Nuclear Theory·nucl-th

Thursday·January 12, 2023

10 papers—5 primary·5 cross-listed

01
Collective flows of protons and deuterons in Au + Au collisions at $E_{b e am}$ = 1.23 $A$ GeV by the IQMD model
Ling-Meng Fang🇨🇳 · Yu-Gang Ma🇨🇳 · Song Zhang🇨🇳
Collective flows of protons and deuterons for Au + Au collisions at beam energy $E_{b e am}$ = 1.23 $A$ GeV were simulated by an Isospin dependent Quantum Molecular Dynamics (IQMD) model. Two coalescence models, namely naive coalescence and dynamical coalescence models, for the formation of deuterons are compared. After reasonable match of rapidity spectra of protons and deuterons to the High Acceptance DiElectron Spectrometer (HADES) data is reached, we apply an event-plane method to calculate the first four-order collective flow coefficients as well as the ratios of $< v_{4} > / < v_{2} >^{2}$ and $< v_{3} > / < v_{1} >< v_{2} >$ , and observe the number of constituent nucleon scaling among protons and deuterons. In addition, the dependence of $ϵ_{n}$ and $v_{n}$ as well as the ratio $< v_{n} >$ / $ϵ_{n}$ on the centrality is obtained. Lastly, we further investigate the Pearson coefficients $cor r (v_{n}, v_{m})$ between the first four harmonic flows for protons and deuterons as a function of rapidity and centrality.
nucl-thPRC(2023)·10 citations
02
Chiral uncertainties in ab initio nucleon-nucleus elastic scattering
R.B. Baker · M. Burrows · Ch. Elster · K.D. Launey · P. Maris · G. Popa · S.P. Weppner
The effective interaction between a nucleon and a nucleus is one of the most important ingredients for reaction theories. Theoretical formulations were introduced early by Feshbach and Watson, and efforts of deriving and computing those `optical potentials' in a microscopic fashion have a long tradition. However, only recently the leading order term in the Watson multiple scattering approach could be calculated fully {\it ab initio}, meaning that the same nucleon-nucleon (NN) interaction enters both the structure as well as the reaction pieces on equal footing. This allows the uncertainties from the underlying chiral effective NN interaction to be systematically explored in nucleon-nucleus elastic scattering observables. In this contribution the main ingredients for arriving at the {\it ab initio} leading order of the effective nucleon-nucleus interaction in the Watson approach will be reviewed. Concentrating on one specific chiral NN interaction from the LENPIC collaboration and light nuclei with a 0 $^{+}$ ground state, the leading order nucleon-nucleus interaction is calculated using up to the third chiral order (N2LO) in the nucleon-nucleon potential, and elastic scattering observables are extracted. Then pointwise as well as correlated uncertainty quantification is used for the estimation of the chiral truncation error. Elastic scattering observables for $^{4}$ He, $^{12}$ C, and $^{16}$ O for between 65 and 200 MeV projectile energy will be analyzed.
nucl-th7 citations
03
Elastic scatering cross-sections obtained on the basis of the potential of the modified Thomas-Fermi method and taking the core into account
V.A. Nesterov · O.I. Davydovska · V.Yu. Denisov
Nucleon density distributions and nucleus-nucleus interaction potentials for the reactions $^{16}$ O+ $^{40}$ Ca, $^{16}$ O+ $^{56}$ Fe and $^{16}$ O+ $^{90}$ Zr have been calculated in the framework of the modified Thomas-Fermi method and considering all terms up to the second order in $ℏ$ in the quasi-classical expansion of the kinetic energy. Skyrme forces dependent on the nucleon density are used as the nucleon-nucleon interaction. A parametrization of the nucleus-nucleus interaction potential, which well describes the potential value calculated within the modified Thomas-Fermi approach with density-dependent Skyrme forces, is found. On the basis of the obtained potentials, the cross-sections of elastic scattering are calculated in a good agreement with experimental data.
