Nuclear Theory·nucl-th

Friday·April 30, 2021

11 papers—3 primary·8 cross-listed

01
[Submitted on 29 Apr 2021]
Proton decays in $^{16}$ Ne and $^{18}$ Mg and isospin-symmetry breaking in carbon isotopes and isotones
N. Michel🇨🇳 · J. G. Li🇨🇳 · F. R. Xu🇨🇳 · W. Zuo🇨🇳
Proton-rich nuclei possess unique properties in the nuclear chart. Due to the presence of both continuum coupling and Coulomb interaction, phenomena such as halos, Thomas-Ehrman shift, and proton emissions can occur. Experimental data are difficult to be obtained therein, so that theoretical calculations are needed to understand nuclei at drip-lines and guide experimentalists for that matter. In particular, the $^{16}$ Ne and $^{18}$ Mg isotopes are supposed to be one-proton and/or two-proton emitting nuclei, but associated experimental data are either incomplete or even unavailable. Consequently, we performed Gamow shell model calculations of carbon isotones bearing $A = 15 - 18$ . Isospin-symmetry breaking occurring in carbon isotones and isotopes is also discussed. It is hereby shown that the mixed effects of continuum coupling and Coulomb interaction at drip-lines generate complex patterns in isospin multiplets. Added to that, it is possible to determine the one-proton and two-proton widths of $^{16}$ Ne and $^{18}$ Mg. Obtained decay patterns are in agreement with those obtained in previous experimental and theoretical works. Moreover, up to the knowledge of authors, this is the first theoretical calculation of binding energy and partial decay widths of $^{18}$ Mg in a configuration interaction picture.
Comments:
12 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2104.14093 [pdf]
PRC(2021)·23 citations
02
[Submitted on 29 Apr 2021]
Hybrid model with viscous relativistic hydrodynamics: a role of constraints on the shear-stress tensor
A. S. Khvorostukhin🇷🇺 · E. E. Kolomeitsev🇸🇰 · V. D. Toneev🇷🇺
We present the hybrid hadron string dynamic (HydHSD) model connecting the parton-hadron-string dynamic model (PHSD) and a hydrodynamic model taking into account shear viscosity within the Israel-Stewart approach. The performance of the code is tested on the pion and proton rapidity and transverse mass distributions calculated for Au+Au and Pb+Pb collision at AGS--SPS energies. The influence of the switch time from transport to hydro models, the viscous parameter, and freeze-out time are discussed. Since the applicability of the Israel-Stewart hydrodynamics assumes the perturbative character of the viscous stress tensor, $π^{μν}$ , which should not exceed the ideal energy-momentum tensor, $T_{id}^{μν}$ , hydrodynamical codes usually rescale the shear stress tensor if the inequality $∥ π^{μν} ∥ ≪ ∥ T_{id}^{μν} ∥$ is not fulfilled in some sense. We show that the form of the corresponding condition plays an important role in the sensitivity of hydrodynamic calculations to the viscous parameter -- a ratio of the shear viscosity to the entropy density, $η / s$ . It is shown that the constraints used in the vHLLE and MUSIC models give the same results for the observables. With these constraints, the rapidity distributions and transverse momentum spectra are most sensitive to a change of the $η / s$ ratio. As an alternative, a strict condition is used. We performed global fits the rapidity and transverse mass distribution of pion and protons. It was also found that $η / s$ as a function of the collision energy monotonically increases from $E_{lab} = 6 A$ GeV up to $E_{lab} = 40 A$ GeV and saturates for higher SPS energies. We observe that it is difficult to reproduce simultaneously pion and proton rapidity distribution within our model with the present choice of the equation of state without a phase transition.
