Nuclear Theory·nucl-th

Wednesday·July 1, 2020

14 papers—8 primary·6 cross-listed

01
[Submitted on 30 Jun 2020]
The outer crust of a cold, non-accreting neutron star within the Quark-Meson Coupling (QMC) model
Sofija Antić🇦🇺 · Jirina R. Stone🇺🇸 · John C. Miller🇬🇧 · Kay Marie L. Martinez🇦🇺 · Anthony William Thomas🇦🇺 · Pierre A. M. Guichon🇫🇷
The outer crust properties of cold non-accreting neutron stars are studied within the framework of the quark-meson coupling (QMC) model, which includes the effects of modifications of the quark structure inside individual nucleons when they are within a high-density nuclear medium. With a unique set of five well-constrained adjustable parameters, which have a clear physical basis, the QMC model gives predictions for the ground state observables of even-even nuclei which agree with experiment as well as traditional models. Furthermore, it gives improved theoretical values for nuclei thought to play a role in the outer crusts of neutron stars but for which experimental data is not available. Using the latest experimental data tables wherever possible but otherwise the predictions from the QMC model, we construct an equation of state for the outer crust which is then used within stellar model calculations to obtain an equilibrium sequence of crustal layers, each characterized by a particular neutron rich nuclei. Various properties of the layers are calculated for a range of neutron-star masses, and comparisons are made with alternative equations of state from the literature. This leads to the conclusion that the QMC model successfully predicts the outer crust properties and is fully comparable with the more traditional mass models, which all depend on a larger number of parameters.
Comments:
Minor changes in the text (typos and phrasing), additional cross-listing, 35 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
2006.16521 [pdf]
PRC(2020)·9 citations
02
[Submitted on 30 Jun 2020]
$ΛΛ N$ - $Ξ N N$ $S$ wave resonance
H. Garcilazo · A. Valcarce
We use an existing model of the $ΛΛ N - Ξ N N$ three-body system based in two-body separable interactions to study the $(I, J^{P}) = (1/2, 1/ 2^{+})$ three-body channel. For the $ΛΛ$ , $Ξ N$ , and $ΛΛ - Ξ N$ amplitudes we have constructed separable potentials based on the most recent results of the HAL QCD Collaboration. They are characterized by the existence of a resonance just below or above the $Ξ N$ threshold in the so-called $H$ -dibaryon channel, $(i, j^{p}) = (0, 0^{+})$ . A three-body resonance appears {2.3} MeV above the $Ξ d$ threshold. We show that if the $ΛΛ - Ξ N$ $H$ -dibaryon channel is not considered, the $ΛΛ N - Ξ N N$ $S$ wave resonance disappears. Thus, the possible existence of a $ΛΛ N - Ξ N N$ resonance would be sensitive to the $ΛΛ - Ξ N$ interaction. The existence or nonexistence of this resonance could be evidenced by measuring, for example, the $Ξ d$ cross section.
Comments:
11 pages, 5 figures. To be published in Chinese Physics C
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2006.16567 [pdf]
CPC(2020)·6 citations
03
[Submitted on 30 Jun 2020]
Shape phase transitions in odd-A Zr isotopes
K. Nomura · T. Nikšić · D. Vretenar
Spectroscopic properties that characterize shape phase transitions in neutron-rich odd-A Zr isotopes are investigated using the framework of nuclear density functional theory and particle-core coupling. The interacting-boson Hamiltonian of the even-even core nuclei, and the single-particle energies and occupation probabilities of the unpaired neutron are completely determined by deformation constrained self-consistent mean-field calculations based on the relativistic Hartree-Bogoliubov model with a choice of a universal energy density functional and pairing interaction. The triaxial $(β, γ)$ deformation energy surfaces for even-even $^{94 - 102}$ Zr indicates transition from triaxial or $γ$ -soft ( $^{94, 96}$ Zr) to prolate ( $^{98}$ Zr), and triaxial ( $^{100, 102}$ Zr) shapes. The corresponding low-energy excitation spectra of the odd-A Zr isotopes are in very good agreement with recent experimental results. Consistent with the structural evolution of the neighboring even-even Zr nuclei, the state-dependent effective deformations and their fluctuations in the odd-A isotopes indicate a pronounced discontinuity around the transitional nucleus $^{99}$ Zr.
Comments:
15 pages, 10 figures, 4 tables
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2006.16662 [pdf]
PRC(2020)·17 citations
04
[Submitted on 30 Jun 2020]
Femtoscopy scales and particle production in the relativistic heavy ion collisions from Au+Au at 200 AGeV to Xe+Xe at 5.44 ATeV within the integrated hydrokinetic model
V. M. Shapoval🇺🇦 · M. D. Adzhymambetov🇺🇦 · Yu. M. Sinyukov🇺🇦
The recent results on the main soft observables, including hadron and photon yields and particle number ratios, $p_{T}$ spectra, flow harmonics, as well as the femtoscopy radii, obtained within the integrated hydrokinetic model (iHKM) for high-energy heavy-ion collisions are reviewed and re-examined. The cases of different nuclei colliding at different energies are considered: Au+Au collisions at the top RHIC energy $s_{N N} = 200$ GeV, Pb+Pb collisions at the LHC energies $s_{N N} = 2.76$ TeV and $s_{N N} = 5.02$ TeV, and the LHC Xe+Xe collisions at $s_{N N} = 5.44$ TeV. The effect of the initial conditions and the model parameters, including the utilized equation of state (EoS) for quark-gluon phase, on the simulation results, as well as the role of the final afterburner stage of the matter evolution are discussed. The possible solution of the so-called ``photon puzzle'' is considered. The attention is also paid to the dependency of the interferometry volume and individual interferometry radii on the initial transverse geometrical size of the system formed in the collision.
Comments:
34 pages, 18 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2006.16697 [pdf]
EPJA(2020)·11 citations
05
[Submitted on 30 Jun 2020]
Revisiting the hypertriton lifetime puzzle
A. Pérez-Obiol🇯🇵 · D. Gazda🇨🇿 · E. Friedman🇮🇱 · A. Gal🇮🇱
Conflicting values of the hypertriton ( $_{Λ}^{3}$ H) lifetime were extracted in recent relativistic heavy-ion collision experiments. The ALICE Collaboration's reported $_{Λ}^{3}$ H lifetime $τ (_{Λ}^{3}$ H) is compatible within measurement uncertainties with the free $Λ$ lifetime $τ_{Λ}$ , as naively expected for a loosely bound $Λ$ hyperon in $_{Λ}^{3}$ H, whereas STAR's reported range of $τ (_{Λ}^{3}$ H) values is considerably shorter: $τ_{STAR} (_{Λ}^{3}$ H) $\sim$ (0.4-0.7) $τ_{Λ}$ . This $_{Λ}^{3}$ H lifetime puzzle is revisited theoretically using $_{Λ}^{3}$ H three-body wavefunctions generated in a chiral effective field theory approach to calculate the decay rate $Γ (_{Λ}^{3}$ H $\to^{3}$ He $+ π^{-}$ ). Significant but opposing contributions arise from $Σ N N$ admixtures in $_{Λ}^{3}$ H and from $π^{-}$ - $^{3}$ He final-state interaction. Evaluating the inclusive $π^{-}$ decay rate $Γ_{π^{-}} (_{Λ}^{3}$ H) via a branching ratio $Γ (_{Λ}^{3}$ H $\to^{3}$ He+ $π^{-}) / Γ_{π^{-}} (_{Λ}^{3}$ H) determined in helium bubble-chamber experiments, and adding $Γ_{π^{0}} (_{Λ}^{3}$ H) through the $Δ I = \frac{1}{2}$ rule, we derive $τ (_{Λ}^{3}$ H) assuming several different values of the $Λ$ separation energy $B_{Λ} (_{Λ}^{3}$ H). It is concluded that each of ALICE and STAR reported $τ (_{Λ}^{3}$ H) intervals implies its own constraint on $B_{Λ} (_{Λ}^{3}$ H): $B_{Λ} ≲ 0.1$ MeV for ALICE, $B_{Λ} ≳ 0.2$ MeV for STAR.
