Nuclear Theory·nucl-th

Thursday·April 24, 2025

6 papers—2 primary·4 cross-listed

01
Energy Rates Due to Weak Decay Rates of Vanadium Isotopes in Stellar Environment
Ramoona Shehzadi🇵🇰 · Jameel-Un Nabi🇵🇰 · Huma Ali🇵🇰
The neutrino cooling and gamma heating rates are considered as an important input needed to study the final phases of the evolution of high-mass stars. The weak-interaction mediated processes, namely the $β$ -decay and electron capture, significantly change the lepton to baryon ratio and accelerate the contraction of the core. The emission of resulting neutrinos/antineutrinos tends to cool the stellar core. On the other hand, gamma rays are produced because of electron capture and $β$ -decay to excited states in daughter nuclei. These gamma rays heat the core and contribute to an increase of entropy which may cause convection to occur. In the present work, the weak-interaction heating and cooling rates on a chain of twenty-two isotopes of vanadium having mass in the range $43 - 64$ have been estimated using the proton-neutron quasiparticle random phase approximation theory. The rates have been computed for the temperature ranging from ( $1 0^{7} - 3 \times 1 0^{10}$ )\;K and for the density range ( $10 - 1 0^{11}$ )\;g/cm $^{3}$ . Our calculated neutrino energy loss rates have also been compared with the previously reported rates calculated using other theoretical models. At high stellar temperatures, our rates are larger by 1-2 orders of magnitude as compared to previous results.
nucl-thAstrophys.Space Sci.(2020)·3 citations
02
Impact of spin polarization on the QCD equation of state
De-Xian Wei🇨🇳
Spin polarization provides a novel probe of the rotational properties of the quark-gluon plasma formed in relativistic heavy-ion collisions. This work investigates the equation of state, particularly its transport and thermodynamic coefficients in noncentral O+O collisions, employing a parton distribution function that incorporates spin polarization induced by thermal vorticity. Within a kinetic theory framework, one finds that the magnitude of the squared speed of sound ( $c_{s}^{2}$ ) is only weakly modified by spin polarization, whereas the specific shear viscosity ( $η / s$ ), specific bulk viscosity ( $ζ / s$ ), and mean free path ( $λ$ ) show substantial changes. When spin polarization is included, both $c_{s}^{2}$ and $ζ / s$ develop a nonmonotonic dependence on the collision energy, with an inflection point near $s_{N N} = 27$ GeV, corresponding to an average parton chemical potential of $⟨ μ_{p} ⟩ = 0.021$ GeV. These results suggest that spin polarization may serve as a useful probe for constraining the effective equation of state of QCD matter.
nucl-thPRC(2026)·1 citation
03
A New Look At Small- $x$ Helicity Phenomenology: Investigating Uncertainties And The Impact Of Polarized Proton-proton Data
Nicholas Baldonado🇺🇸
This dissertation highlights the contributions I have made to the field of theoretical nuclear physics, specifically in high-energy Quantum Chromodynamics (QCD). High-energy QCD is a robust subject and my research is refined to the sub-field of small- $x$ spin physics; small- $x$ physics is characterized by high-energy and density collisions and is well-suited for the Color Glass Condensate (CGC) effective field theory. Small- $x$ spin physics takes the ultra-relativistic description of high-energy QCD and gives special attention to spin-dependent interactions suppressed by powers of the center-of-mass energy. My expertise lies in exploring the theory and phenomenology relating to the KPS-CTT small- $x$ helicity evolution equations, a rubric that allows one to make predictions of the quarks' and gluons' distributions of spin at small- $x$ . These predictions are heavily influenced by the initial conditions of the evolution, and the initial conditions are determined through analyses of world polarized data. My contributions focus on Bayesian parameter analysis, numerical and analytical calculations to discretize and cross-check the evolution equations, and the incorporation of a new observable into the pool of analyzed data. The results of such work show that the net amount of spin from quarks and gluons in the small- $x$ regime is predicted to be negative and/or potentially small; an analysis of polarized deep-inelastic scattering (DIS) and semi-inclusive DIS (SIDIS) data resulted in a net small- $x$ spin prediction that can be large and negative, but new results with the inclusion of data for single-inclusive jet production in polarized proton-proton ( $pp$ ) collisions now estimate that the net amount of parton spin at small $x$ is small, with 1- $σ$ uncertainty that spans zero.
↳ hep-phhep-thnucl-th0 citations
04
Criteria of Renormalizability in Effective Field Theories
A. M. Gasparyan🇩🇪 · E. Epelbaum🇩🇪
Any effective field theory relies on power counting rules that allow one to perform a systematic expansion of calculated quantities in terms of some soft scales. However, a naive power counting can be violated due to the presence of various hard scales in a given scheme. A typical example of such a scale is an ultraviolet regulator. This issue is particularly challenging when the interaction is nonperturbative. The power counting is expected to be restored in the course of renormalization, that is by redefining bare low-energy constants in the effective Lagrangian. Whether this procedure eventually leads to a self-consistent framework is not a priory obvious. We discuss various criteria of renormalizability in application to nuclear chiral effective field theory and provide several instructive counterexamples.
↳ hep-phnucl-thPoS(2026)·2 citations
05
Medium-induced coherent gluon radiation for $2 \to 2$ processes with general kinematics
Greg Jackson🇫🇷 · Stéphane Peigné🇫🇷 · Kazuhiro Watanabe🇯🇵
High-energy proton-nucleus (pA) collisions offer valuable insight into the role of cold nuclear matter effects in hadron production. In particular, multiple rescatterings of an incoming parton by the nuclear target are known to induce the radiation of many soft gluons. Hadron production is affected by fully coherent energy loss (FCEL), owing to those radiated gluons with a long formation time. Here we present a recently derived formula for the induced single soft gluon radiation spectrum beyond leading logarithmic accuracy, whose main features are demonstrated with the example of $q g \to q g$ scattering.
↳ hep-phnucl-thEPJ Web Conf.(2025)·0 citations
06
Particles in finite volumes and a toy model of decaying neutrons
Christian Käding🇦🇹
It is well-known that the momentum spectra of particles confined to finite spatial volumes deviate from the continuous spectra used for unconfined particles. In this article, we consider real scalar particles confined to finite volumes with periodic boundary conditions, such that the particles' spectra are discrete. We directly compute the density matrices describing the decay processes $ϕ \to φ^{2}$ and $ϕ \to φ χ ν$ , and subsequently derive expressions for the decay probabilities both for confined and unconfined particles. The latter decay process is used as a rough toy model for a neutron decaying into a proton, an electron, and an anti-electron neutrino. We propose that finite volume effects can have an impact on the outcomes of experiments measuring the neutron lifetime. In addition, our findings at the toy model level suggest that taking into account possible initial correlations between neutrons and their daughter particles might be relevant as well.
↳ hep-phhep-thnucl-exnucl-th+1EPJC(2025)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE

Energy Rates Due to Weak Decay Rates of Vanadium Isotopes in Stellar Environment

Impact of spin polarization on the QCD equation of state

A New Look At Small-x Helicity Phenomenology: Investigating Uncertainties And The Impact Of Polarized Proton-proton Data

Criteria of Renormalizability in Effective Field Theories

Medium-induced coherent gluon radiation for 2→2 processes with general kinematics

Particles in finite volumes and a toy model of decaying neutrons

Affiliations

A New Look At Small- $x$ Helicity Phenomenology: Investigating Uncertainties And The Impact Of Polarized Proton-proton Data

Medium-induced coherent gluon radiation for $2 \to 2$ processes with general kinematics