Nuclear Theory·nucl-th

Tuesday·October 13, 2020

15 papers—9 primary·6 cross-listed

01
[Submitted on 9 Oct 2020]
Impact of Three-Body Forces on Elastic Nucleon-Nucleus Scattering Observables
Matteo Vorabbi🇺🇸 · Michael Gennari🇨🇦 · Paolo Finelli🇮🇹 · Carlotta Giusti🇮🇹 · Peter Navrátil🇨🇦 · Ruprecht Machleidt🇺🇸
In a previous series of papers we investigated the domain of applicability of chiral potentials to the construction of a microscopic optical potential (OP) for elastic nucleon-nucleus scattering. The final expression of the OP was a folding integral between the nucleon-nucleon ( $N N$ ) $t$ matrix and the nuclear density of the target. In these calculations $N N$ and three-nucleon ( $3 N$ ) chiral interactions were used for the target density and only the $N N$ interaction for the $N N$ $t$ matrix. The purpose of this work is to achieve another step towards the calculation of a more consistent OP introducing the $3 N$ force also in the dynamic part of the OP. In the present work this is approximated with a density dependent $N N$ interaction obtained after the averaging over the Fermi sphere. In practice, in our model the $3 N$ force acts as a medium correction of the bare $N N$ interaction used to calculate the $N N$ $t$ matrix. Even if the $3 N$ force is treated in an approximate way, this method naturally extends our previous model of the OP and allows a direct comparison of our present and previous results. We consider as case studies the elastic scattering of nucleons off $^{12}$ C and $^{16}$ O. We present results for the differential cross section and the spin observables for different values of the projectile energy. From the comparison with the experimental data and with the results of our previous model we assess the importance of the $3 N$ interaction in the dynamic part of the OP. Our analysis indicates that the contribution of the $3 N$ force in the $t$ matrix is small for the differential cross section and it is sizable for the spin observables, in particular, for the analyzing power. A chiral expansion order-by-order analysis of the scattering observables confirms the convergence of our results at the next-to-next-to-next-to-leading-order, as already established in our previous work.
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2010.04792 [pdf]
PRC(2021)·19 citations
02
[Submitted on 10 Oct 2020]
Electroweak decay of quark matter within dense astrophysical combustion flames
J. A. Rosero-Gil🇧🇷 · G. Lugones🇧🇷
We study the weak interaction processes taking place within a combustion flame that converts dense hadronic matter into quark matter in a compact star. Using the Boltzmann equation we follow the evolution of a small element of just deconfined quark matter all along the flame interior until it reaches chemical equilibrium at the back boundary of the flame. We obtain the reaction rates and neutrino emissivities of all the relevant weak interaction processes without making any assumption about the neutrino degeneracy. We analyse systematically the role the initial conditions of unburnt hadronic matter, such as density, temperature, neutrino trapping and composition, focusing on typical astrophysical scenarios such as cold neutron stars, protoneutron stars, and post merger compact objects. We find that the temperature within the flame rises significantly in a timescale of 1 nanosecond. The increase in $T$ strongly depends on the initial strangeness of hadronic matter and tends to be more drastic at larger densities. Typical final values range between $20$ and $60 MeV$ . The nonleptonic process $u + d \to u + s$ is always dominant in cold stars, but in hot objects the process $u + e^{-} \leftrightarrow d + ν_{e}$ becomes relevant, and in some cases dominant, near chemical equilibrium. The rates for the other processes are orders of magnitude smaller. We find that the neutrino emissivity per baryon is very large, leading to a total energy release per baryon of $2 - 60 MeV$ in the form of neutrinos along the flame. We discuss some astrophysical consequences of the results.
Comments:
19 pages, 16 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2010.04861 [pdf]
PRC(2021)·1 citation
03
[Submitted on 10 Oct 2020]
Hypertriton states from inverse scattering theory
Emile Meoto🇿🇦 · Mantile Lekala🇿🇦
The primary goal of this paper is to demonstrate that inverse scattering theory is a viable method for the simulation of lambda-nucleon potentials in hypernuclear few-body studies. To this end, we investigate the hypertriton, modelled as a $Λ n p$ three-body system in the $J^{π} = 1/ 2^{+}$ and $3/ 2^{+}$ channels. This three-body problem is solved using a hyperspherical-harmonic expansion of the Faddeev equations. The $Λ p$ and $Λ n$ interactions are modelled by the GLM-YN0 potentials. These simulated potentials were recovered through Gel'fand--Levitan--Marchenko inverse scattering theory as phase-equivalent simulations of the NSC97f meson-exchange model. The neutron-proton interaction is described by the semi-realistic Malfliet--Tjon I/III potential, with both singlet and triplet channels retained. For the ground state ( $J^{π} = 1/ 2^{+}$ ), we obtain a binding energy of $- 2.335$ ~MeV, corresponding to a $Λ$ separation energy of $B_{Λ} = + 0.104$ ~MeV relative to the $Λ + d$ breakup threshold. This value is comparable to those from lambda-nucleon potentials that are simulated through G-matrix methods. The excited $J^{π} = 3/ 2^{+}$ state is found to have a lambda separation energy of $B_{Λ} = - 1.444$ ~MeV relative to the $Λ + d$ breakup threshold, confirming that there is no bound excited hypertriton state.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2010.05070 [pdf]
1 citation
04
[Submitted on 11 Oct 2020]
Two-proton radioactivity within a generalized liquid drop model
J. P. Cui · Y. H. Gao · Y. Z. Wang · J. Z. Gu
The generalized liquid drop model (GLDM) is firstly extended to study the two-proton ( $2 p$ ) radioactivity half-lives of the ground-state of nuclei. According to the comparison between the calculated half-lives and the experimental data, it is shown that the GLDM describes the $2 p$ radioactivity half-lives well. In addition, by comparing its accuracy with other models, it is found that the GLDM has a comparable accuracy with them. Finally, the $2 p$ radioactivity half-lives of some most probable candidates are predicted with the GLDM by inputting the \textit{Q} $_{2 p}$ values (the released energy of the $2 p$ radioactivity) from the updated AME 2016 Mass Table, which may be useful for future experiments.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2010.05157 [pdf]
PRC(2020)·50 citations
05
[Submitted on 11 Oct 2020]
Reaction rate weighted multilayer nuclear reaction network
H. L. Liu · D. D. Han · P. Ji · Y. G. Ma
Nuclear reaction rate ( $λ$ ) is a significant factor in the process of nucleosynthesis. A multi-layer directed-weighted nuclear reaction network in which the reaction rate as the weight, and neutron, proton, $^{4}$ He and the remainder nuclei as the criterion for different reaction-layers is for the first time built based on all thermonuclear reactions in the JINA REACLIB database. Our results show that with the increase of the stellar temperature ( $T_{9}$ ), the distribution of nuclear reaction rates on the $R$ -layer network demonstrates a transition from unimodal to bimodal distributions. Nuclei on the $R$ -layer in the region of $λ = [1, 2.5 \times 1 0^{1}]$ have a more complicated out-going degree distribution than the one in the region of $λ = [1 0^{11}, 1 0^{13}]$ , and the number of involved nuclei at $T_{9} = 1$ is very different from the one at $T_{9} = 3$ . The redundant nuclei in the region of $λ = [1, 2.5 \times 1 0^{1}]$ at $T_{9} = 3$ prefer $(γ, p)$ and $(γ, α)$ reactions to the ones at $T_{9} = 1$ , which produce nuclei around the $β$ stable line. This work offers a novel way to the big-data analysis on nuclear reaction network at stellar temperatures.
Comments:
6 pages, 4 figures, 2 tables
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2010.05257 [pdf]
Chin.Phys.Lett.(2020)·5 citations
06
[Submitted on 11 Oct 2020]
Azimuthal anisotropy and multiplicities of hard photons and free nucleons in intermediate-energy heavy-ion collisions
S. S. Wang🇨🇳 · Y. G. Ma🇨🇳 · X. G. Cao🇨🇳 · D. Q. Fang🇨🇳 · C. W. Ma🇨🇳
Anisotropic flow can offer significant information of evolution dynamics in heavy-ion collisions. A systematic study of the directed flow $v_{1}$ and elliptic flow $v_{2}$ of hard photons and free nucleons is performed for $^{40}$ Ca+ $^{40}$ Ca collisions in a framework of isospin dependent quantum molecular dynamics (IQMD) model. The study firstly reveals that thermal photons emitted in intermediate-energy heavy-ion collisions have the behaviors of directed and elliptic flows. The interesting phenomena of incident energy dependence of $v_{1}$ and $v_{2}$ for thermal photons in central collisions also confirmed that it can be regarded as a good probe of evolution dynamics. Moreover, the multiplicities of hard photons and free nucleons and their correlation are also investigated. We find that direct photon emission is positively related to free nucleons emission, however, there exists an anti-correlation for thermal photons with free nucleons.
Comments:
9 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2010.05261 [pdf]
EPJA(2020)·4 citations
07
[Submitted on 12 Oct 2020]
Effect of the crust on neutron star empirical relations
Márcio Ferreira🇵🇹 · Constança Providência🇵🇹
We analyze how the crust equation of state affects several neutron star properties and how it impacts on possible constraints inferred from astrophysical observations. Using three distinct crusts, we generate three sets of model-independent equations of state describing stellar matter from a Taylor expansion around saturation density. The equations of state are thermodynamically consistent, causal, and compatible with astrophysical observations. The relations between the tidal deformability $Λ$ and compactness $C$ , Love number $k_{2}$ and radius of neutron star with mass $M$ are studied, and the effect of the crust equation of state on these relations analyzed. In most of the relations, the impact of the crust equation of state is not larger that 2\%. If, however, a fixed neutron star mass is considered, the relation between the tidal deformability and the radius depends on the crust. We have found that the relation $Λ_{M_{i}} = α R_{M_{i}}^{β}$ becomes almost exact and crust independent for massive neutron stars. It is shown that it is possible to determine the tidal deformability of an 1.4 $M_{⊙}$ star from the GW179817 effective tidal deformability $Λ ~$ with an accuracy of at least $\approx 10%$ . A high correlation between $Λ ~$ and the radius of the most massive star of the neutron star binary was confirmed, however, it was demonstrated that the crust has an effect of $\approx 14%$ on this relation. We have found that the relation $Λ_{1} / Λ_{2} = q^{a}$ depends on $M_{chirp}$ as $a \sim M_{chirp}$ .
Comments:
16 pages, 14 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
2010.05588 [pdf]
PRD(2020)·11 citations
08
[Submitted on 12 Oct 2020]
Optimization and Supervised Machine Learning Methods for Fitting Numerical Physics Models without Derivatives
Raghu Bollapragada · Matt Menickelly · Witold Nazarewicz · Jared O'Neal · Paul-Gerhard Reinhard · Stefan M. Wild
We address the calibration of a computationally expensive nuclear physics model for which derivative information with respect to the fit parameters is not readily available. Of particular interest is the performance of optimization-based training algorithms when dozens, rather than millions or more, of training data are available and when the expense of the model places limitations on the number of concurrent model evaluations that can be performed. As a case study, we consider the Fayans energy density functional model, which has characteristics similar to many model fitting and calibration problems in nuclear physics. We analyze hyperparameter tuning considerations and variability associated with stochastic optimization algorithms and illustrate considerations for tuning in different computational settings.
Comments:
25-page article, 9-page supplement, 1-page notice
Subjects:
Nuclear Theory (nucl-th); math.OC (math.OC)
arXiv:
2010.05668 [pdf]
J.Phys.G(2021)·10 citations
09
[Submitted on 12 Oct 2020]
Modeling quasielastic interactions of monoenergetic kaon decay-at-rest neutrinos
Alexis Nikolakopoulos🇧🇪 · Vishvas Pandey🇺🇸 · Joshua Spitz🇺🇸 · Natalie Jachowicz🇧🇪
Monoenergetic muon neutrinos at 236 MeV are readily produced in intense medium-energy proton facilities ( $≳$ 2-3~GeV) when a positive kaon decays at rest (KDAR; $K^{+} \to μ^{+} ν_{μ}$ ). These neutrinos provide a unique opportunity to both study the neutrino interaction and probe the nucleus with a monoenergetic weak-interaction-only tool. We present cross section calculations for quasielastic scattering of these 236~MeV neutrinos off $^{12}$ C and $^{40}$ Ar, paying special attention to low-energy aspects of the scattering process. Our model takes the description of the nucleus in a mean-field (MF) approach as the starting point, where we solve Hartree-Fock (HF) equations using a Skyrme type nucleon-nucleon interaction. Thereby, we introduce long-range nuclear correlations by means of a continuum random phase approximation (CRPA) framework where we solve the CRPA equations using a Green's function method. The model successfully describes ( $e, e^{'}$ ) data on $^{12}$ C and $^{40}$ Ca in the kinematic region that overlaps with the KDAR $ν_{μ}$ phase space. In addition to these results, we present future prospects for precision KDAR cross section measurements and applications of our calculations in current and future experiments that will utilize these neutrinos.
