Nuclear Theory·nucl-th

Friday·August 11, 2023

8 papers—5 primary·3 cross-listed

01
Examining the justification for the introduction of a fermion localization function
Aurel Bulgac
Becke and Edgecombe suggested in 1990 a theoretical tool to describe electron localization in atoms and molecules, an idea which was borrowed by a large number of nuclear theorists since 2011 to describe nucleon localization in nuclear systems. I argue here that these arguments are highly questionable and cannot be used in interacting systems, where effects beyond the naive mean field or the simple Hartree-Fock framework are important and the inclusion of correlations induced by particle interactions is necessary in order to introduce such a localization function. I also describe several aspects of the exchange and irreducible 2-body density matrices, which depend on the character and strength of the 2-particle interaction and, which can be useful in justifying the derivation of an appropriate energy density functional.
nucl-thcond-mat.str-elPRC(2023)·3 citations
02
Comparing pion production in transport simulations of heavy-ion collisions at $270 A$ MeV under controlled conditions
Jun Xu🇨🇳 · Hermann Wolter🇩🇪 · Maria Colonna🇮🇹 · Mircea Dan Cozma🇷🇴 · Pawel Danielewicz🇺🇸 · Che Ming Ko🇺🇸 · Akira Ono🇯🇵 · ManYee Betty Tsang🇺🇸 · Ying-Xun Zhang🇨🇳 · Hui-Gan Cheng🇨🇳 · Natsumi Ikeno🇯🇵 · Rohit Kumar🇺🇸 and 11 other authors
Within the TMEP, we present a detailed study of the performance of different transport models in Sn+Sn collisions at $270 A$ MeV, and put particular emphasis on the production of pions and $Δ$ resonances, which have been used as probes of the nuclear symmetry energy. We prescribe a common and rather simple physics model, and follow in detail the results of 4 BUU models and 6 QMD models. The nucleonic evolution of the collision and the nucleonic observables in these codes do not completely converge, but the differences among the codes can be understood as being due to several reasons: the basic differences between BUU and QMD models in the representation of the phase-space distributions, computational differences in the mean-field evaluation, and differences in the adopted strategies for the Pauli blocking in the collision integrals. For pionic observables, we find that a higher maximum density leads to an enhanced pion yield and a reduced $π^{-} / π^{+}$ yield ratio, while a more effective Pauli blocking generally leads to a slightly suppressed pion yield and an enhanced $π^{-} / π^{+}$ yield ratio. We specifically investigate the effect of the Coulomb force, and find that it increases the total $π^{-} / π^{+}$ yield ratio but reduces the ratio at high pion energies, although differences in its implementations do not have a dominating role in the differences among the codes. Taking into account only the results of codes that strictly follow the homework specifications, we find a convergence of the codes in the final charged pion yield ratio to a $1 σ$ deviation of about $5%$ . However, the uncertainty is expected to be reduced to about $1.6%$ if the same or similar strategies and ingredients, i.e., an improved Pauli blocking and calculation of the non-linear term in the mean-field potential, are similarly used in all codes.
nucl-thnucl-exPRC(2024)·33 citations
03
Radiative decay of the sub-threshold $1_{1}^{-}$ and $2_{1}^{+}$ states of $^{16}$ O in cluster effective field theory
Shung-Ichi Ando
Radiative decay of the sub-threshold $1_{1}^{-}$ and $2_{1}^{+}$ states of $^{16}$ O is studied in cluster effective field theory. The wave function normalization factors for initial and final states of the radiative decay amplitudes are deduced by using the phase shift data of elastic $α$ - $^{12}$ C scattering for $l = 0, 1, 2$ , which are related to the asymptotic normalization coefficients of $0_{1}^{+}$ , $1_{1}^{-}$ , $2_{1}^{+}$ states of $^{16}$ O for the two-body $α$ - $^{12}$ C channel; then only one unfixed parameter remains in each of the radiative decay amplitudes. We fit the parameters to the experimental radiative decay rates and apply the fitted parameters to the study of radiative $α$ capture on $^{12}$ C, $^{12}$ C( $α$ , $γ$ ) $^{16}$ O. The order of magnitude of astrophysical $S$ factors of $E 1$ and $E 2$ transitions of $^{12}$ C( $α$ , $γ$ ) $^{16}$ O is reproduced compared to the experimental data, and we discuss an improvement in the calculation of $S$ factors of $^{12}$ C( $α$ , $γ$ ) $^{16}$ O.
nucl-thnucl-exPRC(2024)·4 citations
04
Alpha-Clustering in Nuclei and Its Impact on Nuclear Symmetry Energy
