Nuclear Theory·nucl-th

Monday·December 11, 2023

12 papers—7 primary·5 cross-listed

01
Ultracentral heavy ion collisions, transverse momentum and the equation of state
Govert Nijs🇨🇭 · Wilke van der Schee🇨🇭
Ultracentral heavy ion collisions due to their exceptionally large multiplicity probe an interesting regime of quark-gluon plasma where the size is (mostly) fixed and fluctuations in the initial condition dominate. Spurred by the recent measurement of the CMS collaboration we investigate the driving factors of the increase of transverse momentum, including a complete analysis of the influence of the QCD equation of state. Particularly interesting is the influence of the centrality selection as well as the initial energy deposition.
nucl-thhep-phnucl-exPLB(2024)·25 citations
02
Far-off-equilibrium early-stage dynamics in high-energy nuclear collisions
Chandrodoy Chattopadhyay🇺🇸 · Ulrich Heinz🇺🇸 · Thomas Schaefer🇺🇸
We explore the far-off-equilibrium aspects of the (1+1)-dimensional early-stage evolution of a weakly-coupled quark-gluon plasma using kinetic theory and hydrodynamics. For a large set of far-off-equilibrium initial conditions the system exhibits a peculiar phenomenon where its total equilibrium entropy decreases with time. Using a non-equilibrium definition of entropy based on Boltzmann's H-function, we demonstrate how this apparently anomalous behavior is consistent with the second law of thermodynamics. We also use the H-function to formulate `maximum-entropy' hydrodynamics, a far-off-equilibrium macroscopic theory that can describe both free-streaming and near-equilibrium regimes of quark-gluon plasma in a single framework.
nucl-thEPJ Web Conf.(2024)·1 citation
03
Understanding oscillating features of the timelike nucleon electromagnetic form factors within the extending vector meson dominance model
Bing Yan🇨🇳 · Cheng Chen🇨🇳 · Xia Li🇨🇳 · Ju-Jun Xie🇨🇳
We investigate the nonmonotonic behavior observed in the time-like nucleon electromagnetic form factors. Using a phenomenological extending vector meson dominance model, where the ground states $ρ$ and $ω$ and their excited states $ρ (2 D)$ , $ω (3 D)$ , and $ω (5 S)$ are taken into account, we have successfully reproduced the cross sections of $e^{+} e^{-} \to p p ˉ$ and $e^{+} e^{-} \to n n ˉ$ reactions. Furthermore, we have derived the nucleon electromagnetic form factors in the time-like region, and it is found that the so-called periodic behaviour of the nucleon effective form factors is not confirmed. However, there are indeed nonmonotonic structures in the line shape of nucleon effective form factors, which can be naturally reproduced by considering the contributions from the low-lying excited vector states.
nucl-thhep-exhep-phnucl-exPRD(2024)·12 citations
04
Improved description of nuclear charge radii: Global trends beyond $N = 28$ shell closure
Rong An · Xiang Jiang · Na Tang · Li-Gang Cao · Feng-Shou Zhang
Charge radii measured with high accuracy provide a stringent benchmark for characterizing nuclear structure phenomena. In this work, the systematic evolution of charge radii for nuclei with $Z = 19$ - $29$ is investigated through relativistic mean field theory with effective forces NL3, PK1, and NL3 $^{*}$ . The neutron-proton ( $n p$ ) correlation around Fermi surface originated from the unpaired neutron and proton has been taken into account tentatively in order to reduce the overestimated odd-even staggering of charge radii. This improved method can give an available description of charge radii across $N = 28$ shell closure. A remarkable observation is that the charge radii beyond $N = 28$ shell closure follow the similarly steep increasing trend, namely irrespective of the number of protons in the nucleus. Especially, the latest results of charge radii for nickel and copper isotopes can be reproduced remarkably well. Along $N = 28$ isotonic chain, the sudden increase of charge radii is weakened across $Z = 20$ , but presented evidently across $Z = 28$ closed shell. The abrupt changes of charge radii across $Z = 22$ are also shown along $N = 32$ and $34$ isotones, but the latter with a less slope. This seems to provide a sensitive indicator to identify the new magicity of a nucleus with universal trend of charge radii.
nucl-thnucl-exPRC(2024)·17 citations
05
Role of initial transverse momentum in a hybrid approach
Niklas Götz🇩🇪 · Lucas Constantin🇩🇪 · Hannah Elfner🇩🇪
The purpose of this work is to study the effect of exchanging initial condition models in a modular hybrid approach. The focus lies on the event-by-event correlations of elliptic and triangular flow. This study is performed in the hybrid approach SMASH-vHLLE, composed of the hadronic transport approach SMASH and the (3+1)d viscous hydrodynamic code vHLLE. The initial condition models investigated are SMASH IC, Trento and IP-Glasma. Correlations are calculated on an event-by-event basis between the eccentricities and momentum anisotropies of the initial state as well as the momentum anisotropies in the final state, both for ultra-central and off-central collisions for AuAu collisions at $s_{N N} = 200$ GeV. This work demonstrates that, although averaged values for the eccentricities of these models are very similar, substantial differences exist both in the distributions of eccentricities, the correlations amongst the initial state properties as well as in the correlations between initial state and final state properties. Notably, whereas initial state momentum anisotropy is shown to not affect the final state flow, the presence of radial flow affects the emergence of final state momentum anisotropies. Inclusion of radial flow in the linear fit improves the prediction of final state flow from initial state properties. The presence of momentum in the initial state has an effect on the emergence of flow and is therefore a relevant part of initial state models, challenging the common understanding of final state momentum anisotropies being a linear response to initial state eccentricity only.
nucl-thhep-phnucl-exPRC(2024)·5 citations
06
Feasibility of perturbative generation of bound-states from resonances or virtual states
C.-J. Yang🇷🇴
I investigate whether it is possible to generate bound-states from resonances or virtual states through first-order perturbation theory. Using contact-type potentials as those appeared in pionless effective field theory, I show that it is possible to obtain negative-energy states by sandwiching a next-to-leading order (NLO) interaction with the leading-order (LO) wavefunctions, under the presence of LO resonances or virtual states. However, at least under the framework of time-independent Schrödinger equation and Hermitian Hamiltonian, there is an inability to create bound-states with structure similar to those formed by the non-perturbative treatments.
nucl-thquant-phPRC(2024)·5 citations
07
Relativistic Faddeev 3D Equations for Three-Body Bound States Without Two-Body $t -$ Matrices
M. Mohammadzadeh · M. Radin · M. R. Hadizadeh
This paper explores a novel revision of the Faddeev equation for three-body (3B) bound states, as initially proposed in Ref. \cite{golak2013three}. This innovative approach, referred to as \tmatrixfree in this paper, directly incorporates two-body (2B) interactions and completely avoids the 2B transition matrices. We extend this formalism to relativistic 3B bound states using a three-dimensional (3D) approach without using partial wave decomposition. To validate the proposed formulation, we perform a numerical study using spin-independent Malfliet-Tjon and Yamaguchi interactions. Our results demonstrate that the relativistic \tmatrixfree Faddeev equation, which directly implements boosted interactions, accurately reproduces the 3B mass eigenvalues obtained from the conventional form of Faddeev equation, referred to as \tmatrixdependent in this paper, with boosted 2B $t -$ matrices. Moreover, the proposed formulation provides a simpler alternative to the standard approach, avoiding the computational complexity of calculating boosted 2B $t -$ matrices and leading to significant computational time savings.
nucl-thphysics.comp-phPTEP(2024)·3 citations
08
Solving the Lipkin model using quantum computers with two qubits only with a hybrid quantum-classical technique based on the Generator Coordinate Method
Yann Beaujeault-Taudiere🇫🇷 · Denis Lacroix🇫🇷
The possibility of using the generator coordinate method (GCM) using hybrid quantum-classical algorithms with reduced quantum resources is discussed. The task of preparing the basis states and calculating the various kernels involved in the GCM is assigned to the quantum computer, while the remaining tasks, such as finding the eigenvalues of a many-body problem, are delegated to classical computers for post-processing the generated kernels. This strategy reduces the quantum resources required to treat a quantum many-body problem. We apply the method to the Lipkin model. Using the permutation symmetry of the Hamiltonian, we show that, ultimately, only two qubits is enough to solve the problem regardless of the particle number. The classical computing post-processing leading to the full energy spectrum can be made using standard generalized eigenvalues techniques by diagonalizing the so-called Hill-Wheeler equation. As an alternative to this technique, we also explored how the quantum state deflation method can be adapted to the GCM problem. In this method, variational principles are iteratively designed to access the different excited states with increasing energies. The methodology proposed here is successfully applied to the Lipkin model with a minimal size of two qubits for the quantum register. The performances of the two classical post-processing approaches with respect to the statistical noise induced by the finite number of measurements and quantum devices noise are analyzed. Very satisfactory results for the full energy spectra are obtained once noise correction techniques are employed.
↳ quant-phnucl-thPRC(2024)·16 citations
09
Prediction of $P_{cc}$ states in quark model
Ye Yan🇨🇳 · Hongxia Huang🇨🇳 · Xinmei Zhu🇨🇳 · Jialun Ping🇨🇳
Inspired by the observation of hidden-charm pentaquark $P_{c}$ and $P_{cs}$ states by the LHCb Collaboration, we explore the $q q c c ˉ c$ ( $q = u$ or $d$ ) pentaquark systems in the quark delocalization color screening model. The interaction between baryons and mesons and the influence of channel coupling are studied in this work. Three compact $q q c c ˉ c$ pentaquark states are obtained, whose masses are 5259 MeV with $I (J^{P})$ = $0 (1/ 2^{-})$ , 5396 MeV with $I (J^{P})$ = $1 (1/ 2^{-})$ , and 5465 MeV with $I (J^{P})$ = $1 (3/ 2^{-})$ . Two molecular states are obtained, which are $I (J^{P})$ = $0 (1/ 2^{-})$ $Λ_{c} J / ψ$ with 5367 MeV and $I (J^{P})$ = $0 (5/ 2^{-})$ $Ξ_{cc}^{*} D ˉ^{*}$ with 5690 MeV. These predicted states may provide important information for future experimental search.
↳ hep-phhep-exnucl-thPRD(2024)·10 citations
10
Off-lightcone Wilson-line operators in gradient flow
Nora Brambilla🇩🇪 · Xiang-Peng Wang🇩🇪
Off-lightcone Wilson-line operators are constructed using local operators connected by time-like or space-like Wilson lines, which ensure gauge invariance. Off-lightcone Wilson-line operators have broad applications in various contexts. For instance, space-like Wilson-line operators play a crucial role in determining quasi-distribution functions (quasi-PDFs), while time-like Wilson-line operators are essential for understanding quarkonium decay and production within the potential non-relativistic QCD (pNRQCD) framework. In this work, we establish a systematic approach for calculating the matching from the gradient-flow scheme to the $MS$ scheme in the limit of small flow time for off-lightcone Wilson-line operators. By employing the one-dimensional auxiliary-field formalism, we simplify the matching procedure, reducing it to the matching of local current operators. We provide one-loop level matching coefficients for these local current operators. For the case of hadronic matrix element related to the quark quasi-PDFs, we show at one-loop level that the finite flow time effect is very small as long as the flow radius is smaller than the physical distance $z$ , which is usually satisfied in lattice gradient flow computations. Applications include lattice gradient flow computations of quark/gluon quasi-PDFs, gluonic correlators related to quarkonium decay and production in pNRQCD, and spin-dependent potentials in terms of chromoelectric and chromomagnetic field insertions into a Wilson loop.
↳ hep-phhep-latnucl-thJHEP(2024)·20 citations
11
Measurement of yields and angular distributions of $γ$ -quanta from the interaction of $14.1$ MeV neutrons with oxygen, phosphorus and sulfur
D.N. Grozdanov · N.A. Fedorov · S.B. Dabylova · Yu.N. Kopatch · I.N. Ruskov · V.R. Skoy · T.Yu. Tretyakova · C. Hramco · P.I. Kharlamov · G.V. Pampushik · P.G. Filonchik · A.V. Andreev
A study of the inelastic scattering of neutrons with an energy of $14.1$ ~MeV on the nuclei of oxygen, phosphorus and sulfur was carried out at the TANGRA facility at JINR (Dubna). The purpose of the experiment was to refine existing and obtain new data on the yields and angular distributions of $γ$ -quanta emitted by the studied nuclei as a result of neutron-induced nuclear reactions using the tagged neutron method. Two types of detector systems were used to register $γ$ -quanta. The $γ$ -ray yields were measured using a high-purity germanium (HPGe) detector. The angular distributions of $γ$ -rays were obtained using a system of 18 scintillation detectors based on bismuth germanite Bi $_{4}$ Ge $_{3}$ O $_{12}$ (BGO) located around the sample. As a result of the studies carried out, the yields of two transitions for the reaction of tagged neutrons with $^{16}$ O, nine transitions for the reaction with $^{31}$ P, and nine transitions for the reaction with $^{32}$ S were measured for the first time. The angular anisotropy of the $γ$ -radiation accompanying the inelastic scattering of neutrons with an energy of $14.1$ ~MeV on $^{31}$ P nuclei was also measured for the first time.
↳ nucl-exnucl-thCPC(2024)·6 citations
12
Gravitational $p \to Δ^{+}$ transition form factors in chiral perturbation theory
H. Alharazin🇩🇪 · B.-D. Sun🇩🇪 · E. Epelbaum🇩🇪 · J. Gegelia🇩🇪 · U.-G. Meißner🇬🇪
The gravitational form factors of the transition from the proton to the $Δ^{+}$ resonance are calculated to leading one-loop order using a manifestly Lorentz-invariant formulation of chiral perturbation theory. We take into account the leading electromagnetic and strong isospin-violating effects. The loop contributions to the transition form factors are found to be free of power-counting violating pieces, which is consistent with the absence of tree-level diagrams at the considered order. In this sense, our results can be regarded as predictions of chiral perturbation theory.
↳ hep-phnucl-thJHEP(2024)·22 citations

Affiliations

first authorsco-authorsvia INSPIRE