Nuclear Theory·nucl-th

Tuesday·November 14, 2023

16 papers—8 primary·8 cross-listed

01
Dilepton production at next-to-leading order and intermediate invariant-mass observables
Jessica Churchill🇨🇦 · Lipei Du🇨🇦 · Charles Gale🇨🇦 · Greg Jackson🇺🇸 · Sangyong Jeon🇨🇦
The thermal QCD dilepton production rate is calculated at next-to-leading order in the strong coupling and at finite baryon chemical potential. The two-loop virtual photon self-energy is evaluated using finite temperature field theory and combined consistently with the self-energy in the Landau-Pomeranchuk-Migdal regime. We present new results for a dense baryonic plasma. The rates are then integrated using (3+1)-dimensional fluid-dynamical simulations calibrated to reproduce hadronic experimental results obtained at RHIC at energies ranging from those of the Beam Energy Scan to $s_{_{NN}} = 200$ GeV. We elaborate on the ability for dileptons to relay information about the plasma baryonic content and temperature.
nucl-thhep-exhep-phnucl-exPRC(2024)·40 citations
02
Pion-sigma meson vortices in rotating systems
D. N. Voskresensky🇷🇺
Possibilities of the formation of the pion-sigma meson field vortices in a rotating empty vessel (in vacuum) and in the pion-sigma Bose-Einstein condensates at a dynamically fixed particle number are studied within the linear $σ$ model at zero temperature. The charged $σ π^{\pm}$ and neutral $σ π^{0}$ complex field ansatze (models 1 and 2) are studied. First it is analysed, which of these configurations is energetically favorable in case of the system at rest. Then conditions are found, at which a chiral field storm can arise in a rotating empty vessel. In the model 1 an important role played by the electric field is demonstrated. Its appearance may allow for formation of a supervortex (vortex with a large angular momentum) in case of the empty vessel rotating with an overcritical angular velocity. Influence of magnetic field is also studied. Field configurations in presence and absence of the meson self-interaction are found in both models. Then it is shown that description of the charged (in model 1) and neutral (in model 2) rotating pion-sigma Bose-Einstein condensates is analogous to that for the Bose-Einstein condensates in cold atomic gases. Various field configurations such as vortex lines, rings and spirals are discussed. Conditions for existence of the rigid-body rotation of the vortex lattice are then analysed. Observational effects for vortex fields in rotating vessels, energetic heavy-ion collisions and in rotating superheavy nuclei and nuclearites are discussed.
nucl-thcond-mat.supr-conhep-phPRD(2024)·7 citations
03
Cluster properties of heavy nuclei predicted with the Barcelona-Catania-Paris-Madrid energy density functional
Samuel A. Giuliani · Luis M. Robledo
We study the cluster emission properties of 224Ra and 238Pu employing the Barcelona-Catania-Paris-Madrid (BCPM) energy density functional (EDF). Starting from two-dimensional potential energy surfaces, coexisting fission paths are identified. A fission valley located at large octupole deformations, corresponding to a highly-asymmetric mass distribution, is found in both nuclei. As the corresponding fragments are dominated by the presence of 208Pb, we can relate this fission path to the emergence of cluster emission. Using the octupole moment as collective degree of freedom, we compute the cluster decay half-lives and study the impact of collective inertias, pairing strength and collective zero-point energy. The agreement with experimental data resembles the results obtained for spontaneous fission half-lives, indicating the capability of BCPM to consistently describe a large variety of fission phenomena, including cluster emission.
nucl-thEPJA(2023)·6 citations
04
Virtual Photons Shed Light on the Early Temperature of Dense QCD Matter
Jessica Churchill🇨🇦 · Lipei Du🇨🇦 · Charles Gale🇨🇦 · Greg Jackson🇺🇸 · Sangyong Jeon🇨🇦
Dileptons produced during heavy-ion collisions represent a unique probe of the QCD phase diagram, and convey information about the state of the strongly interacting system at the moment their preceding off-shell photon is created. In this study, we compute thermal dilepton yields from Au+Au collisions performed at different beam energies, employing a (3+1)-dimensional dynamic framework combined with emission rates accurate at next-to-leading order in perturbation theory and which include baryon chemical potential dependencies. By comparing the effective temperature extracted from the thermal dilepton invariant mass spectrum with the average temperature of the fluid, we offer a robust quantitative validation of dileptons as effective probe of the early quark-gluon plasma stage.
