Nuclear Theory·nucl-th

Thursday·January 4, 2024

5 papers—1 primary·4 cross-listed

01
Shell-model representations of the microscopic version of the Bohr-Mottelson collective model
H. G. Ganev
The structure of the irreducible collective spaces of the group $S p (12, R)$ , which many-particle nuclear states are classified according to the chain $S p (12, R) \supset U (6) \supset S O (6) \supset S U_{p n} (3) \otimes S O (2) \supset S O (3)$ of the proton-neutron symplectic model (PNSM), is considered in detail. This chain of the PNSM was shown to correspond to a microscopic shell-model version of the Bohr-Mottelson collective model. The construction of the relevant shell-model representations of the $S p (12, R)$ group along this chain is considered for three nuclei with varying collective properties and from different mass regions. It is shown that the $S U_{p n} (3)$ basis states of the $S p (12, R)$ representations are always Pauli allowed for $υ \geq υ_{0}$ , but organized in a different way into different $S O (6)$ shells. This is in contrast to the case of filling the levels of the standard three-dimensional harmonic oscillator and using the plethysm operation. Although the $S U_{p n} (3)$ multiplets with $υ < υ_{0}$ are not all Pauli forbidden, it is safe to discard them, as it was actually done in the practical applications.
nucl-thCommun.Theor.Phys.(2024)·0 citations
02
Constraining MeV to 10 GeV majoron by Big Bang Nucleosynthesis
Sanghyeon Chang🇰🇷 · Sougata Ganguly🇰🇷 · Tae Hyun Jung🇰🇷 · Tae-Sun Park🇰🇷 · Chang Sub Shin🇰🇷
We estimate the Big Bang nucleosynthesis (BBN) constraint on the majoron in the mass range between $1 MeV$ to $10 GeV$ which dominantly decays into the standard model neutrinos. When the majoron lifetime is shorter than $1 sec$ , the injected neutrinos mainly heat up background plasma, which alters the relation between photon temperature and background neutrino temperature. For a lifetime longer than $1 sec$ , most of the injected neutrinos directly contribute to the protons-to-neutrons conversion. In both cases, deuterium and helium abundances are enhanced, while the constraint from the deuterium is stronger than that from the helium. $^{7} Li$ abundance gets decreased as a consequence of additional neutrons, but the parameter range that fits the observed $^{7} Li$ abundance is excluded by the deuterium constraint. We also estimate other cosmological constraints and compare them with the BBN bound.
↳ hep-phnucl-thPRD(2024)·17 citations
03
Heavy-flavor transport and hadronization in a small fireball
Andrea Beraudo🇮🇹 · Arturo De Pace🇮🇹 · Daniel Pablos🇮🇹 · Francesco Prino🇮🇹 · Marco Monteno🇮🇹 · Marzia Nardi🇮🇹
We study heavy-flavor hadron production in high-energy pp collisions, assuming the formation of a small, deconfined and expanding fireball where charm quarks can undergo rescattering and hadronization. We adopt the same in-medium hadronization mechanism developed for heavy-ion collisions, which involves Local Color-Neutralization (LCN) through recombination of charm quarks with nearby opposite color charges from the background fireball. Diquark excitations in the hot medium favor the formation of charmed baryons. The recombination process, involving closely aligned partons from the same fluid cell, effectively transfers the collective flow of the system to the final charmed hadrons. This framework can qualitatively reproduce the observed experimental findings in heavy-flavor particle-yield ratios, $p_{T}$ -spectra and elliptic-flow coefficients. Our results provide new, complementary support to the idea that the collective phenomena observed in small systems have the same origin as those observed in heavy-ion collisions.
↳ hep-phnucl-thEPJ Web Conf.(2024)·0 citations
04
Conservation, crossing symmetry, and completeness in diagrammatic theories
Frederick Green
The diagrammatic analysis of interacting particle assemblies harbors a fundamental mismatch between two of its main implementations: Phi-derivable (conserving) approximations and parquet (crossing symmetric) models. No termwise expansion, short of the exact theory itself, can be both conserving and crossing symmetric. This work applies the Kraichnan embedded-Hamiltonian formalism for strongly coupled systems to investigate consistency of the interplay between purely pair-mediated correlations and pair-irreducible ones. The approach sheds a different light on the issue of crossing symmetry versus conservation. In the process, the parquet equations acquire a different formulation.
↳ cond-mat.str-elnucl-thPRA(2024)·1 citation
05
Transverse momentum balance of dijets in Xe+Xe collisions at the LHC
Yao Li🇨🇳 · Shu-Wan Shen🇨🇳 · Sa Wang🇨🇳 · Ben-Wei Zhang🇨🇳
We present a theoretical study of the medium modifications of the $p_{T}$ balance ( $x_{J}$ ) of dijets in Xe+Xe collisions at $s_{N N} = 5.44$ TeV. The initial production of dijets was carried out using the POWHEG+PYTHIA8 prescription, which matches the next-to-leading-order (NLO) QCD matrix elements with the parton shower (PS) effect. The SHELL model described the in-medium evolution of nucleus-nucleus collisions using a transport approach. The theoretical results of the dijet $x_{J}$ in the Xe+Xe collisions exhibit more imbalanced distributions than those in the p+p collisions, consistent with recently reported ATLAS data. By utilizing the Interleaved Flavor Neutralisation, an infrared-and-collinear-safe jet flavor algorithm, to identify the flavor of the reconstructed jets, we classify dijets processes into three categories: gluon-gluon ( $g g$ ), quark-gluon ( $q g$ ), and quark-quark ( $q q$ ), and investigated the respective medium modification patterns and fraction changes of the $g g$ , $q g$ , and $q q$ components of the dijet sample in Xe+Xe collisions. It is shown that the increased fraction of $q g$ component at a small $x_{J}$ contributes to the imbalance of the dijet; in particular, the $q_{1} g_{2}$ (quark-jet-leading) dijets experience more significant asymmetric energy loss than the $g_{1} q_{2}$ (gluon-jet-leading) dijets traversing the QGP. By comparing the $Δ ⟨ x_{J} ⟩ = ⟨ x_{J} ⟩_{pp} - ⟨ x_{J} ⟩_{AA}$ of inclusive, $c c ˉ$ and $b b ˉ$ dijets in Xe+Xe collisions, we observe $Δ ⟨ x_{J} ⟩_{in c l .} > Δ ⟨ x_{J} ⟩_{c c ˉ} > Δ ⟨ x_{J} ⟩_{b b ˉ}$ . Moreover, $ρ_{X e, P b}$ , the ratios of the nuclear modification factors of dijets in Xe+Xe to those in Pb+Pb, were calculated, which indicates that the yield suppression of dijets in Pb+Pb is more pronounced than that in Xe+Xe owing to the larger radius of the lead nucleus.
↳ hep-phnucl-thNucl.Sci.Tech.(2024)·17 citations

Affiliations

first authorsco-authorsvia INSPIRE

Shell-model representations of the microscopic version of the Bohr-Mottelson collective model

Constraining MeV to 10 GeV majoron by Big Bang Nucleosynthesis

Heavy-flavor transport and hadronization in a small fireball

Conservation, crossing symmetry, and completeness in diagrammatic theories

Transverse momentum balance of dijets in Xe+Xe collisions at the LHC

Affiliations