Nuclear Theory·nucl-th

Tuesday·June 23, 2026

31 papers—16 primary·15 cross-listed

17
UHECR Clustering: Lightest Nuclei from Local Sheet Galaxies
Daniele Fargion🇮🇹 · Pier Giorgio De Sanctis Lucentini🇷🇺 · Maxim Yu. Khlopov🇷🇺
The ultra-high-energy cosmic ray (UHECR) puzzle is reviewed under the hints of a few basic results: clustering, anisotropy, asymmetry, bending, and composition changes with energies. We show how the lightest UHECR nuclei from the nearest AGN or Star-Burst sources, located inside a few Mpc Local Sheets, may explain, at best, the observed clustering of Hot Spots at tens EeV energy. Among the possible local extragalactic candidate sources, we derived the main contribution of very few galactic sources. These are located in the Local Sheet plane within a distance of a few Mpc, ejecting UHECR at a few tens of EeV energy. UHECR also shine at lower energies of several EeV, partially feeding the Auger dipole by LMC and possibly a few nearer galactic sources. For the very recent highest energy UHECR event, if a nucleon, it may be explained by a model based on the scattering of UHE ZeV neutrinos on low-mass relic neutrinos. Such scatterings are capable of correlating, via Z boson resonance, the most distant cosmic sources above the GZK bound with such an enigmatic UHECR event. Otherwise, these extreme events, if made by the heaviest composition, could originate from the largest bending trajectory of heaviest nuclei or from nearby sources, even galactic ones. In summary, the present lightest to heavy nuclei model UHECR from the Local Sheet could successfully correlate UHECR clustering with the nearest galaxies and AGN. Heavy UHECR may shine by being widely deflected from the Local Sheet or from past galactic, GRB, or SGR explosive ejection.
↳ astro-ph.HEastro-ph.COastro-ph.GAhep-ph+1Universe(2024)·8 citations
18
Neural Wavefunctions in Quantum Field Theory I: Asymptotic Freedom
Paulo F. Bedaque🇺🇸 · Hersh Kumar🇺🇸 · Suryansh Rajawat🇺🇸 · Gregory Ridgway🇺🇸
We present a variational approach to quantum field theory based on wavefunctions parameterized by neural networks. While variational methods have a celebrated history across many fields, their application to quantum field theory has been limited by well-known challenges. We show that neural-network wavefunctions, combined with modern machine-learning techniques, enable competitive variational calculations in nontrivial field theories. As a demonstration, we reproduce the essential features of the two-dimensional nonlinear $σ$ -model: asymptotic freedom, dynamical mass generation and the model's step-scaling function.
↳ hep-lathep-phhep-thnucl-th+10 citations
19
Event-Level QCD Inference Framework for Quark-Gluon Imaging
Patrick Barry🇺🇸 · Pi-Yueh Chuang🇺🇸 · Ian Cloët🇺🇸 · Emil Constantinescu🇺🇸 · Arkaprabha Ganguli🇺🇸 · Chao Peng🇺🇸
We introduce and demonstrate an event-level analysis framework for quark-gluon imaging. For a first application we use it for the inference of parton distribution functions from synthetic deep inelastic scattering data. This framework removes the need for unfolding of detector effects and the binning of events, and therefore eliminates two key sources of information loss. We contrast this event-level framework with the traditional histogram approach by performing a closure test for parton distribution functions from event data obtained from a known ground truth. In this study we assume a perfect detector, which makes unfolding straightforward. The elimination of binning in the event-level framework is demonstrated to have important benefits over the traditional histogram approach, and performs better in the closure test, particularly for a smaller number of events. For example, defining a mean-squared error distance metric, we find that the event-level framework performs around $35%$ better than the traditional approach for a moderate number of events. The benefits of an event-level framework should increase for inference associated with 3D quark-gluon imaging, because these differential cross sections are of higher dimension and the comparative number of measured events is significantly reduced.
↳ hep-phhep-exnucl-th0 citations
20
Gluon GTMD at strong coupling: fixed-spin saddle factorization and Reggeization
Kiminad A. Mamo🇺🇸 · Ismail Zahed🇺🇸
Generalized transverse-momentum-dependent parton distributions (GTMDs) are the most complete two-parton correlation functions in QCD, encoding the joint spatial and momentum structure of hadrons. Through appropriate projections and limits they yield generalized parton distributions (GPDs), transverse-momentum-dependent distributions (TMDs), parton distribution functions (PDFs), and phase-space (Wigner) distributions. We construct conformal moments of unpolarized gluon GTMDs at strong coupling using gauge/string duality. For fixed even conformal spin $j$ , we distinguish the local boundary limit at $b_{T} = 0$ from the finite-separation regime $b_{T} > 0$ , where the planar semiclassical amplitude is governed by a minimal worldsheet. There the GTMD moment factorizes into a universal staple-worldsheet soft factor and a stripped spin- $j$ Witten amplitude carrying target dependence. The cusp of the renormalized minimal area generates the rapidity-logarithmic Collins-Soper structure. We derive universal ultraviolet and infrared endpoint reductions. As $b_{T} \to 0^{+}$ , the finite-separation sector matches onto the local conformal moment through a universal overlap kernel. At large $b_{T}$ , after cusp/perimeter subtraction, it factorizes into target projections and infrared transfer kernels. The ultraviolet endpoint is universal within the leading saddle, whereas the infrared tail depends on the holographic completion: soft-wall, gap-matched hard-wall, and repulsive-wall backgrounds generate algebraic, exponential, and Gaussian falloffs, respectively. Analytic continuation in $j$ yields the low- $x$ Regge regime governed by the holographic Pomeron spectral curve. The framework describes hadron tomography, transverse structure, rapidity evolution, and Reggeization for GTMD moments and provides a unified starting point for holographic studies of observables relevant to the Electron-Ion Collider.
↳ hep-phhep-thnucl-th0 citations
21
Pion structure from its light-front wave function
Khépani Raya · Zhen-Ni Xu · Zhao-Qian Yao · José Rodríguez-Quintero
Understanding the structural properties of the pion is essential for elucidating the mechanisms of mass generation within the Standard Model and their role in the emergence and properties of the hadronic matter. Light-front wave functions encode extensive information about the internal structure of these systems and provide the link to measurable quantities such as generalized parton distributions and transverse-momentum-dependent distributions. Guided by recent progress in continuum Schwinger methods, we derive well-founded and practical representations of these quantities, enabling the exploration of several facets of the pion structure, including distribution amplitudes and distribution functions, elastic and gravitational form factors, and the associated momentum and spatial distributions. The results presented here are consistent with expectations and can be tested at modern experimental facilities, including the new generation of electron-ion colliders.
↳ hep-phnucl-th1 citation
22
Evidence of the Excited X(5)-like Critical-Point Symmetry Structures in 152Sm
S. Basak🇮🇳 · S. Rajbanshi🇮🇳 · T. Bhattacharjee🇮🇳 · D. Kumar🇮🇳 · A. Pal🇮🇳 · S. S. Alam🇮🇳 · A. Saha🇮🇳 · A. K. Sikdar🇮🇳 · J. Nandi🇮🇳 · Ananya Das🇮🇳 · Shabir Dar🇸🇪 · S. Samanta and 14 other authors
The positive-parity structure of 152Sm has been investigated through high-statistics {\gamma}-ray spectroscopy following the (150Nd({\alpha},2n)152Sm reaction at Elab = 26 MeV. Several collective structures built on excited 0+ states have been extended through the observation of new levels and {\gamma}-ray transitions, and spin-parity assignments have been established using directional-correlation and linear-polarization measurements. Electromagnetic transition strengths (B(E2)), deduced from measured branching ratios and known level lifetimes, reveal pronounced collectivity among the excited configurations. The resulting level scheme provides evidence for a sequence of excited collective bands extending beyond the well-known ground-state and first excited 0+ structures. The excitation energies and transition strengths are examined within the framework of the X(5) critical-point description of the first-order U(5)-SU(3) shape-phase transition. In addition to the established X(5)-like features of the low-lying spectrum, the observed systematics of the higher-lying bands are found to be consistent with excited collective structures exhibiting X(5)-like characteristics. The results provide new constraints on the realization of critical-point behavior in finite nuclei and on the evolution of collectivity in the N=90 region.
↳ nucl-exnucl-thPLB(2026)·0 citations
23
A New Scaling of Neutron Star Tidal Deformability for Directly Probing the Core Equation of State
Jian-Hao Shi🇨🇳 · Bao-Jun Cai🇨🇳 · Bao-An Li🇺🇸 · Yu-Gang Ma🇨🇳
The dimensionless tidal deformability, $Λ$ , of neutron stars (NSs), inferred from gravitational-wave (GW) observations, has thus far been used primarily to constrain the pressure of dense matter near twice nuclear saturation density, leaving the core equation of state (EOS) largely inaccessible to inspiral-phase GW observations. We show that the core EOS can be probed directly through $Λ$ using a perturbative analysis of the dimensionless stellar-structure and tidal-response equations formulated in terms of scaled intrinsic variables, without invoking any specific EOS model. We uncover a remarkable EOS-insensitive scaling relation between $Λ$ and the central EOS parameter $X \equiv P_{c} / ε_{c}$ , where $P_{c}$ and $ε_{c}$ denote the central pressure and energy density, respectively. The relation is validated against a broad ensemble of physically viable EOSs. Applying it to tidal deformabilities inferred from events such as GW170817 enables a direct determination of $X$ . We further derive a tight lower bound, $Λ_{TOV} ≳ 9. 2_{- 1.2}^{+ 1.2}$ , for maximum-mass NSs along stable mass-radius sequences, quantitatively demonstrating that even the most compact stable NSs remain distinctly separated from black holes, for which $Λ_{BH} = 0$ . These findings reveal a previously unrecognized connection between inspiral-phase tidal deformability and the core EOS, establishing a direct link between GW observables and the microphysics of ultradense matter in the strong-gravity regime. The resulting scaling establishes inspiral-phase tidal deformability as a direct and largely model-insensitive probe of the EOS of NS cores.
↳ astro-ph.HEgr-qcnucl-exnucl-th2 citations
24
The shear viscosity of quark-gluon matter calculated with parton transport and comparisons with the Chapman-Enskog results
Mason Alexander Ross🇺🇸 · Zi-Wei Lin🇺🇸
We numerically calculate the shear viscosity of quark-gluon matter via the Green-Kubo relation with an improved ZPC model. We include all $2 \leftrightarrow 2$ parton cross sections at finite temperature, which are based on perturbative QCD and screened with thermal masses, and consider massless quark-gluon systems with Boltzmann statistics in chemical equilibrium. We then compare the Green-Kubo results with the analytical results from the leading-order Chapman-Enskog method for the same parton cross sections over the temperature range $150 - 600$ MeV. We also examine the simpler case of isotropic and constant parton cross sections. Overall, we find that the two methods agree rather well. Specifically, the Green-Kubo results are greater than the Chapman-Enskog results by an average of $\sim 9%$ for isotropic and constant cross sections and by an average of $\sim 3%$ for finite-temperature pQCD cross sections, where the difference between the two methods is presumably due to higher-order corrections to the leading-order Chapman-Enskog results.
↳ hep-phnucl-th1 citation
25
Proton's isovector PDF with updated analysis of large-momentum lattice data
Xiangdong Ji🇨🇳 · Yushan Su🇺🇸
The proton's unpolarized $u (x) - d (x)$ parton distribution function (PDF) has been studied by a number of lattice QCD groups through large momentum expansion. However, due to lattice artifacts (excited state contaminations, unphysical pion masses, and discretization effects) and less-advanced theoretical analysis (renormalizations, large-distance extrapolations, and large-log resummations), the resulting PDFs cannot be compared strictly with experimental data. By using the state-of-the-art theoretical tools and mitigating the lattice artifacts empirically, we reanalyze the available datasets in the literature and find that the new PDF in the physical limits is consistent with global fittings within $\sim 1 σ$ . This provides compelling evidence that large momentum expansion is capable of accurately predicting the $x$ -dependence of the PDFs when ideal lattice data become available.
