Mon·Dec 22, 2025Monday·December 22, 2025

1. 01*

   Dark light shining on $B\to K^{(\ast )}{E}_{\mathrm{miss}}$

   Patrick D. Bolton🇸🇮 · Jernej F. Kamenik🇸🇮 · Martín Novoa-Brunet🇪🇸

   Recent Belle II data on $B^{+}\to K^{+}{E}_{\mathrm{miss}}$ show an excess consistent with a two-body decay involving a light invisible particle with mass around $2.1\mathrm{GeV}$. We present a UV-complete explanation based on a Higgsed $U(1{)}^{\prime }$ gauge symmetry with a light vector boson $Z^{\prime }$ and a vector-like top partner, which naturally enhances $b\to s$ transitions. While the minimal model can reproduce the required $B\to K^{(\ast )}{Z}^{\prime }$ rate, it is excluded by LHCb searches for resonant dimuon decays due to unavoidable loop-induced couplings of $Z^{\prime }$ to charged leptons. We show that a minimal extension with an additional light $U(1{)}^{\prime }$-charged singlet fermion allows $Z^{\prime }$ to decay dominantly invisibly, evades existing constraints coming also from dark photon and collider searches as well as Higgs measurements, and can simultaneously account for the Belle II excess and the observed dark matter abundance through resonant thermal freeze-out.

   hep-phPRD(2026)·3 citations
2. 02*

   Intrinsic Properties of Large CP Violation in the Complex Two-Higgs-Doublet Model

   Soojin Lee🇹🇼 · A. Hammad🇯🇵 · Dongjoo Kim🇰🇷 · Jeonghyeon Song🇰🇷

   We investigate the parameter space supporting large CP violation (CPV) in the complex two-Higgs-doublet model with softly broken $Z_2$ symmetry, where the 125~GeV Higgs boson is identified as the lightest neutral Higgs boson $H_1$. Through a comprehensive global scan of Type-I and Type-II models under theoretical, collider, and eEDM constraints, we identify distinct structures that facilitate large CPV. In Type-I, gauge-sector CPV is maximized when the 125~GeV Higgs boson is nearly degenerate with a second neutral scalar. For the ensemble of physically viable points, the predicted eEDM values typically exceed $10^{-31}e\cdot \mathrm{cm}$, placing the model largely within the sensitivity of next-generation experiments. Conversely, Type-II models strongly suppress gauge-sector CPV while allowing for nearly maximal CPV in the Yukawa sector. Destructive interference among various contributions allows for $|d_e|$ values as low as $O(10^{-35})e\cdot \mathrm{cm}$, resulting in no phenomenologically relevant lower bound. Finally, we uncover the phenomenon of ``hidden CPV'' in the near-alignment limit, characterized by CP-violating mixing between the heavy neutral Higgs bosons governed by the angle ${\alpha }_3$. We demonstrate that this hidden CPV can be experimentally probed at future colliders via CP-violating Yukawa interactions of $H_2$ and $H_3$, as well as the robust $H_2$-$H_3$-$Z$ coupling.

   hep-phhep-exPRD(2026)·2 citations
3. 03*

   Early-Time Dynamics of Heavy-Ion Collisions through Energy Correlators: celestial blocks and the spacetime structure of out-of-equilibrium QCD matter

   João Barata🇨🇭 · José Guilherme Milhano🇵🇹 · Andrey V. Sadofyev🇵🇹 · João M. Silva🇵🇹

   Ultrarelativistic heavy-ion collisions provide a unique window into far-from-equilibrium states of QCD matter. The initial stages of these events are characterized by highly anisotropic, nonthermal dynamics that precede hydrodynamization, yet they remain largely inaccessible through conventional soft observables. In this work, we show that the substructure of mid-rapidity jets provides direct sensitivity to the spacetime structure of this early, anisotropic phase. Using classical Yang-Mills simulations and effective kinetic theory to model the early-time evolution of the jet quenching parameter, we compute the azimuthally differential energy-energy correlator within the BDMPS-Z framework. By decomposing the result into celestial blocks, we isolate the coefficients that encode the anisotropic geometry and dynamics of the underlying medium. We identify an observable that couples directly to spatial anisotropies in the out-of-equilibrium QCD matter and also discuss the impact of medium response on its behavior. We further extend our study to mid-rapidity jets generated with the JEWEL Monte-Carlo, adjusted to incorporate an anisotropic medium background, and find qualitative agreement with the analytical expectations. Finally, we discuss how higher-point energy correlators and generalized energy-flow operators can enhance the sensitivity to the microscopic structure of far-from-equilibrium QCD matter.

   hep-phhep-exnucl-th14 citations
4. 04*

   Economical Jet Taggers -- Equivariant, Slim, and Quantized

   Antoine Petitjean🇩🇪 · Tilman Plehn🇩🇪 · Jonas Spinner🇬🇧 · Ullrich Köthe🇩🇪

   Modern machine learning is transforming jet tagging at the LHC, but the leading transformer architectures are large, not particularly fast, and training-intensive. We present a slim version of the L-GATr tagger, reduce the number of parameters of jet-tagging transformers, and quantize them. We compare different quantization methods for standard and Lorentz-equivariant transformers and estimate their gains in resource efficiency. We find an order-of-magnitude reduction in energy cost for an moderate performance decrease, down to 1000-parameter taggers. This might be a step towards trigger-level jet tagging with small and quantized versions of the leading equivariant transformer architectures.

   hep-phhep-ex11 citations
5. 05*

   Expanding the Reach of Laboratory SME Searches Using Higher-Precision Boost Transformations

   Jay D. Tasson🇺🇸

   Additional sensitivities to Lorentz violation can be obtained from existing experiments by considering additional boost-suppressed effects. The additional Lorentz-violating signals arise as variations in experimental observables at the commonly-used sidereal frequency as well as more novel frequencies. In this work we provide some examples that serve to illustrate how interesting signals arise from the structure of the relevant boost transformations.

   hep-ph1 citation
6. 06*

   Another Fit Bites the Dust: Conformal Prediction as a Calibration Standard for Machine Learning in High-Energy Physics

   Jack Y. Araz🇬🇧 · Michael Spannowsky🇬🇧

   Machine-learning techniques are essential in modern collider research, yet their probabilistic outputs often lack calibrated uncertainty estimates and finite-sample guarantees, limiting their direct use in statistical inference and decision-making. Conformal prediction (CP) provides a simple, distribution-free framework for calibrating arbitrary predictive models without retraining, yielding rigorous uncertainty quantification with finite-sample coverage guarantees under minimal exchangeability assumptions, without reliance on asymptotics, limit theorems, or Gaussian approximations. In this work, we investigate CP as a unifying calibration layer for machine-learning applications in high-energy physics. Using publicly available collider datasets and a diverse set of models, we show that a single conformal formalism can be applied across regression, binary and multi-class classification, anomaly detection, and generative modelling, converting raw model outputs into statistically valid prediction sets, typicality regions, and p-values with controlled false-positive rates. While conformal prediction does not improve raw model performance, it enforces honest uncertainty quantification and transparent error control. We argue that conformal calibration should be adopted as a standard component of machine-learning pipelines in collider physics, enabling reliable interpretation, robust comparisons, and principled statistical decisions in experimental and phenomenological analyses.

   hep-phcs.AIhep-ex5 citations
7. 07*

   A Brief History and Outlook of Hadronic Physics in Indonesia

   Ahmad Jafar Arifi🇯🇵 · Parada. T. P. Hutauruk🇰🇷 · Terry Mart🇮🇩 · Chalis Setyadi🇮🇩

   Hadronic physics has gradually emerged as one of the growing research frontiers in Indonesia, driven by efforts to better understand the properties of the strong interaction and the internal structure of hadrons from the fundamental principles of Quantum Chromodynamics. In the last few decades, Indonesian researchers have made significant contributions to developing various theoretical and phenomenological aspects of hadrons. In addition, on the experimental side, Indonesian scientists have participated in hadron experiment facilities overseas, such as the ALICE collaboration at CERN, which has strengthened the scientific activities and networks and has supported the training of young Indonesian researchers. In the present paper, we review Indonesian scientists' contributions to hadronic physics, highlight ongoing research directions in both experimental and theoretical, and outline strategies for future development toward integration into the international hadronic physics community.

   hep-phnucl-thphysics.soc-ph0 citations
8. 08*

   Higgs-Portal Stueckelberg Dark Matter

   Antonio De Felice🇯🇵 · Takehiro Ogura🇯🇵 · Shinji Tsujikawa🇯🇵 · Kimiko Yamashita🇯🇵

   We study dark photon dark matter $X$ associated with a dark $U(1{)}_X$ gauge symmetry. To evade laboratory and cosmological constraints on kinetic mixing with the Standard Model $U(1{)}_Y$, we assign a $Z_2$-odd dark parity to $X$ that forbids such mixing. The leading interactions then arise from gauge-invariant dimension-6 Higgs-portal operators, including both parity-even and parity-odd terms. We assume that the dark matter mass is generated via the Stueckelberg mechanism, which also induces a dimension-4 Higgs-portal operator $(H^{†}H)X_{\mu }{X}^{\mu }$ and additional dimension-6 operators. We investigate freeze-in production of $X$ from Higgs-pair annihilations after reheating, incorporating both gauge-invariant and Stueckelberg-induced operators. First, we consider the case in which the Wilson coefficients of the gauge-invariant dimension-6 operators, $C$ and $\tilde{C}$, are of order unity. We find that, in this case, the Stueckelberg contributions remain subdominant in dark matter production. This result follows from the requirement that the effective scale implied by perturbative unitarity must exceed the cutoff scale of the effective field theory. Next, we explore a more general situation in which $C$ and $\tilde{C}$ are smaller than unity. In this second case, Stueckelberg-induced operators can become comparable and lead to distinctive features in the dark-matter parameter space, including interference effects. For both cases, we show that there exists a wide parameter space consistent with the observed dark matter relic density.

   hep-ph3 citations
9. 09*

   Running of neutrino mass parameters in the Zee model

   Michael A. Schmidt🇦🇺 · James Vandeleur🇦🇺

   We analyse the size of quantum corrections in the Zee model using effective field theory techniques. We derive the relevant 1-loop matching conditions and use them together with the existing renormalisation group equations in the two Higgs doublet model to calculate quantum corrections to the neutrino mass squared differences, mixing angles, and phases. Using four benchmark scenarios, we demonstrate when quantum corrections have to be included in studies of neutrino mass parameters in the Zee model.

   hep-phJHEP(2026)·0 citations
10. 10*

    Detecting Axion Dark Matter with an Organic Molecular Maser

    Hongliang Wu🇨🇳 · Yuchen Han🇨🇳 · Zhengtao Wang🇨🇳 · Dezhi Zheng🇨🇳 · Yeliang Wang🇨🇳 · Liu Yang🇨🇳 · Zhiwei Wang · Bo Zhang🇨🇳 · Dmitry Budker🇩🇪 · Jun Zhang🇨🇳

    We present a novel quantum sensing approach to search for axion-electron interactions around the axion mass of 6 \mueV. In this region, laboratory searches are relatively scarce, and our direct experiment measuring the axion-electron coupling constant reaches the sensitivity of 8 \times 10^{-6} GeV^{-1}. The method, based on an organic molecular maser establishes a proof-of-principle for quantum-enhanced detection, with a corresponding magnetic field sensitivity of 0.85 fT/\sqrt{\rm{Hz}}. The methodology is generic and can be readily extended to other physical systems, further broadening its applicability in quantum sensing and dark matter searches.

    hep-phquant-ph1 citation
11. 11*

    Complete computation of all three-loop five-point massless planar integrals

    Dmitry Chicherin🇫🇷 · Yu Wu🇨🇳 · Zihao Wu🇨🇳 · Yongqun Xu🇨🇳 · Shun-Qing Zhang🇩🇪 · Yang Zhang🇨🇳

    We calculate all three-loop, five-point, massless planar Feynman integral families in the dimensional regularization scheme. This is a new milestone in Feynman integral computations. The analysis covers four distinct families of Feynman integrals for this configuration, for all of which we derive the canonical differential equations. Our results also confirm a prediction on the three-loop five-point alphabet. The boundary values are analytically determined. Using these differential equations, the integrals can be evaluated to high precision efficiently. Our work establishes the foundation for next-to-next-to-next-to-leading-order (N${}^3$LO) calculation of the production of three massless final states, as well as corresponding bootstrap studies in gauge theories.

    hep-phhep-th13 citations
12. 12*

    Kaon physics in the SMEFT

    Jason Aebischer🇨🇭

    Kaon physics observables are highly sensitive to New Physics (NP) effects and form in combination with the Standard Model Effective Field Theory (SMEFT) a powerful tool to study physics that goes beyond the Standard Model paradigm. We review recent SMEFT analyses in the Kaon sector and point out novel directions that might be investigated in the future.

    hep-ph1 citation
13. 13*

    GUT-based NMSSM with Singlino Dark Matter: Describing the ATLAS/CMS Excesses

    E. Bagnaschi🇮🇹 · M. Chakraborti🇬🇧 · S. Heinemeyer🇪🇸 · I. Saha🇮🇳

    One of the main goals of the ongoing LHC program is the search for BSM physics, with EW SUSY partners still allowed with masses as low as a few hundred GeV. Over the last years, searches for the ``golden channel'', $pp\to {\tilde{\chi }}_2^0{\tilde{\chi }}_1^{\pm }\to {\tilde{\chi }}_1^0{Z}^{(\ast )}{\tilde{\chi }}_1^0{W}^{\pm (\ast )}$ show consistent excesses between CMS and ATLAS in the 2 soft-lepton and 3 soft-lepton plus missing $E_T$ searches, favoring mass scales of $m_{{\tilde{\chi }}_2^0}\approx m_{{\tilde{\chi }}_1^{\pm }}\ge 200$ GeV and $\Delta m_{21}:=m_{{\tilde{\chi }}_2^0}-m_{{\tilde{\chi }}_1^0}\approx 20$ GeV. We analyze these excesses in the framework of the Next-to-Minimal Supersymmetric Standard Model (NMSSM). We assume a singlino dominated lighest neutralino, ${\tilde{\chi }}_1^0$, as our Dark Matter (DM) candidate. The second and third lightest neutralinos, ${\tilde{\chi }}_{2,3}^0$ are higgsino like, with the higgsino mixing parameter $\mu$ being smaller than the soft SUSY-breaking bino and wino masses, $M_1$ and $M_2$. In particular, we assume the approximate GUT relations $M_1\sim M_2/2\sim M_3/6$, yielding a gluino mass $m_{\tilde{g}}\sim M_3\ge 2$ TeV, in agreement with the LHC search limits. The scalar masses are assumed to heavy and do not play a role in our analysis. We demonstrate that this scenario is in agreement with all relevant experimental constraints, comprising the DM direct detection limits and the upper limit on the DM relic density, the LHC searches for SUSY particles and additional Higgs bosons, as well as the LHC Higgs-boson rate measurements. This constitutes the first explanation of the soft-lepton excesses in a model with GUT relations among the soft SUSY-breaking parameters.

    hep-ph0 citations
14. 14*

    The Lund $b$-jet plane

    Andrea Ghira🇩🇪 · Simone Marzani🇮🇹 · Gregory Soyez🇫🇷

    We compute the primary Lund plane density for jets initiated by a massive ($b$) quark to single logarithmic accuracy in Quantum Chromodynamics (QCD). In order to capture mass effects, we consider quasi-collinear factorisation and we include contributions from the running of the QCD coupling and from collinear evolution, in a variable flavour-number scheme. Furthermore, the resummation of soft logarithms, including clustering effects, is performed numerically, keeping the full dependence on the $b$-quark mass. While our all-order results can be applied to both hadron and lepton colliders, we present, as first phenomenological application, the resummed calculation of the Lund plane density in $e^{+}{e}^{-}$ collisions at $\sqrt{s}=M_Z$, matched to tree-level matrix elements.

    hep-phhep-exJHEP(2026)·6 citations
15. 15*

    Evidence for dynamical chiral condensate in high-energy heavy ion collisions

    Tobias Bruschke🇩🇪 · Andreas Kirchner🇺🇸 · Stefan Floerchinger🇩🇪

    Quantum chromodynamics with light quarks features an approximate global symmetry, known as chiral symmetry, that is believed to be spontaneously broken by the vacuum expectation value of a scalar and isoscalar composite field, in addition to a small explicit breaking due to finite quark masses. For a high enough temperature, as achieved in the early universe or the fireball created by a high-energy heavy ion collision, this symmetry is expected to be restored. We show theoretically that a coherent deviation of the corresponding quantum field from its usual vacuum expectation value on the freeze-out hypersurface of a heavy-ion collision leads, after resonance decays, to a characteristic contribution to the transverse momentum spectrum of charged pions, in the very soft regime, consistent with experimental data from the Relativistic Heavy Ion Collider and the Large Hadron Collider. Taken together, the experimental data with the new theoretical results provide compelling support for the existence of a chiral condensation mechanism with partial restoration of chiral symmetry at high temperature.

    hep-phnucl-th2 citations
16. 16*

    Expected flavor composition of supernova neutrinos

    Antonio Capanema🇮🇹 · Yago Porto🇩🇪 · Maria Manuela Saez🇯🇵

    We revisit the flavor composition of neutrinos from core-collapse supernovae (SN), focusing on robust predictions that are insensitive to the poorly known dynamics of collective flavor conversion in the inner core. Assuming that the many different trajectories and microscopic histories of neutrinos lead to decoherence of the ensemble at the boundary between the region of collective effects and the Mikheyev-Smirnov-Wolfenstein (MSW) dominated layers, we show that standard matter effects alone strongly constrain the electron-flavor fraction at Earth. For normal mass ordering (NO) we obtain $f_{{\nu }_e}^{\mathrm{NO}}\lesssim 0.5$ at all times and energies, while for inverted ordering (IO), we predict $f_{{\nu }_e}^{\mathrm{IO}}\simeq 1/3$, i.e.\ near flavor equipartition. Shock-wave propagation through the high (H) MSW resonance drives the system toward equipartition also in NO. In this way our framework links simple assumptions about decoherence and standard matter effects to robust expectations for the flavor evolution inside core-collapse supernovae. This contribution summarizes the main results of arXiv:2403.14762.

    hep-ph1 citation
17. 17*

    Proton Structure from a Soft-Wall Holographic QCD Model: Mass Spectrum, Form Factors, and Mechanical Properties

    Jiali Deng🇨🇳 · Defu Hou🇨🇳

    Understanding the internal structure of the proton-including its mass spectrum, electromagnetic and gravitational form factors, and mechanical properties-remains a central challenge in hadronic physics. While lattice QCD and experimental measurements provide valuable insights, a holographic framework with a single parameter set capable of simultaneously describing these diverse observables is still lacking. Here, we employ the soft wall model, a phenomenological holographic approach that incorporates gluon condensation and linear confinement, to compute the proton mass spectrum, electromagnetic form factors (EMFFs), and gravitational form factors (GFFs). Our results show good agreement with recent experimental data and lattice QCD calculations. Despite its phenomenological nature, the model's ability to simultaneously describe multiple observables suggests that it effectively mimics some key QCD features.

    hep-phEPJC(2026)·4 citations
18. 18*

    How much color do we really need? Two-loop subleading-color effects in photon and jet physics

    Michał Czakon🇩🇪 · Rene Poncelet🇵🇱

    In recent years, the complete set of cross sections for Large Hadron Collider (LHC) processes ending with three resolved final states consisting of either photons or jets has been evaluated at next-to-next-to-leading order in QCD and leading order in QED. Results for three photons or three jets have only been obtained using the leading-color approximation of the virtual two-loop amplitudes. In the meantime, the required amplitudes have become available without recourse to the color expansion. In the present publication, we quantify the effects of the subleading-color contributions, and show that they do not exceed 2\% for most of the previously published results. The one exception is the ratio of three- to two-jet cross sections, where subleading-color effects can reach up to 5\%. Furthermore, we show that these conclusions hold for both popular infrared renormalization schemes, minimal subtraction and Catani's. The size of the effects is usually overshadowed by the size of the remaining uncertainty due to the truncation of the perturbation series. This is particularly important in the case of three-jet distributions that have already been used for the extraction of the strong-coupling constant at the very high energies available at the LHC.

    hep-phJHEP(2026)·3 citations
19. 19*

    Only slightly "Amplifying nonresonant production of dark sector particles in scattering dominance regime''

    S.V. Demidov🇷🇺 · D.S. Gorbunov🇷🇺 · A.L. Polonski🇷🇺

    In recent article [PhysRevD.109.055041 (2024)] it has been argued that production of dark photons -- hypothetical massive vectors -- in nuclear reactors via mixing with the visible photons is considerably enhanced (by a factor of 10) due to Compton scattering of the latter. We revisit the production of dark photons in the reactor environment and find that although the scattering of photons indeed leads to a larger number of produced dark photons, the overall enhancement is considerably smaller than what has been obtained in Ref. [PhysRevD.109.055041 (2024)]. Our findings are validated using GEANT simulations, which take into account oscillations between ordinary and visible photons and interaction of the latter with matter. The correction to the limit on mixing parameter between dark and visible photons is expected to be below 30% for all masses. It's application must be accompanied with an update on the original spectrum of photons produced in nuclear reactions inside the nuclear reactor.

    hep-phPRD(2026)·1 citation
20. 20*

    Two-lepton tales: Dalitz decays of heavy quarkonia

    Pietro Colangelo🇮🇹 · Fulvia De Fazio🇮🇹 · Riccardo Pinto🇮🇹

    We study the Dalitz decays of heavy quarkonia, which result from the internal virtual photon conversion into an ${\ell }^{+}{\ell }^{-}$ lepton pair. Heavy-quark symmetries allow us to establish systematic relations between transitions of different quarkonium states, and to precisely determine the branching fractions for several charmonium and bottomonium decay modes. For charmonium, existing data on ${\chi }_{cJ}(1P)\to J/\psi {\ell }^{+}{\ell }^{-}$ and $\psi (2S)\to {\chi }_{cJ}(1P){\ell }^{+}{\ell }^{-}$ enable us to determine the parameters of the transition form factors and to predict the rates of yet-unobserved modes. The Dalitz transitions of ${\chi }_{c1}(3872)$ are important, as they can help assessing the structure of this meson. For bottomonium, recent LHCb measurements allow us to predict the branching fractions of ${\chi }_{bJ}(nP)\to {\rm Y}(1S){\ell }^{+}{\ell }^{-}$ and $h_b(nP)\to {\eta }_b(1S){\ell }^{+}{\ell }^{-}$ ($n=1,2)$. We also investigate the sensitivity of heavy quarkonia Dalitz modes to the contribution of a new light vector mediator, such as the putative $X(17)$.

    hep-phhep-exhep-latPRD(2026)·3 citations
21. 21*

    Leptogenesis and Dark Matter in an Inverse Seesaw from gauged B-L breaking

    Enrique Fernández-Martínez🇪🇸 · Ana Luisa Foguel🇧🇷 · Xabier Marcano🇮🇹 · Daniel Naredo-Tuero🇪🇸 · Vsevolod Syvolap🇪🇸 · Kevin A. Urquía-Calderón🇩🇰

    We study a dynamical realization of the low-scale Inverse Seesaw mechanism in which the approximate $B-L$ symmetry is gauged and spontaneously broken. Anomaly cancellation requires additional chiral fermions, one of which becomes a stable dark matter candidate after symmetry breaking, while another remains massless and contributes to dark radiation. Focusing on the regime of feeble gauge interactions, we compute the dark matter relic abundance produced via the freeze-in mechanism through the $B-L$ gauge boson and identify the parameter space consistent with cosmological and laboratory constraints. We show that the same region naturally avoids thermalization of heavy neutral leptons, preserving the viability of ARS leptogenesis. The interplay between dark matter production, dark radiation constraints, and leptogenesis requirements leads to a predictive scenario where future cosmological surveys and intensity-frontier experiments such as SHiP can probe significant portions of the viable parameter space.

    hep-ph1 citation
22. 22*

    Baryogenesis and EDMs in the 2HDM+CS

    Björn Garbrecht🇩🇪 · Edward Wang🇩🇪

    We perform the first joint analysis of baryogenesis from initial Higgs charges (also called Higgsogenesis) and EDMs in a model with two Higgs doublets, a complex scalar and a Majorana fermion. In our proposed scenario, baryogenesis happens in three steps: (1) The decay of the scalar produces an asymmetry between the two Higgs doublets which is partly transferred to fermions via Standard Model processes. (2) This asymmetry is converted into a $B-L$ charge via interactions mediated by the Majorana fermion. (3) The weak sphaleron processes partially convert the resulting $B-L$ charge into a $B$ asymmetry. We perform a numerical analysis of baryogenesis and the EDM contributions and find that, due to resonant enhancement, baryogenesis is possible with singlet masses as low as $10^5$ GeV. We also find that for some parameters, the model can give large contributions to the electron and neutron EDM while also producing baryogenesis. The present scenario offers a new perspective on interpreting observational bounds in terms of cosmology: Because it relies on out-of-equilibrium decays, the questions of baryogenesis and $CP$ violation in the Higgs sector may be linked with EDM signals without the additional assumption of a first order electroweak phase transition.

    hep-phastro-ph.COhep-ex2 citations
23. 23*

    Boiling away asymmetries: low-scale phase transitions, gravitational waves and leptogenesis

    Leonardo Grimaldi🇮🇹 · Michele Lucente🇮🇹 · Silvia Pascoli🇮🇹

    Leptogenesis is one of the most popular mechanisms to account for the observed baryon asymmetry of the Universe. A generic feature of leptogenesis is a large separation of scales between the epoch of baryon asymmetry production (sphaleron freeze-out at temperature $T\sim 130$ GeV) and the one where it affects the big bang nucleosynthesis processes (BBN at $T\sim 1$ MeV). Any entropy release between these two epochs would lead to a dilution of previously produced relics, such as the baryons. Motivated by the recent evidence of a stochastic gravitational waves background (SGWB) in the nHz frequency range, we consider the case of supercooled first-order phase transition and we study the impact of the induced entropy dilution on the leptogenesis parameter space. We employ the Type-I seesaw with 2 right-handed neutrinos as benchmark scenario, and demonstrate that the viable leptogenesis parameter space is significantly reduced. Interestingly, the values of dilution predicted by the SGWB best fit points in several first order phase transition scenarios would completely exclude the leptogenesis parameter space testable by future experiments, thus establishing a phenomenological interconnection between leptogenesis, SGWB, first order phase transition and neutrino mass generation. Our analysis can be generalised to different leptogenesis models and entropy dilution mechanisms.

    hep-phastro-ph.CO0 citations
24. 24*

    Unified study of $B_s^0\to X(3872){\pi }^{+}{\pi }^{-}(K^{+}{K}^{-})$ and $B_s^0\to \psi (2S){\pi }^{+}{\pi }^{-}(K^{+}{K}^{-})$ processes

    Yun-Hua Chen🇨🇳

    We perform a unified description of the experimental data of the ${\pi }^{+}{\pi }^{-}$ invariant mass spectra of $B_s^0\to \psi (2S){\pi }^{+}{\pi }^{-}$, the ${\pi }^{+}{\pi }^{-}$ and $K^{+}{K}^{-}$ invariant mass spectra of $B_s^0\to X(3872){\pi }^{+}{\pi }^{-}(K^{+}{K}^{-})$, and the ratio of branch fractions $\mathcal{B}[B_s^0\to X(3872)(K^{+}{K}^{-}{)}_{\mathrm{non}-\varphi }]/\mathcal{B}[B_s^0\to X(3872){\pi }^{+}{\pi }^{-})$. The strong final state interactions between the two pseudoscalars are taken into account using a parametrization fulfilling unitarity and analyticity. We find that there is universality in the coupling constants for $B_s^0\to \psi (2S){\pi }^{+}{\pi }^{-}$ and $B_s^0\to J/\psi {\pi }^{+}{\pi }^{-}$ processes. While the couplings of $B_s^0\to X(3872){\pi }^{+}{\pi }^{-}$ are about half of magnitude smaller than the couplings of $B_s^0\to \psi (2S){\pi }^{+}{\pi }^{-}$, which indicates that the $X(3872)$ is different from a pure charmonium state. Furthermore, we find that the $f_0(1500)$ plays an important role in the $B_s^0\to \psi (2S){\pi }^{+}{\pi }^{-}$ and the $B_s^0\to X(3872){\pi }^{+}{\pi }^{-}(K^{+}{K}^{-})$ processes, though the phase space of $B_s^0\to X(3872)f_0(1500)$ is small. Also we predict the ratio of branch fractions $\mathcal{B}[B_s^0\to \psi (2S)(K^{+}{K}^{-}{)}_{\mathrm{non}-\varphi }]/\mathcal{B}[B_s^0\to \psi (2S){\pi }^{+}{\pi }^{-}]$ and the $K^{+}{K}^{-}$ invariant mass distribution of $B_s^0\to \psi (2S)K^{+}{K}^{-}$.

    hep-phhep-exhep-latnucl-thEPJC(2026)·0 citations
25. 25*

    From Lead to Helium: Discovery Potential for Jet Quenching in the Smallest Collision Systems

    Coleridge Faraday🇿🇦 · Ben Bert🇿🇦 · Jack Brand🇿🇦 · Werner Vogelsang🇩🇪 · W. A. Horowitz🇿🇦

    We present perturbative quantum chromodynamics (pQCD) predictions for the modification to the yield of high-momentum particles in very light ion collisions - ${}^{10}\mathrm{B}+{}^{10}\mathrm{B}$, ${}^6\mathrm{Li}+{}^6\mathrm{Li}$, ${}^4\mathrm{He}+{}^4\mathrm{He}$, and ${}^3\mathrm{He}+{}^3\mathrm{He}$ - both with and without medium-induced energy loss. We show that there is non-trivial suppression expected from our partonic energy loss model in symmetric systems from ${}^{208}\mathrm{Pb}+{}^{208}\mathrm{Pb}$ to ${}^3\mathrm{He}+{}^3\mathrm{He}$ and in asymmetric systems $A+B$, and that the energy loss scales approximately with $(\sqrt{AB}{)}^{1/3}$. Further, we find that deep inelastic scattering measurements in ${}^3\mathrm{He}$ and ${}^6\mathrm{Li}$ tightly constrain the nPDF baseline, making these isotopes a particularly clean environment for observing final-state partonic energy loss induced by the formation of a quark-gluon plasma in these very small systems.

    hep-phnucl-th4 citations
26. 26*

    Dijet production in DIS off a large nucleus at next-to-eikonal accuracy in a Gaussian model within the CGC framework

    Pedro Agostini🇵🇱 · Tolga Altinoluk🇵🇱 · Néstor Armesto🇪🇸 · Guillaume Beuf🇵🇱 · Florian Cougoulic🇵🇱 · Swaleha Mulani🇵🇱

    We develop a Gaussian model to evaluate the decorated dipole and quadrupole operators that arise beyond the eikonal approximation in the Color Glass Condensate framework. While the method is general and applicable to arbitrary beyond-eikonal Wilson line structures, we employ it for dijet production in deep inelastic scattering at next-to-eikonal accuracy. After validating the model at the eikonal level, we compute all next-to-eikonal operator structures entering the dijet cross section. We show that some of them do not contribute to this observable, while others vanish identically. Therefore, in the Gaussian model next-to-eikonal corrections to dijet production in deep inelastic scattering originate solely from a given type of operators and from next-to-eikonal three-point correlators. The resulting expressions are provided in a form suitable for numerical implementation.

    hep-phPRD(2026)·7 citations
27. 27*

    Probing electroweak pair production of heavy neutral leptons with displaced vertices at the LHC

    Stéphane Lavignac🇫🇷 · Anibal D. Medina🇦🇷 · Nicolás I. Mileo🇦🇷 · Santiago Tanco🇦🇷

    We study the sensitivity of displaced vertex searches at the LHC to heavy neutral leptons (also known as sterile neutrinos) that are produced in pairs with an electroweak-size cross section. We work within the context of a supersymmetric model in which the sterile neutrino is produced along with Standard Model particles in higgsino decays. By making use of model-independent reconstruction efficiencies provided by the ATLAS collaboration in their search for displaced vertices with multiple jets, we obtain constraints on this model from $139$ fb${}^{-1}$ of data collected by ATLAS during the LHC Run~2, and assess the discovery reach of Run~3 and of the high-luminosity LHC (HL-LHC). Depending on the higgsino mass parameter, sterile neutrino masses between $20\mathrm{GeV}$ and $230\mathrm{GeV}$ and active-sterile neutrino mixings in the range $4\times 10^{-14}\lesssim V_N^2\lesssim 3\times 10^{-10}$ can be excluded. At the HL-LHC, discovery-level significances could be reached for sterile neutrinos masses up to $295\mathrm{GeV}$ and values of $V_N^2$ down to $3\times 10^{-14}$. Finally, moving away from the supersymmetric scenario, we study to which extent these results can be generalized to a broader class of models in which the sterile neutrinos are produced in the decays of heavier particles that are themselves pair-produced with an electroweak-size cross section.

    hep-phJHEP(2026)·1 citation
28. 28*

    Probing new physics in the Boosted $HH\to b\bar{b}\gamma \gamma$ channel at the LHC

    Mohamed Belfkir🇦🇪

    This paper presents the first dedicated study of the boosted $HH\to b\bar{b}\gamma \gamma$ topology as a key probe of physics beyond the Standard Model (SM) in the high-energy double-Higgs boson regime. The analysis presented in this paper, focuses on two classes of new-physics scenarios: non-resonant deviations of the quartic gauge--Higgs interaction, parameterized by the coupling modifier ${\kappa }_{2V}$, and resonant enhancement arising from the decay of a heavy scalar state, modeled within a two-Higgs-doublet framework. We demonstrate that the boosted reconstruction category enhances sensitivity to beyond SM effects that populate the high-$m_{HH}$ tail, yielding improved constraints on ${\kappa }_{2V}$ and extending the discovery reach for heavy resonances.

    hep-phhep-exPRD(2026)·1 citation
29. 29*

    The role of charm and unflavored mesons in prompt atmospheric lepton fluxes

    Laksha Pradip Das🇺🇸 · Diksha Garg🇺🇸 · Maria Vittoria Garzelli🇩🇪 · Mary Hall Reno🇺🇸 · Günter Sigl🇩🇪

    The all-sky very-high-energy ($10^4-10^6$ GeV) atmospheric muon flux measured by IceCube shows a spectral hardening at the highest energies, indicating the presence of a prompt component. IceCube has also measured the atmospheric muon neutrino flux at high energy. However, since this flux is dominated by astrophysical neutrinos, only an upper bound can be placed on the prompt atmospheric ${\nu }_{\mu }+{\bar{\nu }}_{\mu }$ contribution. In this work, we provide a new evaluation of the prompt atmospheric muon flux including an intrinsic charm component in the cosmic ray-air interactions. The latter enhances the forward production of ${\bar{D}}^0$, $D^{-}$, and ${\Lambda }_c$, which subsequently decay into final states containing muons and muon neutrinos. We show how the increase in the prompt muon flux due to intrinsic charm is accompanied by a corresponding enhancement in the prompt muon neutrino flux. We implement different intrinsic charm production models in \texttt{MCEq} to calculate the resulting lepton fluxes. We discuss the challenges of achieving predictions that are simultaneously consistent with both IceCube's high-energy atmospheric muon flux measurements and IceCube upper bounds on the prompt muon neutrino flux, and we quantify the resulting discrepancies. As possible solutions, we explore scaling of the unflavored meson contributions to the prompt atmospheric muon flux to assess how such adjustments can reconcile these differences. The tensions emphasized in our work call for a refinement of the hadronic interaction models, especially the production of unflavored mesons, and for new experimental data sensitive to unflavored meson and heavy flavor production with reliable estimates of the associated uncertainties. We suggest that the energy and zenith angle dependence of muon and neutrino flux ratios from future neutrino telescope measurements may help to disentangle different scenarios.

    hep-ph0 citations
30. 30*

    Feasibility to probe the dynamical scotogenic model at the LHC

    Gustavo Ardila-Tafurth🇨🇴 · Andrés Flórez🇨🇴 · Cristian Rodríguez🇨🇴 · Maud Sarazin🇨🇴 · Óscar Zapata🇨🇴

    We perform a feasibility study to probe dark matter (DM) production at the LHC within a global $U(1{)}_L$ scotogenic model. The study is conducted using the Markov Chain Monte Carlo numerical method, considering the viable parameter space of the model allowed by experimental constraints such as neutrino oscillation data, the Higgs to invisible branching fraction, and DM observables. The production of scalar and fermionic DM candidates, predicted by the model, is then studied under the LHC conditions for different luminosity scenarios imposing compressed mass spectra conditions between the lightest fermion and the ${\mathbb{Z}}_2$ odd scalars. We studied two production mechanisms, Drell-Yan and Vector Boson Fusion. It was found that the Drell-Yan mechanism gives better detection prospects for fermionic DM masses between 100-220~\textrm{GeV} at high luminosity scenarios.

    hep-phPRD(2026)·1 citation
31. 31*

    Dynamical equation for quark spin polarization in the rotating medium

    Tianyang Li🇨🇳 · Yunfei Fan🇺🇸 · Anping Huang🇨🇳 · Baoyi Chen🇨🇳

    In non-central relativistic heavy-ion collisions, the produced quark-gluon plasma (QGP) behaves approximately as a rotating fluid due to the system's initial angular momentum. In this rotating fluid, the spins of quarks become polarized due to the coupling between spin and angular momentum, as well as random spin-spin interactions. Since the Landau-Lifshitz (LL) equation effectively describes the spin polarization of fermions in a medium with a magnetic field, we derive a phenomenological equation analogous to the LL equation for heavy quark spin dynamics in the rotating medium. The spin-angular momentum coupling and random spin-spin interactions are incorporated, leading to a detailed balance of heavy quark spin distributions. This equation provides insight into the spin dynamics of heavy quarks and quarkonium in relativistic heavy-ion collisions.

    ↳ nucl-thhep-phPRD(2026)·1 citation
32. 32*

    On Signatures of a Possible New Physics Resonance in Atmospheric Air Showers Using a Parameterized Model

    Jiri Kvita🇨🇿

    We present a parameterized model of atmospheric particle showers initiated by cosmic rays. Few physics shower parameters are tuned in a comparison to the Conex generator. Resulting shower properties are studied, with a comment on the cases where multiple shower maxima develop. Finally, we implement simple models of new physics resonance of masses of 100 GeV and 1 TeV and examine their effects on the shower profile, depth and maximum variation in dependence of the decay channel of the hypothetical resonance. It is shown that a new resonance effects can appear at the energy threshold and can persist for about a decade in ${\log }_{10}E/\mathrm{eV}$. Various assumed decay modes of the hypothetical resonance have different effects on the direction and shape of the modified average shower depth as function of the energy, with possible implications for current or future measurements. It is shown that, within the presented model, the visibility of the resonance in modified shower depth strongly depends on the resonance width. A significant modification at 10\% width gradually diminishes towards the percent-level width. We propose that looking at the 2D distributions of the two first individual shower moments can also reveal signatures of new physics.

    ↳ astro-ph.HEhep-exhep-ph0 citations
33. 33*

    Quantum state of interacting primordial inhomogeneities: de-squeezing and decoherence

    Amaury Micheli🇯🇵 · Yuto Oshima🇯🇵 · Tomo Takahashi🇯🇵

    We investigate how interactions affect the quantum state of scalar perturbations during inflation and the quantum correlations they may exhibit. Focusing on the case of scalar perturbations in single-field inflation, we model interactions using a Lindblad equation with a non-unitary contribution quadratic in the scalar perturbations, and of parametrisable amplitude and time dependence. We compute the quantum state of these interacting perturbations, which is fully described by its purity and squeezing parameters. First, we show that, in most of the parameter space, not only the purity but also the squeezing parameter is significantly reduced by interactions. Second, we show that this de-squeezing induced by the interactions, on top of the purity loss, causes a further suppression of quantum correlations. We thus emphasise that the quantum or classical character of the correlations exhibited by the perturbations cannot be correctly determined by computing the effect of interactions on the purity alone. Since the phenomenological framework adopted in this paper encompasses a wide class of possible interactions, our results provide general insights into the nature of decoherence processes in primordial fluctuations.

    ↳ hep-thastro-ph.COgr-qchep-ph+1PRD(2026)·6 citations
34. 34*

    Simulating vacuum birefringence with a diffractive beam propagation code

    Aimé Matheron🇩🇪 · Michal Šmíd🇩🇪 · Matt Zepf🇩🇪 · Felix Karbstein🇩🇪

    Ninety years after their prediction, quantum vacuum nonlinearities in macroscopic electromagnetic fields still await a direct experimental verification in the laboratory. A particularly promising route towards their first measurement is the collision of counter-propagating laser beams in a pump-probe type experiment. Here, the key challenge is to separate the small quantum vacuum signal at the oscillation frequency of the probe that is mainly emitted in the vicinity of its forward cone from the large probe background. While quantitatively accurate predictions of the associated quantum vacuum signals are available, to date there is no framework that combines these predictions with a diffractive beam propagation code. Such codes are designed to holistically model optical experiments and can reliably account for diffraction and absorption losses of optical devices, like lenses and apertures. The latter inevitably influence and modify both the induced signal and background components prior to their detection in experiment. The present work addresses this topical issue and reports on the first implementation of a quantum vacuum signals emission module in an established diffractive beam propagation toolkit designed for the realistic modelling of optical experiments.

    ↳ physics.opticshep-phPRD(2026)·3 citations
35. 35*

    Towards a fluid-dynamic description of an entire heavy-ion collision: from the colliding nuclei to the quark-gluon plasma phase

    Andreas Kirchner🇺🇸 · Federica Capellino🇩🇪 · Eduardo Grossi🇮🇹 · Stefan Floerchinger🇩🇪

    The fluid-dynamical modeling of a nuclear collision at high energy usually starts shortly after the collision. A major source of uncertainty comes from the detailed modeling of the initial state. While the collision itself likely involves far-from-equilibrium dynamics, it is not excluded that a fluid theory of second order can reasonably well describe its soft features. Here we explore this possibility and discuss how the state before the collision can be described in that setup, examine the required fluid-dynamical equations of motion and study the resulting entropy production. While we do here only first steps, we outline a larger program, which could lead to a dynamical description of heavy-ion collisions where the only uncertainty lies in the thermodynamic and transport properties of quantum chromodynamics.

    ↳ nucl-thhep-phEPJ Web Conf.(2026)·0 citations
36. 36*

    Active learning emulators for nuclear two-body scattering in momentum space

    A. Giri🇮🇳 · J. Kim🇺🇸 · C. Drischler🇺🇸 · Ch. Elster🇺🇸 · R. J. Furnstahl🇺🇸

    We extend the active learning emulators for two-body scattering in coordinate space with error estimation, recently developed by Maldonado et al. [Phys. Rev. C 112, 024002], to coupled-channel scattering in momentum space. Our full-order model (FOM) solver is based on the Lippmann-Schwinger integral equation for the scattering $t$-matrix as opposed to the radial Schrödinger equation. We use (Petrov-)Galerkin projections and high-fidelity calculations at a few snapshots across the parameter space of the interaction to construct efficient reduced-order models (ROMs), trained by a greedy algorithm for locally optimal snapshot selection. Both the FOM solver and the corresponding ROMs are implemented efficiently in Python using Google's JAX library. We present results for emulating scattering phase shifts in coupled and uncoupled channels and cross sections, and assess the accuracy of the developed ROMs and their computational speedup factors. We also develop emulator error estimation for both the $t$-matrix and the total cross section. The software framework for reproducing and extending our results is publicly available. Together with our recent advances in developing active-learning emulators for three-body scattering, these emulator frameworks set the stage for full Bayesian calibrations of chiral nuclear interactions and optical models against scattering data with quantified emulator errors.

    ↳ nucl-thhep-phnucl-exphysics.data-anPRC(2026)·2 citations
37. 37*

    Trails of clouds in binary black holes

    Mateja Bošković🇩🇪 · Rafael A. Porto🇩🇪 · Matthias Koschnitzke🇩🇪

    Superradiant instabilities of rotating black holes can give rise to long-lived bosonic clouds, offering natural laboratories to probe ultralight particles across a wide range of parameter space. The presence of a companion can dramatically impact both the cloud's evolution and the binary's orbital dynamics, generating a trail of feedback effects that require detailed modelling. Using a worldline effective field theory approach, we develop a systematic framework for binaries on generic (eccentric and inclined) orbits, capturing both resonant and non-resonant transitions without relying solely on balance laws. We demonstrate the existence of ``co-rotating'' floating orbits that can deplete the cloud prior to entering the detector's band, triggering eccentricity growth towards a sequence of fixed points. Likewise, we show that ``counter-rotating'' orbits can also deplete the cloud, driving (unbounded) growth of eccentricity. Furthermore, we uncover novel features tied to orbital inclination. Depending on the mass ratio, equatorial orbits can become unstable, and fixed points may arise not only for aligned or anti-aligned configurations but, strikingly, also at intermediate inclinations. We derive flow equations governing spin-orbit misalignment and eccentricity and identify distinctive signatures that can reveal the presence of boson clouds in the binary's history, as well as key features of possible in-band transitions. These results refine and extend earlier work, yielding a more faithful description of the imprints of ultralight particles in gravitational-wave signals from binary black holes, signatures that are within reach of future detectors such as LISA, Cosmic Explorer, and the Einstein~Telescope.

    ↳ gr-qcastro-ph.COastro-ph.HEhep-ph+1PRD(2026)·8 citations
38. 38*

    Achieving angular-momentum conservation with physics-informed neural networks in computational relativistic spin hydrodynamics

    Hidefumi Matsuda🇨🇳 · Koichi Hattori🇨🇳 · Koichi Murase🇯🇵

    We propose physics-informed neural networks (PINNs) as a numerical solver for relativistic spin hydrodynamics and demonstrate that the total angular momentum, i.e., the sum of orbital and spin angular momentum, is accurately conserved throughout the fluid evolution by imposing the conservation law directly in the loss function as a training target. This enables controlled numerical studies of the mutual conversion between spin and orbital angular momentum, a central feature of relativistic spin hydrodynamics driven by the rotational viscous effect. We present two physical scenarios with a rotating fluid confined in a cylindrical container: one case in which initial orbital angular momentum is converted into spin angular momentum in analogy with the Barnett effect, and the opposite case in which initial spin angular momentum is converted into orbital angular momentum in analogy with the Einstein-de Haas effect. We investigate these conversion processes governed by the rotational viscous effect by analyzing the spacetime profiles of thermal vorticity and spin potential. Our PINNs-based framework provides the first numerical evidence for spin-orbit angular momentum conversion with fully nonlinear computational relativistic spin hydrodynamics.

    ↳ physics.flu-dyngr-qchep-phnucl-th+13 citations
39. 39*

    First-Principles Formalism for Simulating Self-Interacting Dark Matter

    Maria Ramos🇨🇭 · Timothy Cohen🇨🇭 · Mariangela Lisanti🇺🇸

    It is plausible that the dark matter particles have non-gravitational interactions among themselves. If such self interactions are large enough, they could leave an imprint on the morphology of galaxies. These effects can be studied with numerical simulations, which serve as the primary tool to predict the non-linear evolution of galactic structure. A standard assumption is that the course-grained phase-space distribution of the macroscopic simulation particles follows the same evolution equation as that of the fundamental dark matter particles. This Letter tests this assumption directly for the case of frequent dark matter scatterings, demonstrating that this is not generically true. Specifically, we develop a first-principles map from a microscopic particle physics description of self-interacting dark matter to a representation of macroscopic simulation particles for theories in the short-mean-free-path regime. Using this procedure, we show the emergence of an effective force between the simulation particles and derive their interaction cross section, which depends on the one from fundamental particle physics. This work provides the first explicit map from particle physics to simulation, which will facilitate exploring the phenomenological implications for galactic dynamics.

    ↳ astro-ph.GAastro-ph.COhep-ph3 citations
40. 40*

    The Clustering of Little Red Dots from Ultra-Strongly Self-Interacting Dark Matter

    M. Grant Roberts🇺🇸 · Aarna Garg🇺🇸 · Tesla Jeltema🇺🇸 · Stefano Profumo🇺🇸

    We predict the effective clustering bias parameter, $b_{\mathrm{eff}}$, at $z\sim 5$ for Little Red Dots (LRDs) seeded by Ultra-Strongly Self-Interacting Dark Matter (uSIDM). From our model, we find that $b_{\mathrm{eff}}\sim 4.5$, thus we infer that LRDs seeded by uSIDM would populate halos of typical masses $\sim 8\times 10^{10}{M}_{\odot }$; this bias factor is consistent with LRDs being a distinct population from high redshift quasars. To the extent that we are aware, this is the first formation-based theoretical prediction of LRD clustering from a model consistent with the LRD mass function. We find that this bias and clustering is insensitive to a wide range of the underlying uSIDM microphysics parameters, including the uSIDM cross-section $\sigma /m$ and uSIDM fraction $f$. This is therefore a robust prediction from the uSIDM model, and will allow for direct probes of the uSIDM paradigm as the origin of LRDs in the next few years. Upcoming \texttt{JWST} observations will constrain the population of LRDs, including directly measuring their clustering.

    ↳ astro-ph.COastro-ph.GAhep-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.