Nuclear Theory·nucl-th

Thursday·November 21, 2024

15 papers—7 primary·8 cross-listed

01
Intertwined Quantum Phase Transitions in Bose and Bose-Fermi Systems
A. Leviatan
Pronounced structural changes within individual configurations (Type I QPT), superimposed on an abrupt crossing of these configurations (Type II QPT), define the notion of intertwined quantum phase transitions (QPTs). We discuss and present evidence for such a scenario in finite Bose and Bose-Fermi systems. The analysis is based on algebraic models with explicit configuration mixing, where the two types of QPTs describe shape-phase transitions in-between different dynamical symmetries and shape-coexistence with crossing.
nucl-thcond-mat.quant-gasquant-phJ.Phys.Conf.Ser.(2024)·0 citations
02
Untangling the interplay of the Equation-of-State and the Collision Term towards the generation of Directed and Elliptic Flow at intermediate energies
Tom Reichert🇩🇪 · Jörg Aichelin🇩🇪
The mechanism for generating directed and elliptic flow in heavy-ion collisions is investigated and quantified for the SIS18 and SIS100 energy regimes. The observed negative elliptic flow $v_{2}$ , at midrapidity has been explained either via (in-plane) shadowing or via (out-of-plane) squeeze-out. To settle this question, we employ the Ultra-relativistic Quantum Molecular Dynamics model (UrQMD) to calculate Au+Au collisions at E $_{lab} = 0.6 A$ GeV, E $_{lab} = 1.23 A$ GeV and $s_{NN} = 3.0$ GeV using a hard Skyrme type Equation-of-State to calculate the time evolution and generation of directed flow and elliptic flow. We quantitatively distinguish the impact of collisions and of the potential on $v_{1}$ and $v_{2}$ during the evolution of the system. These calculations reveal that in this energy regime the generation of $v_{1}$ and $v_{2}$ follows from a highly intricate interplay of different processes and is created late, after the system has reached its highest density and has created a matter bridge between projectile and target remnant, which later breaks. Initially, we find a strong out-of-plane pressure. Then follows a strong stopping and the built up of an in-plane pressure. The $v_{2}$ , created by both processes, compensate to a large extend. The finally observed $v_{2}$ is caused by the potential, reflects the freeze-out geometry and can neither be associated to squeeze-out nor to shadowing. The results are highly relevant for experiments at GSI, RHIC-FXT and the upcoming FAIR facility, but also for experiments at FRIB, and strengthens understanding on the Equation-of-State at large baryon densities.
nucl-thnucl-exPRC(2025)·12 citations
03
Examining the potential synthesis of new elements with $^{294}$ Og
Shuai Zhang · Gao-Chan Yong · J. L. Rodríguez-Sánchez · J. Cugnon
In the relentless pursuit of expanding the periodic table, the discovery of element 119 remains elusive, despite two decades of dedicated research efforts. The traditional fusion-evaporation approach, although fruitful in the past, now appears to be approaching its operational limits. This scenario sets the stage for considering innovative methodologies essential for further advancements in the field of superheavy elements. Here, we introduce a pioneering strategy aimed at synthesizing element 119 by adapting and extending the nuclear reaction processes previously successful in producing element $^{294}$ Og. This involved the fusion of $^{48}$ Ca and $^{249}$ Cf. Building on this, our novel approach incorporates an additional reactive target -- specifically, hydrogen -- positioned strategically behind the $^{249}$ Cf. This configuration is designed to facilitate an immediate secondary reaction of the nascent $^{294}$ Og with hydrogen, potentially forging new pathways to element 119. Preliminary insights also suggest that employing isotopes like deuterium or helium-3 as targets may not only enhance the production rates of element 119 but might also pave the way for the synthesis of even heavier elements, extending up to elements 120 and 121. We delve into the technicalities and feasibility of employing a dual-target method using a $^{48}$ Ca beam, exploring new horizons in the quest for the superheavy unknown.
nucl-thnucl-ex0 citations
04
Constraining the Phase-Transition EoS using the Energy Dependence of Directed Flow
Zhi-Min Wu🇨🇳 · Gao-Chan Yong🇨🇳 · Qingfeng Li🇨🇳
We propose a hybrid equation of state (VDF+MIT EoS) to describe the hadron-quark phase transition in dense nuclear matter. By coupling this EoS with the AMPT-HC transport model and comparing to recent experimental data on proton and $Λ$ directed flow $v_{1}$ , we constrain the transition to likely occur near $5 ρ_{0}$ -- $6 ρ_{0}$ , ruling out transitions below $3 ρ_{0}$ . Furthermore, we introduce the energy derivative of the mid-rapidity $v_{1}$ slope, $d (d v_{1} / d y) / d (s_{N N})$ , as a weakly model-dependent observable. Its zero crossing provides a direct signature of the phase transition critical point, offering a new tool for mapping the QCD phase diagram in future experiments.