Shuo Yang · Ruijia Li · Chang Xu
Nuclear symmetry energy is a fundamental quantity currently under intense investigation in both nuclear physics and astrophysics. The {\it softness} or {\it stiffness} of symmetry energy is still under debate and the extraction of symmetry energy from neutron skin thickness $R_{skin}$ remains a challenge. Parity-violating measurements PREX and CREX provide important opportunities for constraining $R_{skin}$ in $^{208}$ Pb and $^{48}$ Ca. We investigate the occurrence of $α$ -cluster at the surface of nuclei and its impact on the extraction of symmetry energy from $R_{skin}$ . Our result indicates that the $α$ -clustering probability in $^{208}$ Pb is small and the extracted density slope of symmetry energy $L$ is almost unaffected. In contrast, the $α$ -clustering probability in $^{48}$ Ca is sizeable and the corresponding correction to $L$ should be taken into account. This correction progressively increases with the $α$ -clustering probability, leading to a modification of the $L$ - $R_{skin}$ correlation, a fact may have important implications in constraining nuclear symmetry energy.
nucl-thPRC(2023)·15 citations
05
Doubly heavy tetraquarks including one-pion exchange potential
Qi Meng🇨🇳 · Emiko Hiyama🇯🇵 · Makoto Oka🇯🇵 · Atsushi Hosaka🇯🇵 · Chang Xu🇨🇳
Spectrum of the doubly heavy tetraquarks is studied in a constituent quark model including one-pion exchange (OPE) potential. Central and tensor forces induced by OPE between two light quarks are considered. Our results show that $I (J^{P}) = 0 (1^{+})$ compact bound states are shifted up because of the repulsive central force between $q ˉ q ˉ$ . This effect possibly leads to the small binding energy in $T_{cc}$ . In addition, a $I (J^{P}) = 1 (1^{+})$ resonant state is reported with $E = 10641 MeV, Γ = 15 MeV$ and $E = 10640 MeV, Γ = 15 MeV$ , without and with including OPE potential, respectively. The repulsive central force and attractive tensor force almost cancel with each other and leave a small energy difference when OPE potential is included.
nucl-thPLB(2023)·20 citations
06
Fuzzy gauge theory for quantum computers
Andrei Alexandru🇺🇸 · Paulo F. Bedaque🇺🇸 · Andrea Carosso🇺🇸 · Michael J. Cervia🇺🇸 · Edison M. Murairi🇺🇸 · Andy Sheng🇺🇸
Continuous gauge theories, because of their bosonic degrees of freedom, have an infinite-dimensional local Hilbert space. Encoding these degrees of freedom on qubit-based hardware demands some sort of ``qubitization'' scheme, where one approximates the behavior of a theory while using only finitely many degrees of freedom. We propose a novel qubitization strategy for gauge theories, called ``fuzzy gauge theory,'' building on the success of the fuzzy $σ$ -model in earlier work. We provide arguments that the fuzzy gauge theory lies in the same universality class as regular gauge theory, in which case its use would obviate the need of any further limit besides the usual spatial continuum limit. Furthermore, we demonstrate that these models are relatively resource-efficient for quantum simulations.
↳ hep-lathep-thnucl-thquant-phPRD(2024)·36 citations
07
Nucleon axial-vector coupling constant in magnetar environments
C.A. Dominguez🇿🇦 · Marcelo Loewe🇿🇦 · Cristian Villavicencio🇨🇱 · R. Zamora🇨🇱
The nucleon axial-vector coupling constant $g_{A}$ is studied in the presence of an external magnetic field, and in dense nuclear environments, to emulate nuclear matter in magnetars. For this purpose we use QCD finite energy sum rules for two-current and three-current correlators, the former involving nucleon-nucleon correlators and the latter involving proton-axial-neutron currents. As a result, the axial-vector coupling constant decreases both with baryon density as well as with magnetic field. The axial-vector coupling evaluated with baryon density near the nuclear density $ρ_{0}$ leads to $g_{A}^{*} \approx 0.92$ . In the presence of magnetic fields $g_{A}$ decreases in general, but $g_{A}^{*}$ does not show significant changes.
↳ hep-phnucl-thPRD(2023)·16 citations
08
"QGP Signatures" Revisited
John W. Harris🇺🇸 · Berndt Müller🇺🇸
We revisit the graphic table of QCD signatures in our 1996 Annual Reviews article "The Search for the Quark-Gluon Plasma" and assess the progress that has been made since its publication towards providing quantitative evidence for the formation of a quark-gluon plasma in relativistic heavy-ion collisions and its characteristic properties.
↳ hep-phnucl-exnucl-thEPJC(2024)·129 citations

Affiliations

first authorsco-authorsvia INSPIRE