Nuclear Theory·nucl-th

Tuesday·December 10, 2024

14 papers—6 primary·8 cross-listed

01
Signatures of Jet Drift in QGP Hard Probe Observables
Joseph Bahder🇺🇸 · Hasan Rahman🇺🇸 · Matthew D. Sievert🇺🇸 · Ivan Vitev🇺🇸
Hard probe tomography of the quark-gluon plasma (QGP) in heavy ion collisions has long been a preeminent goal of the high-energy nuclear physics program. In service of this goal, the isotropic modification of jets and high-energy hadrons has been studied in great detail at the leading-power (eikonal) level, with effects originating from sub-eikonal $O (μ / E)$ anisotropic interactions presumed to be small. We present the first investigation of sub-eikonal, collective-flow-induced asymmetric jet broadening (jet drift) in event-by-event $s = 5.02$ TeV PbPb collisions at the Large Hadron Collider using the new Anisotropic Parton Evolution (APE) computational framework. We show that jet drift imparts a sizeable enhancement of elliptic flow ( $v_{2}$ ) and increases the mean acoplanarity for low and intermediate energy particles ( $p_{T} < 10$ GeV). Importantly, these novel modifications to hard probe observables are shown to survive averaging over events and collision geometry. They couple to the collective flow of the medium seen by the jet and encode information about the QGP dynamics inaccessible to studies considering only isotropic, eikonal level effects.
nucl-thPRResearch(2026)·14 citations
02
Spin polarization of an expanding and rotating system
Nora Weickgenannt🇫🇷 · Jean-Paul Blaizot🇫🇷
We study the longitudinal spin polarization of a relativistic fluid of massive spin-1/2 particles undergoing a boost-invariant expansion in the longitudinal direction and rotating in the transverse plane. We express the polarization vector in terms of spin moments and derive closed equations of motion for the latter using spin kinetic theory with a nonlocal relaxation time approximation. These equations of motion are valid at any time of the evolution, from the free-streaming regime to the hydrodynamic regime. At late time, the polarization features contributions from gradients of the fluid velocity and of the temperature, that emerge from the nonlocal part of the collision term. Our results can be used to explore polarization phenomena in the context of heavy-ion collisions.
nucl-thhep-phPRD(2025)·7 citations
03
Large-scale shell-model study of 2 $ν$ ECEC process in $^{78}$ Kr
Deepak Patel · Praveen C. Srivastava
In this work, we present the systematic study of $2 ν$ ECEC process in the $^{78}$ Kr using large-scale shell-model calculations with the GWBXG effective interaction. We first validate the efficiency of the utilized interaction by comparing the theoretical low-lying energy spectra, the kinematic moment of inertia, and reduced transition probabilities with the experimental data for both the parent and grand-daughter nuclei $^{78}$ Kr and $^{78}$ Se, respectively. Additionally, we examine the shell-model level densities of the $1^{+}$ states in the intermediate nucleus $^{78}$ Br, comparing them with the predictions from the Back-shifted Fermi gas model. We analyze the variation of cumulative nuclear matrix elements (NMEs) for the $2 ν$ ECEC process in $^{78}$ Kr as a function of $1^{+}$ state energies in the intermediate nucleus $^{78}$ Br up to the saturation level. Our estimated half-life for $^{78}$ Kr, extracted from the shell-model predicted NMEs, shows good agreement with the experimental value. The Gamow-Teller transitions from the lowest $1^{+}$ state of $^{78}$ Br via both the EC $+ β^{+}$ and $β^{-}$ -channels are also discussed.
nucl-thnucl-exPhys.Scripta(2025)·2 citations
04
Implications of latest NICER data for the neutron star equation of state
Len Brandes🇩🇪 · Wolfram Weise🇩🇪
As an update to our previously performed Bayesian inference analyses of the neutron star matter equation-of-state and related quantities, the additional impact of the recently published NICER data of PSR J0437-4751 is examined. Including the mass and radius distributions of this pulsar in our data base results in modest shifts from previously inferred median posterior values of radii $R$ and central densities $n_{c}$ for representative $1.4 M_{⊙}$ and $2.1 M_{⊙}$ neutron stars: radii are reduced by about $0.2 - 0.3$ km to values of $R_{1.4} = 12.1 \pm 0.5$ km and $R_{2.1} = 11. 9_{- 0.6}^{+ 0.5}$ km (at the 68\% level), and central densities increase slightly to values of $n_{c} (1.4 M_{⊙}) / n_{0} = 2.8 \pm 0.3$ and $n_{c} (2.1 M_{⊙}) / n_{0} = 3. 8_{- 0.7}^{+ 0.6}$ (in units of equilibrium nuclear matter density, $n_{0} = 0.16$ fm $^{- 3}$ ), i.e., they still fall below five times nuclear saturation density at the 68\% level. As a further significant result, the evidence established by analyzing Bayes factors for a negative trace anomaly measure, $Δ = 1/3 - P / ε < 0$ , inside heavy neutron stars is raised to strong.
nucl-thastro-ph.HEgr-qcnucl-exPRD(2025)·31 citations
05
Identifying weak critical fluctuations of intermittency in heavy-ion collisions with topological machine learning
Rui Wang🇨🇳 · Chengrui Qiu🇨🇳 · Chuan-Shen Hu🇸🇬 · Zhiming Li🇨🇳 · Yuanfang Wu🇨🇳
Large density fluctuations of conserved charges have been proposed as a promising signature for exploring the QCD critical point in heavy-ion collisions. These fluctuations are expected to exhibit a fractal or scale-invariant behavior, which can be probed by intermittency analysis. Recent high-energy experimental studies reveal that the signal of critical fluctuations related to intermittency is very weak and thus could be easily obscured by the overwhelming background particles in the data sample. Employing a point cloud neural network with topological machine learning, we can successfully classify weak signal events from background noise by the extracted distinct topological features, and accurately determine the intermittency index for weak signal event samples.
nucl-thhep-phnucl-exPLB(2025)·6 citations
06
Estimating theoretical uncertainties of the two-nucleon observables by using backpropagation
K. Topolnicki · R. Skibiński · J. Golak
We present a novel approach to calculating theoretical uncertainties in few-nucleon calculations, making use of automatic differentiation via backpropagation, which is particularly efficient when there are many input variables but only a few outputs. The methods described in this paper constitute tools that can be used to investigate the properties of scalar functions used to define nuclear potentials and quantify their contribution to the uncertainty of few nucleon calculations. We demonstrate these methods in deuteron bound state and nucleon - nucleon scattering calculations. Backpropagation, implemented in the Python pytorch library, is used to calculate the gradients with respect to model parameters and propagate errors from these parameters to the deuteron binding energy and selected phase-shift parameters. The uncertainty values obtained using this approach are validated by directly sampling from the potential parameters. We find very good agreement between two ways of estimating that uncertainty.
nucl-thEPJA(2025)·0 citations
07
$q_{T}$ -slicing with multiple jets
Rong-Jun Fu🇨🇳 · Rudi Rahn🇦🇹 · Ding Yu Shao🇨🇳 · Wouter J. Waalewijn🇳🇱 · Bin Wu🇪🇸
Modern collider phenomenology requires unprecedented precision for the theoretical predictions, for which slicing techniques provide an essential tool at next-to-next-to-leading order (NNLO) in the strong coupling. The most popular slicing variable is based on the transverse momentum $q_{T}$ of a color-singlet final state, but its generalization to final states with jets is known to be very difficult. Here we propose two generalizations of $q_{T}$ that can be used for jet processes, providing proof of concept with an NLO slicing for $pp \to 2$ jets. We present factorization formulae that enable our approach to NNLO, calculate the NNLO collinear-soft function and demonstrate slicing at this order for $e^{+} e^{-} \to 2$ jets. One of these generalizations of $q_{T}$ only applies to planar Born processes, such as $pp \to 2$ jets, but offers a dramatic simplification of the soft function. We also discuss how our approach can directly be extended to obtain predictions for the fragmentation of hadrons. This presents a promising path for high-precision QCD calculations with multi-jet final states.
↳ hep-phnucl-thPRL(2025)·16 citations
08
Superfluid fraction in the crystalline crust of a neutron star: role of BCS pairing
Nicolas Chamel
The breaking of translational symmetry in the inner crust of a neutron star leads to the depletion of the neutron superfluid reservoir similarly to cold atomic condensates in optical lattices and in supersolids. This effect is studied in the general framework of the self-consistent time-dependent Hartree-Fock-Bogoliubov (HFB) theory, treating the crust as a perfect crystal. The superfluid fraction is derived in the Bardeen-Cooper-Schrieffer approximation for superfluid velocities much smaller than Landau's critical velocity within the linear-response theory. The different assumptions made in previous studies are clarified. Fully three-dimensional band-structure calculations of superfluid neutrons in a body-centered cubic lattice are carried out. Although the formation of Cooper pairs is essential for the occurrence of superfluidity, the superfluid fraction is found to be insensitive to the pairing gap, as in uniform neutron matter. In the intermediate region of the inner crust at the average baryon number density 0.03 fm $^{- 3}$ , only 8\% of the free neutrons are found to participate to the superflow. Such very low superfluid fraction challenges the classical interpretation of pulsar frequency glitches and calls for more systematic calculations within the full HFB approach.
↳ astro-ph.HEnucl-thPRC(2025)·13 citations
09
On the quarkonium-in-jet collinear fragmentation at moderate-to-large transverse momentum
Francesco Giovanni Celiberto🇪🇸
We report progress on the Heavy-Flavor Non-Relativistic Evolution (HF-NRevo) setup, a novel methodology to address quarkonium formation within the fragmentation approximation. Our study sheds light on the moderate to large transverse-momentum sector, where the leading-twist collinear fragmentation of a single parton prevails over the higher-twist fragmentation from a constituent heavy-quark pair produced in the hard scattering. As for the initial energy-scale inputs, we rely on nonrelativistic next-to-leading calculations for all the parton-to-quarkonia fragmentation channels. Preliminary sets of variable-flavor number-scheme (VFNS) fragmentation functions, named NRFF1.0, are built via an evolution-threshold enhanced DGLAP scheme. Taking NRFF1.0 as a starting point, we use HF-NRevo to address the collinear fragmentation of quarkonia inside jets.
↳ hep-phhep-exnucl-exnucl-thActa Phys.Polon.Supp.(2025)·15 citations
10
Effective theory for strongly attractive one-dimensional fermions
Timothy G. Backert · Fabian Brauneis · Matija Čufar · Joachim Brand · Hans-Werner Hammer · Artem G. Volosniev
We study a one-dimensional system of two-component fermions in the limit of strong attractive particle-particle interactions. First, we analyze scattering in the corresponding few-body problem, which is analytically solvable via Bethe ansatz. This allows us to engineer effective interactions between the system's effective degrees of freedom: fermions and bosonic dimers (tightly bound pairs of fermions). We argue that, although these interactions are strong, the resulting effective problem can be mapped onto a weakly interacting one, paving the way for the use of perturbation theory. This finding simplifies studies of many-fermion systems under confinement that are beyond reach of state-of-the-art numerical methods. We illustrate this statement by considering an impurity atom in a Fermi gas.
↳ cond-mat.quant-gascond-mat.str-elnlin.SInucl-thPRL(2025)·2 citations
11
Testing for isospin symmetry breaking with extensive calculations of isotope shift factors in potassium
Vaibhav Katyal🇮🇳 · A. Chakraborty🇮🇳 · B. K. Sahoo🇮🇳 · Ben Ohayon🇮🇱 · Chien-Yeah Seng🇺🇸 · Mikhail Gorchtein🇩🇪 · John Behr🇨🇦
Precise evaluation of the isotope shift (IS) factors for seven low-lying potassium (K) states is achieved using relativistic coupled-cluster (RCC) theory. The energies of these states are assessed and compared with experimental data to confirm the accuracy of the wave functions calculated at varying RCC theory approximations and highlight the significance of many-body and relativistic effects in determining the energies and IS factors of K. Various methods are used to compute the IS factors, with the finite-field (FF) approach yielding results that align with observed and semi-empirical data. This consistency is attributed to orbital relaxation effects that are naturally present in the FF method but emerge only through complex interactions in other techniques. Using the IS factors derived from FF, we review the mean square radius difference between $^{38 m}$ K and $^{39}$ K. From this difference and muonic atom x-ray spectroscopy, we deduce the absolute radius of $^{38 m}$ K using an updated calculation of the nuclear polarizability effect. Finally, we evaluate the isospin symmetry breaking (ISB) in this isotriplet by integrating the radius of $^{38 m}$ K with an updated radius of $^{38}$ Ca, concluding that the ISB is compatible with zero. This finding offers a stringent benchmark for nuclear model calculations of ISB corrections in nuclear beta decay, which play a key role in determining the $V_{u d}$ matrix element.
↳ physics.atom-phhep-phnucl-exnucl-thPRA(2025)·13 citations
12
Quasiparticle second-order dissipative hydrodynamics at finite chemical potential
Asaad Daher🇵🇱 · Leonardo Tinti🇵🇱 · Amaresh Jaiswal🇮🇳 · Radoslaw Ryblewski🇵🇱
We extend the derivation of second-order relativistic viscous hydrodynamics to incorporate the effects of baryon current, a non-vanishing chemical potential, and a realistic equation of state. Starting from a microscopic quantum theory, we employ a quasiparticle approximation to describe the evolution of hydrodynamic degrees of freedom and establish its connection to the Wigner formalism. Using methods from relativistic kinetic theory, we perform a second-order expansion to derive a closed set of equations for the components of the stress-energy tensor and the baryon current. The resulting transport coefficients, which depend on the equation of state, are obtained through a unified prescription that ensures thermodynamic consistency.
↳ hep-phnucl-thPRD(2025)·5 citations
13
Mapping spatial distributions within pseudoscalar mesons
K. Raya🇪🇸 · A. Bashir🇪🇸 · J. Rodríguez-Quintero🇪🇸
Several aspects of the internal structure of pseudoscalar mesons, accessible through generalized parton distributions in their zero-skewness limit, are examined. These include electromagnetic and gravitational form factors related to charge and mass densities; and distributions in the impact parameter space. To this end, we employ an algebraically viable framework that is based upon the valence-quark generalized parton distribution expressed explicitly in terms of the associated distribution function and a profile function that governs the off-forward dynamics. The predominantly analytical nature of this scheme yields several algebraic results and relations while also facilitating the exploration of insightful limiting cases. With a suitable input distribution function, guided either by experiment or theory, and with an appropriate choice of the profile function, it is possible to provide testable predictions for spatial distributions of valence quarks inside pseudoscalar mesons. When comparison is possible, these predictions align well with existing experimental data as well as the findings of reliable theoretical approaches and lattice QCD.
↳ hep-phnucl-thChin.Phys.Lett.(2025)·9 citations
14
$f$ -mode oscillations of dark matter admixed quarkyonic neutron star
D. Dey🇮🇳 · Jeet Amrit Pattnaik🇮🇳 · R. N. Panda🇮🇳 · M. Bhuyan🇮🇳 · S. K. Patra🇮🇳
We systematically investigate $f -$ mode oscillations ( $ℓ$ = 2) in quarkyonic neutron stars with dark matter, employing the Cowling approximation within the framework of linearized general relativity. The relativistic mean-field approach is used to compute various macroscopic properties of neutron stars. The analysis focuses on three key free parameters in the model: transition density, QCD confinement scale, and dark matter (DM) Fermi momentum, all of which significantly affect the properties of $f -$ mode oscillations. The inclusion of dark matter in quarkyonic equations of state leads to notable variations in $f -$ mode frequencies. Despite these changes, several universal relations among the oscillation properties are found to hold, demonstrating their robustness in the presence of dark matter.
↳ astro-ph.HEnucl-thJCAP(2025)·18 citations

Affiliations

first authorsco-authorsvia INSPIRE