Nuclear Theory·nucl-th

Thursday·August 8, 2024

12 papers—6 primary·6 cross-listed

01
Neutrinoless $β β$ decay nuclear matrix elements complete up to N $^{2}$ LO in heavy nuclei
Daniel Castillo🇪🇸 · Lotta Jokiniemi🇨🇦 · Pablo Soriano🇪🇸 · Javier Menéndez🇪🇸
We evaluate all nuclear matrix elements (NMEs) up to next-to-next-to leading order (N $^{2}$ LO) in chiral effective field theory ( $χ$ EFT) for the neutrinoless double-beta ( $0 ν β β$ ) decay of the nuclei most relevant for experiments, including $^{76}$ Ge, $^{100}$ Mo, and $^{136}$ Xe. We use the proton-neutron quasiparticle random-phase approximation (pnQRPA) and the nuclear shell model to calculate the N $^{2}$ LO NMEs from very low-momentum (ultrasoft) neutrinos and from loop diagrams usually neglected in $0 ν β β$ studies. Our results indicate that the overall N $^{2}$ LO contribution is centered around $- (5$ - $10) %$ for the shell model and $+ (10$ - $15) %$ for the pnQRPA, with sizable uncertainties due to the scale dependence of the ultrasoft NMEs and the short-range nature of the loop NMEs. The sign discrepancy between many-body methods is common to all studied nuclei and points to the different behaviour of the intermediate states of the $0 ν β β$ decay. Within uncertainties, our results for the ultrasoft NME are of similar size as contributions usually referred to as ``beyond the closure approximation''.
nucl-thhep-exhep-phnucl-exPLB(2025)·19 citations
02
Effect of neutrino electromagnetic properties on the quasielastic neutral-current neutrino-nucleus scattering
K. S. Kim🇰🇷 · P. T. P. Hutauruk🇰🇷 · Seung-il Nam🇰🇷 · Chang Ho Hyun🇰🇷
In the quasielastic region, we investigate the effect of neutrino electromagnetic properties constrained from the recent experiments on the electroweak neutral current reaction process of the neutrino- $^{12}$ C scattering. For a relativistic description of the nuclear dynamics, we employ the relativistic mean-field model, which has been proven to describe the data nicely in the quasielastic region. In the present work, we analyze the influence beyond the Standard Model by considering the neutrino magnetic and electric dipole form factors and charge radius on the neutrino electroweak interactions within $^{12}$ C. To this end, we use the values of the neutrino charge radius and the magnetic moment at the squared four momentum transfer $Q^{2} = 0$ obtained from the recent experiments and calculate the neutrino differential cross section of the neutrino- $^{12}$ C scattering. We find that the effect of the charge radius and the electric dipole form factor is very small, but the role of the magnetic dipole form factor is sensitive to $Q^{2}$ and becomes sizable at small momentum transfer.
nucl-thCPC(2025)·0 citations
03
The Wood-Saxon proton optical potential for p-nuclei
Sukhendu Saha · Dipali Basak · Chinmay Basu
A phenomenological mass-energy dependent proton optical model potential has been computed for p-nuclei. The parameters of the Wood-Saxon optical potential are found to be a good fit for proton elastic scattering data involving p-nuclei and elements with mass numbers near p-nuclei (within the range of 74 < A < 148) at energies around the Coulomb barrier of the system. The elastic scattering data were meticulously fitted using the SFRESCO code, allowing for the calculation of the real and imaginary parts of the Wood Saxon optical potential. To validate the model, experimental proton capture cross-sections for 106Cd and 113In near the Coulomb barrier were compared with results obtained using the TALYS-1.96 code, showing better agreement than the available global proton optical model potential.
nucl-thEPJ Web Conf.(2025)·1 citation
04
Feasibility of dark matter admixed neutron star based on recent observational constraints
Prashant Thakur🇮🇳 · Tuhin Malik🇵🇹 · Arpan Das🇮🇳 · T. K. Jha🇮🇳 · B. K. Sharma🇮🇳 · Constança Providência🇵🇹
The equation of state (EOS) for neutron stars is modeled using the Relativistic Mean Field (RMF) approach with a mesonic nonlinear (NL) interaction, a modified sigma cut potential (NL- $σ$ cut), and the influences of dark matter in the NL (NL DM). Using a Bayesian analysis framework, we evaluate the plausibility and impact of each scenario. Experimental constraints on the general properties of finite nuclei and heavy ion collisions, along with astrophysical observational data on neutron star radii and tidal deformation, have been taken into account. It was shown that all models, including the PREX-II data, were less favored, indicating that this experimental data seemed to be in tension with the other constraints included in the inference procedure, and were incompatible with chiral effective field theoretical calculations of pure neutron matter. Considering the models with no PREX-II constraints, we find the model NL- $σ$ cut with the largest Bayes evidence, indicating that the constraints considered favor the stiffening of the EOS at large densities. Conversely, the neutron star with a dark matter component is the least favorable case in light of recent observational constraints, among different scenarios considered here. The $f$ and $p$ modes were calculated within the Cowling approximation, and it can be seen that $f$ modes are sensitive to the EOS. An analysis of the slopes of the mass-radius curves and $f$ -mode mass curves has indicated that these quantities may help distinguish the different scenarios.We also analyzed the impact of new PSR J0437-4715 measurements on neutron star mass-radius estimates, noting a $\sim$ 0.2 km reduction in the 90\% CI upper boundary across all models and a significant Bayes evidence decrease, indicating potential conflicts with previous data or the necessity for more adaptable models.
nucl-thastro-ph.HEgr-qchep-phAstron.Astrophys.(2025)·25 citations
05
Nucleon-quark mixed matter and neutron star EOS
Y. Yamamoto🇯🇵 · N. Yasutake🇯🇵 · Th. A. Rijken🇯🇵
The nucleon-quark mixed matter is defined in the Brueckner-Hartree-Fock framework, in which quark densities are determined by equilibrium conditions between nucleon and quark chemical potentials, and nucleon-quark interactions play critical roles for resulting EoSs (equation of state). The two models of EoSs are derived from the nucleon-quark mixed matter (NQMM): The NQMM-A EoSs are based on the simple assumption that nucleons and free quarks occupy their respective Fermi levels and their Fermi spheres overlap from each other. In NQMM-B EoSs, the quark Fermi repulsion effect is incorporated on the basis of quakyonic matter, meaning that the nucleon Fermi levels are pushed up from the quark Fermi sphere by the Pauli exclusion principle. For the NQMM-A EoSs, the neutron-star mass-radius ( $M R$ ) curves are pushed up above the region of $M \sim 2.1 M_{⊙}$ and $R_{2.1 M_{⊙}} \sim$ 12.5 km indicated by the recent observations, as the $q N$ repulsions increase. For the NQMM-B EoSs, the similar results are obtained by the combined contributions from the $q N$ repulsion and the quark Fermi repulsion. In both models of EoSs, the important roles of the $q N$ di-quark exchange repulsions are demonstrated to reproduce reasonable values of $M_{ma x}$ and $R_{2.1 M_{⊙}}$ .
