Fri·May 8, 2026Friday·May 8, 2026

1. 01*

   All-loop four-quark Bethe-Salpeter kernel

   Piotr Bargiela🇬🇧

   We analytically calculate the all-loop bare perturbative part of the four-quark Bethe-Salpeter kernel using modern scattering amplitude methods. We work to subleading order in the large number of quark flavors approximation of massless Quantum Chromodynamics, which simultaneously makes an all-loop calculation feasible, is systematically improvable, and preserves asymptotic freedom. It also allows for avoiding the ambiguity of choosing a truncation scheme in Dyson-Schwinger equations. We exploit state-of-the-art methods in Integration-By-Parts reduction of Lorentz scalar Feynman integrals into a minimal Master Integral basis, and direct integration into Generalized Polylogarithms. As a byproduct of our calculation, we also provide the result for the gluon and quark propagators. We discuss a path towards nonperturbative formulation and potential future phenomenological applications.

   hep-phhep-lathep-th0 citations
2. 02*

   Evidence for Q-Dependent Nuclear Transverse-Momentum Redistribution Beyond Broadening from AI-driven analysis of p-Cu Drell-Yan

   I. P. Fernando🇺🇸 · D. Keller🇺🇸

   We extract a target-side Cu transverse-momentum profile from fixed-target $p$--Cu Drell--Yan data by holding a momentum-space proton reference fixed and training only an asymmetric Cu kernel in the small-$q_T$ region. In the supported window, $0.15\le x_{Cu}\le 0.46$ and $7.5\le Q_M\le 15.75$ GeV, the nuclear modification is not a universal width increase. It appears as $Q$-dependent redistribution: an $\mathcal{O}(1\mathrm{GeV})$ shoulder and compensating probability flow between shoulder and resolved-tail regions, beyond one-parameter broadening.

   hep-ph0 citations
3. 03*

   Squeezed spectra and back-to-back correlations of protons and antiprotons at RHIC energies

   Yong Zhang🇨🇳

   This study constrains the range of in-medium mass modification through a comparison of theoretical calculations with experimental transverse momentum spectra and the yield ratio {\bar{p}}/p of protons and antiprotons. Based on the constrained range and a Gaussian source model with radial ow, the theoretical predictions for the fermion back-to-back correlation (fBBC) of p{\bar{p}} pairs at RHIC energies are presented. The results reveal a strong sensitivity of the fBBC signal to the assumed source time distribution: a Lorentzian form generates a pronounced high-momentum signal, whereas an {\alpha}-stable Lévy form leads to a marked low-momentum signal. Moreover, the in-medium mass modification is shown to enhance the yield ratio {\bar{p}}/p. Therefore, events characterized by a larger {\bar{p}}/p ratio are predicted to have a significantly higher probability of exhibiting a detectable fBBC signal. This study may propose a promising new direction for the experimental observation of this phenomenon

   hep-phnucl-thPRC(2026)·0 citations
4. 04*

   $T_{c\bar{s}0}^a(2900)$, $T_{cs0}^{\ast }(2900{)}^0$, and other singly heavy tetraquark states

   Zi-Long Man🇨🇳 · Yu-Nan Liu🇨🇳 · Yan-Rui Liu

   We systematically study the mass spectra of $S$-wave singly heavy tetraquark states $Qq\bar{q}\bar{q}$ ($Q=c,b$; $q=u,d,s$) in a mass splitting model. We adopt the assumption that the $X(4140)$ is the lowest $J^{PC}=1^{++}$ $cs\bar{c}\bar{s}$ tetraquark and use this state as a reference to determine the mass splittings. According to the obtained results, we also estimate the rearrangement decay widths of the tetraquarks within a simple scheme. We find that the recently observed states $T_{c\bar{s}0}^a(2900{)}^{++/0}$ and $T_{cs0}^{\ast }(2900{)}^0$ by the LHCb Collaboration can be consistently interpreted as the second highest $I(J^P)=1(0^{+})$ $cn\bar{s}\bar{n}$ ($n=u,d$) and the higher $I(J^P)=0(0^{+})$ $cs\bar{n}\bar{n}$ tetraquark states, respectively. We predict several narrow tetraquark candidates: the lowest $cn\bar{s}\bar{n}$ and $cs\bar{n}\bar{n}$ with $I(J^P)=0(0^{+})$ and $0(1^{+})$, and their bottom counterparts. The obtained information from mass spectrum and rearrangement decay properties will help search for the new singly heavy tetraquark states.

   hep-phPRD(2026)·0 citations
5. 05*

   Massive hybrid stars within the extended three-flavor quark-meson diquark model

   Jens O. Andersen🇳🇴 · Manuel Linares🇳🇴 · Mathias P. Nødtvedt🇳🇴

   We discuss the properties of the extended three-flavor quark-meson diquark (EQMD) model as a renormalizable low-energy effective model for QCD. The effective degrees of freedom are quarks, scalar- and pseudoscalar mesons, diquarks, vector- and axial-vector mesons. We calculate the equation of state (EoS) in the mean-field approximation at $T=0$ imposing charge neutrality for electric and color charges. We match the EoS with a low-density nuclear equation of state. We discuss how the choice of parameters in the model affects the EoS and thereby the mass-radius for hybrid stars. We show that it is possible to construct hybrid stars whose masses and radii are in agreement with recent astrophysical observations and perturbative QCD (pQCD). The addition of vector and axial vector mesons to the quark-meson diquark is essential, since it makes the EoS sufficiently stiff for intermediate densities. Our results suggest that stars with a mass larger than $M\sim 2M_{\odot }$ have a quark core with a central density $n_B\ge 3.9n_{\mathrm{sat}}$, where $n_{\mathrm{sat}}\approx 0.165$fm${}^{-3}$ is the saturation density. The speed of sound has a double-peak structure and relaxes to the conformal limit from above for large baryon chemical potentials ${\mu }_B$. This structure is caused by the decrease in the mass of the $s$ quark as ${\mu }_B$ increases.

   hep-phastro-ph.HEnucl-thPLB(2026)·2 citations
6. 06*

   Top-associated Higgs-boson production using perturbative fragmentation functions at next-to-leading-order

   Colomba Brancaccio🇮🇹 · Michal Czakon🇩🇪 · Terry Generet🇬🇧 · Benedikt Gurdon🇩🇪

   Under certain conditions, the production of a Higgs boson in association with a top-anti-top pair at hadron colliders can be described via a factorisation theorem using perturbative fragmentation functions. The latter describe the nearly collinear emission of a Higgs boson from a top-quark and reproduce the leading mass dependence of the exact next-to-leading-order (NLO) calculation. Although the NLO fragmentation functions have been calculated a few years ago, it has not been possible up to now to demonstrate the applicability of the approximation in a realistic setup. At NLO, we analyse two different ways of treating the top-quark mass, called the zero-mass-top-quark (ZMTQ) and the hybrid prescription. We show that the method yields reliable results at LHC center-of-mass (cms) energies in the hybrid prescription. In the ZMTQ prescription, the results at LHC cms energies are only reliable in the quark-anti-quark channel, but become viable for the full $pp\to t\bar{t}H$ process at a 100 TeV hadron collider. In addition, we discuss some subtleties and complications arising when extending the formalism to next-to-next-to-leading-order (NNLO) and beyond.

   hep-ph0 citations
7. 07*

   Interaction and correlation functions for $\pi f_1(1285)$, $\eta f_1(1285)$

   Wen-Hao Jia🇨🇳 · Hai-Peng Li🇨🇳 · Wei-Hong Liang🇨🇳 · Jing Song🇨🇳 · Eulogio Oset🇪🇸

   We have studied the interaction of ${\pi }^0(\eta )f_1(1285)$ assuming the $f_1(1285)$ to be a molecular state of $K^{\ast }\bar{K}-{\bar{K}}^{\ast }K$. We use a framework in which a ${\pi }^0(\eta )f_1(1285)$ optical potential is obtained, which is later used as the kernel of the Lippmann-Schwinger equation, following the standard method for the interaction of particles with nuclei. The optical potential is obtained using the fixed center approximation to the Faddeev equations, where a cluster, here the $f_1(1285)$, remains unchanged during the interaction, appropriate to the situation that one has here. We have obtained the scattering matrix for this system, the scattering length and effective range, plus the correlation functions. The framework used has been previously tested in the study of the $p{f}_1(1285)$ interaction and has been shown to give results in agreement with the recent experimental measurement of the $p{f}_1(1285)$ correlation function. On the other hand, from this interaction we do not obtain clear signals for the ${\pi }_1(1400)$ or ${\pi }_1(1600)$, nor for the ${\eta }_1(1855)$ resonances, which in other approaches have been claimed to arise from the same dynamics. We, however, obtain a structure in the ${\pi }^0{f}_1(1285)$ amplitude around $1500-1600\mathrm{MeV}$ and a strong cusp at the $\eta f_1(1285)$ threshold of $1833\mathrm{MeV}$.

   hep-ph1 citation
8. 08*

   Kaon Portal to Freeze-in Dark Matter

   Motoi Endo🇯🇵 · Takumu Yamanaka🇯🇵

   We investigate freeze-in production of light dark matter through the quark flavor-changing operator $(\bar{s}{\gamma }_{\mu }d)(\bar{\chi }{\gamma }^{\mu }\chi )$ in a low-reheating cosmology. For reheating temperatures below the QCD crossover, kaon decays and scatterings generate the dark matter abundance through $K\to \pi \chi \bar{\chi }$ and $K\pi \to \chi \bar{\chi }$. The same interaction induces the rare kaon decays $K^{+}\to {\pi }^{+}\chi \bar{\chi }$ and $K_L\to {\pi }^0\chi \bar{\chi }$. This links the freeze-in relic abundance to searches at NA62, KOTO, and KOTO II. We find that lower reheating temperatures require larger couplings to compensate for the Boltzmann-suppressed kaon abundance, making kaon-driven freeze-in dark matter testable at rare kaon decay experiments.

   hep-phastro-ph.COhep-ex1 citation
9. 09*

   Quark-gluon vertex in the complex plane

   M.N. Ferreira🇧🇷 · A.S. Miramontes🇪🇸 · J.M. Morgado🇪🇸 · J. Papavassiliou🇪🇸

   In the present work we explore for the first time the general structure and properties of the nonperturbative quark-gluon vertex in the complex plane. Specifically, we focus on the transversely-projected quark-gluon vertex that emerges from a recently developed symmetry-preserving approach for the study of meson properties beyond the rainbow-ladder approximation. The analysis focuses on the so-called "soft-gluon" limit, which reduces the momentum-dependence of the corresponding vertex form factors to a single momentum variable. The complexification of this variable inside the defining integrals furnishes unambiguously all eight vertex form factors within a concrete domain of the complex variable, delimited by a characteristic parabola. The extent of this reliable domain is determined by the appearance of the first singularity in the integrands of the vertex integrals, where the standard Wick rotation must be duly supplemented by additional crucial contributions. This primary analytic region may be extended considerably by resorting to standard extrapolation methods, which remain valid up until the appearance of complex structures associated with the onset of physical processes. The generalization of the method to arbitrary gluon momenta, and its relevance for the determination of the quark propagator in the complex plane, are briefly discussed.

   hep-phhep-latEPJC(2026)·0 citations
10. 10*

    A Comparative Study of Mass Extraction Schemes and ${\pi }^{\pm }-{\rho }^{\pm }$ Mixing

    Ziyue Wang🇨🇳

    We study the origin of the non-monotonic magnetic-field dependence of the lowest charged pion excitation observed in lattice QCD. In a magnetic field, the charged pion mixes with the longitudinally polarized charged rho meson, which shares the same quantum numbers. Within the SU(2)${}_f$ Nambu--Jona-Lasinio model supplemented by a gauge invariant tree-level $\pi -\rho$ mixing operator constrained by the experimental ${\rho }^{\pm }\to {\pi }^{\pm }\gamma$ decay width, we compare four mass-extraction schemes: rest-mass reconstruction, local bosonization, direct determinant solving with Landau projection, and near-pole expansion. The rest-mass scheme cannot reproduce the lattice-type turnover, while in the local derivative-expansion scheme the turnover presence but is weak which occurs at large magnetic field. By contrast, the direct determinant and near-pole schemes both retain a robust non-monotonic lowest mode. The former is most faithful to the Landau-level kinematics of the charged excitation, while the latter most clearly shows that residue suppression enhances the effective mixing after canonical normalization. Our results indicate that the lattice behavior is a genuine quasiparticle mixing effect, but one whose robustness depends crucially on how the charged-meson pole structure is extracted in a magnetic field.

    hep-phnucl-th0 citations
11. 11*

    Towards Precision Neutrino Fits in GUTs: Relevance of One-Loop Finite Corrections

    Chee Sheng Fong🇧🇷 · Shaikh Saad🇸🇮

    In this work, we perform a dedicated analysis of fermion mass fits in the minimal $SO(10)$ grand unified theory (GUT), going beyond the tree-level approximation by incorporating one-loop finite corrections to the neutrino mass matrix. We show that parameter regions that successfully reproduce all fermion masses and mixings at tree level can lead to significant deviations in neutrino masses and leptonic mixing parameters once the radiative corrections are included. These results expose a limitation of conventional tree-level fitting procedures and highlight the sensitivity of neutrino observables to loop effects. Since in the minimal $SO(10)$ GUT the same set of Yukawa parameters simultaneously governs quark masses, charged lepton masses, and neutrino properties, these radiative corrections propagate across all fermion sectors, reshaping the viable parameter space in a highly non-trivial and correlated manner. We find that the largest corrections to the masses and mixing angles are of order $\mathcal{O}(30\%)$-$\mathcal{O}(40\%)$, therefore, cannot be neglected. In light of the current precision of neutrino oscillation measurements, and the expected improvements from ongoing and future experiments, we demonstrate that the inclusion of one-loop effects is essential for a consistent and reliable exploration of the parameter space, with important implications for the predictivity of $SO(10)$ GUTs.

    hep-ph0 citations
12. 12*

    A High-Precision Statistical Analysis of the SN1987A Neutrino Temporal Distribution

    Riccardo Maria Bozza🇮🇹 · Vigilante di Risi🇮🇹 · Veronica Oliviero🇮🇹 · Giulia Ricciardi🇮🇹 · Francesco Vissani🇮🇹

    The interpretation of the SN1987A neutrino data remains limited by significant absolute timing uncertainties across independent detectors and a long-standing tension in the angular distributions. This work presents a high-precision statistical framework that resolves these issues by formalizing the mathematical distinction between intrinsic and relative timing offsets (ITOs and RTOs). By performing a simultaneous ${\chi }^2$-alignment of the Kamiokande-II and Baksan data with the IMB clock, we systematically incorporate non-Gaussian statistical correlations, reducing the temporal uncertainty by two orders of magnitude to the sub-second level. The ${\chi }^2$-analysis shows that Baksan's absolute timestamps require an advancement of $30.4$s, while those of Kamiokande-II require a delay of about $6.4$s. Establishing this unified, high-precision timeline is critical to test the physical nature of the first Kamiokande-II event (K1), specifically whether its distinct angular features signal the onset of the prompt neutronization burst. Previous literature often assumes that K1 originated from inverse beta decay (IBD) on qualitative grounds. By contrast, our multidimensional likelihood analysis incorporates energy, direction, and MSW flavor-conversion effects to provide the first quantitative constraint on its origin. We find a likelihood ratio of 3-6 in favor of an accretion-phase ${\bar{\nu }}_e$ origin over a neutronization-burst origin, thereby turning a traditional assumption into a statistically bounded physical inference. This framework provides the most stringent constraints to date on the chronology of SN1987A and establishes a precise methodology for future multimessenger observations of Galactic supernovae.

    hep-phastro-ph.HEhep-ex0 citations
13. 13*

    GTMDs, orbital angular momentum, and pretzelosity

    Brean Maynard🇺🇸 · Peter Schweitzer🇺🇸

    The leading Generalized Transverse Momentum Dependent parton distributions (GTMDs) are studied in the bag model. The model description is shown to be theoretically consistent. The orbital angular momentum is studied in terms of the GTMD $F_{1,4}^q$ and Ji sum rule. Analytical proofs of the associated sum rules are given. A deeper relationship between orbital angular momentum and the pretzelosity TMD is established in this model.

    hep-phnucl-th1 citation
14. 14*

    Quantum spin dynamics of heavy quarks and polarization observables in relativistic heavy-ion collisions

    Sunil Jaiswal🇺🇸 · Sourav Dey🇮🇳 · Amaresh Jaiswal🇮🇳

    We develop a quantum spin-density-matrix framework for heavy-quark spin dynamics in relativistic heavy-ion collisions. Starting from an initial polarization induced along the magnetic-field direction, we derive the evolution equation for spin polarization within this framework and obtain analytic solutions. The evolved polarization is connected to open heavy-flavor observables via a fragmentation-based hadronization prescription. For vector mesons, the spin-alignment parameter ${\rho }_{00}$ is constructed by coupling the heavy-quark spin to that of the light antiquark produced during fragmentation. We confront our results with recent ALICE measurements of prompt $D^{\ast +}$ spin alignment in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$ and extract an effective depolarization strength that determines the spin-relaxation time scale. Using this fitted parameter, we provide benchmark estimates for ${\Lambda }_c^{+}$ and ${\bar{\Lambda }}_c^{-}$ polarization, up to an overall spin-transfer normalization. We further estimate the recently proposed elliptic polarization harmonic arising from path-length-dependent depolarization in an anisotropic fireball.

    hep-phnucl-th2 citations
15. 15*

    Probing unknown nonperturbative effects in $b\to s\ell \ell$ with inclusive and exclusive observables

    P. Alvarez-Cartelle🇪🇸 · B. Capdevila🇪🇸 · E. Lunghi🇺🇸 · J. Matias🇪🇸

    In this paper we revisit, from a different perspective, a long-standing question: ``Is the systematic deficit observed in all branching ratios mediated by a $b\to s\mu \mu$ transition due to New Physics, or to a hypothetical constant unknown universal hadronic contribution that mimics New Physics?'' The key observation that allows us to distinguish between these two possibilities is that non-perturbative contributions associated with $c\bar{c}$ loops affect inclusive $B\to X_s\ell \ell$ and exclusive $B\to K^{(\ast )}\ell \ell$ modes differently. In inclusive decays, factorizable contributions are exactly determined from data on $e^{+}{e}^{-}\to \mathrm{hadrons}$, while non-factorizable corrections are described by resolved-photon contributions at low $q^2$ and by local power corrections at high $q^2$. In exclusive decays, by contrast, hypothetical charming-penguin effects, beyond those already included in current uncertainty estimates, could appear, in a worst-case scenario, as a constant, universal contribution that it seems, in principle, indistinguishable from genuine New Physics. We identify two observables, constructed from ratios of exclusive to inclusive modes, that can discriminate between a New Physics contribution and a constant hadronic contribution. Moreover, these ratios can be measured directly by LHCb, as they do not require any normalisation to $J/\psi K^{(\ast )}$ branching fractions from B factories. A preliminary evaluation of these observables with present data shows some preference for the New Physics interpretation. In a complementary test, a comparison between inclusive measurements and the corresponding sum of exclusive modes at high $q^2$ similarly disfavours an explanation based on a constant hadronic contribution. Finally, we provide projections for the new observables based on expected LHCb and Belle II measurements in the near future.

    hep-phhep-ex1 citation
16. 16*

    TMDs in the Lens of Generative AI: A Pixel-Based Approach to Partonic Imaging

    Marco Zaccheddu🇺🇸 · Leonard Gamberg🇺🇸 · Wally Melnitchouk🇺🇸 · Daniel Pitonyak🇺🇸 · Alexei Prokudin🇺🇸 · Jian-Wei Qiu🇺🇸 · Nobuo Sato🇺🇸

    This work introduces a novel, nonparametric pixel-based framework for the Bayesian inference and imaging of transverse momentum dependent (TMD) parton distributions. The methodology is built upon a fully differentiable framework that integrates TMD evolution with the Collins-Soper-Sterman formalism, enabling the simultaneous extraction of partonic distributions and the nonperturbative evolution kernel. To achieve efficient and exact sampling of the high-dimensional posterior, we leverage generative AI through a hybrid normalizing flow-driven Metropolis-Hastings approach. The framework is validated through multi-scale closure tests of increasing complexity, ranging from basic functional models to convoluted structure functions. Using singular value decomposition (SVD), we rigorously characterize the uncertainty of the reconstructed distributions and reveal the existence of null TMDs, which are functional components in the null space of the kernel that remain unconstrained by observables. The new framework provides the first integration of pixel-based discretization, generative AI, and SVD within a Bayesian context to solve the TMD inverse problem. This synergy between machine learning and multi-scale data removes inherent degeneracies and enables unbiased 3D partonic imaging.

    hep-ph2 citations
17. 17*

    Unbinned extraction of $\gamma$ from $B\to DK$ with normalizing flows

    Yuval Grossman🇺🇸 · Tony Menzo🇺🇸 · Stefan Schacht🇬🇧 · Chinhsan Sieng🇺🇸 · Jure Zupan🇺🇸

    We introduce an unbinned method for extracting the CKM angle $\gamma$ from the decay chain $B^{\pm }\to (D\to K_S{\pi }^{+}{\pi }^{-})K^{\pm }$ using normalizing flows (NFs). The NFs, trained on $D$ decay data, learn a faithful continuous representation of the amplitude and strong phase variation over the $D\to K_S{\pi }^{+}{\pi }^{-}$ Dalitz plot whose fidelity improves with increased data sample sizes. With this input, the $B$ decay data can be used to extract the parameters $r_B$, ${\delta }_B$, and $\gamma$. We test the method on Monte Carlo generated data, where it successfully recovers the injected value of $\gamma$ within uncertainties. The present implementation propagates statistical uncertainties from finite training data via an ensemble of independently trained flows, and does not attempt to capture the effects of systematic experimental errors. We explore two versions of the method that differ in how the trigonometric constraint on phase variation is encoded, and comment on the possible extension to Bayesian NFs, which would provide direct uncertainty estimates on the learned densities without requiring ensemble training.

    hep-phhep-ex0 citations
18. 18*

    SIRENA -- Sum-Integral REductioN Algorithm

    Luis Gil🇪🇸 · Javier López Miras🇪🇸 · Adrián Moreno-Sánchez🇪🇸

    We present SIRENA, a Python and C++ implementation of the Laporta algorithm for the automatic reduction of multi-loop sum-integrals via integration-by-parts identities. The method builds on established techniques for zero-temperature Feynman integrals and extends them to finite-temperature quantum field theory by consistently accounting for the Matsubara sum structure. We validate the framework by reproducing several known results from the literature up to 3-loop order, and we further provide, for the first time, reductions for selected 3-loop fermionic sum-integrals. In addition to the package, we derive an analytic factorization formula for arbitrary 2-loop fermionic sum-integrals, extending on a previous result for the bosonic case.

    hep-ph3 citations
19. 19*

    Neutrino-Antineutrino Conversion from Ultralight Vector Dark Matter

    Asher Berlin🇺🇸 · Rodolfo Capdevilla🇺🇸 · Ting Cheng🇺🇸 · Matheus Hostert🇺🇸 · Pedro A. N. Machado🇺🇸

    We show that Majorana neutrinos convert into antineutrinos in a background of ultralight vector dark matter coupled to lepton number, such as the gauge boson of $\text{U}(1{)}_{B-L}$ or $\text{U}(1{)}_{L_i-L_j}$ with $i,j=e,\mu ,\tau$. This effect is suppressed by the small neutrino mass, but the enhancement by long astrophysical baselines can enable future searches for solar and supernova neutrinos to explore uncharted parameter space. For instance, for $\text{U}(1{)}_{B-L}$ dark matter, the observation of a supernova neutrino burst at DUNE, Hyper-Kamiokande, and JUNO could probe gauge couplings as small as $e^{\prime }\sim 10^{-32}-10^{-25}$ for dark matter masses of $m_{A^{\prime }}\sim 10^{-22}\text{eV}-10^{-14}\text{eV}$, beyond the capability of other future probes.

    hep-phastro-ph.HEhep-ex0 citations
20. 20*

    The structure of multi-axion solutions to the strong CP problem

    Mario Fernández Navarro🇨🇭 · Marta F. Zamoro🇪🇸 · Marko Pesut🇨🇭 · Xavier Ponce Díaz🇨🇭

    A broad experimental program is targeting the QCD axion band predicted by single-axion solutions to the strong CP problem. Multi-axion theories provide a well-motivated departure from this canonical picture, since additional states generically modify the mass-photon-coupling relation. We investigate the general structure of multi-axion solutions to the strong CP problem and study the different qualitative mass-coupling patterns that arise, including axions to the right of the QCD band, axions in the experimentally accessible region to its left, and scenarios in which the QCD axion band itself is displaced. This general treatment reveals a broad set of phenomenological possibilities that are not captured by more restrictive assumptions. In particular, we identify the structure of Peccei-Quinn symmetry breaking and the relative alignment between the QCD and electromagnetic anomalies as key ingredients determining the location of the axions in parameter space. Combining these ingredients, we derive a general sum rule for $N$-axion systems that incorporates both general PQ breaking and non-universal anomaly coefficients. We apply the framework to the two-axion system and to general multi-axion setups, identifying UV-complete theories in which the different phenomenological regimes arise naturally. Our results motivate an extended axion search program and have implications for our understanding of fundamental physics and the ultraviolet completion of the Standard Model.

    hep-phastro-ph.COhep-exhep-thPRD(2026)·7 citations
21. 21*

    Plasma heating during the chiral plasma instability

    Balin Armstrong🇺🇸 · Andrew J. Long🇺🇸 · Károly Seller🇩🇪 · Günter Sigl🇩🇪

    The presence of a chiral asymmetry in a relativistic plasma opens a tachyonic instability toward the growth of a helical magnetic field. We study the transfer of energy from the chiral asymmetry into the magnetic field during the development of this chiral plasma instability. We find that there is more energy stored in the initial chiral asymmetry than goes into growing magnetic field and that the excess energy is transferred to the thermal bath. Consequently, we find that the chiral plasma instability is accompanied by a heating of the plasma, and the temperature increase is parametrically $\delta T\sim {\mu }_5^2/T$ if the ratio of chemical potential to temperature is small, i.e. ${\mu }_5/T\ll 1$. We briefly remark on possible observable implications for early universe cosmology.

    hep-phastro-ph.COJCAP(2026)·0 citations
22. 22*

    Decaying spin-3/2 dark matter from baryon number violation

    Francesco Costa🇨🇿 · Gabriel M. Salla🇩🇪

    We explore an uncharted corner of dark matter phenomenology: non-supersymmetric spin-$3/2$ dark matter with baryon number violating interactions. In an effective field theory description, we identify the leading baryonic portal between the spin-$3/2$ state and Standard Model quarks and show that it can account for the observed dark matter abundance through UV freeze-in and Boltzmann-suppressed freeze-in, while the freeze-out region is completely excluded. The resulting phenomenology is distinctive, with relic production controlled by the competition between baryon-violating single-particle processes and baryon-conserving pair production. We map the viable parameter space against indirect detection, direct detection, and LHC monojet bounds, finding strong complementarity between these probes and especially stringent limits when production and decay are tied to the same operator. We also present a dark QCD-like ultraviolet completion in which the spin-$3/2$ particle arises as a composite baryon, naturally generating the effective interactions and mitigating the main theoretical obstacles of elementary higher-spin states. This framework opens a novel and testable connection between baryonic portals, confining dark sectors, and higher-spin dark matter.

    hep-phastro-ph.CO0 citations
23. 23*

    Carroll fermions from null reduction: A case of good and bad fermions

    Sucheta Majumdar🇫🇷 · Aditya Sharma🇨🇱 · Sourav Singha🇮🇳

    We derive Carrollian fermionic actions using the null reduction method from Bargmann spacetimes. In the Lorentzian light-cone formulation, the Dirac spinor naturally decomposes into dynamical and constrained degrees of freedom $-$ the so-called `good' and `bad' fermions ${\Psi }_{(\pm )}$. These light-cone projections are intrinsically adapted to the null frame and, unlike the chiral decomposition into left- and right-handed spinors ${\Psi }_{L(R)}$, are valid in arbitrary spacetime dimensions, both even and odd. As in the case of bosons, the magnetic Carroll sector for fermions is governed by the dynamical modes of the parent theory, while the electric sector arises from the constrained modes. Upon deforming to a Bargmann spacetime, these constraints are removed, promoting the `bad' fermions to dynamical modes that describe the electric Carroll fermions. We construct the Clifford algebra on the Carroll manifold through its embedding in the ambient Bargmann manifold, and obtain both electric and magnetic Carroll fermion actions from a \textit{single} Bargmann-invariant Dirac action. We analyze the canonical structure of both theories, establish their invariance under Carroll transformations, and compute the corresponding two-point functions, which exhibit the expected behavior in both sectors. We conclude with some comments on the quantization of these Carrollian theories.

    ↳ hep-thhep-ph7 citations
24. 24*

    Wormholes and the imaginary distance bound

    Juan Maldacena🇺🇸 · Alexander Maloney🇺🇸 · Brian McPeak🇺🇸

    Some of the simplest wormhole solutions involve massless scalar fields that take imaginary values. Massless fields can be interpreted as coupling constants in asymptotically flat or asymptotically AdS gravity theories. We argue that wormhole effects imply an imaginary distance bound, an upper limit for the analytic continuation of the theory to imaginary values of these couplings. In string theory examples, we find explicit effects that render the low-energy theory invalid either before or precisely at this wormhole limit. We argue that the existence of such effects enforcing the distance bound is a general feature of string theories containing wormholes. In some cases, the bounds we discuss coincide with the weak gravity conjecture, and with the Kontsevich-Segal-Witten condition on complex metrics.

    ↳ hep-thgr-qchep-ph19 citations
25. 25*

    Perturbations in the parametrized wormhole spacetime and their related quasinormal modes

    Shauvik Biswas🇮🇳 · Sayan Chakrabarti🇮🇳

    We study electromagnetic perturbations and the associated quasinormal modes (QNMs) of parametrized static, spherically symmetric wormhole spacetimes, focusing on Damour-Solodukhin and braneworld geometries as well as their galactic extensions. Using the Bronnikov-Konoplya-Pappas (BKP) parametrization, we express the metric functions in terms of a compactified radial coordinate and characterize the spacetime through far-field and near-throat parameters. The far-field coefficients govern the asymptotic structure and post-Newtonian behaviour, while the near-throat continued-fraction expansion captures the strong-field geometry near the throat. We first apply the parametrization to isolated wormholes and identify its range of validity, showing that the non-analytic metric functions can limit the applicability of the BKP scheme. Moreover we have shown that such issues can indeed hamper the primary ringdown waveform. We then extend the framework to a galactic Damour-Solodukhin wormhole embedded in a Hernquist dark matter halo. Imposing observational bounds from the shadow of Sgr A${}^{\ast }$, we constrain the galactic compactness and deformation parameters and obtain an observationally viable parametrized metric. Within the allowed parameter space, we compute the fundamental QNM frequencies using the transfer matrix method and analyze the corresponding time-domain ringdown signals. We find that the damping rate is more sensitive to galactic compactness, whereas the oscillation frequency remains comparatively stable. Although the spectral shifts are small within the shadow-allowed region, the framework provides a systematic link between geometric parametrization, shadow constraints, and dynamical response. Our results establish an observationally consistent parametrized description of wormhole perturbations for strong-field tests of horizonless compact objects.

    ↳ gr-qcastro-ph.GAhep-phphysics.space-ph1 citation
26. 26*

    Quantum Simulation of the Real-time Dynamics in the multi-flavor Gross-Neveu Model at the utility scale using Superconducting Quantum Computers

    Talal Ahmed Chowdhury🇺🇸 · Seokwon Choi🇰🇷 · Kyoungchul Kong🇺🇸 · Kwangmin Yu🇺🇸

    We present a scalable quantum simulation framework for real-time dynamics of the multi-flavor Gross-Neveu model in 1+1 dimensions. Using superconducting quantum processors at utility scale, we develop a hardware-efficient Trotterization whose per-step circuit depth scales with fermion flavor number rather than total system size, enabling simulations beyond 100 qubits. A central contribution of this work is the Localized Diagonal Operator Approximation (LDOA), which systematically reduces the overhead associated with quartic interactions. We formulate diagonal unitary synthesis as a structured least-squares problem in phase space and obtain analytic solutions via the Moore-Penrose pseudoinverse. This formulation provides a principled and quantitatively controlled approximation: in the small Trotter-step regime, the unitary error is directly linked to the phase reconstruction error and vanishes asymptotically as the Trotter step size decreases. This establishes a clear mathematical foundation for the LDOA while significantly reducing two-qubit gate counts and circuit depth, and is broadly applicable to diagonal quantum operators with long-range structure, making it particularly well suited for quantum hardware with limited qubit connectivity. Using these techniques, we run large-scale simulations on IBM superconducting processors and study real-time observables, including density-density correlators. We benchmark against exact diagonalization and tensor network-based methods, finding strong agreement across system sizes. These results show that combining hardware-aware circuit design with rigorous approximations enables practical near-term simulation of interacting fermionic field theories and provides a scalable pathway toward more complex quantum field theory simulations.

    ↳ quant-phhep-ph1 citation
27. 27*

    Self-interacting dark matter and core formation in field low-surface-brightness galaxies

    Noriaki Kitazawa🇯🇵

    Dark matter may play an important role in galaxy formation through its non-trivial properties. For example, self-interacting dark matter may contribute to the formation of the widely observed core structures in galaxies. However, galaxy formation is a complex process, and such core structures can also arise from baryonic effects within the cold dark matter framework. To clarify the role of dark matter self-interactions, it is necessary to study systems that evolve without significant baryonic disturbances. Low-surface-brightness galaxies in the field, which are gravitationally isolated and have evolved with minimal external influence, are suitable candidates for this purpose. Since these galaxies typically contain only a small amount of baryonic matter, strong baryonic effects are not expected in their evolutionary history. In this study, we assume that these galaxies decoupled from proto-clusters at high redshift. Based on this assumption, we set initial conditions and estimate the time required for core formation, which we compare with the time corresponding to the redshift of proto-clusters. We examine five low-surface-brightness galaxies in the field and three observed proto-clusters at redshifts z=2.45, 7.66 and 7.88. Our analyses, based on order-of-magnitude estimates without numerical simulations, excludes a self-interaction cross section of sigma/m = 1 cm^2/g, while sigma/m = 0.1 cm^2/g is favored. This result is consistent with constraints derived from the shapes of present-day cluster cores.

    ↳ astro-ph.COhep-ph0 citations
28. 28*

    Charmonium production in low energy nuclear collisions at SPS and FAIR: achievements $\&$ prospects

    Partha Pratim Bhaduri🇮🇳

    In this article, we review the status of the charmonium production in low energy fixed target proton-nucleus (p-A) and nucleus-nucleus (A-A) collisions as measured by different experimental collaborations at CERN-SPS, Fermilab and HERA accelerator facilities. The interplay of different cold and hot medium effects influencing the production of these $c\bar{c}$ bound states at low collision energies is discussed in detail. Prospect for upcoming charmonium measurements close to kinematic production threshold, in the CBM experiment at FAIR SIS100 and NA60+ experiment at CERN-SPS facilities are also investigated.

    ↳ nucl-exhep-ph0 citations
29. 29*

    Squeezed Gravitons and One-Loop Self-Energy under Light-Cone Smearing

    Hiroki Matsui🇯🇵

    We investigate light-cone smearing induced by quantum fluctuations of gravitons and its implications for the ultraviolet structure of quantum field theory. By treating the first-order correction to Synge's world function as an operator, we show that the retarded Green's function is smeared by the variance of graviton fluctuations. The smearing width depends on the quantum state of gravitons: vacuum fluctuations generate a Gaussian smearing of the light cone, coherent states shift the light-cone position, and squeezed states modify the smearing width itself. We then apply the smeared Feynman propagator to one-loop self-energies in interacting scalar field theories. Within a phenomenological finite-resolution prescription that keeps the effective width nonzero, the ultraviolet-sensitive short-distance terms in the ${\varphi }^3$ bubble and ${\varphi }^4$ tadpole diagram expressions are finite. For the illustrative choice that the coarse-graining scale is the Planck length, primordial gravitons induce a relative correction of order $10^{-10}$ to the one-loop self-energy. Our results suggest that the quantum state of gravitons can leave a finite imprint on the causal and short-distance structure of quantum field theory.

