Nuclear Theory·nucl-th

Friday·April 25, 2025

11 papers—6 primary·5 cross-listed

07
Baryon Number Violation: From Nuclear Matrix Elements to BSM Physics
Leah J. Broussard🇺🇸 · Andreas Crivellin🇨🇭 · Martin Hoferichter🇨🇭 · Sergey Syritsyn🇺🇸 · Yasumichi Aoki🇯🇵 · Joshua L. Barrow🇺🇸 · Arnau Bas i Beneito🇪🇸 · Zurab Berezhiani🇮🇹 · Nicola Fulvio Calabria🇮🇹 · Svjetlana Fajfer🇸🇮 · Susan Gardner🇺🇸 · Julian Heeck🇺🇸 and 10 other authors
Processes that violate baryon number, most notably proton decay and $n n ˉ$ transitions, are promising probes of physics beyond the Standard Model (BSM) needed to understand the lack of antimatter in the Universe. To interpret current and forthcoming experimental limits, theory input from nuclear matrix elements to UV complete models enters. Thus, an interplay of experiment, effective field theory, lattice QCD, and BSM model building is required to develop strategies to accurately extract information from current and future data and maximize the impact and sensitivity of next-generation experiments. Here, we briefly summarize the main results and discussions from the workshop "INT-25-91W: Baryon Number Violation: From Nuclear Matrix Elements to BSM Physics," held at the Institute for Nuclear Theory, University of Washington, Seattle, WA, January 13-17, 2025.
↳ hep-phhep-exhep-latnucl-ex+1J.Phys.G(2025)·10 citations
08
Charge Radii Measurements of Exotic Tin Isotopes in the Proximity of $N = 50$ and $N = 82$
F.P. Gustafsson🇧🇪 · L. V. Rodríguez🇩🇪 · R.F. Garcia Ruiz🇺🇸 · T. Miyagi🇯🇵 · S.W. Bai🇨🇳 · D.L. Balabanski🇷🇴 · C.L. Binnersley🇬🇧 · M.L. Bissell🇬🇧 · K. Blaum🇩🇪 · B. Cheal🇬🇧 · T.E. Cocolios🇧🇪 · G.J. Farooq-Smith🇧🇪 and 42 other authors
We report nuclear charge radii for the isotopes $^{104 - 134}$ Sn, measured using two different collinear laser spectroscopy techniques at ISOLDE-CERN. These measurements clarify the arch-like trend in charge radii along the isotopic chain and reveal an odd-even staggering that is more pronounced near the $N = 50$ and $N = 82$ shell closures. The observed local trends are well described by both nuclear density functional theory and valence space in-medium similarity renormalization group calculations. Both theories predict appreciable contributions from beyond-mean-field correlations to the charge radii of the neutron-deficient tin isotopes. The models, however, fall short of reproducing the magnitude of the known $B (E 2)$ transition probabilities, highlighting the remaining challenges in achieving a unified description of both ground-state properties and collective phenomena.
↳ nucl-exnucl-thPRL(2025)·21 citations
09
Gaussian generally covariant hydrodynamics
G.M.Sampaio🇧🇷 · G.Rabelo-Soares🇧🇷 · G.Torrieri🇧🇷
We develop a version of fluctuating relativistic hydrodynamics in a way very different from the usual derivation: Instead of treating it as a coarse-grained deterministic theory expanded in gradients of equilibrium quantities, we treat it as a stochastic theory, characterized by partition functions in each cells, expanded in cumulants. We show that the Gaussian ansatz allows us, via the gravitational Ward identities acting as a constraint between the variance and the average, to maintain full general covariance, with hydrodynamic flow emerging as an approximate Killing vector. If the symmetry of relativistic hydrodynamics, volume-preserving diffeomorphisms, is preserved, we show that linear response formulae are also generally covariant. We discuss our results and argue that in this approach, the applicability of the effective theory is parametrized around a very different quantity than the Knudsen number, offering hope of understanding the applicability of hydrodynamics to small systems.
↳ hep-thgr-qchep-phnucl-thPRD(2025)·8 citations
10
(2+2)D Collective Model based on a relativistic Boltzmann equation in the Isotropization Time Approximation: CoMBolt-ITA
S. F. Taghavi🇩🇪 · S. M. A. Tabatabaee Mehr🇮🇷 · F. Taghinavaz🇮🇷
