Nuclear Theory·nucl-th

Thursday·January 9, 2025

10 papers—3 primary·7 cross-listed

04
Decay spectroscopy of heavy and superheavy nuclei
Dieter Ackermann🇫🇷
After more than half a century since the first predictions of the so-called "island of stability of superheavy nuclei", exploring the limits of nuclear stability at highest atomic numbers is still one of the most prominent challenges in low-energy nuclear physics. These exotic nuclear species reveal their character and details of some of their properties through their induced or spontaneous disintegration. The achievements in the field of superheavy nuclei (SHN) research, which involves studying the production and decay of the heaviest nuclear species, have been reported in a number of review papers. In the introduction of this paper, references are provided to review papers, summarizing the many aspects of SHN research in other disciplines, like chemistry, atomic physics, and earlier work on nuclear structure, including in-beam spectroscopy, and superheavy element (SHE) synthesis. This review is an attempt to summarize the experimental progress that has been made in recent years by employing the versatile tool park of Decay Spectroscopy After Separation (DSAS) for the heaviest isotopes from Z=99 (einsteinium) to Z=118 (oganesson). DSAS, with its major instrumentation components heavy-ion accelerator, separator and decay detection, is the only way to access the heaviest nuclei up to oganesson. While in-beam {\gamma}-spectroscopy has reached 256Rf in terms of the highest atomic number Z and mass number A, SHE chemistry succeeded to sort flerovium (Z = 114) as the heaviest element into the periodic table. Laser spectroscopy and precise mass measurements are limited basically to the nobelium/fermium region, with high-precision Penning-trap mass-measurements being performed for 256Lr and 257Rf, and with the 257Db mass obtained, using a multi-reflection time-of-flight mass spectrometer (MRToF MS).
↳ nucl-exnucl-thPPNP(2026)·6 citations
05
A Bogomol'nyi-Prasad-Sommerfield bound with a first-order system in the $2 D$ Gross-Pitaevskii equation
Fabrizio Canfora🇨🇱 · Pablo Pais🇨🇱
A novel Bogomol'nyi-Prasad-Sommerfield (BPS) bound for the Gross-Pitaevskii equations in two spatial dimensions is presented. The energy can be bounded from below in terms of the combination of two boundary terms, one related to the vorticity (but ``dressed'' by the condensate profile) and the second to the ``skewness'' of the configurations. The bound is saturated by configurations that satisfy a system of two first-order partial differential equations. When such a BPS system is satisfied, the Gross-Pitaevskii equations are also satisfied. The analytic solutions of this BPS system in the present manuscript represent configurations with fractional vorticity living in an annulus. Using these techniques, we present the first analytic examples of this kind. The hydrodynamical interpretation of the BPS system is discussed, and the implications of these results are outlined.
↳ cond-mat.quant-gashep-phhep-thnlin.SI+1EPJC(2025)·6 citations
06
Two-loop form factors for $P$ -wave quarkonium production and decay
Melih A. Ozcelik🇫🇷
We present the analytical results for the two-loop form factors needed for $χ_{Q, J}$ production and decay. We consider the two-loop corrections to the process $γ γ \leftrightarrow^{3} P_{J}^{[1]}$ , that has been known only numerically before, and the processes $g g \leftrightarrow^{3} P_{J}^{[1]}$ , $γ g \leftrightarrow^{3} P_{J}^{[8]}$ and $g g \leftrightarrow^{3} P_{J}^{[8]}$ , which have not been computed before. We observe that the NRQCD pole structure of the two-loop amplitude in the $g g$ channel is more involved for the spin-triplet $P$ -wave case than for the pseudo-scalar $S$ -wave case. It involves in addition to the standard Coulomb singularity also a new singularity whose cancellation requires the inclusion of the $g g \leftrightarrow^{3} S_{1}^{[8]}$ form factor. We give the high precision numerical results for the hard functions that can be used to compute $χ_{Q, J}$ production and decay up to NNLO accuracy.
↳ hep-phnucl-thJHEP(2025)·2 citations
07
On the $θ$ -angle physics of QCD under pressure: The strange and isospin phase diagram
Jahmall Bersini🇯🇵 · Alessandra D'Alise🇮🇹 · Clelia Gambardella🇮🇹 · Francesco Sannino🇮🇹
We unveil the impact of the $θ$ -angle on the QCD phase diagram at nonzero isospin and strangeness chemical potentials for three light flavors and different quark mass ratios. We establish the phase boundaries as well as the nature of the associated phase transitions. The order parameters and the physical spectrum in the different phases are determined. We further elucidate the physics around $θ = π$ where we discover a novel parity-preserving superfluid phase. Finally, we comment on Dashen's phenomenon in the superfluid phases when varying the number of light flavors.
