Mon·Sep 1, 2025Monday·September 1, 2025

1. 01*

   Heavy Quarkonia in the Light-Front Quark Model

   Muhammad Ridwan🇮🇩 · Ahmad Jafar Arifi🇯🇵 · Terry Mart🇮🇩

   We present recent progress in constructing heavy quarkonia light-front wave functions from the light-front quark model, a relativistic framework well-suited for describing partonic structure and hadronic form factors. In this proceeding, we discuss the recent application of the model to the $M1$ radiative transition such as $J/\psi \to {\eta }_c\gamma$ among other transitions. Additionally, we compare our results on the transition form factor with available lattice QCD data. These show our efforts to deepen our understanding of the structure of heavy quarkonia from light-front model perspective.

   hep-phnucl-thPoS(2026)·0 citations
2. 02*

   Vacuum Cherenkov radiation for nonminimal dimension-5 Lorentz violation

   A. Yu. Petrov🇧🇷 · M. Schreck🇧🇷 · A. R. Vieira🇧🇷

   Vacuum Cherenkov radiation is investigated in the Lorentz-violating Standard-Model Extension for isotropic dim-5 operators $\hat{m}$ and ${\hat{a}}^{\mu }$ in the fermion sector. Both the kinematics and dynamics of this process are analyzed by analytical and numerical means, leading to its decay and radiated-energy rates as functions of the initial-fermion momentum. We adopt the point of view that vacuum Cherenkov radiation is actually a physical phenomenon expected to occur for a charged, massive fermion in the presence of Lorentz violation, when some additional requirements are satisfied. The absence of this effect in ultrahigh-energy cosmic rays detected on Earth allows us to infer stringent bounds on isotropic dim-5 Lorentz violation in protons, quarks, and electrons.

   hep-phhep-thEPJC(2026)·5 citations
3. 03*

   Production of the $X(3872)$ state via the $B^0\to K^{\ast 0}X(3872)$ decay

   Luciano M. Abreu🇧🇷

   In this work the production of the state $X(3872)$ is estimated via the reaction $B^0\to K^{\ast 0}X(3872)$ through triangle mechanisms described by the sequence $B^0\to D_s^{(\ast )+}(\to K^{\ast 0}{D}^{(\ast )+})D^{(\ast )-}\to K^{\ast 0}(D^{(\ast )+}{D}^{(\ast )-})\to K^{\ast 0}X(3872)$. The molecular configuration $(D{\bar{D}}^{\ast }-c.c.)$ of the $X(3872)$ is considered. By means of the effective Lagrangian approach, the branching ratio $\mathcal{B}(B^0\to K^{\ast 0}X(3872))$ is calculated as a function of the strength of the coupling of the charged components $(D^{+}{\bar{D}}^{\ast -}-c.c.)$ to the $X(3872)$ and compared with experimental data. Besides, employing the decay $B^0\to K^{\ast 0}\psi (2S)$ as a normalization channel, the ratio of branching fractions $R=\frac{\mathcal{B}(B^0\to K^{\ast 0}X(3872))}{\mathcal{B}(B^0\to K^{\ast 0}\psi (2S))}\times \frac{\mathcal{B}(X(3872)\to J/\psi {\pi }^{+}{\pi }^{-})}{\mathcal{B}(\psi (2S)\to J/\psi {\pi }^{+}{\pi }^{-})}$ is also estimated. The findings provide another concrete example for the vital role of charged components in achieving a quantitatively correct description of the $X(3872)$.

   hep-phPRD(2025)·2 citations
4. 04*

   Quadrupole forces between quark/gluon subsystems inside higher-spin particles

   June-Young Kim🇺🇸 · Hyun-Chul Kim🇰🇷

   We generalize the mechanical interpretation of the forces between quark and gluon subsystems, previously studied for the nucleon, to arbitrary higher-spin particles. For spin-0 and spin-1/2 particles, this force is characterized by the non-conserved $\bar{c}(t)$ form factor. However, such an interpretation has not yet been established for higher-spin particles due to the intricate structure of the non-conserved energy-momentum tensor (EMT) form factors. By performing a multipole expansion, we identify the physically meaningful combinations of the non-conserved covariant EMT form factors and provide them with a clear mechanical interpretation.

   hep-phhep-exhep-latPRD(2025)·4 citations
5. 05*

   Testing Non-Standard Neutrinos in Purely Leptonic Lepton Decays

   Han Zhang🇨🇳 · Bai-Cian Ke🇨🇳 · Yao Yu🇨🇳

   We propose a method to probe sterile neutrinos using polarization observables in the purely leptonic decays ${\ell }^{\prime -}\to {\ell }^{-}{\bar{\nu }}_{\ell }{\nu }_{{\ell }^{\prime }}$. By analyzing angular distributions and asymmetries derived from polarized decay rates, we identify distinctive signatures of sterile neutrino mixing. In particular, we demonstrate that sterile neutrinos can induce singularities in certain asymmetry parameters as functions of the invariant mass squared of the neutrino pair. These singularities occur for sterile neutrino masses $m_{4\nu }$ satisfying $m_{4\nu }^2<m_{{\ell }^{\prime }}^2/2$, providing a clear target for experimental investigation. Our results motivate the incorporation of polarized beam sources at future colliders to enhance sensitivity to sterile neutrinos and other new physics.

   hep-phhep-exPLB(2026)·0 citations
6. 06*

   Optimizing $pp\to A\to Z^{\ast }h\to {\ell }^{+}{\ell }^{-}b\bar{b}$ Searches at the LHC in the 2HDM Type-I with Inverted Hierarchy

   S. Alanazi🇬🇧 · S. Moretti🇬🇧 · A.G. Akeroyd🇬🇧

   In this study, we investigate the Large Hadron Collider (LHC) search for the signal process $pp\to A\to Z^{\ast }h\to {\ell }^{+}{\ell }^{-}b\bar{b}$ ($\ell =e,\mu$) within the framework of the 2-Higgs-Doublet Model (2HDM) Type-I, considering an Inverted Hierarchy (IH) scenario wherein the Standard Model (SM)-like Higgs boson $H$ is heavier than $h$ (i.e., $m_h<m_H=125$ GeV). We reproduce the dominant background distributions from a CMS analysis of $pp\to H\to ZA\to {\ell }^{+}{\ell }^{-}b\bar{b}$ (for a on-shell $Z$), which we do for validation purposes, so that we can explore different invariant mass selection criteria to enhance the signal significance of our target process. Specifically, we compare the CMS baseline cuts ($70$ GeV $<m_{{\ell }^{+}{\ell }^{-}}<110$ GeV, no $m_{b\bar{b}}$ restriction) with the alternative selections $20\mathrm{GeV}<m_{{\ell }^{+}{\ell }^{-}}<50$ GeV with $m_{b\bar{b}}<100$ GeV. The latter cuts are enforced to account for the off-shellness of the $Z^{\ast }$ boson and the low mass Higgs state in our case. We show that these modifications reduce drastically the dominant Drell-Yan (DY) and top-(anti)quark pair backgrounds, leading to a significant excess from the analysis of the reconstructed $m_{{\ell }^{+}{\ell }^{-}b\bar{b}}$ invariant mass in the illustrative ranges 145 GeV $<m_A<$ 150 GeV and 68 GeV $<m_h<$ 75 GeV. Our results demonstrate that such cuts enable effective signal discrimination, suggesting an optimized strategy in future searches for an established topology but in a new kinematical regime, which is of particular relevance to the 2HDM Type-I with IH in its mass spectrum.

   hep-ph0 citations
7. 07*

   Construction of the $a_4$ family

   Ya-Rong Wang🇨🇳 · Cheng-Qun Pang🇨🇳 · Hao Chen🇨🇳 · Xiao-Hai Liu🇨🇳

   The COMPASS Collaboration recently reported \sout{the observation of a new resonance, $a_4(2610)$}{\blue{a new broad $J^{PC}=4^{++}$ structure, denoted as $a_4(2610)$}}, which has sparked our interest in studying the $a_4$ family with {$I^G{J}^{PC}=1^{-}{4}^{++}$}. In this work, we investigate the mass spectra and Okubo-Zweig-Iizuka-allowed two-body strong decays of the $a_4$ family using the modified Godfrey-Isgur quark model and the quark-pair creation model. We also explore the possibility of identifying $a_4(2610)$ as a $4F$ or $2H$ state, {and our numerical results suggest that it could be a promising candidate for the $a_4(2H)$ state. In addition, we predict the masses and the widths of the $a_4(1H)$ and $a_4(3F)$ states.}

   hep-phhep-ex2 citations
8. 08*

   Prediction of $QQqq\bar{s}$ molecular pentaquarks within the extended local hidden gauge approach

   Zhong-Yu Wang🇨🇳 · Zheng-Wen Long🇨🇳

   We investigate hadronic molecular states with the quark contents $ccqq\bar{s}$, $bbqq\bar{s}$, and $bcqq\bar{s}$ $(q=u,d)$ by employing the extended local hidden gauge approach. Considering that the $S$-wave meson-baryon interactions are dominated by vector meson exchange, the coupled channels scattering amplitudes are obtained by solving the Bethe-Salpeter equation in its on-shell form. We find that the poles appearing on the complex Riemann sheet are potential candidates for dynamically generated molecular pentaquark states. The results suggest the existence of a total of fourteen molecular states with quantum numbers $I(J^P)=0(1/2^{-})$, $0(3/2^{-})$, and $0(5/2^{-})$, which arise from the interactions of the $K^{(\ast )}{\Xi }_{cc}^{(\ast )}$, $K^{(\ast )}{\Xi }_{bb}^{(\ast )}$, $K^{(\ast )}{\Xi }_{bc}^{(\ast )}$, and $K^{(\ast )}{\Xi }_{bc}^{{}^{\prime }}$ channels, respectively. Their binding energies are calculated to be about $0.1-33$ MeV, and this range depends on the free parameter of the theory. Our research contributes to the spectroscopic studies of hadronic molecular pentaquark states.

   hep-phPRD(2025)·5 citations
9. 09*

   Nuclear suppression in diffractive vector meson production within the color glass condensate framework

   Heikki Mäntysaari🇫🇮 · Hendrik Roch🇺🇸 · Farid Salazar🇺🇸 · Björn Schenke🇺🇸 · Chun Shen🇺🇸 · Wenbin Zhao🇺🇸

   We perform a global Bayesian analysis of diffractive $\mathrm{J}/\psi$ production in $\gamma +p$ and $\gamma +\mathrm{Pb}$ collisions within a Color Glass Condensate based framework. Using data from HERA and the LHC, we find that a simultaneous description of $\gamma +p$ and $\gamma +\mathrm{Pb}$ observables is challenging. Introducing a global $K$-factor to account for theoretical uncertainties improves the agreement with data and enhances the framework's predictive power. We present predictions for integrated $\mathrm{J}/\psi$ cross sections at different photon-nucleus energies and study their $A$-dependence relative to a no-saturation baseline, quantifying nuclear suppression and providing insights into the onset of saturation effects.

   hep-phnucl-thEPJ Web Conf.(2026)·2 citations
10. 10*

    Small $x$ behavior in QCD from maximal entanglement and conformal invariance

    Sebastian Grieninger🇺🇸 · Kun Hao🇨🇳 · Dmitri E. Kharzeev🇺🇸 · Vladimir Korepin🇺🇸

    Recent evidence suggests that, at small Bjorken $x$, QCD evolution drives the proton into a state of maximal entanglement. If the evolution kernel is assumed to be conformally invariant -- as is the case for the Balitsky-Fadin-Kuraev-Lipatov (BFKL) equation -- we can describe it by a conformal field theory. Moreover, the central charge $c$ of the corresponding conformal field theory emerges as the key parameter governing the $x$-dependence of both the entanglement entropy and the structure function. Here we apply the exact Bethe Ansatz methods to the quantum spin chain dual to Lipatov's high energy effective action to extract the central charge of the theory, and find that $c=1$. This implies the $\sim x^{-1/3}$ small $x$ behavior for the structure function -- the prediction that can be tested at the forthcoming Electron-Ion Collider.

    hep-phhep-thnucl-exnucl-th+1PRD(2026)·5 citations
11. 11*

    Probing the coupling of axions to tops and gluons with LHC measurements

    Jon Butterworth🇬🇧 · Matthew Cullingworth🇬🇧 · Joseph Egan🇬🇧 · Fabian Esser🇨🇿 · Veronica Sanz🇪🇸 · Maria Ubiali🇬🇧

    We study axion-like particles (ALPs) whose dominant interactions are with gluons and third-generation quarks, and whose couplings to light Standard Model (SM) particles arise at one loop. These loop-induced effects lead to ALP decays and production channels that can be probed at the LHC, even when tree-level couplings are absent. Using an effective field theory (EFT) description that includes momentum-dependent corrections from radiative effects, we reinterpret a wide range of LHC measurements via the CONTUR framework to derive model-independent constraints on the ALP parameter space. We show that LHC data place meaningful bounds in the plane of effective couplings $c_t^0/f_a$ and $c_{\tilde{G}}^0/f_a$, and that these limits are sensitive to the UV origin of the ALP-top and ALP-gluon couplings. We discuss representative scenarios where either $c_t^0$ or $c_{\tilde{G}}^0$ vanishes at the matching scale, and highlight the role of EFT running and mixing in generating observable signals. We also assess the domain of validity of the EFT approach by comparing the typical momentum transfer $\sqrt{\hat{s}}$ in sensitive regions to the underlying scale $f_a$. Our results demonstrate the power of loop-aware EFT reinterpretation of SM measurements in probing otherwise elusive ALP scenarios. The framework presented here can be readily extended to include couplings to other fermions and to accommodate ALP decay or long-lived signatures.

    hep-phhep-exJHEP(2026)·6 citations
12. 12*

    Gluon emission by a $q\bar{q}$ antenna with realistic parton-medium interactions

    Carlota Andres🇺🇸 · Liliana Apolinário🇵🇹 · Néstor Armesto🇪🇸 · André Cordeiro🇵🇹 · Fabio Dominguez🇪🇸 · Pablo Guerrero-Rodríguez🇪🇸 · José Guilherme Milhano🇵🇹