Comments:
This paper is the essentially revised version of our paper arXiv:1810.10303
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2104.14197 [pdf]
EPJA(2021)·8 citations
03
[Submitted on 29 Apr 2021]
Many-body approach to superfluid nuclei in axial geometry
Yinu Zhang🇺🇸 · Antonio Bjelčić🇭🇷 · Tamara Nikšić🇭🇷 · Elena Litvinova🇺🇸 · Peter Ring🇩🇪 · Peter Schuck🇫🇷
Starting from a general many-body fermionic Hamiltonian, we derive the equations of motion (EOM) for nucleonic propagators in a superfluid system. The resulting EOM is of the Dyson type formulated in the basis of Bogoliubov's quasiparticles. As the leading contributions to the dynamical kernel of this EOM in strongly-coupled regimes contain phonon degrees of freedom in various channels, an efficient method of calculating phonon's characteristics is required to successfully model these kernels. The traditional quasiparticle random phase approximation (QRPA) solvers are typically used for this purpose in nuclear structure calculations, however, they become very prohibitive in non-spherical geometries. In this work, by linking the notion of the quasiparticle-phonon vertex to the variation of the Bogoliubov's Hamiltonian, we show that the recently developed finite-amplitude method (FAM) can be efficiently employed to compute the vertices within the FAM-QRPA. To illustrate the validity of the method, calculations based on the relativistic density-dependent point-coupling Lagrangian are performed for the single-nucleon states in heavy and medium-mass nuclei with axial deformations. The cases of $^{38}$ Si and $^{250}$ Cf are presented and discussed.
Comments:
Article: 11 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2104.14513 [pdf]
PRC(2022)·18 citations
04
[Submitted on 28 Apr 2021] (cross-list from hep-ph)
A bound on the nucleon Druck-term from chiral EFT in curved space-time and mechanical stability conditions
Jambul Gegelia🇩🇪 · Maxim V. Polyakov🇩🇪
Using dispersive representations of the nucleon gravitational form factors, the results for their absorptive parts from chiral effective field theory in curved space-time, and the mechanical stability conditions, we obtain a model independent inequality for the value of the gravitational $D (t)$ form factor at zero momentum transfer (Druck-term). In particular, the obtained inequality leads to a conservative bound on the Druck-term in the chiral limit $D \leq - 0.95 (9)$ . This bound implies the restriction on the low-energy constant $c_{8}$ of the effective chiral action for nucleons and pions in the presence of an external gravitational field, $c_{8} \leq - 1.1 (1)$ GeV $^{- 1}$ . For the physical pion mass we obtain a model independent bound $D \leq - 0.20 (2)$ .
Comments:
minor corrections, version accepted for publication
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
arXiv:
2104.13954 [pdf]
PLB(2021)·28 citations
05
[Submitted on 28 Apr 2021] (cross-list from nucl-ex)
The Lowest Broad Alpha Cluster Resonances in $^{19}$ F
A. Volya🇺🇸 · V. Z. Goldberg🇺🇸 · A. K. Nurmukhanbetova🇰🇿 · D. K. Nauruzbayev🇰🇿 · G. V. Rogachev🇺🇸
There is a deep astrophysical interest in the structure of $^{19}$ F states close to the alpha decay threshold. The nuclear structure of these states is important for understanding of the development of $α$ clustering in the $^{20}$ Ne region. Emergence of clustered states and generally states that favor coupling to reaction channels near the corresponding decay thresholds is currently of special interest in theoretical physics. Excitation function for $^{15}$ N( $α$ , $α$ ) elastic scattering was measured by the TTIK method. These new data together with old, high energy resolution data, were analyzed using the R matrix approach. $^{19}$ F nuclear structure was calculated using configuration interaction methods with the recently developed effective interaction Hamiltonian. The parameters of broad low spin $ℓ = 0$ and 1 relative partial wave resonances close to the $α$ decay threshold in $^{19}$ F were identified. Detailed theoretical analysis was carried out identifying all states coupled to the $ℓ = 0$ and 1 alpha cluster channels. Considering hierarchy of states with different harmonic oscillator shell excitations allows to evaluate coupling to the alpha channels with different number of nodes in the relative wave function and helps to explain the distribution of the clustering strength and emergence of broad clustering resonances. Comparison of clustering in $^{20}$ Ne into $^{16}$ O+ $α$ and consideration of spin-orbit splitting of the $^{15}$ N+ $α$ channel provides additional evidence. Detailed analysis of new and old experimental data allows to identify a series of $α$ clustering resonances in $^{19}$ F and to assess the distribution of the clustering strength which is of importance to questions of astrophysics and for theoretical understanding of many-body physics and emergence of clustering in loosely bound or unstable nuclei.
