. The $α$ particles emitted from excited states of $^{12}$ C could be utilized for cancer treatment, where the cluster states are created by a clinical proton beam on the $^{11}$ B target. Although the cross section has been already available, for the nuclear structure side, whether the ground state of $^{11}$ B contains the seeds of the cluster states is a crucial question, since the cluster structure may be washed out by the spin-orbit interaction, which has been known as a driving force to break the $α$ clusters. For this purpose, in addition to the basis states with cluster configurations, we include their breaking effects by employing the antisymmetrized quasi cluster model (AQCM). The inclusion of the breaking effect of $α + α + t$ cluster structure is found to contribute to the lowering of the ground-state energy by about 2 MeV. Assuming the typical three- $α$ cluster state of $^{12}$ C as an equilateral triangular configuration with the relative distances of $\approx 4$ fm, the ground state of $^{11}$ B is found to have a certain squared overlap with such state when a proton approaches. The third $3/ 2^{-}$ state has been suggested as a cluster state both theoretically and experimentally, and we confirmed the well-developed clustering.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2109.09957 [pdf]
PRC(2022)·4 citations
04
[Submitted on 21 Sept 2021]
Skyrmions and Fractional Quantum Hall Droplets Unified by Hidden Symmetries in Dense Matter
Mannque Rho🇫🇷
A chain of connections in compressed baryonic matter, up-to-date glaringly missing in nuclear effective field theory, between intrinsic or emergent symmetries of QCD, mesons-gluons dualities, vector meson dominance and Chern-Simons fields has recently been revealed, presaging a possible new paradigm in nuclear theory. It indicates a ubiquitous role, thus far unexplored, of hidden symmetries -- flavor-local and scale -- permeating from dilute baryonic systems to normal nuclear matter and then to compact-star matter. Here I give a brief account of the possibly "indispensable" relevance of the $η^{'}$ singular ring, a.k.a. fractional quantum Hall (FQH) droplet, to the properties of the lowest-lying vector mesons $ω$ and $ρ$ , relevant to dilepton production processes, argued to be Seiberg-dual to the gluons near the chiral restoration.
Comments:
9 pages, no figures, typos corrected
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2109.10059 [pdf]
2 citations
05
[Submitted on 18 Sept 2021] (cross-list from hep-ph)
Kinetic theory of overpopulated gluon systems with inelastic processes
Zhengyu Chen🇨🇳
In this work, the role of inelastic processes in the formation of a transient Bose-Einstein condensation (BEC) is investigated based on kinetic theory. We calculate the condensation rate for an overpopulated gluon system which is assumed to be in thermal equilibrium and with the presence of a BEC. The matrix elements of the inelastic processes are chosen as the isotropic one and the gluons are considered to have a finite mass. Our calculations indicate that the inelastic processes can hinder the formation of a BEC since the negatively infinite net condensation rate can destroy any BEC instantly.
Comments:
new discussion on the infinite terms; Sec.III, Subsection B deleted; references updated. arXiv admin note: text overlap with arXiv:1703.02495 by other authors
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2109.08887 [pdf]
IJMPE(2023)·0 citations
06
[Submitted on 20 Sept 2021] (cross-list from nucl-ex)
System Size and Flavour Dependence of Chemical Freeze-out Temperatures in ALICE Data from pp, pPb and PbPb Collisions at LHC Energies
Fernando Antonio Flor🇺🇸 · Gabrielle Olinger🇺🇸 · René Bellwied🇺🇸
We present the system size and flavour dependence of the chemical freeze-out temperature ( $T_{ch}$ ) at vanishing baryo-chemical potential calculated via thermal fits to experimental yields for several multiplicity classes in pp, pPb and PbPb collisions measured by ALICE. Using the Thermal-FIST Hadron Resonance Gas model package, we compare the quality of fits across various treatments of strangeness conservation under different freeze-out conditions as a function of the charged particle multiplicity density $⟨ d N_{ch} / d η ⟩$ . Additionally, we examine how the anti-hadron to pion yield ratios of light and strange baryons, as well as the $ϕ$ meson, evolve within a flavour-dependent model. Through a unique two-temperature chemical freeze-out approach, we show that flavour dependence of $T_{ch}$ in a Strangeness Canonical Ensemble leads to a natural explanation of strangeness enhancement from small to large systems at LHC energies without requiring any non-equilibrium particle production at small $⟨ d N_{ch} / d η ⟩$ .
Comments:
7 pages, 5 figures, 2 tables. Submitted to and accepted by Physics Letters B
Subjects:
Nuclear Experiment (nucl-ex); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2109.09843 [pdf]
PLB(2022)·23 citations
07
[Submitted on 21 Sept 2021] (cross-list from hep-lat)
Approaching nuclear interactions with lattice QCD
Marc Illa🇪🇸
Nuclei make up the majority of the visible matter in the Universe; obtaining a first principles description of the nuclear properties and interactions between nuclei directly from the underlying theory of the strong interaction, Quantum Chromodynamics (QCD), is one of the main goals of the nuclear physics community. Although the theory was established nearly fifty years ago, the complexities of QCD at low energies precludes analytical solutions of the simplest hadronic systems, let alone the features of the nuclear forces. In this thesis we follow the lattice QCD approach, according to which QCD is solved non-perturbatively in a discretized space-time via large-scale numerical calculations. Specifically, the interactions between two octet baryons, with strangeness ranging from 0 to -4, are studied at low energies with larger-than-physical quark masses, and the low-energy coefficients in pionless effective field thepry relevant for two-baryon interactions, including those responsible for SU(3) flavor-symmetry breaking, are constrained.
Comments:
PhD thesis, Universitat de Barcelona (September, 2021). Based on arXiv:2009.12357
Subjects:
High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2109.10068 [pdf]
1 citation
08
[Submitted on 21 Sept 2021] (cross-list from hep-lat)
Funny business from the large $N_{c}$ finite temperature crossover
Thomas DeGrand🇺🇸
It is well known that the deconfinement transition temperature for $S U (N_{c})$ gauge theory is almost independent of $N_{c}$ , and the transition is first order for $N_{c} \geq 3$ . In the real world ( $N_{c} = 3$ , light quarks) it is a crossover located far away from the pure gauge value. What happens to the transition temperature at fixed fermion mass if the number of fermion flavors is held constant ( $N_{f} = 2$ ) and $N_{c}$ is varied? There are multiple plausible stories, only one of which appears to be true when the systems are simulated on the lattice. I describe the physics issues which surround the question and my lattice - based answer to it.
Comments:
6 pages, 2 figures, contribution to Lattice 2021
Subjects:
High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2109.10337 [pdf]
PoS(2022)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE