Nuclear Theory·nucl-th

Friday·July 28, 2023

17 papers—8 primary·9 cross-listed

01
Spatial orientation of the fission fragment intrinsic spins and their correlations
Guillaume Scamps · Ibrahim Abdurrahman · Matthew Kafker · Aurel Bulgac · Ionel Stetcu
New experimental and theoretical results obtained in 2021 made it acutely clear that more than 80 years after the discovery of nuclear fission we do not understand the generation and dynamics of fission fragment (FF) intrinsic spins well, in particular their magnitudes, their spatial orientation, and their correlations. The magnitude and orientation of the primary FFs have a crucial role in defining the angular distribution and correlation between the emitted prompt neutrons, and subsequent emission of statistical (predominantly E1) and stretched E2 {\gamma}-rays, and their correlations with the final fission fragments. Here we present detailed microscopic evaluations of the FF intrinsic spins, for both even- and odd-mass FFs, and of their spatial correlations. These point to a well-defined 3D FF intrinsic spin dynamics, characteristics absent in semi-phenomenological studies, due to the presence of the twisting spin modes, which artificially were suppressed in semi-phenomenological studies.
nucl-thPRC(2023)·25 citations
02
Short-range correlations and momentum distributions in mirror nuclei 3H and 3He
Qi Meng · Ziyang Lu · Chang Xu
Motivated by recent high-energy electron and $^{3} H$ and $^{3} He$ nuclei scattering experiment in Jefferson Lab (Nature 609, 41 (2022)), the short-range correlations (SRCs) between nucleon pairs for 3-nucleon systems are microscopically studied using realistic $N N$ 2-body interaction and two-Gaussian type $N N N$ 3-body interaction. The wave functions of both $^{3} H$ and $^{3} He$ are obtained by solving 3-body Schrödinger equations using Gaussian expansion method (GEM). The differences of one-nucleon and nucleon-nucleon momentum distributions between $^{3} H$ and $^{3} He$ are analyzed in detail. The results show that the percentages of $p n$ -SRC pairs are significantly enhanced as compared with those of $nn (pp)$ -SRC ones in $^{3} H$ and $^{3} He$ nuclei, which is consistent with the experimental findings.
nucl-thPRC(2023)·8 citations
03
Three-Dimensional Approach Applied to Quasi-stationary States of Deformed $α$ -Emitters
Ruijia Li · Chang Xu
We apply a three-dimensional (3D) approach to investigate the quasi-stationary states of well-deformed $α$ -emitters. With a splitting of the anisotropic 3D potential into internal and external parts at a separation surface, the 3D $α$ -cluster decay width is determined by the initial wave function of a true bound state of an anisotropic harmonic oscillator potential and a non-resonance scattering wave function of Coulomb potential. Substantial difference between the 1D and 3D decay width is found for typical $α$ -emitters with large quadrupole and hexadecapole deformations.
nucl-thPRC(2023)·3 citations
04
Effects of Critical Point on Quark Gluon Plasma
Md Hasanujjaman🇮🇳
We have used the relativistic second-order causal viscous hydrodynamics equipped with an equation of state which includes the QCD critical point to study the propagation of linear and nonlinear perturbations in quark gluon plasma created in a relativistic heavy-ion collision. We have also studied the behaviour of dynamic structure factor, which is calculated by taking the correlation of dynamical density fluctuation. It is found that the critical point has significant effects on the propagation of linear as well as on nonlinear perturbations. It is also found that the dynamic structure factors are substantially modified with the presence of the QCD critical point.
nucl-th0 citations
05
Elliptic and triangular flow of charmonium states in heavy ion collisions
Sungtae Cho🇰🇷
We study the elliptic and triangular flow of charmonium states, or $J / ψ$ , $ψ (2 S)$ , and $χ_{c} (1 P)$ mesons in heavy ion collisions. Starting from the evaluation of charmonia transverse momentum distributions and yields, we calculate elliptic and triangular flow of charmonium states based on the coalescence model. We show that the internal structure, or the wave function distribution of charmonium states plays a significant role, especially when charmonium states are produced by charm quark recombination, leading to the transverse momentum distribution of the $ψ (2 S)$ meson as half large as that of the $J / ψ$ meson. We also consider the dependence of the elliptic and triangular flow of charmonium states on internal structures of charmonium states, and find that the wave function effects as well as feed-down contributions are averaged out for elliptic and triangular flow, resulting in similar elliptic and triangular flow for all charmonium states. We investigate further the elliptic and triangular flow of charmonium states at low transverse momentum region, and also discuss the quark number scaling of elliptic and triangular flow for charmonium states.
nucl-thhep-phPRC(2024)·4 citations
06
Reexamining charm versus bottom quark energy loss inside a color-deconfined medium
Yichao Dang🇨🇳 · Wen-Jing Xing🇨🇳 · Shanshan Cao🇨🇳 · Guang-You Qin🇨🇳
The general intuition that heavier partons suffer weaker energy loss inside a quark-gluon plasma (QGP) medium is critically re-examined. Within a linear Boltzmann transport model that includes both Yukawa and string types of interactions between heavy quarks and the QGP, we find that while the radiative energy loss is suppressed by the parton mass, heavier partons can experience stronger string potential scatterings with the medium. Their competition may result in less energy loss of bottom quarks than charm quarks at low transverse momentum ( $p_{T}$ ) but an inverse order at high $p_{T}$ . Our model calculation shows a weaker nuclear modification on bottom particles than charm particles at low $p_{T}$ , as observed by both RHIC and LHC experiments, but predicts an opposite hierarchy at high $p_{T}$ . A larger momentum space transport coefficient ( $q^$ ) and a smaller spatial diffusion coefficient ( $D_{s}$ ) are found for bottom quarks than for charm quarks.
nucl-thhep-phnucl-exPRC(2024)·9 citations
07
Triaxial projected shell model approach for negative parity states in even-even nuclei
Nazira Nazir · S. Jehangir · S.P. Rouoof · G.H. Bhat · J.A. Sheikh · N. Rather · Manzoor A. Malik
The triaxial projected shell model (TPSM) approach is generalized to investigate the negative parity band structures in even-even systems. In the earlier version of the TPSM approach, the quasiparticle excitations were restricted to one major oscillator shell and it was possible to study only positive parity states in even-even systems. In the present extension, the excited quasiparticles are allowed to occupy two major oscillator shells, which makes it possible to generate the negative parity states. As a major application of this development, the extended approach is applied to elucidate the negative parity high-spin band structures in $^{102 - 112}$ Ru and it is shown that energies obtained with neutron excitation are slightly lower than the energies calculated with proton excitation. However, the calculated aligned angular momentum ( $i_{x}$ ) clearly separates the two spectra with neutron $i_{x}$ in reasonable agreement with the empirically evaluated $i_{x}$ from the experimental data, whereas proton $i_{x}$ shows large deviations. Furthermore, we have also deduced the transition quadrupole moments from the TPSM wavefunctions along the negative-parity yrast- and yrare- bands and it is shown that these quantities exhibit rapid changes in the bandcrossing region.
nucl-thnucl-exPRC(2023)·9 citations
08
Event Shape Selection Method in Search of the Chiral Magnetic Effect in Heavy-ion Collisions
Zhiwan Xu🇺🇸 · Brian Chan🇺🇸 · Gang Wang🇺🇸 · Aihong Tang🇺🇸 · Huan Zhong Huang🇺🇸
The search for the chiral magnetic effect (CME) in heavy-ion collisions has been impeded by the significant background arising from the anisotropic particle emission pattern, particularly elliptic flow. To alleviate this background, the event shape selection (ESS) technique categorizes collision events according to their shapes and projects the CME observables to a class of events with minimal flow. In this study, we explore two event shape variables to classify events and two elliptic flow variables to regulate the background. Each type of variable can be calculated from either single particles or particle pairs, resulting in four combinations of event shape and elliptic flow variables. By employing a toy model and the realistic event generator, event-by-event anomalous-viscous fluid dynamics (EBE-AVFD), we discover that the elliptic flow of resonances exhibits correlations with both the background and the potential CME signal, making the resonance flow unsuitable for background control. Through the EBE-AVFD simulations of Au+Au collisions at $s_{N N} = 200$ GeV with various input scenarios, we ascertain that the optimal ESS strategy for background control entails utilizing the single-particle elliptic flow in conjunction with the event shape variable based on particle pairs.
nucl-thnucl-exphysics.ins-detPLB(2024)·21 citations
09
Nuclear Reactions in Evolving Stars
Friedrich-Karl Thielemann · Thomas Rauscher
This chapter will go through the important nuclear reactions in stellar evolution and explosions, passing through the individual stellar burning stages and also explosive burning conditions. To follow the changes in the composition of nuclear abundances requires the knowledge of the relevant nuclear reaction rates. For light nuclei (entering in early stellar burning stages) the resonance density is generally quite low and the reactions are determined by individual resonances, which are best obtained from experiments. For intermediate mass and heavy nuclei the level density is typically sufficient to apply statistical model approaches. For this reason, while we discuss all burning stages and explosive burning, focusing on the reactions of importance, we will for light nuclei refer to the chapters by M. Wiescher, deBoer & Reifarth (Experimental Nuclear Astrophysics) and P. Descouvement (Theoretical Studies of Low-Energy Nuclear Reactions), which display many examples, experimental methods utilized, and theoretical approaches how to predict nuclear reaction rates for light nuclei. For nuclei with sufficiently high level densities we discuss statistical model methods used in present predictions of nuclear reaction cross sections and thermonuclear rates across the nuclear chart, including also the application to nuclei far from stability and fission modes.
↳ astro-ph.SRnucl-thHandbook of Nuclear Physics 2023·3 citations
10
Axial-vector transition form factors and $e^{+} e^{-} \to f_{1} π^{+} π^{-}$
Martin Hoferichter🇨🇭 · Bastian Kubis🇩🇪 · Marvin Zanke🇩🇪
We study the transition form factors (TFFs) of axial-vector mesons in the context of currently available experimental data, including new constraints from $e^{+} e^{-} \to f_{1} (1285) π^{+} π^{-}$ that imply stringent limits on the high-energy behavior and, for the first time, allow us to provide an unambiguous determination of the couplings corresponding to the two antisymmetric TFFs. We discuss how these constraints can be implemented in a vector-meson-dominance picture, and, in combination with contributions from the light-cone expansion, construct TFFs as input for the evaluation of axial-vector contributions to hadronic light-by-light scattering in the anomalous magnetic moment of the muon.
↳ hep-phhep-exhep-latnucl-thJHEP(2023)·65 citations
11
Heavy neutron stars from light scalars
Reuven Balkin🇮🇱 · Javi Serra🇪🇸 · Konstantin Springmann🇩🇪 · Stefan Stelzl🇨🇭 · Andreas Weiler🇩🇪
We study how light scalar fields can change the stellar landscape by triggering a new phase of nuclear matter. Scalars coupled to nucleons can develop a non-trivial expectation value at finite baryon density. This sourcing of a scalar reduces the nucleon mass and provides an additional energy density and pressure source. Under generic conditions, a new ground state of nuclear matter emerges, with striking implications for the configuration of stellar remnants. Notably, neutron stars in the new ground state can be significantly heavier than QCD equations of state currently predict. We also find hybrid stellar compositions and stable self-bound objects with sizes as small as the Compton wavelength of the scalar. We discuss several specific realizations of this scenario: the QCD axion and lighter generalizations thereof and linearly or quadratically coupled scalar fields effectively equivalent to a class of scalar-tensor modification of gravity. Lastly, we explore phenomenological signatures relevant to electromagnetic and gravitational wave observations of neutron stars, such as atypical compactness and instability gaps in radii.
↳ hep-phastro-ph.HEgr-qcnucl-thJHEP(2025)·51 citations
12
Fluid dynamics of charm quarks in the quark--gluon plasma
Federica Capellino🇩🇪 · Andrea Dubla🇩🇪 · Stefan Floerchinger🇺🇸 · Eduardo Grossi🇮🇹 · Andreas Kirchner🇩🇪 · Silvia Masciocchi🇩🇪
A fluid-dynamic approach to charm-quark diffusion in the quark-gluon plasma (QGP) is developed for the first time. Results for integrated yields and momentum distributions of charmed hadrons obtained with a fluid-dynamic description for the dynamics of the QGP coupled to an additional heavy-quark-antiquark current are shown. In addition to the thermodynamic Equation of State (EoS), this description uses a heavy-quark diffusion constant which we take from Lattice QCD calculations. The results describe quantitatively experimental data measured at the LHC at the center-of-mass energy of $s_{NN}$ = 5.02 TeV up to $p_{T} \sim$ 4-5 GeV/ $c$ , showing that charm quarks undergo a very fast hydrodynamization in the medium created by ultrarelativistic heavy-ion collisions.
↳ hep-phnucl-thPRD(2023)·27 citations
13
Possible formation of Quark-Gluon Plasma in small collision systems at the Large Hadron Collider: Observations and Challenges
Raghunath Sahoo🇮🇳
With the advent of unprecedented collision energy at the Large Hadron Collider, CERN, Geneva, a new domain of particle production and possible formation of Quark-Gluon Plasma (QGP) in high-multiplicity proton-proton collisions and the collisions of light nuclei has been a much-discussed topic recently. In this review, I discuss some of the recent observations leading to such a possibility, associated challenges, and some predictions for the upcoming light-nuclei collisions at the LHC.
↳ hep-phhep-exnucl-exnucl-thSpringer Proc.Phys.(2024)·2 citations
14
Confronting axial-vector form factor from lattice QCD with MINERvA antineutrino-proton data
Oleksandr Tomalak🇺🇸 · Rajan Gupta🇺🇸 · Tanmoy Bhattacharya🇺🇸
We compare recent MINERvA antineutrino-hydrogen charged-current measurements to phenomenological predictions of the axial-vector form factor based on fits to all available electron scattering and deuterium bubble-chamber data and to representative lattice-QCD (LQCD) determination by the PNDME Collaboration. While there is $1$ -- $2 σ$ agreement in the cross section with MINERvA data for each bin in $Q^{2}$ , we identify three regions with different relevance and opportunity for LQCD predictions. For $Q^{2} ≲ 0.2 GeV^{2}$ , the phenomenological extractions have large number of data points and LQCD is competitive, while MINERvA data have large errors. For $0.2 GeV^{2} ≲ Q^{2} ≲ 1 GeV^{2}$ , LQCD is competitive with the MINERvA determination, and both give values larger than from phenomenological extraction. For $Q^{2} > 1 GeV^{2}$ , the MINERvA data are the most precise. Our analysis indicates that with improving precision of MINERvA-like experiments and LQCD data, the uncertainty in the nucleon axial-vector form factor will be steadily reduced.
↳ hep-lathep-exhep-phnucl-ex+1PRD(2023)·27 citations
15
Single inclusive particle production at next-to-leading order in proton-nucleus collisions at forward rapidities: hybrid approach meets TMD factorization
Tolga Altinoluk🇵🇱 · Néstor Armesto🇪🇸 · Alexander Kovner🇺🇸 · Michael Lublinsky🇮🇱
We revisit the calculation of the cross section for forward inclusive single hadron production in $p A$ collisions within the hybrid approach. We show that the proper framework to perform this calculation beyond leading order is not the collinear factorization, as has been assumed so far, but the TMD factorized framework. Within the TMD factorized approach we show that all the large transverse logarithms appearing in the fixed order calculation, are resummed into the evolution of the TMD PDFs and TMD FFs with factorization scale. The resulting expressions, when written in terms of TMDs evolved to the appropriate, physically well understood factorization scale, contain no additional large logarithms. The absence of any large logarithms in the resummed result should ensure positivity of the cross section and eradicate the persistent problem that have plagued the previous attempts at calculating this observable in the hybrid approach.
↳ hep-phnucl-thPRD(2023)·15 citations
16
Helical Separation Effect and helical heat transport for Dirac fermions
Victor E. Ambruş🇷🇴 · Maxim N. Chernodub🇫🇷
An ensemble of massless fermions can be characterized by its total helicity charge given by the sum of axial charges of particles minus the sum of axial charges of antiparticles. We show that charged massless fermions develop a dissipationless flow of helicity along the background magnetic field. We dub this transport phenomenon as the Helical Separation Effect (HSE). Contrary to its chiral cousin, the Chiral Separation Effect, the HSE produces the helical current in a neutral plasma in which all chemical potentials vanish. In addition, we uncover the Helical Magnetic Heat Effect which generates a heat flux of Dirac fermions along the magnetic field in the presence of non-vanishing helical charge density. We also discuss possible hydrodynamic modes associated with the HSE in neutral plasma.
↳ hep-thcond-mat.mes-hallnucl-thEPJC(2024)·3 citations
17
Lattice quantum chromodynamics at large isospin density: 6144 pions in a box
Ryan Abbott🇺🇸 · William Detmold🇺🇸 · Fernando Romero-López🇺🇸 · Zohreh Davoudi🇺🇸 · Marc Illa🇺🇸 · Assumpta Parreño🇪🇸 · Robert J. Perry🇪🇸 · Phiala E. Shanahan🇺🇸 · Michael L. Wagman🇺🇸
We present an algorithm to compute correlation functions for systems with the quantum numbers of many identical mesons from lattice quantum chromodynamics (QCD). The algorithm is numerically stable and allows for the computation of $n$ -pion correlation functions for $n \in {1, \dots, N}$ using a single $N \times N$ matrix decomposition, improving on previous algorithms. We apply the algorithm to calculations of correlation functions with up to 6144 $π^{+}$ s using two ensembles of gauge field configurations generated with quark masses corresponding to a pion mass $m_{π} = 170$ MeV and spacetime volumes of $(4. 4^{3} \times 8.8) fm^{4}$ and $(5. 8^{3} \times 11.6) fm^{4}$ . We also discuss statistical techniques for the analysis of such systems, in which the correlation functions vary over many orders of magnitude. In particular, we observe that the many-pion correlation functions are well approximated by log-normal distributions, allowing the extraction of the energies of these systems. Using these energies, the large-isospin-density, zero-baryon-density region of the QCD phase diagram is explored. A peak is observed in the energy density at an isospin chemical potential $μ_{I} \sim 1.5 m_{π}$ , signalling the transition into a Bose-Einstein condensed phase. The isentropic speed of sound in the medium is seen to exceed the ideal-gas (conformal) limit ( $c_{s}^{2} \leq 1/3$ ) over a wide range of chemical potential before falling towards the asymptotic expectation at $μ_{I} \sim 15 m_{π}$ . These, and other thermodynamic observables, indicate that the isospin chemical potential must be large for the system to be well described by an ideal gas or perturbative QCD.
↳ hep-lathep-phnucl-thPRD(2023)·80 citations

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