Nuclear Theory
New submissions
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New submissions for Thu, 25 Apr 24
- [1] arXiv:2404.15442 [pdf, other]
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Title: Electromagnetic Form Factors for Nucleons in Short-Range Correlations and the EMC effectComments: arXiv admin note: text overlap with arXiv:2209.13753, arXiv:2307.15821Subjects: Nuclear Theory (nucl-th); High Energy Physics - Phenomenology (hep-ph)
The relationship between medium modifications of nucleon electromagnetic form factors and nucleon structure functions is examined using a model motivated by Light-Front Holographic QCD (LFHQCD). These modifications are closely connected with the influence of short-ranged correlations. The size of the modifications to nucleon form factors is shown to be about the same as the modifications to the structure functions. Thus, small limits on form factors modifications do not rule out an explanation of the EMC effect motivated by the influence of short range correlations, as claimed by a recent paper.
- [2] arXiv:2404.15629 [pdf, other]
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Title: Nuclear incompressibility and its enduring impact on fusion cross-sectionJournal-ref: Physical Review C 109, 044613 (2024)Subjects: Nuclear Theory (nucl-th)
The fusion mechanism of reactions involving even-even $^{112-124}$Sn, doubly magic $^{132}$Sn, $^{208}$Pb as targets, and $^{64}$Ni as the projectile is explored within the relativistic mean field (RMF) formalism. The main aim of choosing these nuclei is to explore the correlation between the nuclear incompressibility and the fusion cross-section. The nucleus-nucleus interaction potential is calculated by folding the axially deformed nuclear densities and the relativistic R3Y nucleon-nucleon (NN) potential obtained for the nonlinear sets of NL3$^*$, hybrid, and NL1, which yield different values for various characteristics of nuclear matter at saturation. The fusion barrier characteristics obtained for different RMF parameterizations are further used to calculate the cross-section within the $\ell$-summed Wong model. We found a decrease in the barrier height and consequently, an increase in the cross-section with a decrease in the incompressibility for all sets of parameters considered. The calculated cross section is satisfactorily consistent with the available experimental data for $^{64}$Ni+$^{208}$Pb system. In contrast, the nuclear potentials obtained for NL3$^*$ and the hybrid parameter sets underestimate the cross-section at below-barrier energies for $^{64}$Ni+$^{112-124,132}$Sn reactions. This discrepancy between the experimental data and the theoretical results for $^{64}$Ni+$^{112-124,132}$Sn reactions can be correlated with the soft behaviour of the Sn isotopes. The compressible nature of Sn-isotopes is inferred to lower the barrier height, which further leads to enhancement of the experimental fusion and/or capture cross-section at below-barrier energies. Thus, the NL1 parameter set with a comparatively soft equation of state (EoS) is observed to be a better choice to describe the sub-barrier nuclear fusion dynamics of reactions involving the Sn-isotopes.
- [3] arXiv:2404.15669 [pdf, ps, other]
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Title: The Coupling Constant of the Pseudovector Pion-nucleon Interaction for the Magnetic Moment of NucleonAuthors: Susumu KinparaComments: 9 pagesSubjects: Nuclear Theory (nucl-th); High Energy Physics - Phenomenology (hep-ph)
The role of the suppression of the coupling constant in the pseudovector pion-nucleon interaction is examined to account for the calculation of the magnetic moment of nucleon. Among three kinds of the higher-order corrections the vacuum polarization of the pion propagator contributes to the numerical value considerably. On the other hand the lowest-order vertex correction for the pion-nucleon-nucleon vertex does not give large effect in the approximation of the on-shell momenta for nucleons.
- [4] arXiv:2404.15832 [pdf, other]
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Title: Primordial Nucleosynthesis with Non-Extensive StatisticsComments: The European Physics Journal, Topical issue "Nuclear Astrophysics: Recent Progress in Understanding Element Formation in the Universe", 19 pages, 5 figuresSubjects: Nuclear Theory (nucl-th); Cosmology and Nongalactic Astrophysics (astro-ph.CO)
The conventional Big Bang model successfully anticipates the initial abundances of 2H(D), 3He, and 4He, aligning remarkably well with observational data. However, a persistent challenge arises in the case of 7Li, where the predicted abundance exceeds observations by a factor of approximately three. Despite numerous efforts employing traditional nuclear physics to address this incongruity over the years, the enigma surrounding the lithium anomaly endures. In this context, we embark on an exploration of Big Bang nucleosynthesis (BBN) of light element abundances with the application of Tsallis non-extensive statistics. A comparison is made between the outcomes obtained by varying the non-extensive parameter q away from its unity value and both observational data and abundance predictions derived from the conventional big bang model. A good agreement is found for the abundances of 4He, 3He and 7Li, implying that the lithium abundance puzzle might be due to a subtle fine-tuning of the physics ingredients used to determine the BBN. However, the deuterium abundance deviates from observations.
- [5] arXiv:2404.15890 [pdf, other]
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Title: Hadronic effects on $Λ$ polarization in relativistic heavy ion collisionsComments: 7 pages, 5 figuresSubjects: Nuclear Theory (nucl-th)
The $\Lambda$ hyperon spin flip and non-flip cross sections are calculated in a simple hadronic model by including both the $s$-channel process involving the spin 3/2, positive parity $\Sigma^*(1358)$ resonance and the $t$-channel process via the exchange of a scalar $\sigma$ meson. Although the $t$-channel process gives a thermally averaged cross section that is about a factor of 1.3 larger than that from the $s$-channel process, the $\Lambda$ spin flip to non-flip cross sections is negligibly small in the $t$-channel compared to the constant value of 1/3.5 in the $s$-channel process. With these cross sections included in a schematic kinetic model, the effects of hadronic scatterings on the $\Lambda$ spin polarization in Au-Au collisions at $\sqrt{s}_{NN}=7.7$ GeV are studied. It is found that the $\Lambda$ spin polarization only decreases by about 7\% during the hadronic stage of these collisions, which thus justifies the assumption in theoretical studies that compare the $\Lambda$ polarization calculated at the chemical freeze out to the measured one at the kinetic freeze out.
- [6] arXiv:2404.15897 [pdf, other]
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Title: Calculations of bound-state $β^-$-decay half-lives of highly ionized $^{163}$Dy$^{66+}$, $^{187}$Re$^{75+}$ and $^{205}$Tl$^{81+}$Comments: 8 pages, 6 figures, 2 tables, Comments and criticisms are welcomeSubjects: Nuclear Theory (nucl-th)
We propose a theoretical method to calculate the bound-state $\beta$-decay half-lives of highly-ionized atoms, which is based on the combination of the Takahashi-Yokoi model and our recently-developed projected shell model that can take into account both allowed and first-forbidden transitions of nuclear $\beta$ decay. Three examples that are of much experimental interests, $^{163}$Dy$^{66+}$, $^{187}$Re$^{75+}$ and $^{205}$Tl$^{81+}$ are taken for calculations. The ground and low-lying states of related nuclei are described reasonably. The bound-state $\beta$-decay half-lives of $^{163}$Dy$^{66+}$ and $^{187}$Re$^{75+}$ are described within a factor of two and four by our calculations without and with the quenching factors in allowed and first-forbidden transitions. The bound-state $\beta$-decay half-life of the last $s$-process branching point $^{205}$Tl$^{81+}$ is predicted to be 58 and 305 days for cases without and with the quenching factors in calculations. The presented method provides a theoretical way to calculate systematically the bound-state $\beta$-decay half-lives of nuclei from light to heavy ones including odd-mass and even-mass cases for the first time.
Cross-lists for Thu, 25 Apr 24
- [7] arXiv:2404.15906 (cross-list from nucl-ex) [pdf, other]
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Title: Magnetic dipole strength in $^{58}$Ni from forward-angle inelastic proton scatteringAuthors: I. Brandherm (1), P. von Neumann-Cosel (1), R. Mancino (1,2,3), G. Martínez-Pinedo (1,2) H. Matsubara (4,5), V.Yu. Ponomarev (1), A. Richter (1), M. Scheck (6,7) A. Tamii (4) ((1) Institut für Kernphysik, Technische Universität Darmstadt, Darmstadt, Germany, (2) GSI Helmholzzentrum für Schwerionenforschung, Planckstraße 1, Darmstadt, Germany, (3), Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic, (4) Research Center for Nuclear Physics, Osaka University, Ibaraki, Osaka, Japan, (5) Faculty of Radiological Technology, Fujita Health University, Aichi, Japan, (6) School of Computing, Engineering, and Physical Sciences, University of the West of Scotland, Paisley, United Kingdom, (7) SUPA, Scottish Universities Physics Alliance, Glasgow, United Kingdom)Comments: 16 pages, 15 figuresSubjects: Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
The aim of the present work is a state-by-state analysis of possible E1 and M1 transitions in $^{58}$Ni with a high-resolution (p,p') experiment at 295 MeV and very forward angles including 0{\deg} and a comparison to results from studies of the dipole strength with the $(\gamma,\gamma')$ and (e,e') reactions. The E1 and M1 cross sections of individual peaks in the spectra are deduced with a multipole decomposition analysis and converted to reduced E1 and spin-M1 transition strengths using the virtual photon and the unit cross-section method, respectively. Despite the high level density good agreement is obtained for the deduced excitation energies of J = 1 states in the three types of experiments indicating that the same states are excited. The B(E1) and B(M1) strengths from the $(\gamma,\gamma^\prime)$ experiments are systematically smaller than in the present work because of the lack of information on branching ratios to lower-lying excited states and the competition of particle emission. Fair agreement with the B(M1) strengths extracted from the (e,e') data is obtained after removal of E1 transitions uniquely assigned in the present work, which belong to a low-energy toroidal mode with unusual properties mimicking M1 excitations in electron scattering. The experimental M1 strength distribution is compared to large-scale shell-model calculations with the effective GXPF1A and KB3G interactions. They provide a good description of the isospin splitting and the running sum of the M1 strength. A quenching factor 0.74 for the spin-isospin part of the M1 operator is needed to attain quantitative agreement with the data.
- [8] arXiv:2404.15988 (cross-list from hep-ph) [pdf, other]
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Title: Symmetries in particle physics: from nuclear isospin to the quark modelComments: 12 figures, 24 pagesSubjects: High Energy Physics - Phenomenology (hep-ph); Nuclear Theory (nucl-th)
We present a concise pedagogic introduction to group representation theory motivated by the historical developments surrounding the advent of the Eightfold Way. Abstract definitions of groups and representations are avoided in favour of the physical intuition of symmetries of the nuclear interaction. The concept of nuclear isospin is used as a physical motivation to introduce SU(2) and discuss the main techniques of representation theory. The discovery of strange particles motivates extending the symmetry group to SU(3), at first in the context of the Sakata model. We highlight the successes in fitting mesons in the SU(3) octet, discuss the drawbacks of the Sakata model for baryonic classifications, and how the Eightfold Way finally led to the quark model. This approach has two major advantages: (i) the main concepts of the theory of Lie groups are introduced and discussed without ever losing touch with its applications in particle physics; (ii) it allows the beginner to study group theory while also becoming acquainted with the historical developments of particle physics that led to the concept of quarks. In particular, in this pedagogical path the quarks appear as yet another class of particles predicted from symmetry principles, rather than being introduced ad hoc for postulating an SU(3) symmetry, as usually done in the literature.
Replacements for Thu, 25 Apr 24
- [9] arXiv:2309.16865 (replaced) [pdf, other]
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Title: A Bayesian study of quark models in view of recent astrophysical constraintsComments: Published VersionJournal-ref: Phys. Rev. D 109, 043054 (2024)Subjects: Nuclear Theory (nucl-th)
- [10] arXiv:2401.07653 (replaced) [pdf, ps, other]
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Title: Correlation of the hyperon potential stiffness with hyperon constituents in neutron stars and heavy-ion collisionsComments: 8 pages, 6 figuresJournal-ref: Phys. Lett. B 853 (2024) 138658Subjects: Nuclear Theory (nucl-th)
- [11] arXiv:2401.09033 (replaced) [pdf, other]
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Title: Mass suppression effect in QCD radiation and hadron angular distribution in jetComments: 7 pages, 4 figures; published version in CPCSubjects: High Energy Physics - Phenomenology (hep-ph); High Energy Physics - Experiment (hep-ex); Nuclear Theory (nucl-th)
- [12] arXiv:2402.12985 (replaced) [pdf, other]
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Title: Lüscher equation with long-range forcesComments: 28 pages, 4 figuresSubjects: High Energy Physics - Lattice (hep-lat); High Energy Physics - Phenomenology (hep-ph); Nuclear Theory (nucl-th)
- [13] arXiv:2403.00451 (replaced) [pdf, other]
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Title: Charge-conjugation asymmetry and molecular content: the $D_{s0}^\ast(2317)^\pm$ in matterComments: 14 pages, 4 figuresJournal-ref: Phys. Lett. B 853 (2024) 138656Subjects: High Energy Physics - Phenomenology (hep-ph); Nuclear Theory (nucl-th)
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