A new model based on the relativistic Boltzmann equation in the isotropization time approximation is developed to investigate the collective behavior of the quark-gluon plasma produced in high-energy heavy-ion collisions. The equation is solved in (2+2)D (two spatial and two momentum-space dimensions). This framework couples pre-equilibrium dynamics with hydrodynamic evolution to simulate the dynamics of quasiparticle evolution. A numerical scheme based on the method of characteristics enables the evolution to begin from a specified initial Boltzmann distribution. In this work, the spatial structure of the initial distribution is modeled using the TrENTo framework. Our results show that a medium initialized at $τ_{0}$ on the order of 1 [fm/ $c$ ] with a small shear viscosity to entropy density ratio ( $η / s = 0.008$ ) evolves consistently with hydrodynamic simulations, such as those performed using the VISH2+1 code, while discrepancies arise for a medium with $η / s = 0.8$ . Furthermore, when initialized with a highly anisotropic momentum distribution in the longitudinal direction at early times, the system exhibits spatially non-uniform thermalization in the transverse plane, leading to the emergence of a nontrivial hypersurface that marks the onset of hydrodynamic applicability. Finally, we compute the $p_{T}$ -spectra for a non-fluctuating initial condition using the hybrid version of CoMBolt-ITA. In this hybrid setup, the description is switched from quasiparticles to hadrons, and UrQMD is used to model the hadron gas dynamics. We compare these results with those obtained from the hybrid VISH2+1 initialized within the same setup. For a small shear viscosity, $η / s = 0.08$ , the two results show a good level of consistency, whereas for a larger value, $η / s = 0.8$ , a noticeable discrepancy emerges.
↳ hep-phhep-thnucl-thPRC(2026)·2 citations
11
Flux tube clustering from magnetic coupling of adjacent type-I and -II superconductors in a neutron star: persistent gravitational radiation
K. H. Thong · A. Melatos
Adjacent type-I and -II proton superconductors in a rotation-powered pulsar are predicted to exist in a metastable state containing macroscopic and quantized flux tubes, respectively. Previous studies show that the type-I and -II regions are coupled magnetically, when macroscopic flux tubes divide dendritically into quantized flux tubes near the type-I-II interface, through a process known as flux branching. The studies assume that the normal-superconducting boundary is sharp, and the quantized flux tubes do not repel mutually. Here the sharp-interface approximation is refined by accounting for magnetic repulsion. It is found that flux tubes in the same flux tree cluster with a minimum-energy separation two to seven times less than that of isolated flux tubes. Neutron vortices pin and cluster about flux trees. We find that the maximum characteristic wave strain $h_{0}$ of the current quadrupole gravitational radiation emitted by a rectilinear array of clustered vortices exceeds by $(1 + N_{v, t})^{1/2}$ the strain $h_{0} \sim 1 0^{- 32} (f /30 Hz)^{5/2} (D /1 kpc)^{- 1}$ emitted by uniformly distributed vortices, where $N_{v, t}$ is the mean number of pinned vortices per flux tree, $f$ is the star's spin frequency, and $D$ is the star's distance from Earth. The factor $(1 + N_{v, t})^{1/2}$ brings $h_{0}$ close to the sensitivity limit of the current generation of interferometric gravitational wave detectors under certain circumstances, specifically when flux branching forms relatively few (and hence relatively large) flux trees.
↳ astro-ph.HEcond-mat.quant-gascond-mat.supr-congr-qc+1MNRAS(2025)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE

Baryon Number Violation: From Nuclear Matrix Elements to BSM Physics

Charge Radii Measurements of Exotic Tin Isotopes in the Proximity of N=50 and N=82

Gaussian generally covariant hydrodynamics

(2+2)D Collective Model based on a relativistic Boltzmann equation in the Isotropization Time Approximation: CoMBolt-ITA

Flux tube clustering from magnetic coupling of adjacent type-I and -II superconductors in a neutron star: persistent gravitational radiation

Affiliations

Charge Radii Measurements of Exotic Tin Isotopes in the Proximity of $N = 50$ and $N = 82$