nucl-thPRC(2024)·6 citations
06
Superfluid quantum criticality and the thermal evolution of neutron stars
Hao-Fu Zhu🇨🇳 · Guo-Zhu Liu🇨🇳 · Jing-Rong Wang🇨🇳 · Xufen Wu🇨🇳
The neutron star starts to cool down shortly after its birth by emitting neutrinos. As it becomes cold enough, the Cooper pairs of neutrons are formed, triggering a superfluid transition. Previous studies on neutron superfluidity focused on finite-temperature transitions, with little attention paid to the potentially important quantum critical phenomena associated with superfluidity. Here, we provide the first theoretical analysis of superfluid quantum criticality, concentrating on its impact on neutron star cooling. Extensive calculations found that superfluidity occurs within a finite range of neutron star density $ρ$ . The density serves as a nonthermal parameter for a superfluid quantum phase transition. In a broad quantum critical region, gapless neutrons are strongly coupled to the quantum critical fluctuations of the superfluid order parameter. We handle this coupling using both perturbation theory and renormalization group methods and find that it leads to non-Fermi liquid behavior, which yields a logarithmic $T ln (1/ T)$ correction to the neutron specific heat $c_{n} \propto T$ and also dramatically alters the neutrino emissivity. Quantum critical phenomena emerge much earlier than the onset of superfluidity and persist throughout almost the entire lifetime of a neutron star. At low temperatures, these phenomena coexist with superfluidity in the neutron star interior but occupy different layers. We incorporate superfluid quantum criticality into the theoretical description of neutron star cooling and show that it substantially prolongs the thermal relaxation time. By varying the strength of superfluid fluctuations and other quantities, we obtain an excellent fit to the observed cooling data of a number of neutron stars. Our results indicate an intriguing correlation between superfluid quantum criticality and the thermal evolution of neutron stars.
nucl-thastro-ph.HEcond-mat.str-elcond-mat.supr-conPRD(2025)·1 citation
07
Euclidean Effective Theory for Partons in the Spirit of Steven Weinberg
Xiangdong Ji🇺🇸
The standard formulation of parton physics involves light-cone correlations of quark and gluon fields in a hadron, which leads to a widespread impression that it can only be studied through real-time Hamiltonian dynamics or light-front quantization, which are challenged by non-perturbative computations with a pertinent regulator for light-cone/rapidity divergences (or zero modes). As such, standard lattice QCD studies have been limited to indirect parton observables such as first few moments and short-distance correlations, which do not provide the $x$ -distributions without solving the model-dependent inverse problem. Here I describe an alternative formulation of partons in terms of equal-time (or Euclidean) correlators, which allows to compute precision-controlled $x$ -distribution through lattice QCD simulations. This approach is in accord with Weinberg's pioneering idea of effective field theory as well as Wilson's renormalization group, in which the large hadron momentum serves as a natural cut-off for light-cone/rapidity divergences and can ultimately be eliminated through a method like the ``perfect action'' program in lattice QCD.
↳ hep-phhep-lathep-thnucl-thNPB(2024)·19 citations
08
Transverse force distributions in the proton from lattice QCD
J. A. Crawford🇦🇺 · K. U. Can🇦🇺 · R. Horsley🇬🇧 · P. E. L. Rakow🇬🇧 · G. Schierholz🇩🇪 · H. Stüben🇩🇪 · R. D. Young🇦🇺 · J. M. Zanotti🇦🇺
Single-spin asymmetries observed in polarised deep-inelastic scattering are important probes of hadron structure. The Sivers asymmetry has been the focus of much attention in QCD phenomenology and is yet to be understood at the quark level. In this Letter, we present a lattice QCD calculation of the spatial distribution of a colour-Lorentz force acting on the struck quark in a proton. We determine a spin-independent confining force, as well as spin-dependent force distributions with local forces on the order of 3 GeV/fm. These distributions offer a complementary picture of the Sivers asymmetry in transversely polarised deep-inelastic scattering.
↳ hep-lathep-phnucl-thPRL(2025)·16 citations
09
Fundamental physical constants, operation of physical phenomena and entropy increase
K. Trachenko
Approaching the problem of understanding fundamental physical constants (FPCs) started with discussing the role these constants play in high-energy nuclear physics and astrophysics. Condensed matter physics was relatively unexplored in this regard. More recently, it was realised that FPCs set lower or upper bounds on key condensed matter properties. Here, we discuss a much wider role played by FPCs in condensed matter physics: at given environmental conditions, FPCs set the observability and operation of entire physical effects and phenomena. We discuss structural and superconducting phase transitions and transitions between different states of matter, with implications for life processes. We also discuss metastable states, transitions between them, chemical reactions and their products. A byproduct of this discussion is that the order of magnitude of the transition temperature can be calculated from FPCs only. We show that the new states emerging as a result of various transitions increase the phase space and entropy. Were FPCs to take different values, these transitions would become inoperative at our environmental conditions and the new states due to these transitions would not emerge. This suggests that the current values of FPCs, by enabling various transitions and reactions which give rise to new states, promote entropy increase. Based on this entropy increase and the associated increase of statistical probability, we conjecture that entropy increase is a selection principle for FPCs considered to be variable in earlier discussions.
↳ cond-mat.stat-mechhep-thnucl-thJ.Phys.Condens.Matter(2025)·0 citations
10
Late-time asymptotic solutions, attractor, and focusing behavior of spin hydrodynamics
Dong-Lin Wang🇨🇳 · Li Yan🇨🇳 · Shi Pu🇨🇳
We have investigated the late-time asymptotic solutions, attractor, and focusing behavior of minimal causal spin hydrodynamics in Bjorken expansion. Using the method of dominant balance, we derive the late-time asymptotic solutions of the evolution equation for spin density and identify the specific conditions necessary for the spin density to exhibit a power-law decay. We then analyze both the late-time and early-time attractors for the decay rate of spin density. Additionally, we report the focusing behavior in spin hydrodynamics, which has not been found in conventional relativistic hydrodynamics in Bjorken expansion. Our findings suggest that spin density can be treated as a conventional hydrodynamic variable at late times under certain conditions.
↳ hep-phhep-thnucl-thPRD(2025)·9 citations
11
Investigation of pion-nucleon contributions to nucleon matrix elements
Constantia Alexandrou🇨🇾 · Giannis Koutsou🇨🇾 · Yan Li🇨🇾 · Marcus Petschlies🇩🇪 · Ferenc Pittler🇨🇾
We investigate contributions of excited states to nucleon matrix elements computed in lattice QCD by employing, in addition to the standard nucleon interpolating operator, pion-nucleon ( $π$ - $N$ ) operators. We solve a generalized eigenvalue problem (GEVP) to obtain an optimal interpolating operator that minimizes overlap with the $π$ - $N$ states. We derive a variant of the standard application of the GEVP method, which allows for constructing 3-point correlation functions using the optimized interpolating operator without requiring the computationally demanding combination that includes $π$ - $N$ operators in both sink and source. We extract nucleon matrix elements using two twisted mass fermion ensembles, one ensemble generated using pion mass of 346 MeV and one ensemble tuned to reproduce the physical value of the pion mass. Especially, we determine the isoscalar and isovector scalar, pseudoscalar, vector, axial, and tensor matrix elements. We include results obtained using a range of kinematic setups, including momentum in the sink. Our results using this variational approach are compared with previous results obtained using the same ensembles and multi-state fits without GEVP improvement. We find that for the physical mass point ensemble, the improvement, in terms of suppression of excited states using this method, is most significant for the case of the matrix elements of the isovector axial and pseudoscalar currents.
↳ hep-lathep-phnucl-thPRD(2024)·19 citations
12
Explaining Snowball-in-hell Phenomena in Heavy-ion Collisions Using a Novel Thermodynamic Variable
Eric Braaten🇺🇸 · Kevin Ingles🇺🇸 · Justin Pickett🇺🇸
A loosely bound hadronic molecule produced by a relativistic heavy-ion collision has been described as a ``snowball in hell'' since it emerges from a hadron resonance gas whose temperature is orders of magnitude larger than the binding energy of the molecule. This remarkable phenomenon can be explained in terms of a novel thermodynamic variable called the ``contact'' that is conjugate to the binding momentum of the molecule. The production rate of the molecule can be expressed in terms of the contact density at the kinetic freezeout of the hadron resonance gas. It approaches a nonzero limit as the binding energy goes to 0.
↳ hep-phnucl-thPRL(2025)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE