Nuclear Theory·nucl-th

Wednesday·July 24, 2024

9 papers—4 primary·5 cross-listed

01
Bulk Viscosity in Dense Nuclear Matter
Steven P. Harris
In this chapter, I describe bulk viscosity as a general concept, and then focus on bulk viscosity in the dense matter present in compact objects. While this review is focused on bulk viscosity in the conditions present in neutron star mergers, I present a history of bulk viscosity research in dense matter, from its role in damping radial oscillations in neutron stars through its current applications in neutron star mergers. The majority of the chapter consists of calculations of the bulk viscosity from Urca processes in generic neutron-proton-electron ( $n p e$ ) matter, and then in dense matter containing muons ( $n p e μ$ matter) as well. I make several approximations in these calculations to keep the focus on the concepts. More precise calculations exist in the literature, to which I refer the reader. One concept I attempt to elucidate is the thermodynamic behavior of a fluid element throughout an oscillation and how that leads to bulk-viscous dissipation. I conclude with a discussion of the recent research into the role of weak interactions and bulk viscosity in neutron star mergers.
nucl-thastro-ph.HE8 citations
02
Equation of state of nuclear matter from collective flows and stopping in intermediate energy heavy-ion collisions
Dan Cozma (IFIN-HH, Bucharest)🇷🇴
The equation of state of nuclear matter, momentum dependence of the effective interaction and in-medium modification of elastic nucleon-nucleon cross-sections are studied by comparing theoretical predictions for stopping, directed and elliptic flows of protons and light clusters in intermediate energy heavy-ion collisions of beam energy between 150 and 800 MeV/nucleon to experimental data gathered by the FOPI Collaboration. A multivariate analysis that takes into account systematic uncertainties induced on model predictions by the coalescence afterburner leads to the following constraint for the equation of state at 68 percent confidence level: compressibility modulus of isospin symmetric matter $K_{0} = 23 0_{- 11}^{+ 9}$ MeV and slope of the symmetry energy $L = 6 3_{- 13}^{+ 10}$ MeV. The momentum dependence of the isoscalar potential is found to be similar to that of the empirical optical potential, with an effective isoscalar mass $m^{*} = 0.69 5_{- 0.018}^{+ 0.014}$ . The isovector potential displays a momentum dependence corresponding to a positive neutron-proton effective mass difference $Δ m_{n p}^{*} = (0.1 7_{- 0.09}^{+ 0.10}) δ$ , close to the world average for this quantity. A suppression of elastic nucleon-nucleon cross-sections in symmetric nuclear matter at saturation by about 60 $%$ relative to vacuum values is deduced, in qualitative agreement with microscopical results. A strong dependence of the suppression factor on isospin asymmetry is evidenced, experimental data for isospin symmetric systems proving crucial for this last conclusion.
nucl-thnucl-exPRC(2024)·16 citations
03
Phase transitions in N = 40, 60 and 90 nuclei
A. Prášek🇨🇿 · P. Alexa🇨🇿 · D. Bonatsos🇬🇷 · G. Thiamová🇫🇷 · D. Petrellis🇨🇿 · P. Veselý🇨🇿
In this paper we focus on three mass regions where first-order phase transitions occur, namely for $N = 40$ , 60 and 90. We investigate four isotopic chains (Se, Zr, Mo and Nd) in the framework of microscopic Skyrme-Hartree-Fock + Bardeen-Cooper-Schrieffer calculations for 15 different parametrizations. The microscopic calculations show the typical behavior expected for first-order phase transitions. To find the best candidate for the critical point phase transition we propose new microscopic position and occupation indices calculated for positive-parity and negative-parity proton and neutron single-quasiparticle states around the Fermi level. The microscopic calculations are completed by macroscopic calculations within the Algebraic Collective Model (ACM), and compared to the experimental data for $^{74}$ Se, $^{102}$ Mo and $^{150}$ Nd, considered to be the best candidates for the critical point nuclei.
nucl-thPRC(2024)·4 citations
04
The Hidden Variables: Harnessing Half-Shell Potentials for Enhanced Precision in Nuclear Reaction Calculations
Hao Liu · Jin Lei · Zhongzhou Ren
We explore the impact of half-shell components on nuclear reaction calculations, focusing on nonelastic breakup cross sections within the Ichimura-Austern-Vincent (IAV) model. By advocating for the use of a consistent Single Folding Model (SFM) for all optical potentials in IAV calculations, we aim to reduce the uncertainties associated with half-shell components and enhance agreement with experimental data. We present results from deuteron-induced reactions on $^{60}$ Ni and $^{208}$ Pb, which serve as surrogate targets for neutron-induced reactions on short-lived nuclei. The application of consistent optical potentials derived from the SFM shows improved alignment with experimental data compared to traditional global phenomenological potentials. Furthermore, we investigate the $^{59}$ Co( $^{6}$ Li, $α X$ ) reaction, which reveals that the half-shell $T$ -matrix plays a pivotal role in accurately modeling nuclear reactions. Our findings suggest that a unified approach to optical potentials, accounting for half-shell effects, is critical for a precise understanding of complex nuclear reactions. This work highlights the significance of the internal dynamics of the wave function, particularly in lighter targets, and underscores the importance of the half-shell $T$ -matrix as a previously underappreciated variable in reaction calculations.
nucl-th0 citations
05
Entanglement Enabled Intensity Interferometry in ultrarelativistic ultraperipheral nuclear collisions
James Daniel Brandenburg🇺🇸 · Haowu Duan🇺🇸 · Zhoudunming Tu🇺🇸 · Raju Venugopalan🇺🇸 · Zhangbu Xu🇺🇸
An important tool in studying the sub-femtoscale spacetime structure of matter in ultrarelativistic heavy-ion collisions is Hanbury-Brown-Twiss (HBT) intensity interferometry of identical particles in the final state of such collisions. We show here that a variant of an entanglement enabled intensity interferometry ( $E^{2} I^{2}$ ) proposed by Cotler and Wilczek provides a powerful alternative to HBT interferometry in extracting fundamental nonperturbative features of QCD at high energies. In particular, we show that the spatial distributions of color singlet (pomeron) configurations in nuclei can be obtained from exclusive resonant decays of $ρ$ -mesons into $π^{\pm}$ -pairs in ultrarelativistic ultraperipheral nuclear collisions (UPCs) at RHIC and the LHC. The $E^{2} I^{2}$ framework developed here is quite general. It can be employed to extract information on the spin structure of pomeron couplings as well as enhance the discovery potential for rare odderon configurations from exclusive vector meson decays into few-particle final states both in UPCs and at the Electron-Ion Collider.
↳ hep-phhep-thnucl-exnucl-thPRResearch(2025)·15 citations
06
The CSS Hamiltonian: high energy evolution of rapidity dependent observables
Haowu Duan🇺🇸 · Alex Kovner🇺🇸 · Michael Lublinsky🇮🇱
We consider evolution of observables which depend on a small but fixed value of longitudinal momentum fraction $x$ , to high rapidity, such that $η > ln 1/ x$ . We show that this evolution is not given by the JIMWLK (or BK) equation. We derive the evolution Hamiltonian - $H_{C S S - J I M W L K}$ which generates this evolution in the cases of dilute and dense projectile wave function. The two limits yield identical results for $H_{C S S - J I M W L K}$ . We show that the resulting evolution for the gluon TMD is identical to the (double logarithmic) perturbative Collins-Soper-Sterman evolution equation in the longitudinal resolution parameter at a fixed and very large transverse resolution.
↳ hep-phhep-thnucl-thPRD(2025)·10 citations
07
COLOSS: Complex-scaled Optical and couLOmb Scattering Solver
Junzhe Liu · Jin Lei · Zhongzhou Ren
We introduce COLOSS, a program designed to address the scattering problem using a bound-state technique known as complex scaling. In this method, the oscillatory boundary conditions of the wave function are transformed into exponentially decaying ones, accommodating the long-range Coulomb interaction. The program implements the Woods-Saxon form of a realistic optical potential, with all potential parameters included in a well-designed input format for ease of use. This design offers users straightforward access to compute $S$-matrices and cross-sections of the scattering process. We provide thorough discussions on the precision of Lagrange functions and their benefits in evaluating matrix elements. Additionally, COLOSS incorporates two distinct rotation methods, making it adaptable to potentials without analytical expressions. Comparative results demonstrate that COLOSS achieves high accuracy when compared with the direct integration method, Numerov, underscoring its utility and effectiveness in scattering calculations.
↳ physics.comp-phnucl-thComput.Phys.Commun.(2025)·4 citations
08
$ω$ meson from lattice QCD
Haobo Yan🇩🇪 · Maxim Mai🇩🇪 · Marco Garofalo🇩🇪 · Ulf-G. Meißner🇩🇪 · Chuan Liu🇨🇳 · Liuming Liu🇨🇳 · Carsten Urbach🇩🇪
Many excited states in the hadron spectrum have large branching ratios to three-hadron final states. Understanding such particles from first principles QCD requires input from lattice QCD with one-, two-, and three-meson interpolators as well as a reliable three-body formalism relating finite-volume spectra at unphysical pion mass values to the scattering amplitudes at the physical point. In this work, we provide the first-ever calculation of the resonance parameters of the $ω$ meson from lattice QCD, including an update of the formalism through matching to effective field theories. The main result of this pioneering study, the pole position of the $ω$ meson at $s_{ω} = (778.0 (11.2) - i 3.0 (5)) MeV$ , agrees reasonably well with experiment. In addition we provide an estimate of the $ω - ρ$ mass difference as $29 (15) MeV$ .
↳ hep-lathep-phnucl-thPRL(2024)·58 citations
09
Joint Inference of Population, Cosmology, and Neutron Star Equation of State from Gravitational Waves of Dark Binary Neutron Stars
Tathagata Ghosh🇮🇳 · Bhaskar Biswas🇩🇪 · Sukanta Bose🇮🇳 · Shasvath J. Kapadia🇮🇳
Gravitational waves (GWs) from binary neutron stars (BNSs) are expected to be accompanied by electromagnetic (EM) emissions, which help identify the host galaxy. Since GWs directly measure their luminosity distances, joint GW-EM observations from BNSs help with the study of cosmology, particularly the Hubble constant, unaffected by cosmic distance ladder systematics. However, detecting the EM emissions is not always possible. Additionally, the tidal deformability of neutron stars (NSs), combined with the knowledge of the NS EoS, can break the degeneracy between mass parameters and redshift, allowing for the inference of the Hubble constant. While several studies have aimed to infer the Hubble constant using dark BNSs (without EM counterparts), none have consistently combined the uncertainties of population, cosmology, and NS EoS within a Bayesian framework. In this study, we propose a novel Bayesian analysis to jointly constrain the NS EoS, population, and cosmological parameters using a population of dark BNSs detected through GW observations. We demonstrate the statistical robustness of our method using $50$ simulated BNS events following Gaussian and double Gaussian mass distributions, detected by Advanced LIGO and Advanced Virgo detectors operating at O5 sensitivity. We show that such measurements can constrain the Hubble constant with a precision of $≲ 35%$ ( $90%$ credible interval). This level of precision is unattainable without incorporating NS EoS, especially when observing BNS mergers without EM counterpart information. We also report the Hubble constant measurements obtained from a more realistic set of $5$ simulated BNS events.
↳ gr-qcastro-ph.COastro-ph.HEnucl-thAstrophys.J.Suppl.(2025)·14 citations

Affiliations

first authorsco-authorsvia INSPIRE