Nuclear Theory·nucl-th

Wednesday·June 21, 2023

18 papers—8 primary·10 cross-listed

01
Polarized Photons from the Early Stages of Relativistic Heavy-Ion Collisions
Sigtryggur Hauksson🇫🇷 · Charles Gale🇨🇦
The polarization of real photons emitted from early-time heavy-ion collisions is calculated, concentrating on the contribution from bremsstrahlung and quark-antiquark annihilation processes at leading order in the strong coupling. The effect of an initial momentum space anisotropy of the parton distribution is evaluated using a model for the non-equilibrium scattering kernel for momentum broadening. The effect on the photon polarization is reported for different degrees of anisotropy. The real photons emitted early during in-medium interactions will be dominantly polarized along the beam axis.
nucl-thhep-phPRC(2024)·13 citations
02
Quantum theory of isomeric excitation of $^{229}$ Th in strong laser fields
Wu Wang · Xu Wang
A general quantum mechanical theory is developed for the isomeric excitation of $^{229}$ Th in strong femtosecond laser pulses. The theory describes the tripartite interaction between the nucleus, the atomic electrons, and the laser field. The nucleus can be excited both by the laser field and by laser-driven electronic transitions. Numerical results show that strong femtosecond laser pulses are very efficient in exciting the $^{229}$ Th nucleus, yielding nuclear excitation probabilities on the order of $1 0^{- 11}$ per nucleus per pulse. Laser-driven electronic excitations are found to be more efficient than direct optical excitations.
nucl-thphysics.atom-phPRResearch(2023)·7 citations
03
Relativistic two-body currents for one-nucleon knockout in electron-nucleus scattering
T. Franco-Munoz · J. García-Marcos · R. González-Jiménez · J.M. Udías
We present a detailed study of the contribution from two-body currents to the one-nucleon knockout process induced by electromagnetic interaction. The framework is a relativistic mean-field model (RMF) in which bound and scattering nucleons are consistently described as solutions of Dirac equation with potentials. We show results obtained with the most general expression of the two-body operator, in which the intermediate nucleons are described by relativistic mean-field bound states; then, we propose two approximations consisting in describing the intermediate states as nucleons in a relativistic Fermi gas, preserving the complexity and consistency in the initial and final states. These approximations simplify the calculations considerably, allowing us to provide outcomes in a reasonable computational time. The results obtained under these approximations are validated by comparing with those from the full model. Additionally, the theoretical predictions are compared with experimental data of the longitudinal and transverse responses of carbon 12. The agreement with data is outstanding for the longitudinal response, where the contribution from the two-body operator is negligible. In the transverse sector, the two-body current increases the response from 30 to 15%, depending on the approximations and kinematics, in general, improving the agreement with data.
nucl-thPRC(2023)·19 citations
04
Constraining the Woods-Saxon potential in fusion reactions based on the neural network
Zepeng Gao · Siyu Liu · Peiwei Wen · Zehong Liao · Yu Yang · Jun Su · Yongjia Wang · Long Zhu
The accurate determination of the nuclear interaction potential is essential for predicting the fusion cross sections and understanding the reaction mechanism, which plays an important role in the synthesis of superheavy elements. In this work, the neural network, which combines with the calculations of the fusion cross sections via the Hill-Wheeler formula, is developed to optimize the parameters of the Woods-Saxon potential by comparing the experimental values. The correlations between the parameters of Woods-Saxon potential and the reaction partners, which can be quantitatively fitted to a sigmoid-like function with the mass numbers, have been displayed manifestly for the first time. This study could promote the accurate estimation of nucleus-nucleus interaction potential in low energy heavy-ion collisions.
nucl-thPRC(2024)·13 citations
05
Analysis of a Skyrme energy density functional with deep learning
N. Hizawa · K. Hagino · K. Yoshida
Over the past decade, machine learning has been successfully applied in various fields of science. In this study, we employ a deep learning method to analyze a Skyrme energy density functional (Skyrme-EDF), that is a Kohn-Sham type functional commonly used in nuclear physics. Our goal is to construct an orbital-free functional that reproduces the results of the Skyrme-EDF. To this end, we first compute energies and densities of a nucleus with the Skyrme Kohn-Sham + Bardeen-Cooper-Schrieffer method by introducing a set of external fields. Those are then used as training data for deep learning to construct a functional which depends only on the density distribution. Applying this scheme to the $^{24}$ Mg nucleus with two distinct random external fields, we successfully obtain a new functional which reproduces the binding energy of the original Skyrme-EDF with an accuracy of about 0.04 MeV. The rate at which the neural network outputs the energy for a given density is about $1 0^{5}$ -- $1 0^{6}$ times faster than the Kohn-Sham scheme, demonstrating a promising potential for applications to heavy and superheavy nuclei, including the dynamics of fission.
nucl-thcond-mat.dis-nnPRC(2023)·15 citations
06
Bulk and neutron-proton asymmetry coefficients of the semi-empirical mass formula tuned to ground state mass excess of AME2020 and/or FRDM(2012)
Dalip Singh Verma · Vivek · Kushmakshi
Davidson et al. has extended Seeger's mass formula to non-zero excitation energies by introducing temperature-dependent coefficients in the liquid drop energy part of the semi-empirical mass formula, without considering the shell effects. The semi-empirical mass formula of Davidson et al. is applicable for the compound nucleus temperatures less than or equal to 4 MeV. The mass excess calculated using this mass formula including shell effects/corrections does not reproduce the ground state mass excesses of the new atomic mass evaluation data AME2020 and/or FRDM(2012) with its coefficients at zero temperature. So, the coefficients of the semi-empirical mass formula are needed to be tuned to reproduce the ground state mass excess of the nuclei in the recent atomic mass evaluation data AME2020 and/or FRDM(2012). The bulk and neutron-proton asymmetry coefficients of the semi-empirical mass formula of Davidson et al. with shell effects have been tuned to reproduce the mass excess data for all the nuclei of AME2020 (Z=1-118 and A=1-295) and the nuclei of FRDM(2012) (Z=8-136 and A=16-339, except 3456 nuclei which are also available in the AME2020 data) at zero temperature, i.e., the coefficients are tuned for 9420 nuclei known at present. The tuned bulk and neutron-proton asymmetry coefficients reproduce the mass excess of the new atomic mass evaluation data AME2020 and/or FRDM(2012) within a difference of less than 1 MeV and can be used for the applications/investigations in the areas of physics where high energies are experienced or nuclei involved are in excited states, e.g., fusion-evaporation and fusion-fission processes in heavy-ion reactions.
nucl-thAtom.Data Nucl.Data Tabl.(2024)·4 citations
07
Floating block method for quantum Monte Carlo simulations
Avik Sarkar🇩🇪 · Dean Lee🇺🇸 · Ulf-G. Meißner🇩🇪
Quantum Monte Carlo simulations are powerful and versatile tools for the quantum many-body problem. In addition to the usual calculations of energies and eigenstate observables, quantum Monte Carlo simulations can in principle be used to build fast and accurate many-body emulators using eigenvector continuation or design time-dependent Hamiltonians for adiabatic quantum computing. These new applications require something that is missing from the published literature, an efficient quantum Monte Carlo scheme for computing the inner product of ground state eigenvectors corresponding to different Hamiltonians. In this work, we introduce an algorithm called the floating block method, which solves the problem by performing Euclidean time evolution with two different Hamiltonians and interleaving the corresponding time blocks. We use the floating block method and nuclear lattice simulations to build eigenvector continuation emulators for energies of $^{4}$ He, $^{8}$ Be, $^{12}$ C, and $^{16}$ O nuclei over a range of local and non-local interaction couplings. From the emulator data, we identify the quantum phase transition line from a Bose gas of alpha particles to a nuclear liquid.
nucl-thcond-mat.quant-gashep-latquant-phPRL(2023)·10 citations
08
Decay properties of undetected superheavy nuclei with Z>110
A. Jain · P. K. Sharma · S. K. Jain · Dashty T. Akrawy · G. Saxena
A comprehensive study of favoured and unfavoured $α$ -decay, cluster decay, weak-decay along with spontaneous fission in undetected superheavy nuclei within the range for proton number 111 $\leq$ Z $\leq$ 118 and neutron number 161 $\leq$ N $\leq$ 192 is performed. Half-lives for various mentioned decays are estimated with good accuracy on the basis of NUBASE2020 and are found in excellent match with the known half-lives. $α$ -decay mode is found most probable in this wide range and correspondingly potential $α$ -decay chains are reckoned. Peculiarly, the chances of cluster emission, as well as weak-decay, are also anticipated in this region of the periodic chart which open new pathways of detection of superheavy nuclei.
nucl-thPhys.Scripta(2023)·6 citations
09
Quark mass difference effects in hadronic Fermi matrix elements from first principles
Chien-Yeah Seng🇺🇸 · Vincenzo Cirigliano🇺🇸 · Xu Feng🇨🇳 · Mikhail Gorchtein🇩🇪 · Luchang Jin🇺🇸 · Gerald A. Miller🇺🇸
It was recently estimated that the strong isospin-symmetry breaking (ISB) corrections to the Fermi matrix element in free neutron decay could be of the order $1 0^{- 4}$ , one order of magnitude larger than the na\"ıve estimate based on the Behrends-Sirlin-Ademollo-Gatto theorem. To investigate this claim, we derive a general expression of the leading ISB correction to hadronic Fermi matrix elements, which takes the form of a four-point correlation function in lattice gauge theory and is straightforward to compute from first principles. Our formalism paves the way for the first determination of such correction in the neutron sector with fully-controlled theory uncertainties.
↳ hep-phhep-exhep-latnucl-ex+1PLB(2023)·7 citations
10
Skyrmions at Finite Density
Fabrizio Canfora🇨🇱 · Scarlett C. Rebolledo-Caceres🇨🇱
In this paper, we will describe recent advances in analytical methods to construct exact solutions of the Skyrme model (and its generalizations) representing inhomogeneous Hadronic condensates living at finite Baryon density. Such novel analytical tools are based on the idea to generalize the well known spherical hedgehog ansatz to situations (relevant for the analysis of finite density effects) in which there is no spherical symmetry anymore. Besides the intrinsic mathematical interest to find exact solutions with non-vanishing Baryonic charge confined to a finite volume, this framework opens the possibility to compute important physical quantities which would be difficult to compute otherwise.
↳ hep-thhep-phnucl-thMod.Phys.Lett.A(2023)·4 citations
11
Core-corona procedure and microcanonical hadronization to understand strangeness enhancement in proton-proton and heavy ion collisions in the EPOS4 framework
K. Werner🇫🇷
The multiplicity dependence of multistrange hadron yields in proton-proton and lead-lead collisions at several TeV allows one to study the transition from very big to very small systems, in particular, concerning collective effects. I investigate this, employing a core-corona approach based on new microcanonical hadronization procedures in the EPOS4 framework, as well as new methods allowing one to transform energy-momentum flow through freeze-out surfaces into invariant-mass elements. I try to disentangle effects due to ``canonical suppression'' and ``core-corona separation'', which will both lead to a reduction of the yields at low multiplicity.
↳ hep-phnucl-thPRC(2024)·72 citations
12
Helicity of Quarks and Gluons at Small Bjorken $x$
Yossathorn Tawabutr🇺🇸
The proton spin puzzle is a longstanding problem in high-energy nuclear physics: how the proton spin distributes among the spin and orbital angular momenta of the quarks and gluons inside. Two of the unresolved pieces of the puzzle are the contributions to quark and gluon spins from the region of small Bjorken $x$ . This dissertation fills the gap by constructing the evolution of these quantities into the small- $x$ region using a modified dipole formalism. The dominant contributions to the evolution equations resum powers of $α_{s} ln^{2} (1/ x)$ , where $α_{s}$ is the strong coupling constant. In general, these evolution equations do not close. However, once the large- $N_{c}$ or large- $N_{c} & N_{f}$ limit is taken, they turn into a system of linear integral equations that can be solved iteratively. At large $N_{c}$ , the evolution equations are shown to be consistent with the gluon sector of the polarized DGLAP evolution in the small- $x$ limit. We numerically solve the equations in the large- $N_{c}$ and large- $N_{c} & N_{f}$ limits and obtain the exponential growth in $ln (1/ x)$ for $N_{f} \leq 5$ , with the intercept decreasing with $N_{f}$ . For the large- $N_{c}$ limit, we have $α_{h} = 3.66$ , which agrees up to the uncertainty with the earlier work by Bartels, Ermolaev and Ryskin. Furthermore, at $N_{f} = 6$ , the asymptotic form attains an oscillation in $ln (1/ x)$ on top of the exponential growth, with the period spanning several units of rapidity. Finally, parts of the single-logarithmic corrections to the small- $x$ helicity evolution is also derived, resumming powers of $α_{s} ln (1/ x)$ . There, the effects of the unpolarized small- $x$ evolution and the running coupling are also included for consistency. The complete single-logarithmic corrections can be derived based on the framework established here. Altogether, these equations will provide the most precise small- $x$ helicity evolution to date.
↳ hep-phhep-exnucl-exnucl-th4 citations
13
Effect of finite volume on thermodynamics of quark-hadron matter
Somenath Pal🇮🇳 · Anton Motornenko🇩🇪 · Volodymyr Vovchenko🇩🇪 · Abhijit Bhattacharyya🇮🇳 · Jan Steinheimer🇩🇪 · Horst Stoecker🇩🇪
The effects of a finite system volume on thermodynamic quantities, such as the pressure, energy density, specific heat, speed of sound, conserved charge susceptibilities and correlations, in hot and dense strongly interacting matter are studied within the parity-doublet Chiral Mean Field (CMF) model. Such an investigation is motivated by relativistic heavy-ion collisions, which create a blob of hot QCD matter of a finite volume, consisting of strongly interacting hadrons and potentially deconfined quarks and gluons. The effect of the finite volume of the system is incorporated by introducing a lower momentum cut-offs in the momentum integrals appearing in the model, the numerical value of the momentum cut-off being related to the de Broglie wavelength of the given particle species. It is found that some of these quantities show a significant volume dependence, in particular those sensitive to pion degrees of freedom, and the crossover transition is generally observed to become smoother in finite volume. These findings are relevant for the effective equation of state used in fluid dynamical simulations of heavy-ion collisions and efforts to extract the freeze out properties of heavy-ion collisions with susceptibilities involving electric charge and strangeness.
↳ hep-phnucl-thPRD(2024)·8 citations
14
Exclusive $η_{c}$ production from small- $x$ evolved Odderon at a electron-ion collider
Sanjin Benić🇭🇷 · Davor Horvatić🇭🇷 · Abhiram Kaushik🇭🇷 · Eric Andreas Vivoda🇭🇷
We compute exclusive $η_{c}$ production in high energy electron-nucleon and electron-nucleus collisions that is sensitive to the Odderon. In perturbative QCD the Odderon is a $C$ -odd color singlet consisting of at least three $t$ -channel gluons exchanged with the target. By using the Color Glass Condensate effective theory our result describes the Odderon exchange at the high collision energies that would be reached at a future electron-ion collider. The Odderon distribution is evolved to small- $x$ using the Balitsky-Kovchegov evolution equation with running coupling corrections. We find that while at low momentum transfers $t$ the cross section off a proton is dominated by the Primakoff process, the Odderon becomes relevant at larger momentum transfers of $∣ t ∣ \geq 1.5$ GeV $^{2}$ . We point that the Odderon could also be extracted at low- $t$ using neutron targets since the Primakoff component is strongly suppressed. In the case of nuclear targets, the Odderon cross section becomes enhanced thanks to the mass number of the nuclear target. The gluon saturation effect induces a shift in the diffractive pattern with respect to the Primakoff process that could be used as a signal for the Odderon.
↳ hep-phnucl-thPRD(2023)·18 citations
15
Two and three photon fusion into charmonium in ultra-peripheral nuclear collisions
R. Fariello🇧🇷 · D. Bhandari🇺🇸 · C.A. Bertulani🇺🇸 · F.S. Navarra🇺🇸
In this paper we investigate the production of charmonium states in two and three photon fusion processes in nucleus -- nucleus collisions at the CERN Large Hadron Collider (LHC) energies. Our results indicate that the experimental study of these processes is feasible and can be used to constrain the theoretical decay widths and give information on the non $c - c ˉ$ components of these states.
↳ hep-phnucl-thPRC(2023)·12 citations
16
Distinctive nuclear signatures of low-energy atmospheric neutrinos
Anna M. Suliga🇺🇸 · John F. Beacom🇺🇸
New probes of neutrino mixing are needed to advance precision studies. One promising direction is via the detection of low-energy atmospheric neutrinos (below a few hundred MeV), to which a variety of near-term experiments will have much-improved sensitivity. Here we focus on probing these neutrinos through distinctive nuclear signatures of exclusive neutrino-carbon interactions -- those that lead to detectable nuclear-decay signals with low backgrounds -- in both neutral-current and charged-current channels. The neutral-current signature is a line at 15.11 MeV and the charged-current signatures are two- or three-fold coincidences with delayed decays. We calculate the prospects for identifying such events in the Jiangmen Underground Neutrino Observatory (JUNO), a large-scale liquid-scintillator detector. A five-year exposure would yield about 16 neutral-current events (all flavors) and about 16 charged-current events (mostly from $ν_{e} + ν ˉ_{e}$ , with some from $ν_{μ} + ν ˉ_{μ}$ ), and thus roughly 25\% uncertainties on each of their rates. Our results show the potential of JUNO to make the first identified measurement of sub-100 MeV atmospheric neutrinos. They also are a step towards multi-detector studies of low-energy atmospheric neutrinos, with the goal of identifying additional distinctive nuclear signatures for carbon and other targets.
↳ hep-phastro-ph.HEnucl-thPRD(2023)·10 citations
17
The $γ$ -process nucleosynthesis in core-collapse supernovae. I. A novel analysis of $γ$ -process yields in massive stars
L. Roberti · M. Pignatari · A. Psaltis · A. Sieverding · P. Mohr · Zs. Fülöp · M. Lugaro
The $γ$ -process nucleosynthesis in core-collapse supernovae is generally accepted as a feasible process for the synthesis of neutron-deficient isotopes beyond iron. However, crucial discrepancies between theory and observations still exist: the average production of $γ$ -process yields from massive stars are too low to reproduce the solar distribution in galactic chemical evolution calculations, and the yields of the Mo and Ru isotopes are by a further factor of 10 lower than the yields of the other $γ$ -process nuclei. We investigate the $γ$ -process in 5 sets of core-collapse supernova models published in literature with initial masses 15, 20, and 25 M $_{⊙}$ at solar metallicity. We compared the $γ$ -process overproduction factors from the different models. To highlight the possible effect of nuclear physics input, we also considered 23 ratios of two isotopes close to each other in mass, relative to their solar values. Further, we investigated the contribution of C-O shell mergers in the supernova progenitors as an additional site of the $γ$ -process. Our analysis shows that a large scatter among the different models exists for both the $γ$ -process integrated yields and the isotopic ratios. We found only 10 ratios that agree with their solar values, all the others differ by at least a factor of 3 from the solar values in all the considered sets of models. The $γ$ -process within C-O shell mergers mostly influence the isotopic ratios that involve intermediate and heavy proton-rich isotopes with $A > 100$ .
↳ astro-ph.SRastro-ph.HEnucl-thAstron.Astrophys.(2023)·21 citations
18
iQMC: Iterative Quasi-Monte Carlo for k-Eigenvalue Neutron Transport Simulations
Samuel Pasmann · Ilham Variansyah · C.T. Kelley · Ryan G. McClarren
The Iterative Quasi-Monte Carlo method, or iQMC, replaces standard quadrature techniques used in deterministic linear solvers with Quasi-Monte Carlo simulation for more accurate and efficient solutions to the neutron transport equation. This work explores employing iQMC in the Monte-Carlo Dynamic Code (MCDC) to solve k-eigenvalue problems for neutron transport with both the standard power iteration and the generalized Davidson method, a Krylov Subspace method. Results are verified with the 3-D, 2-group, Takeda-1 Benchmark problem.
↳ physics.comp-phnucl-th0 citations

Affiliations

first authorsco-authorsvia INSPIRE