nucl-thISSN 2071-0186. Ukr. J. Phys. 2022. Vol. …·1 citation
04
Systematic study of the effect of individual rotational energy levels on the fusion cross-section of \texorpdfstring{ $^{16} O$ }--based reactions of range $480 \leq Z_{P} Z_{T} \leq 592$
Nishu Jain🇮🇳 · M. Bhuyan🇲🇾 · Raj Kumar🇮🇳
The present work aims to investigate the effect of individual rotational energy levels on the fusion cross-sections for $^{16}$ O-based reaction systems, namely, $^{16}$ O + $^{182, 184, 186}$ W, $^{16}$ O + $^{176, 180}$ {Hf}, $^{16}$ O + $^{174, 176}$ {Yb}, $^{16}$ O + $^{166}$ {Er}, $^{16}$ O + $^{148, 152, 154}$ Sm, $^{16}$ O + $^{150}$ Nd at energies below the fusion barrier. Using the CCFULL code, the effect of low-lying rotational energy levels on the fusion cross-section for $^{16}$ O induced reactions has been investigated at energies below and around the Coulomb barrier. The calculations are performed by assuming the fixed value of diffuseness parameter $a_{0} = 0.65$ fm in the Woods-Saxon nuclear potential and the other two parameters are optimised by fitting the experimental data at the above barrier. Here we have determined the $V_{0}$ and $r_{0}$ as a function of $Z_{P} Z_{T}$ , where experimental cross-sections are available. From our calculations, it is observed that the hexadecapole deformation ( $β_{4}$ ) with different magnitudes has a significant influence on the fusion cross sections. For the case of the $+ v e$ value of $β_{4}$ , beyond $1 0^{+}$ , the rotational levels cease to contribute significantly and also there is a significant difference between the contribution of sequential channels. On the other hand, in the case of -ve $β_{4}$ , up to $6^{+}$ levels contribute significantly. Furthermore, we have established an algebraic systematic of fitting, which one can use to determine the parameters $V_{0}$ , $r_{0}$ of Woods-Saxon nuclear potential within the range of $Z_{P} Z_{T}$ lie in between $480 \leq Z_{P} Z_{T} \leq 592$ .
nucl-thPhys.Scripta(2023)·6 citations
05
Pre-Equilibrium Evolution of Conserved Charges with ICCING Initial Conditions
Patrick Carzon🇺🇸 · Mauricio Martinez🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸 · Philip Plaschke🇩🇪 · Soeren Schlichting🇩🇪 · Matthew Sievert🇺🇸
Heavy-ion collisions can be well described through relativistic viscous hydrodynamics, but questions still remain when hydrodynamics is applicable because the initial state may begin very far-from-equilibrium. Thus, a pre-equilibrium evolution phase is used to bridge the gap between the initial state and hydrodynamics. K $ϕ$ MP $ϕ$ ST is one such pre-equilibrium model that propagates the energy-momentum tensor by decomposing it into the background and fluctuations around that background, whose evolution is captured by Green's functions. We extend this formalism to include conserved charges and calculate the corresponding non-equilibrium Green's functions in the relaxation time approximation. The ICCING algorithm initializes conserved charges in the initial state by sampling $g \to q q ˉ$ splitting probabilities and is, thus, perfectly positioned to implement Green's functions for charge propagation. We show that this method alters the initial state charge geometries and is applicable in central to mid-central collisions.
nucl-thhep-phnucl-exPRC(2023)·18 citations
06
Scattering Amplitude from Quantum Computing with Reduction Formula
Tianyin Li🇨🇳 · Wai Kin Lai🇨🇳 · Enke Wang🇨🇳 · Hongxi Xing🇨🇳
Utilizing the Lehmann-Symanzik-Zimmermann reduction formula, we present a new general framework for computing scattering amplitudes in quantum field theory with quantum computers in a fully nonperturbative way. In this framework, one only has to construct one-particle states of zero momentum, and no wave packets of incoming particles are needed. The framework is able to incorporate scatterings of bound states, and is ideal for scatterings involving a small number of particles. We expect this framework to have particular advantages when applied to exclusive hadron scatterings. As a proof of concept, by simulations on classical hardware, we demonstrate that in the one-flavor Gross-Neveu model, the fermion propagator, the connected fermion four-point function, and the propagator of a fermion-antifermion bound state obtained from our proposed quantum algorithm have the desired pole structure crucial to the implementation of the Lehmann-Symanzik-Zimmermann reduction formula.