nucl-thnucl-exPRD(2026)·1 citation
05
Exploring hadron-quark phase transition in heavy-ion collisions using particle emission ratios in heavy and light reaction systems
Xun Zhu🇨🇳 · Gao-Chan Yong🇨🇳
Based on the AMPT model, which incorporates both hadronic and quark degrees of freedom, we studied the productions of lambda, kaon, proton, and pion in reaction systems $^{40}$ Ca+ $^{40}$ Ca, $^{48}$ Ca+ $^{48}$ Ca, and $^{197}$ Au+ $^{197}$ Au. It is found that the ratios of identical particle emissions from heavy and light reaction systems, especially the emission ratios of strange particles $Λ^{0}$ or K $^{+}$ in heavy and light reaction systems, are highly sensitive to the hadron-quark phase transition in heavy-ion collisions. Detailed explanations and validations of these results are given.
nucl-thnucl-exPLB(2025)·1 citation
06
Validity of Brink Axel Hypothesis for calculations of allowed stellar weak rates of heavy nuclei
Fakeha Farooq · Jameel-Un Nabi · Ramoona Shehzadi
The knowledge of beta decay transitional probabilities and GamowTeller (GT) strength functions from highly excited states of nuclides is of particular importance for applications to astrophysical network calculations of nucleosynthesis in explosive stellar events. These quantities are challenging to achieve from measurements or computations using various nuclear models. Due to unavailability of feasible alternatives, many theoretical studies often rely on the Brink Axel (BA) hypothesis, that is, the response of strength functions depends merely on the transition energy of the parent nuclear ground state and is independent of the underlying details of the parent state, for the calculation of stellar rates. BA hypothesis has been used in many applications from nuclear structure determination to nucleosynthesis yield in the astrophysical matter.
nucl-thastro-ph.SRPhys.Scripta(2023)·2 citations
07
Novel features of asymmetric nuclear matter from terrestrial experiments and astrophysical observations of neutron stars
Tsuyoshi Miyatsu🇰🇷 · Myung-Ki Cheoun🇰🇷 · Kyungsik Kim🇰🇷 · Koichi Saito🇯🇵
The accurate measurement of neutron skin thickness of $^{208}$ Pb by the PREX Collaboration suggests a large value of the nuclear symmetry energy slope parameter, $L$ , whereas the smaller $L$ is preferred to account for the small neutron-star radii from NICER observations. To resolve this discrepancy between nuclear experiments and astrophysical observations, new effective interactions have been developed using relativistic mean-field models with the isoscalar- and isovector-meson mixing. We investigate the effects of $δ$ -nucleon coupling and $σ$ -- $δ$ mixing on the ground-state properties of finite nuclei, as well as the characteristics of isospin-asymmetric nuclear matter and neutron stars. Additionally, we explore the role of the quartic $ρ$ -meson self-interaction in dense nuclear matter to mitigate the stiff equation of state for neutron stars resulting from the large $δ$ -nucleon coupling. It is found that the nuclear symmetry energy undergoes a sudden softening at approximately twice the saturation density of nuclear matter, taking into account the PREX-2 result, the recent NICER observation of PSR J0437 $-$ 4715, and the binary neutron star merger, GW170817.
nucl-thnucl-exFront.in Phys.(2024)·9 citations
08
Entanglement entropy of a color flux tube in (1+1)D Yang-Mills theory
Rocco Amorosso🇺🇸 · Sergey Syritsyn🇺🇸 · Raju Venugopalan🇺🇸
In recent work arxiv:2410.00112 , we computed a novel flux tube entanglement entropy (FTE $^{2}$ ) of the color flux tube stretched between a heavy quark-antiquark pair on a Euclidean lattice in (2+1)D Yang-Mills theory. Our numerical results suggested that FTE $^{2}$ can be partitioned into an internal color entanglement entropy and a vibrational entropy corresponding to the transverse excitations of a QCD string, with the latter described by a thin string model. Since the color flux tube does not have transverse excitations in (1+1)D, we analytically compute the contribution of the internal color degrees of freedom to FTE $^{2}$ in this simpler framework. For the multipartite partitioning of the color flux tube, we find the remarkable result that FTE $^{2}$ only depends on the number of times the flux tube crosses the border between two spatial regions, and the dimension of the representation of the color group, but not on the string length. The result holds independently of whether the branching points are placed on the vertices of the lattice or in the center of plaquettes.
