Nuclear Theory·nucl-th

Thursday·July 25, 2024

15 papers—12 primary·3 cross-listed

01
Investigating the rate of $^{10}$ Be(n, $γ$ ) $^{11}$ Be radiative capture reaction within the FRDWBA framework
M. Dan · Shubhchintak · G. Singh · V. Choudhary · Jagjit Singh
This study examines the radiative capture of a neutron by $^{10}$ Be using the Coulomb dissociation approach within the FRDWBA theory. We analyze the elastic Coulomb breakup of $^{11}$ Be on a $^{208}$ Pb target at 72 MeV/A to determine the photodisintegration cross-section and radiative capture cross-section. Utilizing the Maxwell-averaged velocity distribution, we calculate the resulting radiative neutron capture reaction rate for the $^{10}$ Be(n, $γ$ ) $^{11}$ Be reaction. Comparative analyses are conducted with experimental data, theoretical results from direct radiative capture methods, and transfer reaction calculations. Additionally, we contrast our findings with the existing $^{10}$ Be( $α$ , $γ$ ) $^{14}$ C reaction rate and conclude the dominance of neutron capture over $α$ capture by $^{10}$ Be.
nucl-thEur.Phys.J.ST(2024)·1 citation
02
Ab initio Bogoliubov many-body perturbation theory: closed-form constraint on the average particle number
Pepijn Demol🇧🇪 · Thomas Duguet🇧🇪 · Alexander Tichai🇩🇪
Bogoliubov many-body perturbation theory (BMBPT) relying on the breaking of U(1) global gauge symmetry has been recently formulated and applied to extend the applicability of standard perturbation theory to ab initio calculations of atomic nuclei away from shell closures. So far, practical applications have been limited to second-order calculations due to the lack of a generic algorithm to constrain the average particle number of the symmetry-broken state. This limitation is presently lifted and a general BMBPT formalism is presented that allows to constrain the particle-number expectation value at arbitrary order P. The constraint can be incorporated in closed form by solving a polynomial equation of degree P-1. The numerical procedure is illustrated through BMBPT(3) calculations of calcium isotopes using a nuclear Hamiltonian derived within chiral effective field theory.
nucl-thEPJA(2025)·1 citation
03
Shear Viscosity of Collider-Produced QCD Matter I: AMY Formalism vs. A Modified Relaxation Time Approximation in 0-flavor SU(3) Theory
Noah M. MacKay🇩🇪
The AMY formalism is widely used to describe the transport coefficients of asymptotically hot and dense QCD matter, such as shear viscosity $η$ . In literature prior to AMY, the viscosity of an asymptotically hot QCD plasma was expressed by a $q^{2}$ momentum transfer-weighted relaxation time approximation. Recent studies that compared numerical transport calculations and analytical expressions for $η$ demonstrated that asymptotically high temperatures and densities induce anisotropic scatterings, which are exhibited in the quark-gluon plasma produced by relativistic heavy ion collisions. In these studies, the QGP was treated as a Maxwell-Boltzmann-distributed gluon gas with added (anti-)quark degrees of freedom. One such method used in the comparison was the ``modified'' $q^{2}$ transport-weighted RTA. In this study, a comparison between the AMY formalism (both numerical calculations and next-leading-log expression) and the modified RTA expression for $η$ is made in 0-flavor SU(3) theory for collider-produced QGP. The comparison between numerical AMY calculations and the modified RTA method shows perfect agreement under the temperatures relevant for collider-produced QGP. Additionally, AMY is compared with the Chapman-Enskog method, which is well understood to better describe anisotropic collider-produced QGP.
nucl-thhep-th2 citations
04
Pauli nonlocality and the nucleon effective mass
Dao T. Khoa · Doan Thi Loan · Nguyen Hoang Phuc
A study of the nucleon mean-field potential in nuclear matter (NM) is done within an extended Hartree-Fock (HF) formalism, using the CDM3Y6 density dependent version of the M3Y interaction which is associated with the nuclear incompressibility $K ≃ 252$ MeV. The momentum dependence of nucleon optical potential (OP) in NM at the saturation density $ρ_{0}$ is shown to be due mainly to its exchange term up to $k \approx 2$ fm $^{- 1}$ , so that the Pauli nonlocality is expected to be the main origin of the nucleon effective mass at low momenta. Because nucleons in neutron-rich NM at $ρ \approx ρ_{0}$ are either weakly bound or unbound by the in-medium nucleon-nucleon interaction, the determination of the effective mass of nucleon scattered on targets with neutron excess at low energies should be of interest for the mean-field studies of neutron star matter. For this purpose, the folding model is used to calculate the nonlocal nucleon OP for the optical model analysis of elastic nucleon scattering on $^{40, 48}$ Ca, $^{90}$ Zr, and $^{208}$ Pb targets at energies $E < 50$ MeV, to probe the model reliability and validate the WKB local approximation to obtain the local folded nucleon OP. The nucleon effective mass $m^{*}$ is then carefully deduced from the momentum dependence of the local folded nucleon OP which is resulted from the Pauli nonlocality of the exchange term. The neutron-proton effective mass splitting determined at $ρ \approx ρ_{0}$ from the central strength of the real folded nucleon OP for $^{48}$ Ca, $^{90}$ Zr, and $^{208}$ Pb targets has been found to depend linearly on the neutron-proton asymmetry parameter as $m_{n - p}^{*} \approx (0.167 \pm 0.018) δ$ , in a good agreement with the recent empirical constraints.
nucl-thPRC(2024)·3 citations
05
Enhancement of deltaful two-pion exchange nuclear forces
Haiming Chen🇨🇳 · Rui Peng🇨🇳 · Songlin Lyu🇨🇳 · Bingwei Long🇨🇳
The role of the delta isobar degrees of freedom in nucleon-nucleon scattering is revisited. We attempt to understand why the dimensionally regularized two-pion exchanges with the explicit delta isobar is much stronger than the ones with spectral function regularization. When the cutoff value of spectral function regularization is varied, the isoscalar central component exhibits a rather large cutoff variation. This reveals a surprisingly large numerical factor of the deltaful two-pion exchange potentials. The power counting is adjusted accordingly and we discuss the results and how to improve upon this finding.
nucl-thCommun.Theor.Phys.(2024)·0 citations
06
Diagrammatic ab initio methods for infinite nuclear matter with modern chiral interactions
Francesco Marino · Weiguang Jiang · Samuel J. Novario
A comparative study of the equation of state for pure neutron matter and symmetric nuclear matter is presented using three ab initio methods based on diagrammatic expansions: coupled-cluster theory, self-consistent Green's functions, and many-body perturbation theory. We critically evaluate these methods by employing different chiral potentials at next-to-next-to-leading-order -- all of which include both two- and three-nucleon contributions -- and by exploring various many-body truncations. Our investigation yields highly precise results for pure neutron matter and robust predictions for symmetric nuclear matter, particularly with soft interactions. Moreover, the new calculations demonstrate that the $NNL O_{sat} (450)$ and $Δ NNL O_{go} (394)$ potentials are consistent with the empirical constraints on the saturation point of symmetric nuclear matter. Additionally, this benchmark study reveals that diagrammatic expansions with similar architectures lead to consistent many-body correlations, even when applied across different methods. This consistency underscores the robustness of the diagrammatic approach in capturing the essential physics of nucleonic systems.
nucl-thcond-mat.quant-gascond-mat.str-elPRC(2024)·27 citations
07
The nuclear matter effect on parton distribution functions
W. Yang🇨🇳 · C. Li🇨🇳
Parton distribution functions (PDFs) are important quantities in describing nucleon structures. They are universal and process-independent. As a matter of fact, nucleon PDFs are inevitably affected by nuclear matter during nuclear scattering process. In order to study the nuclear PDFs (nPDFs), in this paper, we introduce the nucleon pair PDFs (dPDFs) to describe parton distributions in the nucleon pair which is confined to a nucleus. We first of all construct the nuclear state in terms of the nucleonic states and calculate the operator definition of nPDFs. Neglecting the higher order corrections or multi-nucleon correlations, we find that nPDFs can be written as a sum of two terms which respectively correspond to PDFs and dPDFs. Nucleon pair PDFs which stem from nucleon-nucleon correlation are proportional to common nucleon PDFs but suppressed by a factor. Compared with the experimental data, we find that dPDFs can explain the behaviour of the EMC effect. We further calculate the Paschos-Wolfenstein ratio to study the nuclear matter effect on the extraction of weak mixing angle or $sin^{2} θ_{W}$ by using dPDFs.
nucl-thhep-phNPA(2025)·1 citation
08
Explicitly correlated Gaussians with tensor pre-factors: analytic matrix elements
D.V. Fedorov · A.F. Teilmann · M.C. Østerlund · T.L. Norrbohm
We consider a specific form of explicitly correlated Gaussians -- with tensor pre-factors -- which appear naturally when dealing with certain few-body systems in nuclear and particle physics. We derive analytic matrix elements with these Gaussians -- overlap, kinetic energy, and Coulomb potential -- to be used in variational calculations of those systems. We also perform a quick test of the derived formulae by applying them to p- and d-waves of the hydrogen atom.
nucl-thFew Body Syst.(2024)·0 citations
09
Fine-structure constant sensitivity of the Th-229 nuclear clock transition
Kjeld Beeks · Georgy A. Kazakov · Fabian Schaden · Ira Morawetz · Luca Toscani de Col · Thomas Riebner · Michael Bartokos · Tomas Sikorsky · Thorsten Schumm · Chuankun Zhang · Tian Ooi · Jacob S. Higgins and 3 other authors
State-resolved laser spectroscopy at the 10 $^{- 12}$ precision level recently reported in $a r X i v$ :2406.18719 determined the fractional change in nuclear quadrupole moment between the ground and isomeric state of $^{229} Th$ , $Δ Q_{0} / Q_{0}$ =1.791(2) %. Assuming a prolate spheroid nucleus, this allows to quantify the sensitivity of the nuclear transition frequency to variations of the fine-structure constant $α$ to $K = 5900 (2300)$ , with the uncertainty dominated by the experimentally measured charge radius difference $Δ ⟨ r^{2} ⟩$ between the ground and isomeric state. This result indicates a three orders of magnitude enhancement over atomic clock schemes based on electron shell transitions. We find that $Δ Q_{0}$ is highly sensitive to tiny changes in the nuclear volume, thus the constant volume approximation cannot be used to accurately relate changes in $⟨ r^{2} ⟩$ and $Q_{0}$ . The difference between the experimental and estimated values in $Δ Q_{0} / Q_{0}$ raises a further question on the octupole contribution to the alpha-sensitivity.
nucl-thnucl-exphysics.atom-phNature Commun.(2025)·38 citations
10
Impact parameter dependence of anisotropic flow: Bayesian reconstruction in ultracentral nucleus-nucleus collisions
Mubarak Alqahtani🇸🇦 · Rajeev S. Bhalerao🇮🇳 · Giuliano Giacalone🇨🇭 · Andreas Kirchner🇩🇪 · Jean-Yves Ollitrault🇫🇷
Peculiar phenomena have been observed in analyses of anisotropic flow ( $v_{n}$ ) fluctuations in ultracentral nucleus-nucleus collisions: The fourth-order cumulant of the elliptic flow ( $v_{2}$ ) distribution changes sign. In addition, the ATLAS collaboration has shown that cumulants of $v_{n}$ fluctuations of all orders depend significantly on the centrality estimator. We show that these peculiarities are due to the fact that the impact parameter $b$ always spans a finite range for a fixed value of the centrality estimator. We provide a quantitative determination of this range through a simple Bayesian analysis. We obtain excellent fits of STAR and ATLAS data, with a few parameters, by assuming that the probability distribution of $v_{n}$ solely depends on $b$ at a given centrality. This probability distribution is almost Gaussian, and its parameters depend smoothly on $b$ , in a way that is constrained by symmetry and scaling laws. We reconstruct, thus, the impact parameter dependence of the mean elliptic flow in the reaction plane in a model-independent manner, and assess the robustness of the extraction using Monte Carlo simulations of the collisions where the impact parameter is known. We argue that the non-Gaussianity of $v_{n}$ fluctuations gives direct information on the hydrodynamic response to initial anisotropies, ATLAS data being consistent with a smaller response for $n = 4$ than for $n = 2$ and $n = 3$ , in agreement with hydrodynamic calculations.
nucl-thhep-exhep-phnucl-exPRC(2024)·8 citations
11
Probing collectivity in heavy-ion collisions with fluctuations of the $p_{T}$ spectrum
Tribhuban Parida🇮🇳 · Rupam Samanta🇵🇱 · Jean-Yves Ollitrault🇫🇷
Event-by-event fluctuations in the initial stages of ultrarelativistic nucleus-nucleus collisions depend little on rapidity. The hydrodynamic expansion which occurs in later stages then gives rise to correlations among outgoing particles which depend weakly on their relative rapidity. Azimuthal correlations, through which anisotropic flow ( $v_{n} (p_{T})$ ) is defined, have been the most studied. Here we study a new observable introduced in 2020 by Schenke, Shen and Teaney and dubbed $v_{0} (p_{T})$ , which quantifies the relative change in the $p_{T}$ spectrum induced by a fluctuation. We describe how it can be measured. Using hydrodynamic simulations, we make quantitative predictions for $v_{0} (p_{T})$ of charged and identified hadrons. We then discuss how $v_{0} (p_{T})$ relates to two phenomena which have been measured: The increase of the mean transverse momentum in ultracentral collisions, and the event-by-event fluctuations of the transverse momentum per particle $[p_{T}]$ . We show that $v_{0} (p_{T})$ determines the dependence of these quantities on the $p_{T}$ cuts implemented in the analysis. We quantitatively explain the rise of $σ_{p_{T}}$ observed by ATLAS as the upper $p_{T}$ -cut is increased from $2$ to $5$ ~GeV/ $c$ .
nucl-thhep-exhep-phnucl-exPLB(2024)·38 citations
12
Wave function of $^{9}$ Be in the three-body (alpha-alpha-n)-model
S. A. Rakityansky
A simple analytic expression of the three-body wave function describing the system $(α α n)$ in the ground state $\frac{3}{2}^{-}$ of $^{9} Be$ is obtained. In doing this, it is assumed that the $α$ particles interact with each other via the $S$ -wave Ali-Bodmer potential including the Coulomb term, and the neutron- $α$ forces act only in the $P$ -wave state. This wave function is constructed by trial and error method via solving in this way a kind of inverse problem when the two-body $α α$ potential is recovered from a postulated three-body wave function. As a result, the wave function is an exact solution of the corresponding three-body Schrödinger equation for experimentally known binding energy and for the $α α$ potential whose difference from the Ali-Bodmer one is minimized by varying the adjustable parameters which the postulated wave function depends on.
nucl-thPRC(2024)·2 citations
13
Covariant formulation of spinodal decomposition in rapidly expanding quark gluon plasma
Joseph I. Kapusta🇺🇸 · Mayank Singh🇺🇸 · Thomas Welle🇺🇸
Quantum Chromodynamics (QCD) is expected to have a first order phase transition between the confined hadron gas and the deconfined quark gluon plasma at high baryon densities. This will result in phase boundary effects in the metastable and unstable regions. It is important to include these effects in phenomenological models of heavy ion collisions to identify experimental signatures of a phase transition. This requires building intuition on phase separation in rapidly expanding fluids. In this work we present the covariant equations of relativistic hydrodynamics with a phase boundary, provide prescriptions to extend the equation of state to metastable and unstable regions, and show the effects of spinodal separation in a Bjorken flow.
↳ hep-phnucl-thPRC(2024)·7 citations
14
Far-from-equilibrium attractors in kinetic theory for a mixture of quark and gluon fluids
Ferdinando Frascà🇮🇹 · Andrea Beraudo🇮🇹 · Michael Strickland
We exactly solve an RTA-Boltzmann equation that describes the dynamics of coupled massless quark and gluon fluids undergoing transversally homogeneous longitudinal boost-invariant expansion. We include a fugacity parameter that allows quarks to be out of chemical equilibrium and we account for the different collision rates of quarks and gluons, which are related by Casimir scaling. Based on these assumptions, we numerically determine the evolution of a large set of moments of the quark and gluon distribution functions and reconstruct their entire distribution functions. We find that both late and early-time attractors exist for all moments of the distribution functions containing more than one power of the squared longitudinal momentum. These attractors emerge long before the system reaches the regime where hydrodynamic approximations apply. In addition, we discuss how the shear viscous corrections and entropy density of the fluid mixture evolve and consider the properties of their respective attractors. Finally, the entropy production is also investigated for different initial values of momentum anisotropy and quark abundance.
↳ hep-phnucl-thNPA(2025)·10 citations
15
A soft-hard framework with exact four momentum conservation for small systems
I. Soudi🇺🇸 · W. Zhao🇺🇸 · A. Majumder🇺🇸 · C. Shen🇺🇸 · J. H. Putschke🇺🇸 · B. Boudreaux🇺🇸 · A. Angerami🇺🇸 · R. Arora🇺🇸 · S. A. Bass🇺🇸 · Y. Chen🇺🇸 · R. Datta🇺🇸 · L. Du🇨🇦 and 41 other authors
A new framework, called x-scape, for the combined study of both hard and soft transverse momentum sectors in high energy proton-proton ( $p$ - $p$ ) and proton-nucleus ( $p$ - $A$ ) collisions is set up. A dynamical initial state is set up using the 3d-Glauber model with transverse locations of hotspots within each incoming nucleon. A hard scattering that emanates from two colliding hotspots is carried out using the Pythia generator. Initial state radiation from the incoming hard partons is carried out in a new module called I-matter, which includes the longitudinal location of initial splits. The energy-momentum of both the initial hard partons and their associated beam remnants is removed from the hot spots, depleting the energy-momentum available for the formation of the bulk medium. Outgoing showers are simulated using the matter generator, and results are presented for both cases, allowing for and not allowing for energy loss. First comparisons between this hard-soft model and single inclusive hadron and jet data from $p$ - $p$ and minimum bias $p$ - $P b$ collisions are presented. Single hadron spectra in $p$ - $p$ are used to carry out a limited (in number of parameters) Bayesian calibration of the model. Fair comparisons with data are indicative of the utility of this new framework. Theoretical studies of the correlation between jet $p_{T}$ and event activity at mid and forward rapidity are carried out.
↳ hep-phhep-exhep-thnucl-thPRC(2025)·17 citations

Affiliations

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