Comments:
14 pages, 3 tables, 1 figure. v1 -- before submission for publication. v2 -- minor editorial revisions, as submitted for publication. v3 -- slight editorial revision, few references deleted and few added. v4 -- PLB 811 (2020) 135916 published version
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
2006.16718 [pdf]
PLB(2020)·28 citations
06
[Submitted on 26 Jun 2020]
Description of alpha-clustering of 8Be nucleus states in high-precision theoretical approach
D. M. Rodkin · Yu. M. Tchuvil'sky
Scrupulous theoretical study of 8Be nucleus states, both clustered and non-clustered, is performed over a wide range of the excitation energies. The quantities which characterize the degree of the alpha-clustering of these states: spectroscopic factors, cluster form factors as well as the alpha-decay widths are computed in the framework of an accurate ab initio approach developed. Other basic properties of 8Be spectrum: the binding and excitation energies, mean values of the isospin are calculated simultaneously. In the majority of instances the results of the computations turn out to be in a good agreement with the spectroscopic data. A number of predictions are made and corresponding verification experiment is proposed. Prospects of the developed approach for nuclear spectroscopy are demonstrated.
Comments:
12 pages, 5 figures, 6 tables. arXiv admin note: text overlap with arXiv:2006.14839
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2006.16750 [pdf]
CPC(2020)·10 citations
07
[Submitted on 30 Jun 2020]
Accurate bulk properties of nuclei from $A = 2$ to $\infty$ from potentials with $Δ$ isobars
W.G. Jiang🇺🇸 · A. Ekström🇸🇪 · C. Forssén🇸🇪 · G. Hagen🇺🇸 · G.R. Jansen🇺🇸 · T. Papenbrock🇺🇸
We optimize $Δ$ -full nuclear interactions from chiral effective field theory. The low-energy constants of the contact potentials are constrained by two-body scattering phase shifts, and by properties of bound-state of $A = 2$ to $4$ nucleon systems and nuclear matter. The pion-nucleon couplings are taken from a Roy-Steiner analysis. The resulting interactions yield accurate binding energies and radii for a range of nuclei from $A = 16$ to $A = 132$ , and provide accurate equations of state for nuclear matter and realistic symmetry energies. Selected excited states are also in agreement with data.
Comments:
7 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2006.16774 [pdf]
PRC(2020)·215 citations
08
[Submitted on 28 Jun 2020]
Merging of transport theory with TDHF: multinucleon transfer in U+U collisions
S. Ayik · B. Yilmaz · O. Yilmaz · A.S. Umar
Multinucleon transfer mechanism in the collision of $^{238} U +^{238} U$ system is investigated at $E_{c.m.} = 833$ MeV in the framework of the quantal diffusion description based on the stochastic mean-field approach (SMF). Double cross-sections $σ (N, Z)$ as a function of the neutron and proton numbers, the cross-sections $σ (Z)$ and $σ (A)$ as a function of the atomic numbers and the mass numbers are calculated for production of the primary fragments. The calculation indicates the $^{238} U +^{238} U$ system may be located at an unstable equilibrium state at the potential energy surface with a slightly negative curvature along the beta stability line on the $(N, Z) -$ plane. This behavior may lead to rather large diffusion along the beta stability direction.
Comments:
10 pages, 10 figures. arXiv admin note: text overlap with arXiv:1904.09619
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2006.16809 [pdf]
PRC(2020)·18 citations
09
[Submitted on 29 Jun 2020] (cross-list from hep-ph)
Ellipticity of photon emission from strongly magnetized hot QCD plasma
Xinyang Wang🇨🇳 · Igor A. Shovkovy🇺🇸 · Lang Yu🇨🇳 · Mei Huang🇨🇳
By making use of an explicit representation for the imaginary part of the photon polarization tensor in terms of transitions between the Landau levels of light quarks, we study the angular dependence of direct photon emission from a strongly magnetized quark-gluon plasma. Because of the magnetic field, the leading order photon rate comes from the three processes of the zeroth order in the coupling constant $α_{s}$ : (i) the quark splitting ( $q \to q + γ$ ), (ii) the antiquark splitting ( $q ˉ \to q ˉ + γ$ ), and (iii) the quark-antiquark annihilation ( $q + q ˉ \to γ$ ). In a wide range of moderately high temperatures, $T ≳ m_{π}$ , and strong magnetic fields, $∣ e B ∣ ≳ m_{π}^{2}$ , the direct photon production is dominated by the two splitting processes. We show that the Landau-level quantization of quark states plays an important role in the energy and angular dependence of the photon emission. Among other things, it leads to a nontrivial momentum dependence of the photon ellipticity coefficient $v_{2}$ , which takes negative values at small transverse momenta and positive values at large transverse momenta. The crossover between the two regimes occurs around $k_{T} ≃ ∣ e B ∣$ . In application to heavy-ion collisions, this suggests that a large value of $v_{2}$ for the direct photons could be explained in part by the magnetic field in the quark-gluon plasma.
Comments:
16 pages, 9 multi-panel figures; published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2006.16254 [pdf]
PRD(2020)·56 citations
10
[Submitted on 29 Jun 2020] (cross-list from hep-ph)
Comparison of improved TMD and CGC frameworks in forward quark dijet production
Hirotsugu Fujii🇯🇵 · Cyrille Marquet🇫🇷 · Kazuhiro Watanabe🇺🇸
For studying small- $x$ gluon saturation in forward dijet production in high-energy dilute-dense collisions, the improved TMD (ITMD) factorization formula was recently proposed. In the Color Glass Condensate (CGC) framework, it represents the leading term of an expansion in inverse powers of the hard scale. It contains the leading-twist TMD factorization formula relevant for small gluon's transverse momentum $k_{t}$ , but also incorporates an all-order resummation of kinematical twists, resulting in a proper matching to high-energy factorization at large $k_{t}$ . In this paper, we evaluate the accuracy of the ITMD formula quantitatively, for the case of quark dijet production in high-energy proton-proton( $p + p$ ) and proton-nucleus ( $p + A$ ) collisions at LHC energies. We do so by comparing the quark-antiquark azimuthal angle $Δ ϕ$ distribution to that obtained with the CGC formula. For a dijet with each quark momentum $p_{t}$ much larger than the target saturation scale, $Q_{s}$ , the ITMD formula is a good approximation to the CGC formula in a wide range of azimuthal angle. It becomes less accurate as the jet $p_{t}$ 's are lowered, as expected, due to the presence of genuine higher-twists contributions in the CGC framework, which represent multi-body scattering effects absent in the ITMD formula. We find that, as the hard jet momenta are lowered, the accuracy of ITMD start by deteriorating at small angles, in the high-energy-factorization regime, while in the TMD regime near $Δ ϕ = π$ , very low values of $p_{t}$ are needed to see differences between the CGC and the ITMD formula. In addition, the genuine twists corrections to ITMD become visible for higher values of $p_{t}$ in $p + A$ collisions, compared to $p + p$ collisions, signaling that they are enhanced by the target saturation scale.
Comments:
30 pages, 13 figures. v2: version accepted for publication in JHEP
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2006.16279 [pdf]
JHEP(2020)·39 citations
11
[Submitted on 29 Jun 2020] (cross-list from astro-ph.HE)
Neutron Star Equation of State in light of GW190814
Hung Tan🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸 · Nico Yunes🇺🇸
The observation of gravitational waves from an asymmetric binary opens the possibility for heavy neutron stars, but these pose challenges to models of the neutron star equation of state. We construct heavy neutron stars by introducing non-trivial structure in the speed of sound sourced by deconfined QCD matter, which cannot be well recovered by spectral representations. Their moment of inertia, Love number and quadrupole moment are very small, so a tenfold increase in sensitivity may be needed to test this possibility with gravitational waves, which is feasible with third generation detectors.
Comments:
8 pages, 5 figures, v2 updated figures and text
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
arXiv:
2006.16296 [pdf]
PRL(2020)·178 citations
12
[Submitted on 30 Jun 2020] (cross-list from hep-ph)
QCD sum rules with spectral densities solved in inverse problems
Hsiang-nan Li🇹🇼 · Hiroyuki Umeeda🇹🇼
We construct QCD sum rules for nonperturbative studies without assuming the quark-hadron duality for the spectral density at low energy on the hadron side. Instead, both resonance and continuum contributions to the spectral density are solved with the operator-product-expansion input on the quark side by treating sum rules as an inverse problem. This new formalism does not involve the continuum threshold, does not require the Borel transformation and stability analysis, and can be extended to extract properties of excited states. Taking the two-current correlator as an example, we demonstrate that the series of $ρ$ resonances can emerge in our formalism, and the decay constants $f_{ρ (770)} (f_{ρ (1450)}, f_{ρ (1700)}, f_{ρ (1900)}) \approx$ 0.22 (0.19, 0.14, 0.14) GeV for the masses $m_{ρ (770)} (m_{ρ (1450)}, m_{ρ (1700)}, m_{ρ (1900)}) \approx$ 0.78 (1.46, 1.70, 1.90) GeV are determined. We also show that the decay width $Γ_{ρ (770)} \approx 0.17$ GeV can be obtained by substituting a Breit-Wigner parametrization for the $ρ (770)$ pole on the hadron side. It is observed that quark condensates of dimension-six on the quark side are crucial for establishing those $ρ$ resonances. Handling the conventional sum rules with the duality assumption as an inverse problem, we find that the multiple pole sum rules widely adopted in the literature do not describe the $ρ$ excitations reasonably. The precision of our theoretical outcomes can be improved systematically by including higher-order and higher-power corrections on the quark side. Broad applications of this formalism to abundant low energy QCD observables are expected.
Comments:
17 pages, 14 figures, version accepted for publication in Phys. Rev. D, title is changed
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2006.16593 [pdf]
PRD(2020)·26 citations
13
[Submitted on 30 Jun 2020] (cross-list from hep-ph)
Real time warm pions from the lattice using an effective theory
Sourendu Gupta🇮🇳 · Rishi Sharma🇮🇳
Lattice measurements provide adequate information to fix the parameters of long distance effective field theories in Euclidean time. Using such a theory, we examine the analytic continuation of long distance correlation functions of composite operators at finite temperature from Euclidean to Minkowski space time. We show through an explicit computation that the analytic continuation of the pion correlation function is possible and gives rise to non-trivial effects. Among them is the possibility, supported by lattice computations of Euclidean correlators, that long distance excitations can be understood in terms of (very massive) pions even at temperatures higher than the QCD cross over temperature.
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2006.16626 [pdf]
Int.J.Mod.Phys.A(2020)·6 citations
14
[Submitted on 30 Jun 2020] (cross-list from astro-ph.HE)
Can Pulsars in the inner parsecs from Galactic Centre probe the existence of Dark Matter?
Antonino Del Popolo🇷🇺 · Maksym Deliyergiyev🇵🇱 · Morgan Le Delliou🇨🇳 · Laura Tolos🇩🇪 · Fiorella Burgio🇮🇹
We discuss the formation of dark compact objects in a dark matter environment in view of the possible mass dependence of pulsars on the distribution of dark matter in the Galaxy. Our results indicate that the pulsar masses should decrease going towards the center of the Milky Way due to dark matter capture, thus becoming a probe for the existence and nature of dark matter. We thus propose that the evolution of the pulsar mass in a dark matter rich environment can be used to put constraints, when combined with future experiments, on the characteristics of our Galaxy halo dark matter profile, on the dark matter particle mass and on the dark matter self-interaction strength.
Comments:
5 pages, 2 figures, EPS-HEP2019, Ghent, Belgium, 10-17 July. Conference proceedings
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2006.16838 [pdf]
PoS(2020)·1 citation

Affiliations

first authorsco-authorsvia INSPIRE