    The spectrum of coherent gluon radiation from a quark-anti-quark pair experiencing multiple scatterings within a coloured medium is central for understanding in-medium parton cascades. Despite its foundational importance, current results are limited by reliance on simplified scattering rates, such as the harmonic oscillator approximation, valid only in restricted phase-space regions. Using the formalism introduced in a previous article, we express the gluon emission spectrum as a set of differential equations that can be solved numerically, circumventing conventional approximations. We present the transverse momentum and energy distributions of emitted gluons for realistic interaction models, illustrating the breakdown of colour coherence across the entire accessible phase-space, and consequently enabling a higher-precision description of jet observables.

    hep-phhep-thEPJ Web Conf.(2026)·3 citations
13. 13*

    AI-powered full-data set search for new physics in ultraperipheral and diffractive events

    Simone Ragoni🇺🇸 · Brianna Kinkaid🇺🇸 · Janet Seger🇺🇸 · Christopher Anson🇺🇸 · David Tlusty🇺🇸

    We present possible strategies for anomaly detection of rare particle decays and exotic hadrons, such as pentaquarks, in low-background environments such as those characteristic of diffractive events and ultraperipheral \pp, \pA, or \AAcoll collisions at the CERN Large Hadron Collider (LHC). Our models are trained with toy samples representing the UPC processes measured until now by the ALICE Collaboration. When samples containing rare processes such as $\text{jpsi}\to 4\pi$ and pentaquark production, where the number of injected pentaquark events is estimated based on current experimentally available upper limits, and those for $\text{jpsi}\to 4\pi$ are estimated through the branching ratio of the decay channel, are analyzed, the rare processes are flagged as anomalous by the models. This approach demonstrates the applicability of such a technique for searches for new physics in the current and future data sets at collider experiments with high purity, while also allowing for the measurement of upper limits for the production of exotica.

    hep-phhep-exJHEP(2026)·0 citations
14. 14*

    Removing cutoff artifacts in the NJL model by a Renormalization Group consistent treatment

    Hosein Gholami🇩🇪 · Marco Hofmann🇩🇪 · Michael Buballa🇩🇪

    We summarize how a renormalization-group (RG)-consistent treatment removes well-known artifacts in NJL-model descriptions of color-superconducting quark matter. We introduce two RG-consistent schemes, "minimal" and "massless", and present analytic solutions for the diquark gap at $T=0$ and for the phase boundary $T_c(\mu )$ in symmetric massless matter, representing the high-density limit of the model. We compare the pairing gaps, phase diagram, and speed of sound with results obtained using conventional regularization.

    hep-phastro-ph.HEhep-thnucl-thEPJ Web Conf.(2026)·5 citations
15. 15*

    Searching the possibility of $a_0(1450)$ scalar state being a diquark structure via charmed meson semileptonic decays

    Ya-Lin Song🇨🇳 · Yin-Long Yang🇨🇳 · Ye Cao🇨🇳 · Xue Zheng🇺🇸 · Hai-Bing Fu🇨🇳

    The internal structure of light scalar state $a_0(1450)$ has not been definitively determined, it may consist of multiple possible states. Among them, it has the possibility of being regarded as a diquark state. Based on this possibility, we use QCD light-cone sum rules to study the semileptonic decay process $D\to a_0(1450)\ell {\nu }_{\ell }$ with $\ell =(e,\mu )$ to verify its rationality. Firstly, we construct two types of twist-2 light-cone distribution amplitude schemes based on the light-cone harmonic oscillator model, and present their moments $⟨{\xi }^n⟩{|}_{\mu }$ and Gegenbauer moments $a_n(\mu )$ at ${\mu }_0=1\mathrm{GeV}$ and ${\mu }_k=1.4\mathrm{GeV}$ for $n=(1,3,5)$. In the large recoil region, we obtain the transition form factors (TFFs): $f_{+}^{(S1)}(0)=0.836_{-0.116}^{+0.119}$, $f_{+}^{(S2)}(0)=0.767_{-0.105}^{+0.106}$ and $f_{-}(0)=0.630_{-0.077}^{+0.078}$. A simplified series expansion $z(q^2,t)$ is used to extrapolate TFFs to the entire physical $q^2$-region. For $q^2=10^{-5}{\mathrm{GeV}}^2$, we compute angular distribution of the differential decay width $d\Gamma /d\cos {\theta }_{\ell }$ over the range $\cos {\theta }_{\ell }\in [-1,1]$. Subsequently, we obtain differential decay widths and branching fractions for $D^0\to a_0(1450{)}^{-}{\ell }^{+}{\nu }_{\ell }$ and $D^{-}\to a_0(1450{)}^0{\ell }^{-}{\bar{\nu }}_{\ell }$, where the branching fractions being of order $10^{-6}$. Finally, we analyze three angular observables for the semileptonic decay process $D^{-}\to a_0(1450{)}^0{\ell }^{-}{\bar{\nu }}_{\ell }$, the forward-backward asymmetry ${\mathcal{A}}_{\mathrm{FB}}$, lepton polarization asymmetry ${\mathcal{A}}_{{\lambda }_{\ell }}$ and $q^2$-differential flat term~${\mathcal{F}}_{\mathrm{H}}$.

    hep-phCPC(2026)·2 citations
16. 16*

    A High-Quality Axion from Exact SUSY Chiral Dynamics

    T. Gherghetta🇺🇸 · H. Murayama🇺🇸 · B. Noether🇺🇸 · P. Quílez🇺🇸

    We use supersymmetric chiral dynamics perturbed by anomaly-mediated supersymmetry breaking to obtain a high-quality, composite axion that solves the strong CP problem. The strong dynamics arises from a supersymmetric SU(10) chiral gauge theory with massless matter chiral superfields. This leads to a stable, nonsupersymmetric vacuum, calculated exactly, where a spontaneously broken $U(1)$ global symmetry, identified with the Peccei-Quinn symmetry, gives rise to a composite QCD axion. The chiral gauge theory also admits a discrete ${\mathbb{Z}}_4$ (or ${\mathbb{Z}}_{8,16}$) gauge symmetry that forbids PQ-violating operators up to dimension eight. An extension to an $SU(14)\times {\mathbb{Z}}_{12}$ chiral gauge theory incorporates $SO(10)$ grand unification where the unification scale is identified with the PQ-breaking scale and PQ-violating operators are forbidden up to dimension 20. The supersymmetry breaking scale, near 100 TeV, ameliorates the Higgs hierarchy problem, while colored NGBs may be detected at future colliders via decays to gluons or form heavy isotopes.

    hep-phPRD(2026)·15 citations
17. 17*

    QCD axion from chiral gauge theories

    Ryosuke Sato🇯🇵 · Shonosuke Takeshita🇯🇵

    We present models of axion based on supersymmetric chiral gauge theories. In these models, the PQ symmetry is spontaneously broken by the non-perturbative dynamics of chiral gauge theory. Thanks to supersymmetry, IR dynamics of the models are calculable. We also present an example of a QCD axion model that is compatible with SU(5) grand unification. We find that in order to realize the gauge coupling unification with a certain precision, the GUT scale is the same with the PQ breaking scale, and the SUSY breaking scale is $\mathcal{O}(10^9)\mathrm{GeV}$.

    hep-phhep-th4 citations
18. 18*

    Standard Model Baryon Number Violation at Zero Temperature from Higgs Bubble Collisions

    Nabeen Bhusal🇩🇪 · Simone Blasi🇩🇪 · Martina Cataldi🇩🇪 · Aleksandr Chatrchyan🇸🇪 · Marco Gorghetto🇩🇪 · Geraldine Servant🇩🇪

    We compute for the first time baryon number violation at zero temperature from Higgs bubble collisions and find that it can be of the same order as that from thermal sphalerons in the symmetric phase at electroweak temperatures. We study the dependence of the rate of Chern--Simons number transitions on the shape of the scalar potential and on the Lorentz factor of the bubble walls at collision via large-scale (3+1)D lattice simulations of the Higgs doublet and SU(2) gauge fields. We estimate the resulting baryon asymmetry assuming some CP-violating source activated by the Higgs-field variation during the phase transition.

    hep-phPRL(2026)·6 citations
19. 19*

    Investigating nuclear effects in lepton-ion DIS at the LHC

    Reinaldo Francener🇧🇷 · Victor P. Goncalves🇧🇷 · Diego R. Gratieri🇧🇷

    Recent studies have demonstrated that the far-forward physics program of the Large Hadron Collider (LHC) can be useful to probe the hadron structure with GeV-TeV neutrinos and muons. In particular, these studies indicate that the measurement of the muon-ion and neutrino-ion cross-sections by the same experiment is feasible. In this paper, we investigate the impact of nuclear effects on the muon-tungsten ($\mu W$) and neutrino-tungsten ($\nu W$) deep inelastic scattering (DIS) events at FASER$\nu$ and its proposed upgrade FASER$\nu 2$. We estimate the rates associated with the inclusive cross-sections and for events with a charm tagged in the final state considering different parameterizations for the nuclear parton distribution functions. These results point out that muon and neutrino-induced interactions probe complementary kinematical ranges and that a simultaneous analysis of associated events will allow to test the universality (or not) of the nuclear effects. Moreover, we propose the study of the ratio between the charm tagged and inclusive events in order to discriminate between the distinct modeling of the nuclear effects at small-$x$. Our results indicate that a future experimental reconstruction of $\mu W$ and $\nu W$ DIS events at the LHC is a promising way to improve our understanding of nuclear effects and decrease the current uncertainties in parton distribution functions.

    hep-phhep-exnucl-thJHEP(2026)·4 citations
20. 20*

    Beyond Neutrino Mass: Observable $n$-$\overline{n}$ Oscillations in UV Complete Seesaw Models

    Ilja Dorsner🇭🇷 · Svjetlana Fajfer🇸🇮 · Shaikh Saad🇸🇮

    Next-generation experiments, such as the Deep Underground Neutrino Experiment and the European Spallation Source, are set to improve sensitivity to neutron-antineutron oscillation, a direct probe of $\Delta B=2$ baryon number violation, with particularly significant gains expected at the latter. The discovery of such a rare $\Delta B=2$ process would indicate physics beyond the Standard Model and could point to specific unified theories that allow observable $n-\overline{n}$ transitions. We accordingly examine $n-\overline{n}$ oscillations within a unified framework that accounts for charged fermion masses and generates viable neutrino masses via the seesaw mechanism. More specifically, we show that $n-\overline{n}$ oscillations can arise from two specific topologies within two distinct $SU(5)$ scenarios. One topology requires a presence of two color-sextet scalars in the Type II seesaw framework, whereas the other involves a scalar sextet and a color-octet fermion in the Type III seesaw framework. While the former topology can be realized in the $SO(10)$/Pati-Salam frameworks, the latter finds a natural embedding in $SU(5)$, which constitutes one of the key novelties of our work. Remarkably enough, the same dynamics responsible for fermion masses also induces baryon number violation, thus linking $n-\overline{n}$ oscillations to the flavor structure of the theory. We show that, given a TeV-scale mass for one of the colored states, upcoming searches for such $\Delta B=2$ processes can probe for a presence of the other colored states with masses up to $10^{11}\mathrm{GeV}$, well beyond the reach of colliders. This positions $n-\overline{n}$ oscillations as a rare low-energy portal to grand unification and ultra-heavy new physics.

    hep-phJHEP(2025)·2 citations
21. 21*

    Amplitude Uncertainties Everywhere All at Once

    Henning Bahl🇩🇪 · Nina Elmer🇩🇪 · Tilman Plehn🇩🇪 · Ramon Winterhalder🇮🇹

    Ultra-fast, precise, and controlled amplitude surrogates are essential for future LHC event generation. First, we investigate the noise reduction and biases of network ensembles and outline a new method to learn well-calibrated systematic uncertainties for them. We also establish evidential regression as a sampling-free method for uncertainty quantification. In a second part, we tackle localized disturbances for amplitude regression and demonstrate that learned uncertainties from Bayesian networks, ensembles, and evidential regression all identify numerical noise or gaps in the training data.

    hep-phSciPost Phys.(2026)·21 citations
22. 22*

    Probing the onset of collectivity via scaled particle spectra in ultrarelativistic nuclear collisions

    Thiago S. Domingues🇧🇷 · Fernando G. Gardim🇧🇷 · David D. Chinellato🇦🇹 · Gabriel S. Denicol🇧🇷 · Andre V. Giannini🇵🇹 · Matthew Luzum🇧🇷 · Cicero D. Muncinelli🇧🇷 · Jorge Noronha🇺🇸 · Tiago Nunes da Silva🇧🇷 · Jun Takahashi🇧🇷 · Giorgio Torrieri🇧🇷

    We identify a novel scaling in the transverse momentum spectra of produced particles, obtained by removing the global scales of multiplicity and mean transverse momentum. Hydrodynamic simulations and experimental data reveal an almost universal scaled spectrum across centralities, systems, and even small systems, pointing to its origin in the collective, fluid-like dynamics of the QGP. Comparing this observable with Bayesian a priori distributions shows its independent constraining power on QCD transport properties, while also exposing limitations of current models. A detailed posterior analysis will be pursued in future work, opening a new avenue to refine our understanding of collectivity in heavy-ion collisions.

    ↳ nucl-thhep-phnucl-exEPJ Web Conf.(2026)·3 citations
23. 23*

    Higher-order Chern-Simons extensions to QED in $2+1$ dimensions

    Ricardo Avila🇨🇱 · Albert Yu. Petrov🇧🇷 · Carlos M. Reyes🇨🇱 · César Riquelme🇨🇱 · Angel Sanchez🇲🇽

    In this work, we investigate radiative corrections in the higher-order extension of the Maxwell-Chern-Simons model coupled to standard spinor matter in $2+1$ dimensions. We begin analyzing the higher-order gauge sector, where we find the modes and the polarizations vectors associated to a massive photon and ghost field. The higher-order gauge model is canonically quantized and as expected the resulting algebra of creation and annihilation operators corresponds to an indefinite metric in Hilbert space. Subsequently, we compute all relevant one-loop diagrams in the modified QED starting with the fermion self-energy. We show that the induced corrections to the fermion two-point function produce two independent fermionic degrees of freedom, which can be included in a redefined Lagrangian describing two decoupled fermions fields, one corresponding to a physical particle and the other to a negative-norm ghost state. We take advantage of this decomposition to compute the photon polarization operator and the vertex correction, both of which are found to be finite. Finally, we analyze the causal behavior of the model by computing the commutator of gauge fields at different spacetime points, and found that microcausality is preserved.

    ↳ hep-thhep-ph1 citation
24. 24*

    Fluid dynamics of charm quarks from heavy to light-ion collisions

    Federica Capellino · Andrea Dubla · Rossana Facen · Stefan Floerchinger · Eduardo Grossi · Andreas Kirchner

    Heavy quarks are powerful tools to characterize the quark-gluon plasma (QGP) produced in relativistic nuclear collisions. By exploiting a mapping between transport theory and hydrodynamics, we developed a fluid-dynamic description of heavy-quark diffusion in the QCD plasma. We present results for the transverse momentum distributions of charm hadrons and evolution of charm density and diffusion fields obtained using a fluid-dynamic code coupled with the conservation of a heavy-quark current in the QGP in various collision systems.

    ↳ nucl-thhep-phEPJ Web Conf.(2026)·0 citations
25. 25*

    Long-distance reconstruction of QED corrections to the hadronic vacuum polarization for the muon g-2

    Christoph Lehner🇩🇪 · Julian Parrino🇩🇪 · Andreas Völklein🇩🇪

    The long-distance contribution of QED corrections to the hadronic vacuum polarization is particularly challenging to compute in lattice QCD+QED. Currently, it is one of the limiting factors towards matching the precision of the recent result by the Fermilab E989 experiment for the muon g-2. In this work, we present a method for obtaining high-precision results for this contribution by reconstructing exclusive finite-volume state contributions. We find relations between the pion-photon contributions of individual diagrams and demonstrate the reconstruction method with lattice QCD+QED data at a single lattice spacing of $a^{-1}\approx 1.73$ GeV and $m_{\pi }\approx 275$ MeV.

    ↳ hep-lathep-phhep-thPRD(2026)·4 citations
26. 26*

    Neutron Dark Decay in Neutron Stars: The Role of the Symmetry Energy

    M. Divaris🇬🇷 · Ch.C. Moustakidis🇬🇷

    We conduct a systematic investigation of the influence of the nuclear symmetry energy on the proposed neutron decay into dark matter particles within the cores of neutron stars. Unlike the majority of previous studies that considered only pure neutron matter, the present analysis is extended to encompass $\beta$-stable nuclear matter. Furthermore, in relation to previous studies, the interactions between dark matter and baryons are incorporated and systematically studied regarding their effect on the structure of neutron stars. Our findings indicate that the nuclear symmetry energy plays a critical role in shaping the total equation of state (EoS) for dense neutron star matter containing dark sector components. The strength of interactions among dark matter particles, as well as between dark matter and baryons, is shown to be pivotal in determining both the composition and the macroscopic properties of neutron stars. The concurrent tuning of interaction strengths alongside the symmetry energy parameters may facilitate a more accurate reproduction of recent observational data relevant to neutron star properties. In any case, the extent to which the proposed dark decay of the neutron is affected by the extreme conditions prevailing in the interior of neutron stars remains an open problem.

    ↳ nucl-thastro-ph.SRhep-phnucl-exNucl.Theor.(2025)·2 citations
27. 27*

    Road map for the tuning of hadronic interaction models with accelerator-based and astroparticle data

    Johannes Albrecht🇩🇪 · Julia Becker Tjus🇩🇪 · Noah Behling🇩🇪 · Jiří Blažek🇨🇿 · Marcus Bleicher🇩🇪 · Julian Boelhauve🇩🇪 · Lorenzo Cazon🇪🇸 · Ruben Conceição🇵🇹 · Hans Dembinski🇩🇪 · Luca Dietrich🇩🇪 · Jan Ebr🇨🇿 · Jan Ellbracht🇩🇪 and 43 other authors

    In high-energy and astroparticle physics, event generators play an essential role, even in the simplest data analyses. As analysis techniques become more sophisticated, e.g. based on deep neural networks, their correct description of the observed event characteristics becomes even more important. Physical processes occurring in hadronic collisions are simulated within a Monte Carlo framework. A major challenge is the modeling of hadron dynamics at low momentum transfer, which includes the initial and final phases of every hadronic collision. QCD-inspired phenomenological models used for these phases cannot guarantee completeness or correctness over the full phase space. These models usually include parameters which must be tuned to suitable experimental data. Until now, event generators have been developed and tuned mainly on the basis of data from high-energy physics experiments at accelerators. The wealth of data available from the latest generation of astroparticle experiments has not yet been fully exploited, and in many cases is not satisfactorily described. Both kinds of data sets are complementary as astroparticle experiments provide sensitivity especially to hadrons produced nearly parallel to the collision axis and cover center-of-mass energies up to several hundred TeV, well beyond those reached at colliders so far. In this report, we provide an overview of state-of-the-art event generators and their tuning, including the most relevant inputs from high-energy accelerator and astroparticle experiments. We present a road map that shows, for the first time, how the unified tuning of event generators with accelerator-based and astroparticle data can be performed.

    ↳ astro-ph.HEhep-exhep-phNature Rev.Phys.(2026)·14 citations
28. 28*

    Lattice evidence that scalar glueballs are small

    Ryan Abbott🇺🇸 · Daniel C. Hackett🇺🇸 · Dimitra A. Pefkou🇺🇸 · Fernando Romero-López🇨🇭 · Phiala E. Shanahan🇺🇸

    This work reports the first calculation of the gravitational form factors (GFFs) of the scalar glueball, performed via lattice field theory in Yang-Mills theory at a single lattice spacing. The glueball GFFs are compared with those of other hadrons as determined in previous lattice calculations, providing strong indications that glueballs have a different gluonic structure than typical hadronic states. A mass radius of 0.263(31) fm is predicted, supporting previous suggestions that the scalar glueball is significantly smaller than other hadrons. These results point towards a potential smoking-gun characteristic to target by experimental glueball searches.

    ↳ hep-lathep-phnucl-thPRL(2026)·11 citations
29. 29*

    A generalized study of linear electromagnetic cascades in astrophysical sources

    Damiano F. G. Fiorillo🇩🇪 · Federico Testagrossa🇩🇪 · Chengchao Yuan🇩🇪 · Maria Petropoulou🇬🇷 · Walter Winter🇩🇪

    High-energy gamma rays can trigger electromagnetic cascades via pair production on ambient photons, reprocessing their energy to lower frequencies. A classic example is the cascade from the gamma rays produced by ultra-high-energy cosmic rays in extragalactic photon fields, whose universal spectral shape was first described by Berezinsky in the 1970s. Recently, internal cascades, developing within the gamma-ray sources themselves, have gained a prominent role, as the IceCube data suggest that most detected neutrinos originate in gamma-ray-opaque environments. We analyze under what conditions these internal cascades can approach a universal spectrum. Since the Berezinsky treatment breaks down if synchrotron losses dominate, we present a generalized theory incorporating synchrotron-dominated cascades. We show the emergence of universal cascade spectrum among various examples of high-energy sources containing non-thermal cosmic rays, and discuss the conditions for its appearance.

    ↳ astro-ph.HEastro-ph.COhep-phJCAP(2025)·5 citations
30. 30*

    Mass-deformed Super Yang-Mills theory on ${\mathbb{T}}^4$: sum over twisted sectors, $\theta$-angle, and CP violation

    Mohamed M. Anber🇬🇧 · Erich Poppitz🇨🇦

    We study $SU(N)$ super Yang-Mills theory with a small gaugino mass $m$ and vacuum angle $\theta$ on the four-torus ${\mathbb{T}}^4$ with 't Hooft twisted boundary conditions. Introducing a detuning parameter $\Delta$, which measures the deviation from an exactly self-dual ${\mathbb{T}}^4$, and working in the limits $mLN\ll \Lambda LN\ll 1$ and $\frac{(N-1)m^2{L}^2}{4\pi }\ll \Delta \ll 1$, where $L$ is the torus size and $\Lambda$ the strong-coupling scale, we compute the scalar and pseudo-scalar condensates to leading order in $m^2{L}^2/\Delta$. The twists generate fractional-charge instantons, and we show that summing over all such contributions is crucial for reproducing the correct physical observables in the decompactified strong-coupling regime. From a Hamiltonian perspective, the sum over twisted sectors, already at small torus size, projects in the $m=0$ limit onto a definite superselection sector of the ${\mathbb{R}}^4$ theory. In the massless limit, we recover the exact value of the gaugino condensate $|⟨\lambda \lambda ⟩|=16{\pi }^2{\Lambda }^3$, and demonstrate how a spurious $U(1)$ symmetry eliminates all $CP$-violating effects. Our results are directly testable in lattice simulations, and our method extends naturally to non-supersymmetric gauge theories.

    ↳ hep-thhep-lathep-phJHEP(2025)·5 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.