Nuclear Theory·nucl-th

Friday·December 1, 2023

11 papers—3 primary·8 cross-listed

01
[Submitted on 30 Nov 2023]
Evolution of giant monopole resonance with triaxial deformation
Kouhei Washiyama · Shuichiro Ebata · Kenichi Yoshida
Background: The isoscalar giant monopole resonance (ISGMR) splits into two peaks in prolately deformed nuclei. When a nucleus is triaxially deformed, a peak appears in the middle between the two peaks. Purpose: We investigate the mechanism of the appearance of the middle peak in the ISGMR in triaxial nuclei. Method: We perform the constrained Skyrme-Hartree-Fock-Bogoliubov (CHFB) calculation for arbitrary triaxial shapes in $^{100}$ Mo. We calculate the strength functions of the isoscalar monopole (ISM) and IS quadrupole modes on the CHFB states. Furthermore, we investigate vibrations of matter distributions in $x$ , $y$ , and $z$ directions induced by the external ISM field, with the $z$ axis being the longest axis of the triaxial shape. Results: The middle peak in the ISM strength evolves from the triaxial degree $γ = 0^{\circ}$ to $6 0^{\circ}$ . This is because the difference between the vibration in $x$ direction and that in $y$ direction is evident with an increase in $γ$ and the quadrupole $K = 2$ component of the induced density of the ISM at the middle peak increases as $γ$ increases, where $K$ denotes the $z$ component of the angular momentum. This property is also obtained in the unperturbed ISM strength without the residual fields. Conclusions: The mixing between the monopole and quadrupole modes is primarily determined by the ground-state deformation. Therefore, the ISM strength of the middle peak becomes strong as the triaxial degree in the ground state increases.
Comments:
7 pages, 7 figures
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2311.18317 [pdf]
PRC(2024)·2 citations
02
[Submitted on 30 Nov 2023]
Scaling behaviour of $d N / d y$ in high-energy collisions
Gábor Kasza🇭🇺 · Tamás Csörgő🇭🇺
From a recently found family of analytic, finite and accelerating 1+1-dimensional solutions to perfect fluid relativistic hydrodynamics, we derive simple and powerful formulae to describe the rapidity and pseudorapidity density distributions. By introducing a new scaling function, we notice that the rapidity distribution data of the different experiments all collapse into a single curve. This data-collapsing (or scaling) behaviour in the rapidity distributions suggests that high-energy $p + p$ collisions may be described as collective systems.
Comments:
10 pages, 2 figures. This paper is accepted for publication in MDPI Journal Universe
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
2311.18678 [pdf]
Universe(2024)·2 citations
03
[Submitted on 30 Nov 2023]
Structure in the speed of sound: from neutron stars to heavy-ion collisions
Nanxi Yao🇺🇸 · Agnieszka Sorensen🇺🇸 · Veronica Dexheimer🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸
From the observation of both heavy neutron stars and light ones with small radii, one anticipates a steep rise in the speed of sound of nuclear matter as a function of baryon density up to values close to the causal limit. A question follows whether such behavior of the speed of sound in neutron-rich matter is compatible with the equation of state extracted from low-energy heavy-ion collisions. In this work, we consider a family of neutron star equations of state characterized by a steep rise in the speed of sound, and use the symmetry energy expansion to obtain equations of state applicable to the almost-symmetric nuclear matter created in heavy-ion collisions. We then compare collective flow data from low-energy heavy-ion experiments with results of simulations obtained using the hadronic transport code SMASH with the mean-field potential reproducing the density-dependence of the speed of sound. We show that equations of state featuring a peak in the speed of sound squared occurring at densities between 2-3 times the saturation density of normal nuclear matter, producing neutron stars of nearly M_max~2.5 M_Sun, are consistent with heavy-ion collision data.
Comments:
Updated version for journal submission
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)
arXiv:
2311.18819 [pdf]
PRC(2024)·44 citations
04
[Submitted on 30 Nov 2023] (cross-list from hep-ph)
Recent Developments of Small- $x$ Evolution for Quark and Gluon Helicity
Yossathorn Tawabutr🇫🇮
Helicity of quarks and gluons inside the proton at small Bjorken $x$ is one of the missing pieces of the proton spin puzzle, with limited experimental results due to various challenges. To address the problem, we derive under the framework of color glass condensate (CGC) effective theory a renormalization group equation in rapidity for the parton helicity distributions, which resums double-logarithmic factor, $α_{s} ln^{2} (1/ x)$ , with $α_{s}$ being the strong coupling constant. With running coupling, the equation produces results at Bjorken $x \leq 0.1$ that are consistent with the world polarized scattering data. There is an evidence for a significant parton helicity contribution from the small- $x$ region. However, the helicity estimate still contains a large uncertainty that will dramatically reduce with the upcoming measurements from the Electron-Ion Collider (EIC). Ongoing attempts to reduce the uncertainty of our helicity prediction in the medium term will also be discussed.
Comments:
13 pages, 0 figures, contribution to ISMD2023
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2311.18185 [pdf]
4 citations
05
[Submitted on 30 Nov 2023] (cross-list from cond-mat.quant-gas)
General features and contact modeling of $N$ -body isolated resonances near threshold
Ludovic Pricoupenko
$N$ -body non efimovian bound or quasi-bound states for particles with short range interactions are considered in arbitrary dimensions. The different resonance regimes near the threshold are depicted by using a generalization of the effective range approximation. This two-parameter description can be used in various contexts from ultra-cold to hadronic physics. The universal character of these states makes it possible a formulation in terms of a contact model. The singularity at the contact imposes the introduction of a modified scalar product to solve the normalization catastrophe and to restore the self-adjoint character of the model. An equivalence with the standard scalar product used for realistic finite range models is derived.
Comments:
19 pages, 4 figures ; integration of an appendix in the main text; demonstration of the invariance of the modified scalar product in a reparameterization of the contact model added
Subjects:
Quantum Gases (cond-mat.quant-gas); Nuclear Theory (nucl-th)
arXiv:
2311.18372 [pdf]
SciPost Phys.(2024)·3 citations
06
[Submitted on 30 Nov 2023] (cross-list from hep-ph)
Linear response theory for spin alignment of vector mesons in thermal media
Wen-Bo Dong🇨🇳 · Yi-Liang Yin🇨🇳 · Xin-Li Sheng🇮🇹 · Shi-Zheng Yang🇨🇳 · Qun Wang🇨🇳
We present a calculation of the spin alignment for unflavored vector mesons in thermalized quark-gluon plasma based on the Kubo formula in linear response theory. This is achieved by expanding the system to the first order of the coupling constant and the spatial gradient. The effect strongly relies on the vector meson's spectral functions which are determined by the interaction and medium properties. The spectral functions are calculated for the one-quark-loop self-energy with meson-quark interaction. The numerical results show that the correction to the spin alignment from the thermal shear tensor is of the order $1 0^{- 4} \sim 1 0^{- 5}$ for the chosen values of quark-meson coupling constant, if the magnitude of thermal shear tensor is $1 0^{- 2}$ .
Comments:
22 pages, 5 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2311.18400 [pdf]
PRD(2024)·31 citations
07
[Submitted on 30 Nov 2023] (cross-list from hep-ph)
Effect of color randomization on $p_{T}$ broadening of fast partons in turbulent quark-gluon plasma
B.G. Zakharov🇷🇺
We analyze the effect of the parton color randomization on $p_{T}$ broadening in the quark-gluon plasma with turbulent color fields. We calculate the transport coefficient for a simplified model of fluctuating color fields in the form of alternating sequential transverse layers with homogenous transverse chromomagnetic fields with random orientation in the SU(3) group and gaussian distribution in the magnitude. Our numerical results show that the color randomization can lead to a sizable reduction of the turbulent contribution to $q^$ . The magnitude of the effect grows with increasing ratio of the electric and magnetic screening masses.
Comments:
17 pages, 7 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2311.18607 [pdf]
2 citations
08
[Submitted on 30 Nov 2023] (cross-list from hep-lat)
Moments of parton distribution functions of any order from lattice QCD
Andrea Shindler🇩🇪
We describe a procedure to determine moments of parton distribution functions of any order in lattice quantum chromodynamics (QCD). The procedure is based on the gradient flow for fermion and gauge fields. The flowed matrix elements of twist-2 operators renormalize multiplicatively, and the matching with the physical matrix elements can be obtained using continuum symmetries and the irreducible representations of Euclidean 4-dimensional rotations. We calculate the matching coefficients at one-loop in perturbation theory for moments of any order in the flavor nonsinglet case. We also give specific examples of operators that could be used in lattice QCD computations. It turns out that it is possible to choose operators with identical Lorentz indices and still have a multiplicative matching. One can thus use twist-2 operators exclusively with temporal indices, thus substantially improving the signal-to-noise ratio in the computation of the hadronic matrix elements.
Comments:
10 pages, 2 figures - Version matches published version
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2311.18704 [pdf]
PRD(2024)·44 citations
09
[Submitted on 30 Nov 2023] (cross-list from gr-qc)
Effects of anisotropic pressure on interacting quark star structure
Juan M. Z. Pretel🇧🇷 · Takol Tangphati🇹🇭 · Ayan Banerjee🇿🇦 · Anirudh Pradhan🇮🇳
Perturbative Quantum Chromodynamics (pQCD) corrections and color superconductivity predict that strongly interacting matter can reveal new physical phenomena under extreme conditions. Taking into account these interaction effects, we investigate the role of anisotropic pressure in quark stars composed of interacting quark matter. Adopting two physically well-motivated anisotropy profiles, we numerically solve the stellar structure equations in order to explore the consequences of anisotropic pressure on various macroscopic properties such as radius, gravitational mass, surface redshift, moment of inertia, tidal Love number and oscillation spectrum. Remarkably, for both anisotropy models, negative anisotropies increase the radial stability of interacting quark stars, while the opposite occurs for positive anisotropies. However, for the Bowers-Liang profile, the central density corresponding to the maximum-mass point does not coincide with the central density where the squared oscillation frequency vanishes, indicating that the existence of stable anisotropic interacting quark stars is possible beyond the maximum mass for negative anisotropies. Additionally, we compare our theoretical predictions with several observational mass-radius measurements and tidal deformability constraints, which suggest that both strong interaction effects and anisotropy effects play a crucial role in describing compact stars observed in the Universe.
Comments:
17 pages, 17 figures and 1 table. To appear in Physics Letters B
Subjects:
General Relativity and Quantum Cosmology (gr-qc); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
2311.18770 [pdf]
PLB(2024)·25 citations
10
[Submitted on 30 Nov 2023] (cross-list from hep-lat)
Finite-volume scattering on the left-hand cut
André Baião Raposo🇬🇧 · Maxwell T. Hansen🇬🇧
The two-particle finite-volume scattering formalism derived by Lüscher and generalized in many subsequent works does not hold for energies far enough below the two-particle threshold to reach the nearest left-hand cut. The breakdown of the formalism is signaled by the fact that a real scattering amplitude is predicted in a regime where it should be complex. In this work, we address this limitation by deriving an extended formalism that includes the nearest branch cut, arising from single particle exchange. We focus on two-nucleon ( $N N \to N N$ ) scattering, for which the cut arises from pion exchange, but give expressions for any system with a single channel of identical particles. The new result takes the form of a modified quantization condition that can be used to constrain an intermediate K-matrix in which the cut is removed. In a second step, integral equations, also derived in this work, must be used to convert the K-matrix to the physical scattering amplitude. We also show how the new formalism reduces to the standard approach when the $N \to N π$ coupling is set to zero.
Comments:
62 pages, 9 figures, v2: fix typos and improve discussion of integral equations, additional figure to better explain time-ordered perturbation theory, v3: published version including comparison to previous work
Subjects:
High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2311.18793 [pdf]
JHEP(2024)·67 citations
11
[Submitted on 30 Nov 2023] (cross-list from hep-ph)
Schwinger-Dyson equation on the complex plane -- A four-fermion interaction model at finite temperature --
Hidekazu Tanaka🇯🇵 · Shuji Sasagawa🇯🇵
We extend the Schwinger-Dyson equation (SDE) on the complex plane, which was treated in our previous research, to finite temperature. As a simple example, we solve the SDE for a model with four-fermion interactions in the (1+1) space-time dimensions at strong coupling region. We investigate the properties of the effective mass and energy for the fermions, especially near the phase transition temperature.
Comments:
18 pages, 5 figures
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2311.18831 [pdf]
PTEP(2024)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE