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Nuclear Theory·nucl-th

Friday·June 6, 2025

9 papers—3 primary·6 cross-listed

All9Primary3Cross-lists6
  1. 04

    Cross-Section Bootstrap: Unveiling the Froissart Amplitude

    Miguel Correia🇨🇦 · Alessandro Georgoudis🇬🇧 · Andrea L. Guerrieri🇨🇭

    We derive a universal bound on the integrated total scattering cross-section at \emph{finite} energies, expressed in terms of a single low-energy coefficient constrained by the non-perturbative S-matrix Bootstrap. At high energies, the bound is compared with proton-proton scattering data; at low energies, with numerical bootstrap results obtained by directly maximizing the cross-section. We conjecture that the amplitude saturating the cross-section at high energies lies at a strongly-coupled corner of the allowed space of low-energy parameters. This universal amplitude exhibits a rising total cross-section, a shrinking elastic differential cross-section with multiple diffractive minima, and a surprisingly rich spectrum of resonances aligning along Regge trajectories, including Pomeron-like and daughter trajectories, as well as unusual ``singular" trajectories in the forward limit which appear deeply interconnected with Froissart growth. Remarkably, the eikonal representation reveals that the scattering is localized within an annular region that slowly expands with energy, challenging the traditional ``disk" diffraction picture. Our results open the door to theoretical and phenomenological studies of \emph{soft} high-energy hadronic scattering via the S-matrix Bootstrap.

    ↳ hep-thhep-phnucl-th19 citations
  2. 05

    Unpaired Weyl fermion on an axion string in a finite lattice

    Jonathan D. Kroth🇺🇸 · Srimoyee Sen🇺🇸

    Domain wall fermions use a -dimensional spacetime defect embedded in -dimensional spacetime to realize massless lattice Dirac fermions. Recent work has extended this idea to realize a single unpaired Weyl fermion in a finite lattice. Here, we realize the same using a -dimensional string defect embedded in -dimensional spacetime on a finite lattice for . This string is a lattice version of the continuum axion string described in Callan-Harvey. Our results are obtained in a Hamiltonian formulation in Minkowski spacetime. Extending the results to Euclidean spacetime and to is straightforward. This work has applications to lattice chiral gauge theories and axion cosmology.

    ↳ hep-thhep-latnucl-thPRD(2025)·1 citation
  3. 06

    Reflections on Noether's second theorem and the energy-momentum tensor

    Adam Freese🇺🇸

    Through symmetry of the action under global spacetime translations, Noether's first theorem infamously entails an energy-momentum tensor (EMT) that is neither symmetric nor gauge-invariant. In a prior work [Phys. Rev. D 106, 125012 (2022)], I had obtained a symmetric and gauge-invariant EMT by using Noether's second theorem instead, with local spacetime translations as the symmetry group. However, the derivation therein was flawed, containing a faulty assumption about the transformation rule for spinor fields. In this work, I revisit the derivation of [Phys. Rev. D 106, 125012 (2022)], both correcting the faulty step and simplifying the derivation for broader accessibility. The end result is an EMT for quantum chromodynamics that is gauge-invariant, but not symmetric.

    ↳ hep-phgr-qcnucl-thPRD(2026)·7 citations
  4. 07

    Toward an advanced phenomenology of transition distribution amplitudes

    B. Pire🇫🇷 · K. Semenov-Tian-Shansky🇰🇷 · P. Sznajder🇵🇱 · L. Szymanowski🇵🇱

    We introduce a new approach to modeling transition distribution amplitudes (TDAs) for the processes and . The modeling is flexible, constrained by sparsely available experimental data, and satisfies theoretical requirements, including reduction to nucleon distribution amplitudes in the appropriate limit. We study the sensitivity of observable predictions to various modeling assumptions. We discuss unpolarized cross-sections, as well as the three non-vanishing polarization observables at leading twist, namely, the single transverse target spin asymmetry and the two double spin asymmetries that occur with a polarized lepton beam on either a longitudinally or transversely polarized target. The analysis is complemented by a simple Monte Carlo study to provide guidance for exploring exclusive processes in the so-called backward kinematics. Our work aims to highlight the importance of future measurements to better constrain TDAs and to support upcoming experimental proposals.

    ↳ hep-phhep-exnucl-exnucl-thPRD(2025)·3 citations
  5. 08

    Mapping Parton Distributions of Hadrons with Lattice QCD

    Huey-Wen Lin🇺🇸

    The strong force which binds hadrons is described by the theory of quantum chromodynamics (QCD). Determining the character and manifestations of QCD is one of the most important and challenging outstanding issues necessary for a comprehensive understanding of the structure of hadrons. Within the context of the QCD parton picture, the parton distribution functions (PDFs) have been remarkably successful in describing a wide variety of processes. However, these PDFs have generally been confined to the description of collinear partons within the hadron. New experiments and facilities provide the opportunity to additionally explore the three-dimensional structure of hadrons, which can be described by generalized parton distributions (GPDs), for example. In recent years, a breakthrough was made in calculating the Bjorken- dependence of PDFs in lattice QCD by using large-momentum effective theory (LaMET) and other similar frameworks. The breakthrough has led to the emergence and rapid development of direct calculations of Bjorken---dependent structure. In this review article, we show some of the recent progress made in lattice QCD in PDFs and GPDs and discuss future challenges.

    ↳ hep-lathep-phnucl-thPPNP(2025)·28 citations
  6. 09

    Pion-Nucleon Scattering in Baryon Chiral Perturbation Theory combined with the Expansion

    D. Jayakodige🇺🇸 · J. L. Goity🇺🇸

    This work implements the combined BChPT and 1/Nc expansions for pion-nucleon elastic scattering. The effective theory is based on the baryon sector dynamical spin-flavor SU(4) symmetry emergent in the large Nc limit, whose breaking is controlled by the expansion. The non-commutativity of the chiral and 1/Nc expansions in unitarity corrections (loops) requires a linking of both expansions. As it was shown in the case of baryon masses and currents, the natural linking is the -expansion, in which . The spin-flavor symmetry requires that the ground state baryons span an SU(4) symmetric irreducible representation which implies that in particular and are active degrees of freedom in the effective theory. The scattering amplitude is expanded to the next-to-next-to leading order in the expansion, corresponding to the one-loop contributions with the LO Lagrangian. The results are given for generic in order to demonstrate the consistency of the framework. The spin-flavor symmetry plays a central role in maintaining the consistency of the effective theory with respect to the expansion. This consistency manifests itself in an improvement in the convergence of the low energy expansion with respect to the case of the ordinary BChPT without an explicit dynamical , which is known to be inconsistent with the constraints of scaling. Fits to the S, P and D partial wave amplitudes from the SAID data base are finally used to test the framework and to determine the energy range of its applicability.

    ↳ hep-phnucl-thPRD(2025)·1 citation

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first authorsco-authorsvia INSPIRE