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2010.05794 [pdf]
PRC(2021)·24 citations
10
[Submitted on 11 Oct 2020] (cross-list from math-ph)
Weak asymptotics of wave function for N-particle system and asymptotic filtering
S.L. Yakovlev
Asymptotic representations for large values of the hyperradius are constructed for the scattering wave function of a system of $N$ particles considered as a generalized function of angular variable coordinates. The coefficients of the asymptotic representations are expressed in terms of the $N$ -particle scattering matrix. The phenomenon of asymptotic filtration is discovered, which consists in the fact that only scattering processes contribute to the leading terms of such an asymptotic representation, in which all particles are free both before and after interaction. The obtained representations are used to construct the correct asymptotics of the partial components of the wave function of $N$ particles in the hyperspherical representation.
Comments:
20 pages
Subjects:
Mathematical Physics (math-ph); math.MP (math.MP); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
2010.05319 [pdf]
Teor.Mat.Fiz.(2021)·0 citations
11
[Submitted on 8 Oct 2020] (cross-list from hep-ph)
Bottomonium suppression and elliptic flow using Heavy Quarkonium Quantum Dynamics
Ajaharul Islam🇺🇸 · Michael Strickland🇺🇸
We introduce a framework called Heavy Quarkonium Quantum Dynamics (HQQD) which can be used to compute the dynamical suppression of heavy quarkonia propagating in the quark-gluon plasma using real-time in-medium quantum evolution. Using HQQD we compute large sets of real-time solutions to the Schrödinger equation using a realistic in-medium complex-valued potential. We sample 2 million quarkonia wave packet trajectories and evolve them through the QGP using HQQD to obtain their survival probabilities. The computation is performed using three different HQQD model parameter sets in order to estimate our systematic uncertainty. After taking into account final state feed down we compare our results to existing experimental data for the suppression and elliptic flow of bottomonium states and find that HQQD predictions are good agreement with available data for $R_{AA}$ as a function of $N_{part}$ and $p_{T}$ collected at $s_{NN} =$ 5.02 TeV. In the case of $v_{2}$ for the various states, we find that the path-length dependence of $Υ (1 s)$ suppression results in quite small $v_{2}$ for $Υ (1 s)$ . Our prediction for the integrated elliptic flow for $Υ (1 s)$ in the $10 - 90$ \% centrality class, which now includes an estimate of the systematic error, is $v_{2} [Υ (1 s)]$ = 0.003 $\pm$ 0.0007 $\pm_{0.0013}^{0.0006}$ . We also find that, due to their increased suppression, excited bottomonium states have a larger elliptic flow. Based on this observation we make predictions for $v_{2} [Υ (2 s)]$ and $v_{2} [Υ (3 s)]$ as a function of centrality and transverse momentum.
Comments:
25 pages, 9 figure, 1 table; v2 - published version. arXiv admin note: text overlap with arXiv:2007.10211
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2010.05457 [pdf]
JHEP(2021)·45 citations
12
[Submitted on 12 Oct 2020] (cross-list from hep-ph)
The pole and screening masses of neutral pion in hot and magnetized medium: a comprehensive study in the Nambu--Jona-Lasinio model
Bingkai Sheng🇨🇳 · Yuanyuan Wang🇨🇳 · Xinyang Wang🇨🇳 · Lang Yu🇨🇳
In this work, we investigate not only the pole masses but also the screening masses of neutral pions at finite temperature and magnetic field by utilizing the random phase approximation (RPA) approach in the framework of the two-flavor Nambu--Jona-Lasinio (NJL) model. And two equivalent formalisms in the presence of a magnetic field, i.e. the Landau level representation (LLR) and the proper-time representation (PTR), are applied to obtain the corresponding analytical expressions of the polarization functions (except the expressions for the pole masses in the PTR). In order to evaluate the applicable region of the low-momentum expansion (LME), we compare the numerical results within the full RPA (FRPA) with those within the reduced RPA (RRPA), i.e. the RPA in the LME. It is confirmed that the pole masses of {\pi}0in the FRPA suffer a sudden mass jump at the Mott transition temperature when in the presence of external magnetic field, and the Mott transition temperature is catalyzed by the magnetic field. And by analyzing the behaviors of the directional sound velocities of {\pi}0, which are associated with the breaking of the Lorentz invariance by the heat bath and the magnetic field, we clarify the two problems existing in previous literatures: one is that the transverse sound velocities in the medium are always larger than unity and thus violate the law of causality on account of the non-covariant regularization scheme, the other is that the longitudinal sound velocities are identically equal unity at finite temperature on account of the limitation of the derivative expansion method used.