↳ hep-phhep-lathep-thnucl-thJHEP(2025)·3 citations
08
Understanding thermalization in a non-Abelian gauge theory in terms of its soft modes
Sayak Guin🇮🇳 · Harshit Pandey🇮🇳 · Sayantan Sharma🇮🇳
We measure the maximal Lyapunov exponent $λ_{L}$ of physical states in a SU(2) gauge theory consisting of soft momentum modes both in and out-of-thermal equilibrium conditions using ab-initio lattice techniques. We have implemented different algorithms to appropriately describe the dynamics of soft-modes for a wide range of temperatures and under non-equilibrium conditions. The non-equilibrium state has been realized starting from an over-occupied initial condition for low momentum soft gluons whereas the thermal state comprises of strongly interacting soft gluons at temperatures where these are well separated from the hard momentum modes. Spectra of positive Lyapunov exponents is observed in both these states, similar to a chaotic dynamical system. From the Kolmogorov-Sinai entropy rate measured in terms of this spectrum, we estimate a typical time-scale of $\sim 0.50 (3)$ fm/c to achieve thermalization at $T \sim 600$ MeV starting from the non-thermal state. We also measure, for the first time, the $λ_{L}$ for long wavelength critical modes of SU(2) using the out-of-time-ordered correlator of a classical $Z_{2}$ scalar field theory, which shares the same universal behavior with SU(2), near the deconfinement phase transition. The $λ_{L}$ is observed to maximize at the transition temperature.
↳ hep-lathep-phhep-thnucl-thPLB(2025)·10 citations
09
Isospin strikes back
Francesco Rosini🇮🇹 · Simone Pacetti🇮🇹
Assuming isospin conservation, the decay of a $c c ˉ$ vector meson into the $Λ Σ ˉ^{0} + c.c.$ final state is purely electromagnetic. At the leading order, the $c c ˉ$ vector meson first converts into a virtual photon that, then produces the $Λ Σ ˉ^{0} + c.c.$ final state. Moreover, such a mechanism, i.e., the virtual photon coupling to $Λ Σ ˉ^{0} + c.c.$ , is the solely intermediate process through which, in Born approximation, the reaction $e^{+} e^{-} \to Λ Σ ˉ^{0} + c.c.$ does proceed. It follows that any significant difference between the amplitudes of the processes $c c ˉ \to Λ Σ ˉ^{0} + c.c.$ and $e^{+} e^{-} \to Λ Σ ˉ^{0} + c.c.$ at the $c c ˉ$ mass must be ascribed to an isospin-violating contribution in the $c c ˉ$ decay. In Eur. Phys. J. C $80$ , 903 (2020) we studied the decay of the $ψ (2 S)$ vector meson into $Λ Σ ˉ^{0} + c.c.$ and, on the light of the large branching fraction $BR_{18} (ψ (2 S) \to Λ Σ ˉ^{0} + c.c.) = (1.23 \pm 0.24) \times 1 0^{- 5}$ , published in the 2018 edition of the Review of Particle Physics Phys. Rev. D $98$ , 030001 (2018), we claimed either the presence of a significant isospin-violating contribution or, with a lesser emphasis, a "not complete reliability of the only available datum". In any case, we propose a new measurement. Apparently, our second and considered less serious hypothesis was the right one, indeed the branching fraction published in the 2024 edition of the Review of Particle Physics Phys. Rev. D $110$ , 030001 (2024) is $BR (ψ (2 S) \to Λ Σ ˉ^{0} + c.c.) = (1.6 \pm 0.7) \times 1 0^{- 6}$ , more than seven times lower with the error that increased from $\sim 20%$ to $\sim 45%$ .
↳ hep-phhep-exnucl-thEPJC(2025)·3 citations
10
Pressure inside hadrons: criticism, conjectures, and all that
Cédric Lorcé (Ecole Polytechnique, CPHT)🇫🇷 · Peter Schweitzer (Connecticut U.)🇺🇸
The interpretation of the energy-momentum tensor form factor $D (t)$ of hadrons in terms of pressure and shear force distributions is discussed, concerns raised in the literature are reviewed, and ways to reconcile the concerns with the interpretation are indicated.
↳ hep-phnucl-thActa Phys.Polon.B(2025)·36 citations

Affiliations

first authorsco-authorsvia INSPIRE

Decay spectroscopy of heavy and superheavy nuclei

A Bogomol'nyi-Prasad-Sommerfield bound with a first-order system in the 2D Gross-Pitaevskii equation

Two-loop form factors for P-wave quarkonium production and decay

On the θ-angle physics of QCD under pressure: The strange and isospin phase diagram

Understanding thermalization in a non-Abelian gauge theory in terms of its soft modes

Isospin strikes back

Pressure inside hadrons: criticism, conjectures, and all that

Affiliations

A Bogomol'nyi-Prasad-Sommerfield bound with a first-order system in the $2 D$ Gross-Pitaevskii equation

Two-loop form factors for $P$ -wave quarkonium production and decay

On the $θ$ -angle physics of QCD under pressure: The strange and isospin phase diagram