nucl-thhep-exhep-phnucl-exPRL(2024)·38 citations
05
Optimal colliding energy for the synthesis of superheavy element $Z$ =119
Avazbek Nasirov (1 and 2) · Bakhodir Kayumov (3 and 2) ((1) Joint Institute for Nuclear Research, Dubna, Russia, (2) Institute of Nuclear Physics, Tashkent, Uzbekistan, (3) School of Humanities and Natural Sciences, New Uzbekistan University, Tashkent, Uzbekistan)
The evaporation residue (ER) cross section of 3n and 4n channels related to the synthesis of superheavy element (SHE) with the charge number $Z = 119$ in the $^{51}$ V+ $^{248}$ Cm reaction has been calculated by the dinuclear system (DNS) model as a sum of the partial cross sections of the corresponding channels. The angular momentum distribution of the compound nucleus is estimated by the dynamical trajectory calculations of the capture probability which is considered as the DNS formation probability. The fusion probability decreases by the increase of the DNS angular momentum due to its influence on the intrinsic fusion barrier $B_{fus}^{*}$ . The range $α_{2} = 6 0^{\circ} \div 7 0^{\circ}$ of the orientation angle of the axial symmetry axis of the deformed target nucleus $^{248}$ Cm is favorable for the formation of the compound nucleus. The fusion probability decreases at around $α_{2} = 9 0^{\circ}$ since the number of the partial waves contributing to the capture decreases. Therefore, it is important to calculate the capture cross section dynamically. The 4n channel cross section of the SHE synthesis is larger than the 3n channel cross section maximum value of the ER cross section is 12.3 fb at $E_{c.m.}$ =232 MeV.
nucl-thnucl-exPRC(2024)·17 citations
06
Quantal effect on the opening angle distribution between the fission fragment's spins
Guillaume Scamps🇺🇸
Background: Several approaches are currently trying to understand the generation of angular momentum in the fission fragments. The microscopic TDDFT and statistical FREYA lead to different predictions concerning the opening angle distribution formed between the two spins in particular at 0 and 180 degrees. Purpose: This letter aims to investigate how the geometry and the quantum nature of spins impact the distribution of opening angles to understand what leads to different model predictions. Method: Various assumptions of K distribution (K=0, isotropic, isotropic with total K=0, and from TDFFT) are investigated in a quantum approach. These distributions are then compared to the classical limit using the Clebsch-Gordan coefficients in the limit of $ℏ$ approaches zero. Results: It is shown that in all the schematic scenario the quantal distribution of opening angle lead to the expected behavior in the classical limit. The model shows that the quantal nature of the spins prevents the population of opening angles close to 0 and 180 degrees. The difference in opening angle in the 2D and isotropic 3D distribution is discussed and it is shown that the realistic TDFFT opening angle distribution presents an intermediate behavior between the two cases. Conclusions: The last comparison reveals two key differences between the two models' predictions: the quantal spins' nature in TDDFT and the assumption of zero K values in FREYA.
nucl-thnucl-exquant-phPRC(2024)·12 citations
07
Hydrodynamic theories for a system of weakly self-interacting classical ultra-relativistic scalar particles: causality and stability
Caio V. P. de Brito🇧🇷 · Gabriel S. Rocha🇺🇸 · Gabriel S. Denicol🇧🇷
We investigate the causality and stability of three different relativistic dissipative fluid-dynamical formulations emerging from a system of classical, ultra-relativistic scalar particles self-interacting via a quartic potential. For this particular interaction, all transport coefficients of Navier-Stokes, Bemfica-Disconzi-Noronha-Kovtun and second-order transient theories can be computed in analytical form. We first show that Navier-Stokes theory is acausal and unstable regardless of the matching conditions. On the other hand, BDNK theory can be linearly causal and stable for a particular set of matching choices that does not contain the so-called exotic Eckart prescription. In particular, using the Liénard-Chipart criterion, we obtain a set of sufficient conditions that guarantee the stability of the theory. Last, second-order transient hydrodynamic theory in Landau matching is shown to be linearly causal and stable.
nucl-thhep-thPRD(2024)·10 citations
08
Phase Transition Study meets Machine Learning
Yu-Gang Ma🇨🇳 · Long-Gang Pang🇨🇳 · Rui Wang🇨🇳 · Kai Zhou🇩🇪
In recent years, machine learning (ML) techniques have emerged as powerful tools for studying many-body complex systems, and encompassing phase transitions in various domains of physics. This mini review provides a concise yet comprehensive examination of the advancements achieved in applying ML to investigate phase transitions, with a primary focus on those involved in nuclear matter studies.
nucl-thhep-phChin.Phys.Lett.(2023)·57 citations
09
Heavy-dense QCD, sign optimization and Lefschetz thimbles
Gokce Basar🇺🇸 · Joseph Marincel🇺🇸
We study the heavy-dense limit of QCD on the lattice with heavy quarks at high density. The effective three dimensional theory has a sign problem which is alleviated by sign optimization where the path integration domain is deformed in complex space in a way that minimizes the phase oscillations. We simulate the theory via a Hybrid-Monte-Carlo, for different volumes, both to leading order and next-to-next-to leading order in the hopping expansion, and show that sign optimization successfully mitigates the sign problem at large enough volumes where usual re-weighting methods fail. Finally we show that there is a significant overlap between the complex manifold generated by sign optimization and the Lefschetz thimbles associated with the theory.
↳ hep-thhep-latnucl-thPRC(2024)·4 citations
10
Single-Spin Asymmetry of Neutrons in Polarized pA Collisions
B.Z. Kopeliovich🇨🇱 · I.K. Potashnikova🇨🇱 · Ivan Schmidt🇨🇱
Absorptive corrections, which are known to suppress proton-neutron transitions with a large fractional momentum z -> 1 in pp collisions, become dramatically strong on a nuclear target, and they push the partial cross sections of leading neutron production to the very periphery of the nucleus. The mechanism of the pion and axial vector a1-meson interference, which successfully explains the observed single-spin asymmetry in a polarized pp -> nX, is extended to the collisions of polarized protons with nuclei. When corrected for nuclear effects, it explains the observed single-spin azimuthal asymmetry of neutrons that is produced in inelastic events, which is where the nucleus violently breaks up. This single-spin asymmetry is found to be negative and nearly A-independent.
↳ hep-phnucl-thMDPI Physics(2023)·0 citations
11
Revisit to the yield ratio of triton and $^{3}$ He as an indicator of neutron-rich neck emission
Yijie Wang · Mengting Wan · Xinyue Diao · Sheng Xiao · Yuhao Qin · Zhi Qin · Dong Guo · Dawei Si · Boyuan Zhang · Baiting Tian · Fenhai Guan · Qianghua Wu and 25 other authors
The neutron rich neck zone created in heavy ion reaction is experimentally probed by the production of the $A = 3$ isobars. The energy spectra and angular distributions of triton and $^{3}$ He are measured with the CSHINE detector in $^{86}$ Kr + $^{208}$ Pb reactions at 25 MeV/u. While the energy spectrum of $^{3}$ He is harder than that of triton, known as " $^{3}$ He-puzzle", the yield ratio $R (t /^{3} He)$ presents a robust rising trend with the polar angle in laboratory. Using the fission fragments to reconstruct the fission plane, the enhancement of out-plane $R (t /^{3} He)$ is confirmed in comparison to the in-plane ratios. Transport model simulations reproduce qualitatively the experimental trends, but the quantitative agreement is not achieved. The results demonstrate that a neutron rich neck zone is formed in the reactions. Further studies are called for to understand the clustering and the isospin dynamics related to neck formation.
↳ nucl-exnucl-thNucl.Sci.Tech.(2025)·6 citations
12
Nuclear physics inputs for dense-matter modelling in neutron stars. The nuclear equation of state
A. F. Fantina🇫🇷 · F. Gulminelli🇫🇷
In this contribution, we briefly present the equation-of-state modelling for application to neutron stars and discuss current constraints coming from nuclear physics theory and experiments. To assess the impact of model uncertainties, we employ a nucleonic meta-modelling approach and perform a Bayesian analysis to generate posterior distributions for the equation of state with filters accounting for both our present low-density nuclear physics knowledge and high-density neutron-star physics constraints. The global structure of neutron stars thus predicted is discussed in connection with recent astrophysical observations.
↳ astro-ph.HEnucl-thJ.Phys.Conf.Ser.(2023)·6 citations
13
Angularity in Higgs boson decays via $H \to gg$ at NNLL $^{'}$ accuracy
Jiawei Zhu🇨🇳 · Yujin Song🇨🇳 · Jun Gao🇨🇳 · Daekyoung Kang🇨🇳 · Tanmay Maji🇮🇳
We present improved predictions of a class of event-shape distributions called angularity for a contribution from an effective operator $H \to g g$ in Higgs hadronic decay that suffers from large perturbative uncertainties. In the frame of Soft-Collinear Effective Theory, logarithmic terms of the distribution are resummed at NNLL $^{'}$ accuracy, for which 2-loop constant of gluon-jet function for angularity is independently determined by a fit to fixed-order distribution at NLO corresponding to $O (α_{s}^{2})$ relative to the Born rate. Our determination shows reasonable agreement with the value in a thesis recently released. In the fit, we use an asymptotic form with a fractional power conjectured from recoil corrections at one-loop order and it improves the accuracy of determination in positive values of angularity parameter $a$ . The resummed distribution is matched to the NLO fixed-order results to make our predictions valid at all angularity values. We also discuss the first moment and subtracted moment of angularity as a function of $a$ that allow to extract information on leading and subleading nonperturbative corrections associated with gluons.
↳ hep-phhep-exnucl-thCPC(2025)·7 citations
14
Large $N_{c}$ QCD phase diagram at $μ_{B} = 0$
T.D. Cohen🇺🇸 · L.Ya. Glozman🇦🇹
Lattice studies suggest that at zero baryon chemical potential and increasing temperature there are three characteristic regimes in QCD that are connected by smooth analytical crossovers: a hadron gas regime at T < T_ch ~ 155 MeV, an intermediate regime, called stringy fluid, at T_ch < T < ~ 3 T_ch, and a quark-gluon plasma regime at higher temperatures. These regimes have been interpreted to reflect different approximate symmetries and effective degrees of freedom. In the hadron gas the effective degrees of freedom are hadrons and the approximate chiral symmetry of QCD is spontaneously broken. The intermediate regime has been interpreted as lacking spontaneous chiral symmetry breaking along with the emergence of new approximate symmetry, chiral spin symmetry, that is not a symmetry of the Dirac Lagrangian, but is a symmetry of the confining part of the QCD Lagrangian. While the high temperature regime is the usual quark-gluon plasma which is often considered to reflect "deconfinement" in some way. This paper explores the behavior of these regimes of QCD as the number of colors in the theory, N_c, gets large. In the large N_c limit the theory is center-symmetric and notions of confinement and deconfinement are unambiguous. The energy density is O(N_c^0) in the meson gas, O(N_c^1) in the intermediate regime and O(N_c^2) in the quark-gluon plasma regime. In the large N_c limit these regimes may become distinct phases separated by first order phase transitions. The intermediate phase has the peculiar feature that glueballs should exist and have properties that are unchanged from what is seen in the vacuum (up to 1/N_c corrections), while the ordinary dilute gas of mesons with broken chiral symmetry disappears and approximate chiral spin symmetry should emerge.
↳ hep-phhep-lathep-thnucl-thEPJA(2024)·32 citations
15
Quark production and thermalization of the quark-gluon plasma
Sergio Barrera Cabodevila🇪🇸 · Carlos A. Salgado🇪🇸 · Bin Wu🇪🇸
We first assemble a full set of the Boltzmann Equation in Diffusion Approximation (BEDA) for studying thermalization/hydrodynamization as well as the production of massless quarks and antiquarks in out of equilibrium systems. In the BEDA, the time evolution of a generic system is characterized by the following space-time dependent quantities: the jet quenching parameter, the effective temperature, and two more for each quark flavor that describe the conversion between gluons and quarks/antiquarks via the $2 \leftrightarrow 2$ processes. Out of the latter two quantities, an effective net quark chemical potential is defined, which equals the net quark chemical potential after thermal equilibration. We then study thermalization and the production of three flavors of massless quarks and antiquarks in spatially homogeneous systems initially filled only with gluons. A parametric understanding of thermalization and quark production is obtained for either initially very dense or dilute systems, which are complemented by detailed numerical simulations for intermediate values of initial gluon occupancy $f_{0}$ . For a wide range of $f_{0}$ , the final equilibration time is determined to be about one order of magnitude longer than that in the corresponding pure gluon systems. Moreover, during the final stage of the thermalization process for $f_{0} \geq 1 0^{- 4}$ , gluons are found to thermalize earlier than quarks and antiquarks, undergoing the top-down thermalization.
↳ hep-phnucl-thJHEP(2024)·14 citations
16
Goldberger-Treiman relation and Wu-type experiment in the decuplet sector
Magnus Bertilsson (Uppsala U.)🇸🇪 · Stefan Leupold (Uppsala U.)🇸🇪
The leading-order chiral Lagrangian for the baryon octet and decuplet states coupled to Goldstone bosons and external sources contains six low-energy constants. Five of them are fairly well known from phenomenology, but the sixth one is practically unknown. This coupling constant provides the strength of the (p-wave) coupling of Goldstone bosons to decuplet states. Its size and even sign are under debate. Quark model and QCD for a large number of colors provide predictions, but some recent phenomenological analyses suggest even an opposite sign for the Delta-pion coupling. The Goldberger-Treiman relation connects this coupling constant to the axial charge of the Delta baryon. This suggests a Wu-type experiment to determine the unknown low-energy constant. While this is not feasible in the Delta sector because of the large hadronic width of the Delta, there is a flavor symmetry related process that is accessible: the weak semileptonic decay of the Omega baryon to a spin 3/2 cascade baryon. A broad research program is suggested that can pin down at least the rough size and the sign of the last unknown low-energy constant of the leading-order Lagrangian. It encompasses experimental measurements, in particular the forward-backward asymmetry of the semileptonic decay, together with a determination of the quark-mass dependences using lattice QCD for the narrow decuplet states and chiral perturbation theory to extrapolate to the Delta sector. Besides discussing the strategy of the research program, the present work provides a feasibility check based on a simple leading-order calculation.
↳ hep-phhep-latnucl-thPRD(2024)·6 citations

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