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2010.05716 [pdf]
PRD(2021)·42 citations
13
[Submitted on 12 Oct 2020] (cross-list from nucl-ex)
Assessing the impact of valence sd neutrons and protons on fusion
Varinderjit Singh · J. Vadas · T.K. Steinbach · B.B. Wiggins · S. Hudan · R.T. deSouza
Experimental above-barrier fusion cross-sections for $^{17}$ F + $^{12}$ C are compared to the fusion excitation functions for $^{16, 18}$ O, $^{19}$ F, and $^{20}$ Ne ions on a carbon target. In comparing the different systems both the differing static size of the incident ions and changes in fusion barrier are accounted for by examining the reduced fusion cross-section. Remaining trends of the fusion cross-section above the barrier which reflect the sensitive interplay of the sd protons and neutrons are observed. The experimental data are also compared to both a widely-used analytical model of near-barrier fusion, as well as a time-dependent Hartree-Fock model. Both models fail to describe the trends observed.
Comments:
6 pages, 5 figures
Subjects:
Nuclear Experiment (nucl-ex); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
2010.05720 [pdf]
PRC(2021)·4 citations
14
[Submitted on 12 Oct 2020] (cross-list from hep-ph)
Hyperon--anti-hyperon polarization asymmetry in relativistic heavy-ion collisions as an interplay between chiral and helical vortical effects
Victor E. Ambrus🇷🇴 · M. N. Chernodub🇫🇷
We argue that the enhancement in the spin polarization of anti-hyperons compared to the polarization of the hyperons in noncentral relativistic heavy-ion collisions arises as a result of an interplay between the chiral and helical vortical effects. The chiral vortical effect generates the axial current of quarks along the vorticity axis while the recently found helical vortical effect generates the helicity flow -- the projection of the quark's polarization vector onto its momentum -- along the same axis. For massless fermions, the helical charge corresponds to a difference in the contributions of particles and anti-particles to the axial charge. Assuming that the spin of light quarks transfers to the strange quarks via the vector kaon states ("the spin-vector dominance"), we are able to describe the ratio of the (anti)hyperon spin polarizations, obtained by the STAR group, without fitting parameters. We also argue that the helical vortical effect dominates over the chiral vortical effect and the chiral magnetic effect in the generation of the electric current.
Comments:
9 pages, 3 figures; v2: discussions expanded, chiral magnetic effect and helical vortical effect are compared
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2010.05831 [pdf]
EPJC(2022)·26 citations
15
[Submitted on 12 Oct 2020] (cross-list from hep-ph)
Bottomonium spectroscopy in the quark-gluon plasma
Georg Wolschin🇩🇪
The spectroscopic properties of heavy quarkonia are substantially different in the quark-gluon plasma (QGP) that is created in relativistic heavy-ion collisions as compared to the vacuum situation that can be tested in pp collisions at the same center-of-mass energy. In this article, a series of recent works about the dissociation of the Y(nS) and chi_b(nP) states in the hot QGP is summarized. Quarkonia dissociation occurs due to (1) screening of the real quark-antiquark potential, (2) collisional damping through the imaginary part of the potential, and (3) gluon-induced dissociation. In addition, reduced feed-down plays a decisive role for the spin-triplet ground state. Transverse-momentum and centrality-dependent data are well reproduced in Pb-Pb collisions at LHC energies. In the asymmetric p-Pb system, alterations of the parton density functions in the lead nucleus account for the leading fraction of the modifications in cold nuclear matter (CNM), but the hot-medium effects turn out to be relevant in spite of the small initial spatial extent of the fireball, providing additional evidence for the generation of a quark-gluon droplet.
Comments:
22 pages, 24 figures; Invited Review for Int. J. Mod. Phys. A
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2010.05841 [pdf]
Int.J.Mod.Phys.A(2020)·8 citations

Affiliations

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