↳ hep-lathep-phnucl-th0 citations
26
Quantum Simulation of Generalized Parton Distributions in the Schwinger Model
Tianyin Li🇯🇵 · Hongxi Xing🇨🇳
We present a quantum algorithm for simulating Generalized Parton Distributions (GPDs) in the Schwinger model. Unlike the staggered fermions widely utilized in current quantum simulations, we employ Wilson fermions for lattice discretization. This choice is critical for the quantum computation of GPDs due to their strict preservation of charge conjugation symmetry. We construct a comprehensive algorithmic framework that includes the preparation of hadronic states with non-zero momentum and the measurement of light-cone correlation functions incorporating Wilson lines. We provide a complexity analysis, demonstrating that the resources required for our algorithm scale polynomially with both the number of qubits and the desired precision $ε$ . Finally, we benchmark our approach using exact diagonalization, extracting mass spectra and GPDs (also parton distribution functions) that are consistent with theoretical expectations and fundamental physical constraints.
↳ hep-phhep-latnucl-th0 citations
27
Quantized Irreversible Null-geometry: Foundation and Applications
Si-xue Qin🇨🇳
Formulating a consistent integration measure for quantum geometric fluctuations without violating diffeomorphism invariance remains a theoretical challenge. In this work, a framework rooted in the statistics of discrete Poisson point processes is proposed. The formulation yields a double-exponential probability functional characterized by a capacity limit, which acts as an amplitude regularizer suppressing ultraviolet singularities. To evaluate this model at macroscopic scales, a statistical bifurcation of the stochastic action is identified. First, the macroscopic mean condenses to define the classical continuous spacetime background and its matter distribution. Second, at macroscopic scales, the Law of Large Numbers dictates that the residual ultraviolet noise maps into an infrared continuous zero-mean Gaussian martingale within the bulk. Third, this zero-mean Gaussian noise linearly generates standard quantum kinematic effects. Fourth, evaluating the non-linear exponential action separates the variance of this Gaussian noise from the linear cancellation, rectifying it into a macroscopic drift that manifests as the dark energy density. Diluted by the Bekenstein-Hawking entropy of the observable universe, this bulk variance dictates a continuous field cutoff at 6 TeV. Building upon this framework, broad phenomenological applications are demonstrated: (1) establishing a UV-finite effective field theory preserving gauge symmetries in 4D; (2) constructing a topological model of particles deriving Standard Model hierarchies; (3) formulating a non-singular cosmological model predicting observed large-scale power suppression in the cosmic microwave background; and (4) deriving foundational axioms of quantum mechanics as emergent statistical phenomenologies. Collectively, this framework provides a falsifiable synthesis bridging discrete quantum geometry and continuous macroscopic physics.
↳ hep-thmath-phmath.MPnucl-th0 citations
28
A novel approach for studying two-particle momentum correlation function in relativistic nuclear collisions
Zhi-Lei She🇨🇳 · Wen-Chao Zhang🇨🇳 · An-Ke Lei🇨🇳 · Dai-Mei Zhou🇨🇳 · Hua Zheng🇨🇳 · Li-Lin Zhu🇨🇳 · Qiang Wang🇨🇳 · Yu-Liang Yan🇨🇳 · Zhong-Qi Wang🇨🇳 · Ben-Hao Sa🇨🇳
Two particle momentum correlation functions provide a nontrivial tool for probing the strong interaction and/or extracting particle emission source information in relativistic nuclear collisions. Although transport models can describe the microscopic phase-space evolution of the collision system, calculating correlation functions within the framework of transport models remains challenging. In this paper, we employ the mixed-event technique to calculate two particle momentum correlation function as $C (k^{*}) = N ξ (k^{*}) \frac{N _{same} ( k ^{*} )}{N _{mixed} ( k ^{*} )}$ based on the parton and hadron cascade model PACIAE simulated final hadronic state (FHS) with introducing a modification factor $ξ (k^{*})$ to improve the treatment of final-state interactions and quantum statistics effects in the PACIAE model. The simulated results show good agreement with the ALICE data for $K p$ , $pp$ , $p Λ$ , and $ΛΛ$ momentum correlation functions in $pp$ collisions at $s = 7$ TeV. On the other hand, the particle emission source radius of the correlated pairs are also evaluated based on the simulated FHS self-consistently. Since the PACIAE model employs hadron-hadron cross sections derived from the additive quark model, the calculation of two-particle momentum correlation functions does not require prior assumptions about the interaction between the two correlated particles. This successful ``PACIAE + modification factor" approach may shed light on the future study of momentum correlation functions for dimesons, dibaryons, and even diexotic hadrons.