    ↳ hep-thgr-qchep-phPRD(2026)·1 citation
30. 30*

    Probing the density dependence of nuclear symmetry energy through isospin transport in heavy-ion reactions

    S. Mallik🇮🇳 · F. Gulminelli🇫🇷 · C. Ciampi🇫🇷 · D. Gruyer🇫🇷

    The density dependence of the nuclear symmetry energy remains one of the key uncertainties in contemporary nuclear physics, with significant implications for the structure of exotic nuclei, the dynamics of heavy-ion collisions, and the properties of astrophysical objects such as neutron stars and core-collapse supernovae. However, extracting robust constraints requires observables that are minimally affected by final-state interactions and are reliably predicted by transport models. This review synthesizes recent theoretical and experimental advancements in constraining the symmetry energy by leveraging isospin diffusion in heavy-ion reactions within the Fermi energy domain. Recent results from the INDRA-FAZIA collaboration, including isospin transport ratio data, and Boltzmann-Uehling-Uhlenbeck (BUU) transport model calculations are highlighted. Confidence regions for the symmetry energy are extracted from isospin transport ratios and isospin diffusion currents by utilizing state-of-the-art nuclear functionals, including both ab initio and phenomenological approaches, with a particular focus on the density regions probed by these experiments. The resulting constraints will aid future Bayesian studies of the nuclear equation of state and contribute to a more unified understanding of dense matter in both terrestrial experiments and astrophysical environments.

    ↳ nucl-thhep-phnucl-exUniverse(2026)·0 citations
31. 31*

    The Hagedorn Temperature as a Nonequilibrium Dynamical Bottleneck in String Thermodynamics

    Cesar Damian🇲🇽 · Oscar Loaiza-Brito🇲🇽

    We revisit the Hagedorn regime of string theory from a nonequilibrium perspective using Steepest-Entropy-Ascent Quantum Thermodynamics (SEAQT), which formulates thermodynamic evolution directly on the state manifold without requiring a globally well-defined canonical ensemble. Treating the inverse temperature as an instantaneous, state-dependent quantity, we derive its exact scalar evolution equation, governed in the commuting limit by higher-order fluctuation moments. In an open-system extension we prove that the inverse-temperature mobility equals unity identically on the quasi-canonical family: a divergent Hagedorn variance is necessary but not sufficient for slowing-down. Sustained Hagedorn pinning requires a definite energy-injection topology, realized by a two-sector construction in which the reservoir couples only to light quasi-particle modes; the mobility then collapses, the intensive variable freezes at the Hagedorn scale, and energy condenses into the long-string sector at a finite rate. Promoting the Hagedorn scale to a moduli-dependent quantity along emergent-string limits yields a finite critical distance ${\Delta }_{\ast }$ beyond which pinning activates, with thermodynamic inertia diverging as $({\Delta }_{\ast }-\Delta {)}^{a-3}$ for $1<a<3$, a thermodynamic discriminant between emergent-string and decompactification limits.

    ↳ hep-thhep-ph2 citations
32. 32*

    The strange and flavor-singlet axial form factors of the nucleon from lattice QCD

    Alessandro Barone🇩🇪 · Dalibor Djukanovic🇩🇪 · Georg von Hippel🇩🇪 · Harvey B. Meyer🇩🇪 · Konstantin Ottnad🇩🇪 · Hartmut Wittig🇩🇪

    The singlet axial form factor of the nucleon provides essential input for a complete understanding of the nucleon axial structure. Together with the isovector and isoscalar octet channels, in the forward limit it forms the basis for a full flavor decomposition of the proton spin. In this work we present a lattice QCD determination of the singlet axial form factor $G_A^{u+d+s}(Q^2)$ and related strange contribution $G_A^s(Q^2)$ using a set of $N_f=2+1$ CLS gauge ensembles with $O(a)$-improved Wilson fermions, with a full error budget for the extrapolation to the chiral, continuum and infinite-volume limits. Particular focus is placed on the treatment of the disconnected contributions, which constitute the crucial element for the extraction of the strange component. Together with determinations of the isovector and isoscalar octet axial form factors, this work provides a comprehensive lattice QCD determination of the nucleon axial structure across different flavor channels.

    ↳ hep-lathep-exhep-phPRD(2026)·4 citations
33. 33*

    $F_K/F_{\pi }$ as a precision test of a new four flavor Domain Wall Fermion action

    Renwick J. Hudspith🇺🇸 · Nicolas Garron🇬🇧 · Zack Hall🇺🇸 · Andrew Hanlon🇺🇸 · Henry Monge-Camacho🇺🇸 · Colin Morningstar🇺🇸 · Amy Nicholson🇺🇸 · Dimitra A. Pefkou🇺🇸 · Thomas R. Richardson🇺🇸 · Fernando Romero-López🇨🇭 · Miguel Salg🇨🇭 · Wyatt A. Smith🇺🇸 and 3 other authors

    We present a new set of lattice QCD ensembles with four flavors of smeared Möbius Domain Wall Fermions with good chiral symmetry and small fifth-dimensional extent. A modest amount of computing resources was sufficient to generate 30 publicly-available ensembles spanning five lattice spacings and a broad range of pion masses down to physical. To scrutinize our action we determine $F_{K^{\pm }}/F_{{\pi }^{\pm }}=1.1962(34)$, a key quantity for precision CKM unitarity tests, heralding a future of inexpensive high-precision calculations of hadronic observables with chiral fermions.

    ↳ hep-lathep-phnucl-th0 citations
34. 34*

    BRICKS: Compositional Neural Markov Kernels for Zero-Shot Radiation-Matter Simulation

    Richard Hildebrandt · Evangelos Kourlitis · Baran Hashemi🇩🇪 · Manuel Bünstorf · Thierry Meyer · Nikola Boskov · Michael Kagan🇺🇸 · Dan Rosenbaum · Sanmay Ganguly🇮🇳 · Lukas Heinrich🇩🇪

    We introduce a new strategy for compositional neural surrogates for radiation-matter interactions, a key task spanning domains from particle physics through nuclear and space engineering to medical physics. Exploiting the locality and the Markov nature of particle interactions, we create a \emph{next-particle prediction} kernel using hybrid discrete-continuous transformer models based on Riemannian Flow Matching on product manifolds. The model generates variable-sized typed sets of particles and radiation side effects that are the result of the interaction of an incident particle with a material volume. The resulting kernel can be composed to simulate unseen large-scale material distributions in a zero-shot manner. Unlike mechanistic simulators, our model is designed to be differentiable, provides tractable likelihoods for future downstream applications. A significant computational speed-up on GPU compared to CPU-bound mechanistic simulation is observed for single-kernel execution. We evaluate the model at the kernel level and demonstrate predictive stability over multi-round autoregressive rollouts. We additionally release a novel 20M-event radiation-matter interaction dataset for further research.

    ↳ cs.LGhep-ph2 citations
35. 35*

    When Does Critique Improve AI-Assisted Theoretical Physics? SCALAR: Structured Critic--Actor Loop for Agentic Reasoning

    Vasilis Niarchos🇬🇷 · Constantinos Papageorgakis🇬🇧 · Alexander G. Stapleton🇬🇧 · Sokratis Trifinopoulos🇨🇭

    As large language models (LLMs) show increasing promise on research-level physics reasoning tasks and agentic AI becomes more common, a practical question emerges: How does the interaction between researchers and agents affect the results? We study this using SCALAR (Structured Critic--Actor Loop for Agentic Reasoning), an Actor--Critic--Judge pipeline applied to quantum field theory and string theory problems. The Actor proposes solutions, the Critic provides iterative feedback, and an independent Judge evaluates the transcript against reference solutions. We vary the Actor persona, the Critic feedback strategy, and the Actor model family and scale. Multi-turn dialogue improves over single-shot attempts throughout, but both the mechanism of improvement and the value of different prompting choices depend strongly on the Actor--Critic pairing. Increasing the scale within one model family (e.g. from the 8B-parameter DeepSeek-R1 variant to DeepSeek-R1 70B) improves some easier-problem behavior, but does not remove the hardest bottleneck we observe. Critic feedback strategy matters most clearly in the asymmetric Actor--Critic setting (e.g, a lightweight Haiku Actor guided by a stronger Sonnet Critic), where constructive feedback improves mean-score outcomes. In same-family Actor--Critic settings, strategy effects are weaker: lenient feedback is sometimes favored, while strict and adversarial feedback are not beneficial. Taken together, SCALAR provides a controlled testbed for evaluating which interaction structures help or hinder AI-assisted reasoning on known-answer scientific problems.

    ↳ cs.AIcs.HChep-phhep-th2 citations
36. 36*

    Exploring the Boundaries of Differentiable Radiation Transport and Detector Simulation

    Jeffrey Krupa🇺🇸 · Yiyang Zhao🇨🇳 · Mihaly Novak🇨🇭 · Max Aehle🇩🇪 · Max Sagebaum🇩🇪 · Long Chen🇩🇪 · Nicolas Gauger🇩🇪 · David Lange🇩🇪 · Vassil Vassilev🇺🇸 · Miaoyuan Liu🇺🇸 · Lukas Heinrich🇩🇪 · Michael Kagan🇺🇸

    We present an application of automatic differentiation for particle transport through matter using a Geant4-like radiation transport simulation with a full electromagnetic physics model. When differentiating this step-based transport, we observe exploding gradients driven by rare but extreme sensitivities at material boundaries, which propagate through subsequent transport and shower development. To obtain usable derivatives for optimization, we introduce a targeted mitigation strategy that stops gradient propagation through boundary-crossing operations under identifiable unstable conditions while leaving the forward (primal) simulation unchanged. We demonstrate that this enables stable, optimization-ready gradients in a detector-design problem.

    ↳ physics.ins-dethep-exhep-ph0 citations
37. 37*

    Physics inspired quantum algorithm for QCD splitting functions

    Gabriel Rouxinol🇩🇪 · Yacine Haddad🇺🇸 · Cenk Tüysüz🇨🇭 · Sofia Vallecorsa🇨🇭 · Michele Grossi🇨🇭

    We introduce a modular quantum circuit primitive to model entanglement dynamics in QCD parton splitting and use it as a composable building block for data-driven, physics-consistent event generation. For the pure-gluon channel, we derive an analytic expression for the helicity entanglement generated at the splitting vertex, quantified via the concurrence, and construct a two-qubit circuit whose measurement outcomes encode the momentum shared between outgoing gluons while reproducing the QCD-predicted entanglement structure. Calibrating the circuit parameters to LHC jet substructure data maps, reconstructed momentum-sharing fractions are directly related to circuit rotation angles. Composing multiple splitting primitives yields multi-prong momentum-fraction distributions; we validate the three- and four-prong cases against experimental data and find good agreement. For the three-prong configuration, we execute the circuit on superconducting quantum hardware and obtain results consistent with simulation after standard quality cuts, enabled by the low qubit count and shallow circuit depth. This work provides a concrete framework for quantum-native parton-shower modules that encode quantum correlations at the level of splitting dynamics, and offers physics-informed ansätze for future quantum algorithms for QCD.

    ↳ quant-phhep-phhep-th1 citation
38. 38*

    The Case for Space-Based Particle Colliders: Orbital Infrastructure as a Path to Grand Unification Energy Scales

    Viktor Danchev🇮🇳 · Alex Dyer · Sebastian Grau · Guillaume Vazeille

    The Standard Model of particle Physics has been validated to extraordinarily high precision by the Large Hadron Collider (LHC). Yet it leaves some of the most fundamental questions in Physics unresolved: the nature of dark matter, the hierarchy problem, and the unification of forces. Multiple next-generation terrestrial colliders have been proposed such as the Future Circular Collider (FCC) which will reach centre-of-mass energies of $\approx$100 TeV, yet the energy scales at which hints of Grand Unified Theories (GUTs) and string theory are expected to be observed ($10^{11}-10^{13}$ TeV) remain orders of magnitude beyond the reach of any terrestrial facility. We argue that the path to these energy frontiers inevitably leads to Space. By examining the fundamental scaling law for circular proton colliders, we establish that colliders of radius $10^3-10^5$ km are required to enter the PeV-EeV regime. In addition, Space-based colliders benefit from virtually free ultra-high vacuum ($<10^{10}$ particles/m${}^3$ above 1000 km altitude), passive cryogenic cooling, reduction of geological and political constraints, and perhaps most importantly -- the substantial reduction of the thermodynamic penalty that dominates terrestrial cryogenic power budgets. We survey existing proposals for beyond-Earth colliders, derive order-of-magnitude requirements for an orbital collider constellation, and assess feasibility against current and near-term spacecraft capabilities in formation flying, power generation, and precision attitude control. We conclude that recent developments in orbital infrastructure -- particularly gigawatt-scale orbital power architectures being developed for Space-based data centers -- are converging with the needs of a Space-based mega collider, making serious feasibility studies warranted and promising a more certain path towards the core questions of modern Physics.

    ↳ physics.acc-phhep-phphysics.app-phphysics.space-ph0 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.