Nuclear Theory·nucl-th

Wednesday·August 27, 2025

13 papers—9 primary·4 cross-listed

10
A New Evidence of Interplay Between Tetrahedral and Octahedral Symmetries and Symmetry Breaking: Exotic Rotational Bands in $^{152}$ Sm
S. Basak🇮🇳 · D. Kumar🇮🇳 · T. Bhattacharjee🇮🇳 · I. Dedes🇵🇱 · J. Dudek🇵🇱 · A. Pal🇮🇳 · S. S. Alam🇮🇳 · A. Saha🇮🇳 · A. K. Sikdar🇮🇳 · J. Nandi🇮🇳 · Shabir Dar🇮🇳 · A. Baran🇵🇱 and 21 other authors
We report on an experimental evidence for a new, second tetrahedral band in $_{62}^{152}$ Sm $_{90}$ . It was populated via fusion evaporation reaction, $^{150} Nd (α, 2 n)^{152}$ Sm, employing 26 MeV beam of $α$ particles from K-130 cyclotron at Variable Energy Cyclotron Centre, Kolkata, India. The newly observed possible mixed parity sequence with absence of E2 and strong indication of E3 transitions is consistent with the spectroscopic criteria for a tetrahedral-symmetry rotational band that could be constructed from the allowed spin-parity assignments. This structure differs from the structure of the band previously found in the same nucleus, the new one manifesting tetrahedral symmetry not accompanied by the octahedral one. Our new experimental results are interpreted in terms of group representation theory and collective nuclear-motion theory of Bohr. We propose to generalize the notion of the tetrahedral vibrational bands and believe that our new experimental results support a number of theory predictions related to nuclear tetrahedral symmetry published earlier and bring a new light into the issue of spontaneous symmetry breaking in heavy nuclei.
↳ nucl-exnucl-thPRC(2025)·7 citations
11
Beam-Normal Single-Spin Asymmetry in $^{208}$ Pb at low energy: discrepancy resolved or new kinematic puzzle?
A. Esser · N. Kozyrev · K. Aulenbacher · S. Baunack · M. Dehn · A. Del Vincio · L. Doria · M. Hoek · F. Keil · F. Maas · H. Merkel · M. Mihovilovic and 8 other authors
A longstanding discrepancy between measured and predicted beam-normal single-spin asymmetries $A_{n}$ in elastic electron scattering off $^{208}$ Pb has challenged our understanding of two-photon exchange (TPE) in heavy nuclei. We report a new measurement at 570 MeV and $Q^{2}$ =0.04 $G e V^{2}$ / $c^{2}$ , yielding $A_{n} = (- 9.1 \pm 2.1 (stat) \pm 0.7 (syst)) ppm$ . This nonzero value contrasts with previous results at higher energies and suggests a kinematic dependence of TPE effects not captured by current theory, prompting a reevaluation of earlier interpretations.
↳ nucl-exhep-exnucl-thPRL(2025)·4 citations
12
Single pion-production and pion propagation in Achilles
Joshua Isaacson🇺🇸 · William Jay🇺🇸 · Alessandro Lovato🇺🇸 · Pedro Machado🇺🇸 · Alexis Nikolakopoulos🇺🇸 · Noemi Rocco🇺🇸 · Noah Steinberg🇺🇸
We extend the applicability of Achilles (A CHIcagoLand Lepton Event Simulator) by incorporating the single-pion production mechanism in a fully exclusive fashion. The electroweak interaction vertex is modeled by combining the state-of-the-art Dynamical Coupled-Channels approach with realistic hole spectral functions, which account for correlations in both the initial target state and the residual spectator system. Final-state interactions are treated using a semi-classical intranuclear cascade that leverages nuclear configurations to determine the correlated spatial distribution of protons and neutrons. The meson-baryon scattering amplitudes used in the cascade are computed within the Dynamical Coupled-Channels framework, consistent with the electroweak vertex. To model pion absorption, we employ the optical potential approach of Oset and Salcedo. As an alternative approach, we explicitly model the production and propagation of resonances which mediate pion-nucleon scattering and pion absorption. We validate out approach against pion-nucleon and pion-nucleus scattering data, and present comparisons with electron- and neutrino-nucleus measurements from e4 $ν$ , T2K, MINER $ν$ A, and MicroBooNE.
↳ hep-phhep-exnucl-thPRD(2026)·5 citations
13
Classification of color superconductivity by one-gluon exchange helicity amplitudes and renormalization group equations
Yuki Fujimoto🇯🇵
Quark matter at high baryon density exhibits diverse pairing patterns classified by color, flavor, and angular momentum quantum numbers. We compute one-gluon exchange (OGE) helicity amplitudes and introduce a nonrelativistic classification of the pairing channel, justified by the channel decomposition in a Lorentz-noninvariant medium and the decoupling of renormalization group flows at leading order. We find the new attractive channel in OGE; the medium effects can render the vacuum-repulsive color $6$ channel attractive in the spin-triplet sector. For color $3 ˉ$ with antisymmetric flavor, the dominant pairing is $^{1} S_{0}$ , while for symmetric flavor the same-helicity $^{1} P_{1}$ prevails over $^{3} S_{1}$ , revising the conventional single-flavor picture. With a mismatch of the Fermi momenta, $^{1} S_{0}$ channel, leading to color-flavor locked or two-flavor color superconductor, remains most stable when the separation is small, and the color-spin locked pairing becomes favored as the mismatch gets large. We suggest there are possible quark-hadron continuity in certain cases as expected in the literature.
↳ hep-phnucl-th1 citation

Affiliations

first authorsco-authorsvia INSPIRE

A New Evidence of Interplay Between Tetrahedral and Octahedral Symmetries and Symmetry Breaking: Exotic Rotational Bands in 152Sm

Beam-Normal Single-Spin Asymmetry in 208Pb at low energy: discrepancy resolved or new kinematic puzzle?

Single pion-production and pion propagation in Achilles

Classification of color superconductivity by one-gluon exchange helicity amplitudes and renormalization group equations

Affiliations

A New Evidence of Interplay Between Tetrahedral and Octahedral Symmetries and Symmetry Breaking: Exotic Rotational Bands in $^{152}$ Sm

Beam-Normal Single-Spin Asymmetry in $^{208}$ Pb at low energy: discrepancy resolved or new kinematic puzzle?