Comments:
9 pages 3 figures
Subjects:
Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2104.13987 [pdf]
PRC(2022)·9 citations
06
[Submitted on 28 Apr 2021] (cross-list from hep-ph)
Survival probabilities of charmonia as a clue to measure transient magnetic fields
Sachio Iwasaki🇯🇵 · Daisuke Jido🇯🇵 · Makoto Oka🇯🇵 · Kei Suzuki🇯🇵
We investigate time evolution of $S$ -wave charmonium populations under a time-dependent homogeneous magnetic field and evaluate survival probabilities of the low-lying charmonia to the goal of estimating the magnetic field strength at heavy-ion collisions. Our approach implements mixing between different spin eigenstates and transitions to radially excited states. We show that the survival probabilities can change even by an extremely short magnetic field. Furthermore, we find that the survival probabilities depend on the initial spin states. We propose the sum of the survival probabilities over spin partners as an observable insensitive to the initial states. We also find that the sum can be approximately given as a function of $σ B_{0}^{2}$ with a duration time $σ$ and the maximum strength of the magnetic field $B_{0}$ .
Comments:
8 pages, 7 figures; published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2104.13989 [pdf]
PLB(2021)·9 citations
07
[Submitted on 28 Apr 2021] (cross-list from hep-ph)
A review of quarkonia under strong magnetic fields
Sachio Iwasaki🇯🇵 · Makoto Oka🇯🇵 · Kei Suzuki🇯🇵
We review the properties of quarkonia under strong magnetic fields. The main phenomena are (i) mixing between different spin eigenstates, (ii) quark Landau levels and deformation of wave function, (iii) modification of $Q ˉ Q$ potential, and (iv) the motional Stark effect. For theoretical approaches, we review (i) constituent quark models, (ii) effective Lagrangians, (iii) QCD sum rules, and (iv) holographic approaches.
Comments:
14 pages, 9 figures, invited contribution to the EPJA topical issue "QCD Phase Diagram in Strong Magnetic Fields"; published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2104.13990 [pdf]
EPJA(2021)·46 citations
08
[Submitted on 29 Apr 2021] (cross-list from hep-ph)
Thermomagnetic modification of the anomalous magnetic moment of quarks using the NJL model
Snigdha Ghosh🇮🇳 · Nilanjan Chaudhuri🇮🇳 · Pradip Roy🇮🇳 · Sourav Sarkar🇮🇳
The effective photon-quark-antiquark ( $γ q q$ ) vertex function is evaluated at finite temperature in the presence of an arbitrary external magnetic field using the two-flavor gauged Nambu--Jona-Lasinio (NJL) model in the mean field approximation. The lowest order diagram contributing to the magnetic form factor and the anomalous magnetic moment (AMM) of the quarks is calculated at finite temperature and external magnetic field using the imaginary time formalism of finite temperature field theory and the Schwinger proper time formalism. The Schwinger propagator including all the Landau levels with non-zero AMM of the dressed quarks is considered while calculating the loop diagram. Using sharp as well as smooth three momentum cutoff, we regularize the UV divergences arising from the vertex function and the parameters of our model are chosen to reproduce the well known phenomenological quantities at zero temperature and zero magnetic field, such as pion-decay constant ( $f_{π}$ ), vacuum quark condensate, vacuum pion mass ( $m_{π}$ ) as well as the magnetic moments of proton and neutron. We then study the temperature and magnetic field dependence of the AMM and constituent mass of the quark. We found that, the AMM as well as the constituent quark mass are large at the chiral symmetry broken phase in the low temperature region. Around the pseudo-chiral phase transition they decrease rapidly and at high temperatures both of them approach vanishingly small values in the symmetry restored phase.