↳ hep-phhep-exnucl-thquant-phPRD(2024)·23 citations
07
Speed of sound in QCD matter at finite temperature and density]{Speed of sound in QCD matter at finite temperature and density
Gun-yun Shao🇨🇳 · Xin-ran Yang🇨🇳 · Chong-long Xie🇨🇳 · Wei-bo He🇨🇳
The speed of sound in QCD matter at finite temperature and density is investigated within the Polyakov loop improved Nambu--Jona-Lasinio (PNJL) model. The spinodal structure associated with the chiral first-order chiral phase transition is considered to describe the continuous variation of the speed of sound. The behaviors of the squared sound speed in different phases, including the stable, metastable and unstable phases, are derived. The relation between speed of sound and QCD phase transitions is systematically explored. In particular, the boundary of vanishing sound velocity is derived in the temperature-density phase diagram, and the region where the sound wave equation being broken is pointed out. Some interesting features of speed of sound under different definitions are also discussed.
↳ hep-phnucl-thEur.Phys.J.Plus(2023)·3 citations
08
Self-consistent thermodynamic potential for magnetized QCD matter
Gaoqing Cao🇨🇳 · Jianing Li🇨🇳
Within the two-flavor Nambu--Jona-Lasinio model, we derive a self-consistent thermodynamic potential $Ω$ for a QCD matter in an external magnetic field $B$ . To be consistent with Schwinger's renormalization spirit, counter terms with vacuum quark mass are introduced into $Ω$ and then the explicit $B$ -dependent parts can be regularized in a cutoff-free way. Following that, explicit expressions of gap equation and magnetization can be consistently obtained according to the standard thermodynamic relations. The formalism is able to reproduce the paramagnetic feature of a QCD matter without ambiguity. For more realistic study, a running coupling constant is also adopted to account for the inverse magnetic catalysis effect. It turns out that the running coupling would greatly suppress magnetization at large $B$ and is important to reproduce the temperature enhancement effect to magnetization. The case with finite baryon chemical potential is also explored: no sign of first-order transition is found by varying $B$ for the running coupling and the de Haas-van Alphen oscillation shows up in the small $B$ region.
↳ hep-phnucl-thPRD(2023)·6 citations
09
Phase Transitions in Particle Physics -- Results and Perspectives from Lattice Quantum Chromo-Dynamics
Gert Aarts🇬🇧 · Joerg Aichelin🇫🇷 · Chris Allton🇬🇧 · Andreas Athenodorou🇮🇹 · Dimitrios Bachtis🇬🇧 · Claudio Bonanno🇮🇹 · Nora Brambilla🇩🇪 · Elena Bratkovskaya🇩🇪 · Mattia Bruno🇮🇹 · Michele Caselle🇮🇹 · Costanza Conti🇮🇹 · Roberto Contino🇮🇹 and 29 other authors
Phase transitions in a non-perturbative regime can be studied by ab initio Lattice Field Theory methods. The status and future research directions for LFT investigations of Quantum Chromo-Dynamics under extreme conditions are reviewed, including properties of hadrons and of the hypothesized QCD axion as inferred from QCD topology in different phases. We discuss phase transitions in strong interactions in an extended parameter space, and the possibility of model building for Dark Matter and Electro-Weak Symmetry Breaking. Methodological challenges are addressed as well, including new developments in Artificial Intelligence geared towards the identification of different phases and transitions.
↳ hep-lathep-phhep-thnucl-thPPNP(2023)·152 citations
10
Point Production of a Nonrelativistic Unparticle Recoiling Against a Particle
Eric Braaten🇺🇸 · Hans-Werner Hammer🇩🇪
A nonrelativistic unparticle can be defined as an excitation created by an operator with a definite scaling dimension in a nonrelativistic field theory with an approximate conformal symmetry. The point production rate of an unparticle has power-law dependence on its total energy with an exponent determined by its scaling dimension. We use the exact result for the 3-point function of primary operators in a nonrelativistic conformal field theory to derive the contribution to the point production rate of the unparticle from its decay into another unparticle recoiling against a particle. In the case where the conformal symmetry is broken by a large positive scattering length, we deduce the exponent of the energy in the point production rate of the loosely bound two-particle state recoiling against a particle with large relative momentum.
↳ hep-thhep-phnucl-thPRD(2023)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE