Nuclear Theory·nucl-th

Wednesday·July 30, 2025

10 papers—2 primary·8 cross-listed

03
Hadron Production Processes
Horst Lenske🇩🇪 · Igor Strakovsky🇺🇸
The experimental search for the pion -- proposed in 1935 by Hideki Yukawa as the force carrier of the strong nucleon-nucleon interaction -- was rewarded in 1947 when in cosmic ray photographic emulsion data a charged particle was identified with the proper mass of about 300 times the electron mass, completed three years later by the discovery of the neutral pion. Since then, accelerator-driven pion and meson (photo-)production on the nucleon and the associated production of new baryons have become the key elements for ground-breaking discoveries in numerous areas of particle and nuclear physics, from fundamental symmetries and their breaking to low-energy QCD dynamics, laying also foundations for modern elementary particle physics and the Standard Model. This article is an overview of eight decades of experimental and theoretical meson production physics, from isospin to charm and beyond, forming our understanding of hadrons and their interactions.
↳ hep-phhep-thnucl-th2 citations
04
Gravitational form factors of the nucleon in the Skyrme model based on scale-invariant chiral perturbation theory
Mitsuru Tanaka🇯🇵 · Daisuke Fujii🇯🇵 · Mamiya Kawaguchi🇨🇳
We investigate the role of the QCD scale anomaly in the gravitational form factors of the nucleon -- particularly the $D (t)$ form factor -- as well as the associated stress distribution and internal forces, using a Skyrme model based on the scale-invariant chiral perturbation theory. A distinctive feature of this model is the inclusion of both the pion and the scalar meson, which respectively capture the effects of the current quark mass and gluonic quantum contributions to the scale anomaly. By varying the mass of the scalar meson, we evaluate the sensitivity of the gluonic scale anomaly to the nucleon properties. We find that the gluonic scale anomaly plays a crucial role in satisfying the stability conditions of the nucleon and provides an internal confining force. Moreover, we also evaluate the momentum-transfer dependence of $D (t)$ , which closely reproduces the lattice QCD results. With an appropriate choice of the anomalous dimension associated with the quark mass, its forward-limit value (i.e., the D-term) also matches the lattice data well.
↳ hep-phhep-thnucl-thPRD(2025)·17 citations
05
QCD-Gravity double copy in Regge asymptotics: from $2 \to n$ amplitudes to radiation in shockwave collisions
Himanshu Raj🇺🇸 · Raju Venugopalan🇺🇸
These lectures discuss multi-particle production in QCD and in gravity at ultrarelativistic energies, their double copy relations, and strong parallels in emergent shockwave dynamics. Dispersive techniques are applied to derive the BFKL equation for multi-gluon production in Regge asymptotics. Identical methods apply in gravity and are captured by a gravitational Lipatov equation. The building blocks in both cases are Lipatov vertices and reggeized propagators satisfying double copy relations; in gravity, Weinberg's soft theorem is recovered as a limit of the Lipatov framework. BFKL evolution in QCD generates wee parton states of maximal occupancy characterized by an emergent semi-hard saturation scale. Renormalization group equations in the Color Glass Condensate (CGC) EFT describe wee parton correlations and their rapidity evolution. A shockwave picture of deeply inelastic scattering and hadron-hadron collisions follows, with multi-particle production described by Cutkosky's rules in strong time-dependent fields. Gluon radiation in the CGC EFT has a double copy in gravitational shockwave collisions, with a similar correspondence applicable between gluon and graviton shockwave propagators. Possible extensions of this semi-classical double copy are outlined for computing multi-particle production in gravitational shockwave collisions, self-force and tidal contributions, and classical and quantum noise in the focusing of geodesics.
↳ hep-thgr-qchep-phnucl-thActa Phys.Polon.B(2025)·6 citations
06
Hydrodynamics with multiple charges and holography
Liam Gladden🇬🇧 · Victor Ivo🇺🇸 · Pavel K. Kovtun🇨🇦 · Andrei O. Starinets🇬🇧
We establish the connection between thermodynamic and dynamical instabilities in relativistic hydrodynamics with multiple flavours of conserved U(1) charges. In theories with positive hydrodynamic entropy production, where the underlying perfect fluid has a positive speed of sound squared and satisfies the null energy condition, we show that hydrodynamic instabilities can arise only through negative diffusion coefficients associated with the U(1) charges. The onset of such instabilities is governed by the eigenvalues of the thermodynamic Hessian matrix, while the flavour-space polarisations of the unstable diffusion modes are determined by the corresponding eigenvectors. We illustrate this connection using strongly coupled N=4 supersymmetric Yang-Mills theory at finite densities of the three U(1) R-charges. In the dual holographic description, the five-dimensional STU black brane exhibits unstable quasinormal modes precisely at the onset of thermodynamic instability. We derive analytic expressions for the R-charge diffusion coefficients in several representative cases, including the configuration with three equal chemical potentials.
↳ hep-thgr-qchep-phnucl-thJHEP(2025)·6 citations
07
Hadronic Molecules and $χ_{c J} (2 P)$ Coupled States
Kotaro Miyake🇯🇵 · Yasuhiro Yamaguchi🇯🇵
We investigate hidden-charm exotic mesons based on a coupled-channel framework, where the physical states are described as superpositions of a compact $c c ˉ$ core (identified with the $χ_{c J} (2 P)$ states) and hadronic components such as $D^{(*)} D ˉ^{(*)}$ . We incorporate meson exchange potentials to describe hadron-hadron interactions and determine model parameters to reproduce the observed masses of $X (3872)$ and $Z (3930)$ . The model also predicts a $0^{++}$ bound state consistent with the $X (3860)$ . The internal structure is found to be predominantly molecular for the $X (3872)$ , while the $X (3860)$ and $Z (3930)$ have larger $c c ˉ$ components. The coupling between $c c ˉ$ cores and hadronic components plays a crucial role in generating these states. The resulting wave functions provide insight into the internal structure and decay properties of these exotic states.
↳ hep-phnucl-thPoS(2026)·0 citations
08
Net-Charge Fluctuations in Finite Volume PNJL Model: A Probe for the QCD Critical Point
Amal Sarkar🇮🇳 · Paramita Deb🇮🇳 · Bidhan Mandal · Raghava Varma
The QCD Critical Point is a pivotal feature of the phase diagram of strongly interacting matter. Signatures of the critical point are expected to manifest through the non-monotonic behavior of higher-order moments of conserved quantities, such as net-baryon ( $Δ B$ ), net-charge ( $Δ Q$ ), and net-strangeness ( $Δ S$ ), as a function of collision energy. These moments are connected to the thermodynamic susceptibilities, as well as to the correlation length developed in the system, which diverges at the critical point. The non-monotonic behavior of higher-order moments and their volume-independent products near the critical region supports the presence of a critical point in a finite system existing for a finite time, due to their sensitivity to critical fluctuations. These fluctuations are believed to provide key evidence in the search for the QCD Critical Point. We present the higher order moments, such as mean (M), variance $(σ^{2})$ , skewness (S), and kurtosis $(κ)$ and their volume-independent moment products $(M / σ^{2}, s σ, κ σ^{2})$ of net-charge multiplicity distributions in the three-flavor finite volume, finite density Polyakov loop enhanced Nambu-Jona-Lasinio (PNJL) model. The work has been performed at energies similar to RHIC BES energies from 7.7 GeV to 200 GeV, including 2.4 and 3 GeV in the present model. Our findings are compared with the STAR net-charge data at various collision energies to explore signals of the QCD critical point. Additionally, we contrast our results with predictions from the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model, the Hadron Resonance Gas (HRG) model, and available lattice QCD data. The present results offer a useful tool for extracting the freeze-out parameters in the heavy-ion collision by comparing them with the STAR net-charge result and other net-charge theoretical models.
↳ hep-phnucl-th4 citations
09
Shape evolution in neutron-rich odd-even $^{105 - 109}$ Nb isotopes
M. Abushawish🇫🇷 · E. H. Wang🇨🇳 · J. Dudouet🇫🇷 · A. Navin🇫🇷 · E. Clément🇫🇷 · G. Duchêne🇫🇷 · J. H. Hamilton🇺🇸 · A. Lemasson🇫🇷 · C. Michelagnoli🇫🇷 · O. Stezowski🇫🇷 · S. Bhattacharyya🇮🇳 · F. DidierJean🇫🇷 and 6 other authors
Neutron-rich nuclei around $Z \sim 40$ exhibit multiple shape transitions. This region shows one of the sharpest transitions in the nuclear chart, from a spherical vibrator at $N = 58$ to a strongly deformed prolate shape at $N = 60$ , with largest deformations seen for $_{38}$ Sr and $_{40}$ Zr. Below $Z = 36$ , a spherical-to-oblate transition is predicted, while above $Z = 42$ and $N \geq 60$ , the shape evolves from axial to triaxial. Even- $Z$ nuclei have been well studied, but odd- $Z$ isotopes such as Nb offer additional insights into these mechanisms. The Nb isotopes lie at the boundary between axially deformed Zr and triaxially deformed Mo nuclei. This work explores the structure of neutron-rich Nb nuclei up to $N = 68$ , aiming to understand shape evolution with isospin and the onset of triaxiality. Two complementary fission experiments were used: (i) $^{238}$ U+ $^{9}$ Be at GANIL in inverse kinematics with AGATA, EXOGAM, and VAMOS++, allowing prompt and delayed $γ$ -ray spectroscopy with isotopic identification; (ii) spontaneous fission of $^{252}$ Cf with the Gammasphere array providing high-fold $γ$ -coincidence data. The level scheme of $^{105}$ Nb was significantly extended with two new negative-parity bands. A revised scheme is proposed for $^{107}$ Nb, differing from previous results, and new structures are reported in $^{109}$ Nb. The signature splitting analysis indicates triaxial deformation for positive-parity bands, while negative-parity bands show axial symmetry, similar to Zr. This reveals a shape coexistence in neutron-rich Nb nuclei.
↳ nucl-exnucl-thPRC(2026)·2 citations
10
Neutrino non-radiative decay in matter: constraints and prospects
Pilar Iváñez-Ballesteros (APC, Paris)🇫🇷 · M. Cristina Volpe (APC, Paris)🇫🇷
Neutrinos, being massive, can decay. A heavier neutrino could decay into a lighter one and a massless scalar or pseudoscalar boson, such as the Majoron. Two-body non-radiative decay could occur in dense matter, such as in the inner dense regions of a core-collapse supernova. We first derive novel bounds on neutrino-Majoron couplings using the spectral distortions induced by neutrino non-radiative two-body decay in matter, and two-dimensional likelihood analyses of the 24 $ν ˉ_{e}$ events from SN1987A. We then explore the prospects of neutrino-Majoron couplings from a future galactic core-collapse supernova, leaving either a neutron star or a black-hole. To this aim, we use information from detailed one-dimensional supernova simulations. We consider the supernova neutrino signal associated with inverse-beta decay in the upcoming JUNO and Hyper-Kamiokande detectors, with neutrino-argon scattering in DUNE, or with coherent neutrino-nucleus scattering in the DARWIN experiment. In a full 3 $ν$ framework, based on the spectral distortions induced by neutrino decay in matter, we perform two-dimensional likelihood analyses and provide prospects for the limits on neutrino-Majoron couplings. Our results show that the observation of a future supernova will significantly improve on the current bounds, in particular from SN1987A and neutrinoless double-beta decay. Finally, we explore the impact of neutrino decay in matter on the diffuse supernova neutrino background formed by past supernova explosions. We show for the first time that the effects on black-hole contributions are important and modify the DSNB number of events by several tens of percent in Hyper-Kamiokande.
↳ hep-phastro-ph.SRhep-exnucl-ex+1JCAP(2026)·4 citations

Affiliations

first authorsco-authorsvia INSPIRE