↳ hep-lathep-phhep-thnucl-thPLB(2025)·19 citations
09
Equation of state of isospin asymmetric QCD with small baryon chemical potentials
Bastian B. Brandt🇩🇪 · Gergely Endrodi🇩🇪 · G. Markó🇭🇺
We extend our measurement of the equation of state of isospin asymmetric QCD to small baryon and strangeness chemical potentials, using the leading order Taylor expansion coefficients computed directly at non-zero isospin chemical potentials. Extrapolating the fully connected contributions to vanishing pion sources is particularly challenging, which we overcome by using information from isospin chemical potential derivatives evaluated numerically. Using the Taylor coefficients, we present, amongst others, first results for the equation of state along the electric charge chemical potential axis, which is potentially of relevance for the evolution of the early Universe at large lepton flavour asymmetries.
↳ hep-phhep-latnucl-thPoS(2025)·10 citations
10
Non-Newtonian corrections to radiative viscosity: Israel-Stewart theory as a viscosity limiter
Lorenzo Gavassino
Radiation is a universal friction-increasing agent. When two fluid layers are in relative motion, the inevitable exchange of radiation between such layers gives rise to an effective force, which tries to prevent the layers from sliding. This friction is often modeled as a Navier-Stokes shear viscosity. However, non-Newtonian corrections are expected to appear at distances of about one optical depth from the layers' interface. Such corrections prevent the viscous stress from becoming too large. Here, we set the foundations of a rigorous theory for these corrections, valid along incompressible flows. We show that, in the linear regime, the infinite Chapman-Enskog series can be computed analytically, leading to universal formulas for all transport coefficients, which apply to any fluid, with any composition, with radiation of any type (also neutrinos), and with nearly any type of radiative process. We then show that, with an appropriate shear-heat coupling coefficient, Israel-Stewart theory can correctly describe most non-Newtonian features of radiative shear stresses.
↳ astro-ph.HEgr-qcnucl-thPRD(2025)·2 citations
11
Anomalous propagators and the particle-particle channel: Bethe-Salpeter equation
Antoine Marie🇫🇷 · Pina Romaniello🇫🇷 · Xavier Blase🇫🇷 · Pierre-François Loos🇫🇷
The Bethe-Salpeter equation has been extensively employed to compute the two-body electron-hole propagator and its poles which correspond to the neutral excitation energies of the system. Through a different time-ordering, the two-body Green's function can also describe the propagation of two electrons or two holes. The corresponding poles are the double ionization potentials and double electron affinities of the system. In this work, a Bethe-Salpeter equation for the two-body particle-particle propagator is derived within the linear-response formalism using a pairing field and anomalous propagators. This framework allows us to compute kernels corresponding to different self-energy approximations ( $G W$ , $T$ -matrix, and second-Born) as in the usual electron-hole case. The performance of these various kernels is gauged for singlet and triplet valence double ionization potentials using a set of 23 small molecules. The description of double core hole states is also analyzed.
↳ physics.chem-phcond-mat.mtrl-scimath-phmath.MP+1J.Chem.Phys.(2025)·4 citations
12
Two-pion exchange for coupled-channel scattering of two heavy mesons
J.T. Chacko🇩🇪 · V. Baru🇩🇪 · C. Hanhart🇩🇪 · S.L. Krug🇩🇪
To improve the theoretical understanding of multiquark states like $Z_{b} (10610)$ and $Z_{b} (10650)$ , we calculate the heavy-meson heavy-(anti)meson scattering potential up to next-to-leading order, $O (Q^{2})$ , within chiral effective field theory ( $χ$ EFT) employing a power counting scheme that explicitly keeps track with the large momentum scale $Q \sim 2 μ δ$ (where $δ = m_{V} - m_{P}$ is the vector-pseudoscalar mass difference and $μ$ their reduced mass) introduced by the coupled channel dynamics. We provide expressions for the two-pion exchange (TPE) terms up to $O (Q^{2})$ and their partial-wave decomposition. We show that these potentials are well-approximated by contact terms at $O (Q^{2})$ , with minor residual non-analytic TPE contributions, supporting $χ$ EFT convergence in the theoretical predictions for $Z_{b} (10610)$ and $Z_{b} (10650)$ , as well as their spin partners. These findings are also relevant for $D^{(*)} D^{(*)}$ scattering, especially for the $T_{cc}$ state, for both physical and lattice QCD data with moderately larger pion masses. We further demonstrate that the differences between isovector and isoscalar potentials for heavy mesons are naturally explained by the TPE contributions.
↳ hep-phnucl-thPRD(2025)·11 citations
13
Dispersive Determination of Nucleon Gravitational Form Factors
Xiong-Hui Cao🇨🇳 · Feng-Kun Guo🇨🇳 · Qu-Zhi Li🇨🇳 · De-Liang Yao🇨🇳
Being closely connected to the origin of the nucleon mass, the gravitational form factors of the nucleon have attracted significant attention in recent years. We present the first model-independent determinations of the gravitational form factors of the pion and nucleon at the physical pion mass, using a data-driven dispersive approach. The so-called "last global unknown property" of the nucleon, the $D$ -term, is determined to be $- 3.3 8_{- 0.35}^{+ 0.34}$ . The root mean square radius of the scalar trace density inside the nucleon is determined to be $(0.97 \pm 0.03) fm$ . Notably, this value is larger than the proton charge radius, suggesting a modern structural view of the nucleon where gluons, responsible for most of the nucleon mass, are distributed over a larger spatial region than quarks, which dominate the charge distribution, indicating that the radius of the trace density may be regarded as a confinement radius. We also predict the nucleon angular momentum and mechanical radii, providing further insights into the intricate internal structure of the nucleon.
↳ hep-phhep-exhep-latnucl-ex+1Nature Commun.(2025)·57 citations
14
Global analysis of $μ \to e$ interactions in the SMEFT
Filippo Delzanno🇺🇸 · Kaori Fuyuto🇺🇸 · Sergi Gonzàlez-Solís🇺🇸 · Emanuele Mereghetti🇺🇸
We study current experimental bounds on charged lepton flavor violating (CLFV) $μ$ - $e$ interactions in the model-independent framework of the Standard Model Effective Field Theory (SMEFT). Assuming a generic flavor structure in the quark sector, we consider the contributions of CLFV operators to low-energy observables, including $μ \to e γ$ and $μ \to e$ conversion for quark-flavor conserving operators and CLFV meson decays for quark-flavor violating operators. At high energy, we consider limits on CLFV decays of the Higgs and Z bosons and of the top quark, and obtain bounds on operators with light quarks by recasting searches for production of $e μ$ pairs in $pp$ collisions at the Large Hadron Collider (LHC). We connect observables at low- and high-energy by taking into account renormalization group running and matching between CLFV operators. We also discuss the sensitivity of the future Electron-Ion Collider, where the prospective bounds are derived by imposing simple cuts on final state particles. We find that, in a single operator scenario, bounds on purely leptonic operators are dominated by $μ \to e γ$ and $μ \to e$ conversion. Semileptonic operators with down-type quarks are also dominantly constrained by low-energy observables, while LHC searches lead the bounds on up-type quark-flavor violating operators. Taking simplified multiple-coupling scenarios, we show that it is easy to evade the strongest low-energy bounds from spin-independent $μ \to e$ conversion, and that collider searches are competitive and complementary to constraints from spin-dependent $μ \to e$ conversion and other low-energy probes.
↳ hep-phhep-exnucl-thJHEP(2025)·13 citations
15
Finite-size effects on small- $x$ evolution and saturation in proton and nuclear targets
Heikki Mäntysaari🇫🇮 · Jani Penttala🇺🇸 · Farid Salazar🇺🇸 · Björn Schenke🇺🇸
Within the Color Glass Condensate effective field theory, we assess the importance of including a finite size for the target on observables sensitive to small- $x$ evolution. To this end, we study the Balitsky-Kovchegov (BK) equation with impact-parameter dependence in the initial condition. We demonstrate that neglecting the dependence on the impact parameter can result in overestimated saturation effects for protons, while it has little effect for heavy nuclei at the energies available at current experiments. When fixing the nonperturbative parameters to the energy dependence of the exclusive $J / ψ$ photoproduction cross section with proton targets, predictions for lead targets are not sensitive to the applied running-coupling prescription, the scheme chosen to resum large transverse logarithms in the BK equation, or the infrared regulator in the evolution.
↳ hep-phnucl-thPRD(2025)·29 citations

Affiliations

first authorsco-authorsvia INSPIRE