↳ hep-phnucl-th0 citations
29
Neutron Star Mass-Radius Constraints for EXO 0748 $-$ 676 from 2008-2025 Quiescent X-ray Spectra
Mingyang Wang · Guobao Zhang · Ang Li
We present new constraints on the mass and radius of the neutron star in the neutron star low-mass X-ray binary EXO 0748 $-$ 676 obtained from a joint analysis of 20 quiescent X-ray observations obtained between 2008 and 2025, including 14 Chandra and 6 XMM-Newton exposures. These data sample two quiescent episodes separated by the 2024 $-$ 2025 outburst. We model the 0.5 $-$ 10 keV spectra with a hydrogen-atmosphere model, assuming a source distance of 7.1 kpc. In a global Markov Chain Monte Carlo analysis in which the hydrogen column density, neutron star mass, and radius are tied across all observations, we obtain a neutron-star mass of $1.7 7_{- 0.22}^{+ 0.17} M_{⊙}$ and a radius of $12.6 2_{- 0.74}^{+ 0.56}$ km ( $1 σ$ credible intervals). We further perform independent fits to the first and second quiescent epochs and find that the combined data set significantly reduces the low-mass tail in the posterior distribution, leading to tighter lower bounds on the neutron-star mass. Incorporating the distance uncertainty of $7.1 \pm 1.2$ kpc, we conservatively constrain the neutron-star mass and radius to $M ≃ 1.41 - 2.11 M_{⊙}$ and $R ≃ 10.15 - 15.13$ km, favoring relatively stiff dense-matter equations of state. We also trace the thermal evolution across two quiescent epochs and find evidence for renewed crust cooling following the 2024 $-$ 2025 outburst, providing a unique opportunity to compare the thermal relaxation behavior after two distinct accretion episodes.
↳ astro-ph.HEastro-ph.SRnucl-th0 citations
30
Irrelevance of Anomalous Breaking of Axial U(1) Symmetry and the U(1) Problem
Nodoka Yamanaka🇯🇵
The eta and eta' mesons are conventionally known to receive contribution from the anomalous breaking of axial U(1) symmetry, and they are considered to not be the Nambu-Goldstone (NG) bosons of the spontaneous chiral SU(3)_L x SU(3)_R symmetry breaking of QCD. However, it has recently been shown that this axial U(1) anomaly is not actually physical. In this contribution, we first review this statement and then propose a mechanism in which eta and eta' mesons are indeed NG bosons while being consistent with the axial U(1) problem.
↳ hep-phhep-exnucl-th0 citations
31
Quantification of the Flavor Diagonal Hadronic CP Violation
Nodoka Yamanaka🇯🇵
The flavor diagonal CP violation of elementary particle physics contributes to the atomic, nuclear, and nucleon electric dipole moments (EDMs), T-violating neutron optics, and to the angular correlations of beta decay. In this contribution, we review the basics and the importance of CP violation in the search for new physics beyond the standard model, the recent progress in the quantification of the hadron level CP violation contributing to the aforementioned observables, and finally the current attempt to solve the strong CP problem without additional interactions and fields.
↳ hep-phhep-exhep-thnucl-ex+10 citations

Affiliations

first authorsco-authorsvia INSPIRE