Nuclear Theory·nucl-th

Wednesday·January 28, 2026

17 papers—11 primary·6 cross-listed

12
[Submitted on 25 Aug 2025] (cross-list from hep-ph)
Gravitational $D$ -Form Factor: The $σ$ -Meson as a Dilaton confronted with Lattice Data
Roy Stegeman🇬🇧 · Roman Zwicky🇬🇧
We investigate the nucleon and pion gravitational $D$ -form factors, by fitting a $σ / f_{0} (500)$ -meson pole, together with a background term, to lattice data at $m_{π} \approx 170 MeV$ . We find that the fitted residues are compatible with predictions from dilaton effective theory. In this framework, the $σ$ -meson takes on the role of the dilaton, the Goldstone boson of spontaneously broken scale symmetry. These results support the idea that QCD may be governed by an infrared fixed point and offer a physical interpretation of the $D$ -form factor (or $D$ -term) in the soft limit.
Comments:
27 pages plus refs, 6 figures and 3 tables, better motivation of fit ansatz and residue interpretation (added appendix C with comparison plots to other fits)
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2508.18537 [pdf]
JHEP(2026)·22 citations
13
[Submitted on 26 Jan 2026] (cross-list from hep-ph)
Next-to-next-to-leading power corrections to unpolarized Semi-Inclusive Deep Inelastic Scattering
Ian Balitsky🇺🇸 · Alexei Prokudin🇺🇸
Semi-Inclusive Deep Inelastic Scattering (SIDIS) is a key tool for exploring the three-dimensional structure of the nucleon through Transverse Momentum Dependent parton distributions and fragmentation functions. While leading-power contributions to the SIDIS cross-section are well established, next-to-leading (NLP) of order $1/ Q$ and next-to-next-to-leading power (NNLP) corrections of order $1/ Q^{2}$ to the hadronic tensor have only recently begun to be systematically investigated. These corrections are essential for the reliable phenomenology and interpretation of modern high-precision data. In recent papers by one of the authors, NNLP corrections to Drell-Yan process were derived using rapidity factorization formalism. In the present work we extend this approach to SIDIS and obtain analytic expressions for the unpolarized structure functions. We derive NNLP corrections that include convolutions of unpolarized distributions, $f_{1}$ , with unpolarized fragmentation functions, $D_{1}$ , and Boer-Mulders functions, $h_{1}^{⊥}$ , with Collins fragmentation functions, $H_{1}^{⊥}$ . We compare our results with previous formulations, provide numerical studies, confront our predictions with HERMES and COMPASS measurements, and present predictions for future experiments at Jefferson Lab and the Electron-Ion Collider.
Comments:
30 pages, 15 figures, JHEP published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2601.18882 [pdf]
JHEP(2026)·4 citations
14
[Submitted on 27 Jan 2026] (cross-list from hep-ph)
Origin of the nucleon gravitational form factor $B_{N} (t)$ : Exposition in light-front holographic QCD
Xianghui Cao🇨🇳 · Bheemsehan Gurjar🇨🇳 · Chandan Mondal🇨🇳 · Chen Chen🇨🇳 · Yang Li🇨🇳
Recent lattice QCD simulations and phenomenological models indicate that the nucleon's gravitational form factor $B_{N} (t)$ remains remarkably small at finite momentum transfer $t$ . While $B_{N} (0) = 0$ is a known consequence of the equivalence principle, the physical origin of its suppression at finite $t$ has not been fully elucidated. In this work, we demonstrate that the smallness of $B_{N} (t)$ arises from a fundamental cancellation within the nucleon's wave functions. Using light-front holographic QCD, we show that $B_{N} (t)$ is governed by an antisymmetric factor in the longitudinal dynamics that leads to the exact vanishing of the form factor in the symmetric limit and significant suppression for realistic nucleon structures. Our results suggest that the smallness of $B_{N} (t)$ is a signature of the nucleon's dominant S-wave character, providing a formal justification for its frequent omission in practical applications like near-threshold $J / ψ$ production.
Comments:
7 pages, 4 figures. To appear in Phys. Rev. D as a letter
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
arXiv:
2601.19141 [pdf]
PRD(2026)·2 citations
15
[Submitted on 27 Jan 2026] (cross-list from hep-ph)
Probing New Physics and CP Violation in $ν_{τ} n \to Λ_{c} τ^{-} (π^{-} ν_{τ})$ and $ν ˉ_{τ} p \to Λ τ^{+} (π^{+} ν ˉ_{τ})$
E. Hernández🇪🇸 · J. Nieves🇪🇸 · J. E. Sobczyk🇸🇪
We study the processes $ν_{τ} n \to Λ_{c} τ^{-} (π^{-} ν_{τ})$ and $ν ˉ_{τ} p \to Λ τ^{+} (π^{+} ν ˉ_{τ})$ , with particular emphasis on the pion energy and angular distributions, as a possible signal for lepton flavor universality violation, and in general of physics beyond the Standard Model (SM), as well as a sensitive probe of the $τ$ polarization vector. We work within an effective low-energy extension of the SM with all dimension-six four-fermion operators. In this framework, complex Wilson coefficients which encode new physics can generate CP-violating contributions. We propose an observable that provides a genuine CP-odd signal due to its sensitivity to particular transverse components of the $τ$ polarization vector. Namely, we show that the asymmetry in the azimuthal-angle distribution of the pion in the decay $τ^{\pm} \to π^{\pm} ν_{τ}$ constitutes a smoking-gun prediction of such a beyond the SM scenario. We estimate the strength of this effect extrapolating nucleon-hyperon form factors recently obtained from lattice QCD calculations.
Comments:
18 latex pages, 5 figures and 2 tables
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2601.19397 [pdf]
PRD(2026)·0 citations
16
[Submitted on 27 Jan 2026] (cross-list from gr-qc)
The diffusion equation is compatible with special relativity
Lorenzo Gavassino🇬🇧
Due to its parabolic character, the diffusion equation exhibits instantaneous spatial spreading, and becomes unstable when Lorentz-boosted. According to the conventional interpretation, these features reflect a fundamental incompatibility with special relativity. In this Letter, we show that this interpretation is incorrect by demonstrating that any smooth and sufficiently localized solution of the diffusion equation is the particle density of an exact solution of the relativistic Vlasov-Fokker-Planck equation. This establishes the existence of a causal, stable, and thermodynamically consistent relativistic kinetic theory whose hydrodynamic sector is governed exactly by diffusion at all wavelengths. We further demonstrate that the standard arguments for instability arise from considering solutions that admit no counterpart in kinetic theory, and that apparent violations of causality disappear once signals are defined in terms of the underlying microscopic data.
Comments:
6 pages, 0 figures, published in PRL (see https://journals.aps.org/prl/abstract/10.1103/rkz9-xps2)
Subjects:
General Relativity and Quantum Cosmology (gr-qc); High Energy Physics — Theory (hep-th); Mathematical Physics (math-ph); math.MP (math.MP); Nuclear Theory (nucl-th)
arXiv:
2601.19464 [pdf]
PRL(2026)·6 citations
17
[Submitted on 27 Jan 2026] (cross-list from hep-ph)
The leading Lyapunov exponent in the glasma
Pooja🇫🇮 · Dana Avramescu🇫🇮 · Tuomas Lappi🇫🇮
We show that small perturbations in the boost-invariant color fields of the glasma exhibit an exponential growth with the square root of time. We interpret this growth rate as a Lyapunov exponent, related to entropy production and the thermalization timescale in the earliest stage of heavy-ion collisions. Working in a regime that is linear in this perturbation, we extract the time dependence of this mode as $\sim exp (0.4 g^{2} μτ)$ for SU( $2$ ), where $g^{2} μ$ is proportional to the saturation scale and the square-root dependence is caused by the boost-invariant expansion of the system. We show that the growth rate of this mode is, unlike its amplitude, remarkably insensitive to the details of how the perturbations are initialized. In particular, we show that the unstable mode couples to all momentum scales present in the initial perturbation.
Comments:
18 pages, 9 figures, v2: Updated 1 reference, corrected typo in equation (51). Version accepted for publication in Phys. Rev. D
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
2601.19679 [pdf]
PRD(2026)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE

Gravitational D-Form Factor: The σ-Meson as a Dilaton confronted with Lattice Data

Next-to-next-to-leading power corrections to unpolarized Semi-Inclusive Deep Inelastic Scattering

Origin of the nucleon gravitational form factor BN​(t): Exposition in light-front holographic QCD

Probing New Physics and CP Violation in ντ​n→Λc​τ−(π−ντ​) and νˉτ​p→Λτ+(π+νˉτ​)

The diffusion equation is compatible with special relativity

The leading Lyapunov exponent in the glasma

Affiliations

Gravitational $D$ -Form Factor: The $σ$ -Meson as a Dilaton confronted with Lattice Data

Origin of the nucleon gravitational form factor $B_{N} (t)$ : Exposition in light-front holographic QCD

Probing New Physics and CP Violation in $ν_{τ} n \to Λ_{c} τ^{-} (π^{-} ν_{τ})$ and $ν ˉ_{τ} p \to Λ τ^{+} (π^{+} ν ˉ_{τ})$