Comments:
Version published in Physical Review D
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2104.14112 [pdf]
PRD(2021)·19 citations
09
[Submitted on 29 Apr 2021] (cross-list from hep-ph)
Unveiling the pole structure of S-matrix using deep learning
Denny Lane B. Sombillo🇵🇭 · Yoichi Ikeda🇯🇵 · Toru Sato🇯🇵 · Atsushi Hosaka🇯🇵
Particle scattering is a powerful tool to unveil the nature of various subatomic phenomena. The key quantity is the scattering amplitude whose analytic structure carries the information of the quantum states. In this work, we demonstrate our first step attempt to extract the pole configuration of inelastic scatterings using the deep learning method. Among various problems, motivated by the recent new hadron phenomena, we develop a curriculum learning method of deep neural network to analyze coupled channel scattering problems. We show how effectively the method works to extract the pole configuration associated with resonances in the $π N$ scatterings.
Comments:
7 pages, 3 figures, 2 tables, Added references
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
2104.14182 [pdf]
Rev.Mex.Fis.Suppl.(2022)·10 citations
10
[Submitted on 29 Apr 2021] (cross-list from hep-ph)
Initial- and final-state temperatures of emission source from differential cross-section in squared momentum transfer in high energy collisions
Qi Wang🇨🇳 · Fu-Hu Liu🇨🇳 · Khusniddin K. Olimov🇺🇿
The differential cross-section in squared momentum transfer of $ρ$ , $ρ^{0}$ , $ω$ , $ϕ$ , $f_{0} (980)$ , $f_{1} (1285)$ , $f_{0} (1370)$ , $f_{1} (1420)$ , $f_{0} (1500)$ , and $J / ψ$ produced in high energy virtual photon-proton ( $γ$ $^{*} p$ ), photon-proton ( $γ p$ ), and proton-proton ( $pp$ ) collisions measured by the H1, ZEUS, and WA102 Collaborations are analyzed by the Monte Carlo calculations. In the calculations, the Erlang distribution, Tsallis distribution, and Hagedorn function are separately used to describe the transverse momentum spectra of the emitted particles. Our results show that the initial- and final-state temperatures increase from lower squared photon virtuality to higher one, and decrease with increasing of center-of-mass energy.
Comments:
Updated version, 18 pages, 6 figures. Fixed some errors in particle mass in the code. Conclusions unchanged
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
2104.14271 [pdf]
Adv.High Energy Phys.(2021)·12 citations
11
[Submitted on 29 Apr 2021] (cross-list from cond-mat.quant-gas)
Fourth- and fifth-order virial expansion of harmonically trapped fermions at unitarity
Y. Hou🇺🇸 · K. J. Morrell🇺🇸 · A. J. Czejdo🇺🇸 · J. E. Drut🇺🇸
By generalizing our automated algebra approach from homogeneous space to harmonically trapped systems, we have calculated the fourth- and fifth-order virial coefficients of universal spin-1/2 fermions in the unitary limit, confined in an isotropic harmonic potential. We present results for said coefficients as a function of trapping frequency (or, equivalently, temperature), which compare favorably with previous Monte Carlo calculations (available only at fourth order) as well as with our previous estimates in the untrapped limit (high temperature, low frequency). We use our estimates of the virial expansion, together with resummation techniques, to calculate the compressibility and spin susceptibility.
Comments:
5 pages, 3 figures
Subjects:
Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th)
arXiv:
2104.14440 [pdf]
PRResearch(2021)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE