Tue·Dec 16, 2025Tuesday·December 16, 2025

1. 01*

   Exploring the dark axion portal in the LUXE-NPOD experiment

   Noam Ness🇮🇱 · Barry E. Cimring🇺🇸

   The optical dump at the LUXE experiment has the potential to create a large flux of $O(GeV)$ photons that can be used to look for new physics when directed at a solid material dump. The LUXE-NPOD extension of LUXE, which focuses the hard photons onto a slab of tungsten, offers two interaction points (laser-electron and photon-tungsten), making it well suited to test theories containing two or more new particles. In this paper, we examine the dark axion portal, a scenario involving both dark photons (DPs) and axionlike particles (ALPs) and their mutual interactions, and its implications on the phenomenology at LUXE-NPOD. We focus on the case of strictly massive DPs. To simulate the spectra of particle populations generated at the electron-laser interaction point, we solve a set of extended 1D cascade equations. We recover a photon spectrum consistent with previous analyses and present previously unconsidered DP and ALP spectra. Further, we derive the overall sensitivity of LUXE-NPOD to various parameters of the new particles and show that it is capable of probing potentially uncharted regions in the dark axion parameter space. For ALPs in the $10$-$500$ $MeV$ mass range, and DPs that are either heavier ($\sim GeV$) or significantly lighter $O(10^{-18}$-$10^{-13})$ $eV$, we obtain promising constraints on DP kinetic mixing parameters smaller than $10^{-2}$ and on $O(10^{-4}$-$10^{-3})$ ${GeV}^{-1}$ ALP-photon couplings. We find that restrictions on $O(10^{-3})$ kinetic mixing can be extracted for arbitrarily small DP masses. Our discussion aims to be systematic and demonstrates a practical method of analyzing constraints on multidimensional parameter spaces.

   hep-phPRD(2026)·3 citations
2. 02*

   Melting LHC detectors: a novel search for stopped long-lived particles

   Julia L. Gonski🇺🇸 · Peter W. Graham🇺🇸 · Surjeet Rajendran🇺🇸 · Harikrishnan Ramani🇺🇸 · Samuel S. Y. Wong🇺🇸

   Particles at the TeV scale with lifetimes of a year or longer could have been abundantly produced at the LHC yet escaped detection because of backgrounds, and could still be trapped within detector materials. With gluinos in split-supersymmetry as a working example, we show that these trapped particles can be recovered from detector materials once prepared in liquid form, for example, by melting silicon detectors, extracting liquid argon from the electromagnetic calorimeter, or constructing a large water pool near ATLAS or CMS. These liquid samples can then be processed using iterative centrifugation followed by mass spectrometry, enabling single-particle sensitivity in macroscopic samples. This method can potentially discover gluinos up to 3 TeV in mass at the HL-LHC. It can also improve upon existing limits for other long-lived particles. For example, it can discover the stop up to 2 TeV, and will also be sensitive to integer-charged particles in the TeV range.

   hep-phhep-ex3 citations
3. 03*

   Dynamical scotogenic generation of the Linear and Inverse seesaws

   Asmaa Abada🇫🇷 · Antonio Enrique Cárcamo Hernández🇨🇱 · Salvador Urrea🇫🇷

   We propose an economical model in which the tiny active neutrino masses arise from an interplay of linear and inverse seesaw mechanisms. The Standard Model is extended by a local $U(1{)}^{\prime }$ gauge symmetry and discrete ${\mathbb{Z}}_3\otimes {\mathbb{Z}}_4$ symmetries, together with gauge-singlet scalars and neutral leptons. Owing to the preserved discrete symmetries after spontaneous symmetry breaking, the linear and inverse seesaw mechanisms are dynamically generated at the two-loop level, while the same symmetries ensure the stability of both scalar and fermionic dark matter candidates. One of the distinctive features of the model is a fermionic dark matter candidate whose mass is generated at one loop, whereas scalar dark matter masses arise at tree level. The model satisfies current constraints from neutrino oscillation data, dark matter direct detection, invisible Higgs decays, $Z^{\prime }$ searches, and charged lepton flavor violation, in addition we also discuss predictions for muonium states. The outcome of our analysis is that the inverse seesaw contribution dominates over the linear one, suggesting that atmospheric neutrino mass squared splitting arises from the inverse seesaw mechanism, whereas the solar one is generated from the linear seesaw. Finally, our model offers an explanation of the hierarchy between the atmospheric and solar neutrino mass squared splittings, in addition to the smallness of active neutrino masses, feature not presented in many low-scale seesaw models. In addition, our parameter-space scan shows a slight preference for the normal neutrino mass ordering.

   hep-phJHEP(2026)·2 citations
4. 04*

   Implications of asymptotic safety in two minimal Z-prime models

   Christopher D. Carone🇺🇸

   We consider the implications of asymptotic safety on two U(1) gauge extensions of the standard model that are minimal in the sense that anomaly cancellation only requires the presence of right-handed neutrinos. We study the UV fixed points of the gauge couplings taking into account kinetic mixing between hypercharge and the new U(1) gauge field. We consider the possibility that the top-bottom mass splitting originates from the effect of differing gauge charges on the nontrivial fixed point values of their respective Yukawa couplings and assess the impact of the extended gauge symmetry on the viability of this picture.

   hep-phPRD(2026)·1 citation
5. 05*

   Searching for axion dark matter with magnetic resonance force microscopy

   Elham Kashi🇺🇸 · Muhammad Hani Zaheer🇺🇸 · Ryan Petery🇺🇸 · Swati Singh🇺🇸

   We propose a magnetic resonance force microscopy (MRFM) search for axion dark matter around 1 GHz. The experiment leverages the axion's derivative coupling to electrons, which induces an effective A.C. magnetic field on a sample of electron spins polarized by a D.C. magnetic field and a micromagnet. A second pump field at a nearby frequency enhances the signal, with the detuning matched to the resonant frequency of a magnet-loaded mechanical oscillator. The resulting spin-dependent force is detected with hih sensitivity via optical interferometry. Accounting for the relevant noise sources, we show that current technology can be used to put constraints competitive with those from laboratory experiments with just a minute of integration time. Furthermore, varying the pump field frequency and D.C. magnetic field allows one to scan the axion mass. Finally, we explore this setup's capability to put constraints on other dark matter - Standard Model couplings.

   hep-phastro-ph.IMquant-ph0 citations
6. 06*

   Azimuth Quadrupole Spectra derived from 2.76 TeV Pb-Pb PID Differential $v_2(p_t)$ Data

   Thomas A. Trainor🇺🇸

   $v_2(p_t)$ data are intended to estimate the amplitude of an azimuth component of particle spectra interpreted as representing elliptic flow of a dense QCD medium. As defined, $v_2(p_t)$ is a ratio with a single-particle spectrum appearing in its denominator. Its numerator represents a spectrum Fourier component arising from a boosted particle source. The Cooper-Frye (CF) formalism may be used to describe emission from a boosted source. CF analysis reveals that the $v_2(p_t)$ numerator includes a factor $p_t$ in the boost frame with major consequences for data interpretation. A unique quadrupole $p_t$ spectrum may be isolated from $v_2(p_t)$ data and compared directly with the single-particle spectrum in the $v_2$ denominator and with hydro theory. A monopole boost (aka radial flow) value may be estimated from $v_2(p_t)$ data. Several novel results emerge via the Cooper-Frye analysis.

   hep-phPoS(2026)·0 citations
7. 07*

   Neutral and charged pion Form Factors in the intermediate-energy region from double-dilaton HQCD model

   Héctor Cancio🇪🇸 · Pere Masjuan🇪🇸

   We compute the Form Factors of both neutral and charged pion using a non-perturbative running of the strong coupling constant ${\alpha }_s$ obtained using a double-dilaton Holographic QCD model. These form factors remain poorly understood in the intermediate-energy region, which marks the transition between low- and high-energy physics. In particular, experimental data for the neutral pion Form Factor exhibits a deviation from the expected asymptotic behavior, and the charged pion form factor remains comparatively less explored. To address these issues, we employ the pion distribution amplitude formalism to investigate the Form Factor behavior in this intermediate regime. Our results suggests that non-perturbative physics of the strong interaction is relevant even at energy scales traditionally considered perturbative, implying that the perturbative regime could occur at higher energies than previously thought. Finally, our approach allows us to study isospin-breaking effects through the quadratic pion mass difference.

   hep-phEur.Phys.J.ST(2026)·1 citation
8. 08*

   New Massless Spectra from Cosmic String Cusps

   Amelia Drew🇮🇹 · Ivan Rybak🇰🇷

   In the standard picture of cosmic strings, cusps are generic features of Nambu-Goto loops where the string momentarily reaches the speed of light. They have a characteristic sharp profile, following $y\sim x^{2/3}$ in the $(x,y)$ plane, and produce strong gravitational-wave (GW) bursts with frequency-domain strain $\tilde{\kappa }(\omega )\propto {\omega }^{-4/3}$, making them key targets for current and future GW searches. However, under certain conditions, this generic picture can differ. We identify cusp solutions with different, including smooth, shapes, and compute their massless GW and axion spectra. We derive a general expression for all possible Nambu-Goto cusp spectra with the asymptotic form $\tilde{\kappa }(\omega )\propto {\omega }^{-n/(2n-1)}{\omega }^{-m/(2m-1)}$ where $n,m\ge 2$. We investigate the effect of realistic corrections to the Nambu-Goto description, such as those from backreaction and finite string width, which introduce a high frequency cutoff.

   hep-phastro-ph.COgr-qchep-th4 citations
9. 09*

   Probing the Core of Nuclear Structure through the $\pi N$ Scattering at an Electron-Positron Collider

   Wei Wang🇨🇳 · Ji Xu🇨🇳 · Ya-Teng Zhang🇨🇳 · Xiao-Rong Zhou🇨🇳

   Short-range correlation pairs (SRCs) -- core of nuclear structure, composed of highly off-shell nucleons -- are mostly studied via electron-nucleon scattering, leaving a gap in meson-based probes. We propose probing SRC off-shell nucleons via quasielastic ${\pi }^{+}$-bound proton scattering (${\pi }^{+}p\to {\pi }^{+}p$) at electron-positron colliders, of which the beryllium-based (${}^9$Be) beam pipe of the BESIII experiment operating at BEPCII, addresses a key gap and enables meson-beam investigations of SRCs. We point out that off-shellness of SRC nucleons yields measurable signatures: accumulated missing energy ($\sim 0.1$\,GeV), shifted proton effective mass (0.7-0.8\,GeV), and cross-section differences from free scattering or with only Fermi motion. As an estimate, we find that BESIII's high luminosity and ${\pi }^{+}$ yield support $\sim 10^4$ scattering events, while STCF ($50\times$ higher luminosity) will greatly enhance this number. This first meson-beam SRC study at an electron-positron collider fills ${}^9$Be research gaps and advances understanding of nuclear structure core and nonperturbative QCD.

   hep-phhep-ex1 citation
10. 10*

    Spectrum of $J^{PC}=0^{\pm \pm }$ Gluonic Hidden-Charm Tetraquark States

    Bing-Dong Wan🇨🇳 · Ming-Yang Yuan🇨🇳 · Jun-Hao Zhang🇨🇳 · Yan Zhang🇨🇳

    We investigate gluonic hidden-charm tetraquark states composed of two valence quarks, two valence antiquarks and an explicit valence gluon. In the color configuration $[{\bar{3}}_c{]}_{cq}\otimes [8_c{]}_G\otimes [3_c{]}_{\bar{c}\bar{q}}$, a complete set of eight interpolating currents is constructed for states with quantum numbers ${}^{PC}=0^{++}$, $0^{-+},$ $0^{--}$, and $0^{+-}$. The corresponding mass spectra are systematically analysed within the QCD sum rule framework, including nonperturbative condensate contributions up to dimension eight. Our numerical analysis indicates the possible existence of six gluonic hidden-charm tetraquark states exhibiting stable behaviour in the adopted Borel windows. By replacing the charm quark with the bottom quark, masses for the corresponding hidden-bottom partners are also estimated. Possible production mechanisms and dominant decay channels are discussed, providing phenomenological guidance for experimental searches. These predicted states may be accessible at current and forthcoming facilities, including Belle II, PANDA, SuperB and LHCb, and thus offer an opportunity to probe explicit gluonic degrees of freedom in multiquark systems and deepen our understanding of nonperturbative QCD.

    hep-phEPJC(2026)·6 citations
11. 11*

    Gluon Gravitational $D$-Form Factor: The $\sigma$-Meson as a Dilaton Confronted with Lattice Data II

    Roy Stegeman🇬🇧 · Roman Zwicky🇬🇧

    We investigate the gluon gravitational form factors of the $\pi$, $N$, $\rho$, and $\Delta$ using lattice QCD data at $m_{\pi }\approx 450\text{MeV}$ and $m_{\pi }\approx 170\text{MeV}$. We base the analysis on fits to a simple $\sigma /f_0(500)$-meson pole, supplemented by a polynomial background term. The fitted residues agree with predictions from dilaton effective theory, in which the $\sigma$-meson acts as the dilaton, the pseudo Goldstone boson of spontaneously broken scale symmetry. We derive new dilaton-based predictions for the $\rho$- and $\Delta$-gravitational form factors, and comment on the ${\eta }_c$- and ${\eta }_b$-form factors in the context of the dilaton interpretation. These results reinforce our earlier findings, based on lattice total (quark and gluon) gravitational form factors, and provide further evidence that QCD dynamics may be governed by an infrared fixed point.

    hep-phhep-lathep-thJHEP(2026)·17 citations
12. 12*

    Interference Effects in Resonant Standard Model di-Higgs Production and Decay into $4b$ Final States: the Role of Machine Learning Analysis

    A. Hammad🇯🇵 · S. Moretti🇬🇧 · A.P. Przybyl🇸🇪 · H. Waltari🇸🇪

    The final state with four $b$-quarks has generally the largest event rate in Standard Model (SM)-like Higgs ($h_{\mathrm{SM}}$) pair production, but also the largest backgrounds. We study such a final state using the $gg\to h_{\mathrm{SM}}{h}_{\mathrm{SM}}$ production mechanism and Benchmarks Points (BPs) derived from the Next-to-Minimal Supersymmetric SM (NMSSM) in the boosted case, leading to two (fat) 'Higgs jets'. To suppress the backgrounds we use a combination of both kinematical cuts and jet substructure features exploiting Machine Learning (ML) analysis. We simulate the signal BPs both with and without the interference of the resonant $s$-channel diagram with the non-resonant topologies emerging from both the SM and NMSSM. The ML architecture of choice here is based on a multi-modal Transformer, which performs significantly better than traditional ML algorithms, in two respects: firstly, it enables to achieve higher significances and, secondly, it adapts better to the analysis dataset with interferences even if it was trained on one without these. However, neglecting the effect of the latter in experimental searches could lead to grossly mistaken results.

    hep-phhep-ex1 citation
13. 13*

    The Entropic Skin: Spatial Entanglement from the QCD Confinement Boundary

    Thomas B. Bahder

    Recent investigations into High-Energy QCD have identified entanglement entropy as a crucial observable, linking parton distributions to the structure of the quantum vacuum. While momentum-space entanglement has been extensively studied in Deep Inelastic Scattering (DIS), the spatial realization of this entanglement in confined systems remains an open question. In this Letter, we demonstrate that the confining boundary of the MIT Bag Model acts as an ``Entropic Skin,'' generating maximal Spin-Position entanglement. We calculate the local reduced density matrix for the confined quark and show that the linear boundary condition, $i{\gamma }^{\mu }{n}_{\mu }\psi =\psi$, acts as an entangling gate. The surface entropy density reaches a geometric invariant of $\approx 0.918$ bits ($92\%$ of the qubit limit), independent of the bag radius. We discuss the implications of this result for Chiral Symmetry breaking and propose that this boundary entropy is the precursor to the pion cloud in effective field theories.

    hep-phquant-ph0 citations
14. 14*

    Chasing higgsino dark matter at colliders in the neutrino fog era

    Prudhvi N. Bhattiprolu🇮🇹 · Stephen P. Martin🇺🇸 · James D. Wells🇺🇸

    Higgsinos can be the lightest supersymmetric particles, allowing for either a full or partial dark matter interpretation, with the correct thermal freeze-out abundance obtained for masses near 1.1 TeV. Dark matter direct detection experimental results, now rapidly approaching the neutrino fog, imposes increasingly stringent requirements on higgsino purity. We begin by summarizing the purity constraints implied by the current strong limits from the LUX-ZEPLIN experiment in 2024, presenting them as lower bounds on gaugino masses in scenarios with decoupled sfermions and heavy Higgs bosons. We further quantify how these constraints will evolve as direct detection approaches various neutrino fog discovery and exclusion definitions and future exclusion projections. Finally, given that nearly pure higgsinos remain notoriously challenging to probe directly at colliders, we explore complementary signatures in which higgsinos are produced from the decays of heavier superpartners, where additional leptons and jets can be used for triggering. In particular, we advocate for searches of stop and wino pairs decaying directly to higgsinos as a promising means to probe higgsino dark matter well into the neutrino fog era.

    hep-phPRD(2026)·3 citations
15. 15*

    Space-time Geometry of Small and Large Collision Systems

    Thomas A. Trainor🇺🇸

    Identified-hadron spectra from 2.76 TeV Pb-Pb and $p$-$p$ collisions are analyzed via a two-component (soft + hard) model (TCM) of hadron production in high-energy nuclear collisions. The object of study is evidence for jet suppression in small and large collision systems. Conventional methods include Pb-Pb centrality determination via classical Glauber model and evidence for high-$p_t$ suppression sought via spectrum ratio $R_{\text{AA}}$. Previous $p$-Pb studies questioned the validity of the classical Glauber model. In the present study A-A geometry is determined instead via ensemble-mean ${\bar{p}}_t$ data. Based on certain features of Pb-Pb spectra the validity of the factorization assumption is also questioned. The entire jet contribution is therefore treated without factorization in ratio to a $p$-$p$ spectrum model as reference. These new results indicate that exclusivity (a nucleon may only interact with one nucleon ``at a time'') and time dilation (experienced by participant partons) play an essential role in jet production not incorporated in Glauber model or hard-component factorization. The combination determines an effective number of N-N collisions per participant nucleon given specific Pb-Pb centrality: multiple collisions if associated with low-$x$ (slow) partons, a single collision if associated with high-$x$ (fast) partons experiencing strong time dilation. The effect on parton fragment (jet) distributions on $p_t$ may be misinterpreted as jet suppression, but is similar to projectile-proton fragment distributions on pseudorapidity from fixed-target $p$-A experiments where low-$\eta$ densities scale with A while high-$\eta$ densities are consistent with $p$-$p$ collisions. $p$-Pb and Pb-Pb spectra similarly analyzed reflect the same physics given different geometries. Actual jet suppression related to QGP formation is not evident.

    hep-phPoS(2026)·0 citations
16. 16*

    Signal Modelling with Overdetermined Morphing Technique

    Nikita Belyaev🇺🇸 · Rostislav Konoplich🇺🇸 · Kirill Prokofiev🇨🇳

    Precise modelling of a signal in processes with multiple observables, exhibiting a complex dependency on the underlying parameters, is often a difficult and challenging task. Predicting the results of experimental measurements in high-energy physics reactions serves a good example. The reaction rates and distributions of momenta of the final state particles, depend on the parameters of the underlying physics model in a non-trivial way. The conventional way to predict the experimental of observables is to use the Monte Carlo morphing technique on a finite discrete set of simulated samples. In this article we extend this technique by using the overdetermined morphing basis. We show that our approach yields a better result than the traditional technique in terms of the statistical power and uniformity of the resulting prediction, and delivers better precision. We further demonstrate that the overdetermined morphing is better suited for description of extended regions of phase space than the conventional morphing. We use the modelling of kinematic distributions of the final state particles produced in decays of non-Standard Model Higgs bosons as an example.

    hep-ph0 citations
17. 17*

    Relativistic Bethe-Salpeter study of OZI-rule allowed strong decays: determination of total width of $h_c(2P)$ and ${}^3{P}_0$ model parameter

    Yi-Yi Rui🇨🇳 · Tianhong Wang🇨🇳 · Zhi-Hui Wang🇨🇳 · Tai-Fu Feng🇨🇳 · Guo-Li Wang🇨🇳

    Strong decays allowed by the Okubo-Zweig-Iizuka rule play a decisive role in determining the properties of particles. The widely used ${}^3{P}_0$ model is non-relativistic and contains unknown adjustable parameter $\gamma$ that need to be determined experimentally. Based on the Bethe-Salpeter equation, we have derived a relativistic calculation formula in which the effective strength related to the ${}^3{P}_0$ parameter $\gamma$ is not introduced as an independent fitting parameter, but is consistently determined by the interaction kernel of the Bethe-Salpeter equation. Using this method, we present the total width of $h_c(2P)$ and allows a theoretical determination of the parameter $\gamma$ in the ${}^3{P}_0$ model within the present framework.

    hep-phEPJC(2026)·1 citation
18. 18*

    The post-inflationary cosmology of the VISH$\nu$ axion-majoron model

    Alexei H. Sopov🇦🇺 · Carlos Tamarit🇩🇪 · Raymond R. Volkas🇦🇺

    It was previously shown how several explanatory deficiencies of the Standard Model (including the origin of dark matter, matter-antimatter asymmetry, small active neutrino mass, strong CP-conservation and the seeds for large-scale structure formation) may be economically resolved when an experimentally-accessible QCD axion also plays the role of the majoron, and the scalar partner of the axion is dynamical during inflation. In this paper, we complete this general study of the cosmological history for a unit domain-wall number option of the DFSZ-type, dubbed VISH$\nu$, by performing a detailed lattice-informed analysis of the reheating era. In doing so, we make inflationary and leptogenesis predictions more precise through estimates of the reheating temperature and the expansion history. The viable reheating scenarios, which at the same time satisfy strict conditions for naturalness (radiative stability), are also shown to respect dark radiation bounds. We also characterise the high-frequency spectrum of gravitational waves, and mention other phenomenological implications that distinguish VISH$\nu$ from alternative proposals.

    hep-phastro-ph.CO3 citations
19. 19*

    Peccei-Quinn Genesis

    Eung Jin Chun🇰🇷 · Hyun Min Lee🇰🇷 · Jun-Ho Song🇰🇷

    We propose a cogenesis mechanism that unifies the origin of QCD axion dark matter and the baryon asymmetry of the Universe in the framework of Peccei-Quinn pole inflation. The model integrates the Peccei-Quinn symmetry with the seesaw mechanism for neutrino masses. This allows for spontaneous leptogenesis, which generates the required $B-L$ asymmetry around the seesaw scale. The necessary initial axion kinetic misalignment is naturally sourced by a PQ field driving pole inflation. Analysis within the KSVZ axion model demonstrates that achieving simultaneous correct DM abundance and baryon asymmetry limits the axion decay constant to be smaller than about $10^9$ GeV. This framework offers a unified solution to four fundamental problems: the strong CP problem, neutrino mass, matter-antimatter asymmetry, and inflation.

    hep-phPLB(2026)·4 citations
20. 20*

    Renormalization of chiral perturbation theory with spinless matter field in curved spacetime

    Cheng-Cheng Li🇨🇳 · Xiong-Hui Cao🇨🇳 · Feng-Kun Guo🇨🇳

    We generalize chiral perturbation theory with spinless matter fields in the fundamental representation of $\mathrm{SU}(N)$ to curved spacetime in the presence of an external gravitational field. This work is motivated by recent interest in investigating energy-momentum tensor matrix elements of matter fields. The complete chiral Lagrangian is constructed, including both minimal extensions from flat spacetime and new curvature-induced terms, up to the next-to-next-to-leading order in the chiral expansion, $\mathcal{O}(p^3)$. We perform a systematic one-loop renormalization of the generating functional using the background field method combined with the heat-kernel technique, and explicitly compute the resulting ultraviolet divergences.

    hep-phhep-thJHEP(2026)·0 citations
21. 21*

    Sign Reversal of Boer-Mulders Functions from Semi-inclusive Deep-Inelastic Scattering to the Drell-Yan Process

    Jen-Chieh Peng🇺🇸 · Ming-Xiong Liu🇺🇸 · Guanghua Xu🇺🇸

    A striking prediction of QCD on the properties of the novel Transverse Momentum Dependent (TMD) distribution functions is that the time-reversal odd Sivers and Boer-Mulders functions extracted from semi-inclusive deep-inelastic scattering (SIDIS) will undergo a sign reversal in the Drell-Yan (DY) process. This prediction has been tested by experiments that have focused on the Sivers functions so far. We examine the current status on the theoretical prediction and experimental extraction of the signs of the Boer-Mulders functions from SIDIS and DY. We show that the existing SIDIS and DY data are consistent with the predicted sign reversal of the Boer-Mulders functions for proton's valence quark distribution. Prospects for future experiments at EIC capable of testing the sign reversal of the pion Boer-Mulders functions are also discussed.

    hep-phnucl-exnucl-thPLB(2026)·1 citation
22. 22*

    Energy Loss of a Heavy Quark in a Collisional Quark-Gluon Plasma

    Mingda Cai🇨🇳 · Yun Guo🇨🇳

    We extend our previous work on the energy loss of a heavy fermion in a QED plasma to the Quark-Gluon plasma, using the same Bhatnagar-Gross-Krook collisional kernel. The calculation is carried out with a theoretical method where the hard-thermal-loop resummed gluon propagator is used for arbitrary momentum transfer in the scattering processes. Encoding the collision effect in a self-consistent manner, the resummed gluon propagator regulates the infrared divergence in the scattering amplitude without introducing an artificial cutoff for the transferred momenta and makes the analysis on the hard and soft processes in a unified framework. To place our computation on a more solid foundation, we also explicitly demonstrate the gauge independence of the interaction rate as well as the elimination of unphysical gluon polarizations by the ghost field under the use of the resummed gluon propagator. In addition, with our complete QCD calculation by including both quark-quark and quark-gluon scatterings, we provide a quantitatively reliable result on the collisional energy loss of a heavy quark where the new contribution from quark-gluon scatterings accounts for a larger portion of the total energy loss. In general, collisions between the thermal partons result in an increased energy loss which becomes more pronounced with increasing gauge coupling. Considering a typical coupling constant in QCD, ${\alpha }_s=0.3$, the energy loss increases $\sim 8$% at large incident velocities as compared to the collisionless limit. Such a collision-induced correction is still moderate although it is sightly suppressed as compared to our previous estimate based on a QED calculation using couplings consistent with those expected to be generated in the Quark-Gluon plasma.

    hep-phPRD(2026)·2 citations
23. 23*

    Updated sensitivities to heavy neutral leptons at the LHC far detectors and SHiP

    Zeren Simon Wang🇨🇳 · Yu Zhang🇨🇳

    In recent years, a number of experiments dedicated to searches for long-lived particles (LLPs) have been proposed, approved, or have entered operation. While the sensitivities of these experiments to various LLP scenarios have been extensively studied, key aspects--such as detector geometries, background estimates, and projected operational durations--for several facilities, including MATHUSLA, ANUBIS, and SHiP, have undergone significant updates. In this work, we implement the latest experimental designs in the Displaced Decay Counter tool for calculating detector acceptances and signal-event yields, and re-evaluate their sensitivity reach to one of the most widely studied LLP scenarios, namely minimal heavy neutral leptons.

    hep-phhep-exPRD(2026)·4 citations
24. 24*

    Effective running coupling constant and jet quenching parameter in the spinning background from holography

    Zhou-Run Zhu🇨🇳 · Sheng Wang🇨🇳 · Man-Li Tian🇨🇳 · Defu Hou🇨🇳

    In this work, we study the effective running coupling constant of heavy quark pair and jet quenching parameter in the spinning background. Ultra-locally, the boosted fluid is described by the boosted parameter and dual to a globally rotating system. Our results show that the angular momentum suppresses the effective running coupling constant and reduces its maximum value. The results demonstrate that the angular momentum promotes the dissociation of quarkonium and has a stronger effect on the effective running coupling constant when the axis of $Q\overline{Q}$ is transverse to the direction of the angular momentum. We also find that the angular momentum enhances the jet quenching parameter and has a stronger effect when the jet moves transversely to the direction of the angular momentum, namely ${\hat{q}}_{\perp }>{\hat{q}}_{\parallel }$. We discuss the dependence of the jet quenching parameter on the $\eta /s$ at strong coupling in the presence of the angular momentum.

    hep-phPRD(2026)·2 citations
25. 25*

    The nonleptonic decays of double-charmed baryon ${\Omega }_{cc}^{+}$ within the nonrelativistic quark model

    Yu-Shuai Li🇨🇳

    In this work, we investigate the two-body nonleptonic decays of double-charmed baryon ${\Omega }_{cc}^{+}$ within a nonrelativistic quark model, in which the nonfactorizable amplitudes contributed by $W$-exchange diagrams are evaluated under pole model assumption. To reduce sensitivity of decay amplitudes to arbitrary choice of baryon wave functions, we adopted charmed baryon wave functions obtained by solving the Schrödinger equation with a nonrelativistic quark potential model. Our results show that the branching fractions of CF decays ${\Omega }_{cc}^{+}\to {\Omega }_c^0{\pi }^{+}$ and ${\Xi }_c^{(\prime )+}{\pi }^{+}$, as well as the SCS decays ${\Omega }_{cc}^{+}\to {\Omega }_c^0{K}^{+}$, ${\Sigma }_{cc}^{++}{K}^{-}$, ${\Xi }_c^{\prime +}\eta$ and ${\Lambda }_c^{+}{\bar{K}}^0$ can reach up to a few percents. Particularly for the ${\Omega }_{cc}^{+}\to {\Omega }_c^0{K}^{+}$ mode, owing to the large factorizable amplitude and constructive pole contributions, the branching fraction is comparable to CF decays. These decay modes can serve as the discovery channels for the double-charmed baryon ${\Omega }_{cc}^{+}$ in future experiments like LHCb and Belle II.

    hep-phPRD(2026)·1 citation
26. 26*

    Testable Inverse Seesaw Motivated from a High Quality QCD Axion

    Yannis Georis🇧🇪 · Jie Sheng🇯🇵 · Salvador Urrea🇫🇷 · Tsutomu T. Yanagida🇯🇵

    The QCD axion remains one of the most compelling solutions to the strong CP problem. Meanwhile, the type-I seesaw mechanism offers an elegant explanation for the lightness of the observed neutrino masses; however, its extremely heavy Majorana states place it far beyond experimental reach. Low-scale alternatives such as the inverse seesaw improve testability but typically lack a strong theoretical motivation. In this paper we bridge this gap by showing that gauging the discrete symmetry ${\mathbb{Z}}_4\times {\mathbb{Z}}_3$-motivated by the internal structure of the Standard Model-naturally yields a QCD axion with a high-quality Peccei-Quinn symmetry solving the strong CP problem, while simultaneously enforcing the field content and hierarchy required for a natural inverse seesaw. The resulting model is highly predictive and has the potential to be fully tested by future experiments. Beyond addressing the strong CP problem and the origin of neutrino masses, our scenario also contains a viable dark-matter candidate and offers potential mechanisms for generating the baryon asymmetry of the Universe.

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

    Probing the pion gluon distribution at small-$x$ in photon-induced interactions at LHC

    Victor P. Goncalves🇧🇷 · Juciene T. de Souza🇧🇷 · Diego Spiering🇧🇷

    In this paper we propose the analysis of the heavy quark photoproduction associated with a leading neutron in hadronic collisions at the LHC as an alternative to probe the pion gluon distribution in a kinematical range not covered by previous experiments. We perform an exploratory study of the charm and bottom photoproduction associated with a leading neutron in proton-proton ($pp$) and proton-lead ($pPb$) collisions, and present calculations for the rapidity distributions and cross-sections. Our predictions indicate that experimental studies of these processes are feasible, and that a future measurement of this final state will be useful to constrain the pion gluon distribution at small values of the Bjorken $x$ variable and to improve our understanding of the pion structure.

    hep-phhep-exnucl-exnucl-thPRD(2026)·1 citation
28. 28*

    Cosmic Ray Simulation with PYTHIA

    Leif Lönnblad🇸🇪 · Torbjörn Sjöstrand🇸🇪

    We present recent developments in PYTHIA for the modelling of hadronic cascades in a medium. Several improvements have been made in the Angantyr model for collisions with nuclei, especially in the limit of low collision energies, allowing it to be used throughout the hadronic cascades. Also the simplified nuclear model in the PythiaCascade} module has been updated. We find that the two models give consistent results for cosmic ray air showers initiated by both high energy protons and nuclei.

    hep-phEPJC(2026)·1 citation
29. 29*

    Bottomonium suppression and elliptic flow in an anisotropic quark-gluon plasma using the quantum trajectories method

    Ajaharul Islam🇨🇳

    We study bottomonium dynamics in a momentum-space anisotropic quark-gluon plasma (QGP) using the quantum trajectories (QTraj) framework. The real part of the heavy-quark potential is obtained from a minimal extension of the Karsch-Mehr-Satz (KMS) potential, while the angle-averaged imaginary part is derived to leading order in the anisotropy parameter $\xi$ and modeled to interpolate smoothly between the small- and large -$\xi$ regimes. The resulting anisotropic complex potential is used to solve the real-time Schrödinger equation using QTraj for the evolution of bottomonium in heavy-ion collisions. Nuclear modification factors $R_{AA}$, double ratios, and elliptic flow coefficients $v_2$ for the ${\rm Y}(1S)$, ${\rm Y}(2S)$, and ${\rm Y}(3S)$ states are computed, including feed-down contributions, in Pb-Pb collisions at $\sqrt{s_{NN}}=5.02\text{TeV}$. The QTraj-Aniso predictions successfully reproduce the observed sequential suppression pattern and non-zero elliptic flow, while for $R_{AA}$ and double ratios, the anisotropic implementation provides a modest but systematic improvement over the isotropic baseline, moving the predictions closer to experimental measurements from the ALICE, ATLAS, and CMS collaborations and further demonstrating the relevance of path-length dependent suppression and medium anisotropy in quarkonium phenomenology.

    hep-ph0 citations
30. 30*

    Comparative analysis of critical regions: The renormalized quark-meson model under Polyakov loop, quark back-reaction, and vector interaction effects

    Akanksha Tripathi🇮🇳 · Suraj Kumar Rai🇮🇳 · Vivek Kumar Tiwari🇮🇳

    The critical regions enveloping the critical end point (CEP) in the $\mu$-$T$ plane are mapped by computing the contours of normalized quark number susceptibility within the on shell renormalized 2+1 flavor quark-meson (RQM) and Polyakov loop enhanced renormalized Polyakov quark meson (RPQM) models for $m_{\sigma }=400$ and 500 MeV.The apparent precision for the results of CEP coordinates merely reflects numerical binning of two decimal places rather than the effect of including full thermal and vacuum quantum fluctuations. The renormalized 't Hooft coupling c becomes substantially stronger in the RQM model when the meson self energies due to quark loops are computed using the pole masses of mesons and parameters are fixed on shell in Ref [143] after a consistent treatment of quark one loop vacuum fluctuations while the light and strange chiral symmetry breaking strengths also become weaker. We evaluate the impact of these novel features on critical fluctuations. Furthermore, the improved PolyLog glue form of the Polyakov loop potential from Ref [46] is employed to isolate the effects of the quark back reaction on critical fluctuations, and the results are contrasted against back reaction free outcomes obtained using the logarithmic potential. Utilizing inputs from large $N_c$ standard chiral perturbation theory, phase diagrams are also computed in the light chiral limit ($m_{\pi }=0$), quantifying the proximity of the tricritical point (TCP) to the CEP. The critical regions from the RQM/RPQM models are compared with those reported in Ref [120], where curvature masses are used for parameter fixing. Phase diagrams incorporating vector interactions in the RQM/RPQM model reveal that the CEP and first-order transition survive up to a robust coupling of $g_{\omega }=2.79$, rendering them highly relevant for compact star equations of state and astrophysical phenomenology.

    hep-phPRD(2026)·0 citations
31. 31*

    The heavy quark-antiquark asymmetry in the variable flavor number scheme

    A. Behring🇩🇪 · J. Blümlein🇩🇪 · A. De Freitas🇦🇹 · A. von Manteuffel🇩🇪 · C. Schneider🇦🇹 · K. Schönwald🇨🇭

    The twist-2 heavy-quark and antiquark distributions, as defined in the variable flavor number scheme, turn out to be different due to QCD corrections from three-loop onward. This is caused by terms containing the color factor $d_{abc}{d}^{abc}$ in the heavy-flavor massive pure-singlet operator matrix elements (OMEs) $A_{Qq}^{\mathrm{PS},\mathrm{s},(3)}$ for odd moments in the unpolarized case and for $\Delta A_{Qq}^{\mathrm{PS},\mathrm{s},(3)}$ for even moments in the polarized case. The dependence on the factorization scale of the OMEs is ruled by the anomalous dimensions ${\gamma }_{qq}^{\mathrm{NS},\mathrm{s},(2)}$ and $\Delta {\gamma }_{qq}^{\mathrm{NS},\mathrm{s},(2)}$. The polarized calculations are performed in the Larin scheme. We compute the corresponding three-loop heavy-flavor distributions $(\Delta )f_Q(x,Q^2)-(\Delta )f_{\overline{Q}}(x,Q^2)$. Compared to the sum of the heavy-quark and antiquark parton distributions, their difference is small, however, non-vanishing.

    hep-phhep-exhep-thPLB(2026)·10 citations
32. 32*

    Exploring the freeze-in mechanism for scotogenic singlet dark matter

    Ugo de Noyers🇫🇷 · Björn Herrmann🇫🇷

    We present an exploratory study of the freeze-in mechanism within a scotogenic framework, where dark matter can either be a scalar singlet or a fermion singlet. Based on a random parameter scan, we show that large portions of the parameter space feature a dark matter relic density in agreement with the limits derived by Planck. Moreover, constraints related to lepton flavour violation are mostly respected within such parameter regions. Our study shows that it will be worth to further investigate the freeze-in mechanism within scotogenic frameworks.

    hep-ph0 citations
33. 33*

    Neutrino texture-zeros after JUNO's first results: Implications for long-baseline neutrino experiments

    Debasish Borah🇮🇳 · Pritam Das🇮🇳 · Debajyoti Dutta🇮🇳

    The recent results from the JUNO reactor neutrino experiment have significantly improved our knowledge of the solar mixing angle ${\theta }_{12}$ and the solar mass splitting $\Delta m_{21}^2$. We study the impact of these improved estimates on the validity of texture-zeros in the light neutrino mass matrix by assuming neutrinos to be of Majorana nature. Considering a diagonal charged lepton basis, we revisit the previously allowed one-zero and two-zero textures and check their validity by using updated neutrino data from JUNO. While JUNO data rule out one previously allowed two-zero texture, they also make predictions for other neutrino parameters more precise. We finally study the prospects of probing the currently allowed texture-zeros and their predicted correlations among neutrino parameters at the Deep Underground Neutrino Experiment (DUNE). The inclusion of JUNO and reactor experiments strengthens DUNE's ability to constrain the allowed parameter space of both one-zero and two-zero textures. We also observe that DUNE benefits substantially from the complementarity with the T2HK experiment.

    hep-ph8 citations
34. 34*

    The Potential of HEFT and the scale of New Physics

    Rodrigo Alonso🇬🇧 · Susobhan Chattopadhyay🇮🇳 · James Ingoldby🇬🇧

    We employ a geometric framework to compute the leading high-energy behaviour of tree-level scattering amplitudes in theories containing $N$ Nambu-Goldstone bosons and a single Higgs-like scalar with an arbitrary potential $V$. Using these methods, we obtain closed-form expressions for the leading contribution to the full infinite set of tree amplitudes involving any number of Goldstone and Higgs-like external states. These results are then used to derive total cross sections, decay rates, and perturbative unitarity bounds. We then apply our general formalism to the Standard Model scalar sector using the equivalence theorem, working in the regime of small field-space curvature, and use it to characterise the relation between Higgs Effective Field Theory (HEFT) and the Standard Model Effective Field Theory (SMEFT). We analyse three representative classes of models. Two reproduce previously known behaviours, while the third, based on a dilaton effective theory, exhibits a noteworthy feature within the HEFT framework: a smooth decoupling limit that connects HEFT directly to the Standard Model without passing through a SMEFT regime, providing a possible backdoor to the Standard Model.

    hep-phhep-thJHEP(2026)·9 citations
35. 35*

    One-flavon flavor: A single hierarchical parameter $B$ organizes quarks and leptons at $M_Z$

    Vernon Barger🇺🇸

    Flavor hierarchies emerge from a single hierarchical parameter $B$ in a one-flavon Froggatt--Nielsen scheme. Fixing $B=5.357$ from charged-lepton ratios ($m_e:m_{\mu }:m_{\tau }\propto {ϵ}^5:{ϵ}^2:1$, $ϵ=1/B$), we reproduce quark masses and CKM targets at $M_Z$ with $\text{ordone}$ coefficients. The same $ϵ$ gives viable lepton textures and benchmarks for $U_{\mathrm{PMNS}}$, $\sum m_{\nu }$, and $m_{\beta \beta }$. Compact correlations ($|V_{us}|,|V_{cb}|,|V_{ub}|,{\theta }_{13}^{\mathrm{PMNS}}$) follow from powers of $ϵ$.

    hep-phPRD(2026)·6 citations
36. 36*

    A post-inflationary kinetic axion

    Enrico Morgante🇮🇹 · Riccardo Natale🇮🇹

    We present a novel realization of axion kinetic misalignment, triggered by a Hubble-induced phase transition during a post-inflationary stiff (kination) era. A negative Ricci scalar flips the sign of a non-minimally coupled mass term for a non-minimally coupled complex field $\Phi$, driving its radial mode to large amplitudes via a tachyonic instability. At large $|\Phi |$, higher-dimensional $U(1)$-breaking operators become relevant and impart a kick in the angular direction, generating a conserved $U(1)$ charge that sustains rotation as the symmetry is approximately restored. Because phases randomize across causally disconnected regions, multiple domains with distinct charges form. The subsequent axion potential converts the domain charges into an axion abundance, yielding dark matter even when the net global charge vanishes. We analyze the dynamics through a linear, domain-averaged treatment and identify two thermal histories: (i) Ricci reheating via saxion decays to Higgs bosons; (ii) external reheating with efficient damping of saxion energy by Higgs/fermion scatterings. The mechanism populates regions underabundant in standard misalignment, which are accessible to next generation axion searches.

    hep-phastro-ph.CO2 citations
37. 37*

    The spectrum of axions in a scaling string network

    José Correia🇳🇴 · Mark Hindmarsh🇫🇮 · Joanes Lizarraga🇪🇸 · Asier Lopez-Eiguren🇪🇸 · Kari Rummukainen🇫🇮 · Jon Urrestilla🇪🇸

    Cosmic strings formed when the Peccei-Quinn symmetry breaks post-inflation are expected to emit axions throughout their lifetime. The details of the evolution of this network and the associated spectrum of axions are crucial for obtaining an accurate axion mass prediction, thus guiding searches at haloscopes. In a previous publication, we obtained evidence for the standard scaling of axion string networks, showing that the number of horizon lengths of string per horizon volume asymptotes to an $\mathcal{O}(1)$ constant. In this article, we turn our attention to the axion spectra, studying spectra of all components of the axion current and their unequal time correlators. With the new information we are better able to distinguish the contributions from propagating axions from the field carried by the strings, and show that previous measurements of the axion energy spectrum based only on the timelike component of the current are approximately 30\% derived from the string fields. We introduce a simple model based on an ensemble of string segments, which accounts for the general features of the spectra and time correlations. We conclude that axion emission from a scaling string network is close to scale-invariant ($q\approx 1$), and that the energy spectrum of sub-horizon modes behaves as $p_{\text{ax}}\ln (k\tau )$, where $k$ is the comoving wavenumber, $\tau$ the conformal time and $p_{\text{ax}}\simeq 10$. The number density spectrum evolves towards a single curve for $k\tau \lesssim 10^2$, with higher wavenumber deviations arising from initial conditions and resonant axion production at the string width scale. The total number density of axions produced from strings is $n_{\text{ax}}=1.66(17)f_{\text{a}}^{2}H$, where $f_{\text{a}}$ is the axion decay constant and $H$ the Hubble rate. We report on axion production from the final collapse of the network in a future work.

    hep-ph8 citations
38. 38*

    Improved Standard-Model predictions for ${\eta }^{(\prime )}\to {\ell }^{+}{\ell }^{-}$

    Noah Messerli🇨🇭 · Martin Hoferichter🇨🇭 · Bai-Long Hoid🇩🇪 · Simon Holz🇨🇭 · Bastian Kubis🇩🇪

    The rare decays ${\eta }^{(\prime )}\to {\ell }^{+}{\ell }^{-}$, $\ell \in \{e,\mu \}$, are highly suppressed in the Standard Model, both by their chirality structure and the required loop attaching the lepton line to the ${\eta }^{(\prime )}\to {\gamma }^{\ast }{\gamma }^{\ast }$ matrix element. The latter is described by a single scalar function, the transition form factor, which has recently been studied in great detail for ${\eta }^{(\prime )}$ in the context of the pseudoscalar-pole contributions to hadronic light-by-light scattering in the anomalous magnetic moment of the muon. Based on these results, we evaluate the corresponding prediction for the ${\eta }^{(\prime )}$ dilepton decays, supplemented by an improved evaluation of the asymptotic contributions including pseudoscalar mass effects. In particular, the dispersive representation for the ${\eta }^{(\prime )}$ transition form factors allows us, for the first time, to perform a robust evaluation of the imaginary parts due to subleading channels besides the dominant two-photon cut. Our final results are $\text{Br}[\eta \to e^{+}{e}^{-}]=5.37(4)(2)[4]\times 10^{-9}$, $\text{Br}[\eta \to {\mu }^{+}{\mu }^{-}]=4.54(4)(2)[4]\times 10^{-6}$, $\text{Br}[{\eta }^{\prime }\to e^{+}{e}^{-}]=1.80(2)(3)[3]\times 10^{-10}$, and $\text{Br}[{\eta }^{\prime }\to {\mu }^{+}{\mu }^{-}]=1.22(2)(2)[3]\times 10^{-7}$, where the errors refer to the uncertainty in the normalized branching fraction, the one propagated from $\text{Br}[{\eta }^{(\prime )}\to \gamma \gamma ]$, and the total uncertainty, respectively. The branching fraction for $\eta \to {\mu }^{+}{\mu }^{-}$ exhibits a mild $1.6\sigma$ tension with experiment, and we explore the bounds that can be derived on physics beyond the Standard Model.

    hep-phhep-exhep-latnucl-thJHEP(2026)·7 citations
39. 39*

    Sub-GeV Dark Matter Detection with Dark Rates in Liquid Scintillators

    Lillian Santos-Olmsted🇺🇸 · Rebecca K. Leane🇺🇸 · Carlos Blanco🇺🇸 · John F. Beacom🇺🇸

    It was recently shown that standard sub-GeV dark matter candidates can be effectively probed by large neutrino observatories via annual modulation of the total photomultiplier hit rate. That work focused on the production of light by the excitation of scintillator molecules and considered the JUNO detector, surpassing limits from dedicated dark-matter detectors and reaching theoretical targets. Here, we significantly generalize that work, now also taking into account ionization channels and extending the analysis to other liquid-scintillator detectors, including SNO+, Daya Bay, Borexino, and KamLAND. Last, we present a call to action: with multiple detectors achieving competitive sensitivity, there is an opportunity to validate this new technique across experiments and to refine it using each detector's strengths.

    hep-phhep-exPRD(2026)·2 citations
40. 40*

    Domain Walls in $A_4$ Flavour Models

    Bowen Fu🇨🇳 · Stephen F. King🇬🇧 · Luca Marsili🇪🇸 · Jessica Turner🇬🇧 · Ye-Ling Zhou🇨🇳

    The spontaneous breaking of an $A_4$ flavour symmetry, often used to predict leptonic mixing, can lead to the formation of domain walls which can annihilate and generate a stochastic gravitational wave background. We study this phenomenon in three scenarios where the nature of the scalar field responsible for breaking the $A_4$ symmetry spontaneously differs: real, complex, and supersymmetric. For the real scalar, a biased potential produces metastable walls that decay into oscillating two-wall systems with important consequences for gravitational wave signals. In the complex scalar case, we discuss the interplay between domain walls and global strings and classify the types of domain walls that form in terms of the $A_4$ group symmetries. We investigate the properties of supersymmetric $A_4$ domain walls, and highlight the BPS walls. Through a detailed analysis of these models with non-Abelian symmetries, we discover new kinds of domain walls, which we denote as ``oreo''-type composite domain walls, CP-violating domain walls and SUSY non-Abelian domain walls. Finally we show how these results may be achieved in leptonic $A_4$ flavour models, with and without supersymmetry, and discuss their distinctive gravitational wave signatures.

    hep-phJHEP(2026)·6 citations
41. 41*

    Look everywhere effects in anomaly detection

    Marie Hein🇩🇪 · Benjamin Nachman🇺🇸 · David Shih🇺🇸

    Machine learning-based anomaly detection methods are able to search high-dimensional spaces for hints of new physics with much less theory bias than traditional searches. However, by searching in many directions all at once, the statistical power of these search strategies is diluted by a variant of the look elsewhere effect. We examine this challenge in detail, focusing on weakly supervised methods. We find that training and testing on the same data results in badly miscalibrated $p$-values due to the anomaly detector searching everywhere in the data and overfitting on statistical fluctuations. However, if these $p$-values can be calibrated, they may offer the best sensitivity to anomalies, since this approach uses all of the data. Conversely, training on half of the data and testing on the other half results in perfectly calibrated $p$-values, but at the cost of reduced sensitivity to anomalies. Similarly, regularization methods such as early stopping can help with $p$-value calibration but also possibly at the expense of sensitivity. Finally, we find that k-folding strikes an effective balance between calibration and sensitivity. Our findings are supported by numerical studies with Gaussian random variables as well as from collider physics using the LHC Olympics benchmark anomaly detection dataset.

    hep-phhep-exphysics.data-an6 citations
42. 42*

    Magnetoviscosity of relativistic plasma

    Ritesh Ghosh🇺🇸 · Igor A. Shovkovy🇺🇸

    Using first-principles quantum field-theoretical methods, we investigate the shear and bulk viscosities of strongly magnetized relativistic plasmas. The analysis is performed within the weak-coupling approximation and utilizes known results for the fermion damping rates in the Landau-level representation, ${\Gamma }_n(p_z)$, which are dominated by one-to-two and two-to-one processes in the presence of a strong magnetic field. The transverse and longitudinal components of the viscosities are derived using Kubo's linear response theory. Our results reveal a pronounced anisotropy in both shear and bulk viscosities induced by the magnetic field. In the case of an electron-positron plasma, where the weak-coupling approximation is well justified, the dimensionless longitudinal shear viscosity ${\eta }_{\parallel }/T^3$ increases rapidly with the magnetic field strength, while the transverse component ${\eta }_{\perp }/T^3$ decreases and can even drop below the KSS bound at sufficiently large fields. In contrast, both the dimensionless longitudinal and transverse bulk viscosities, ${\zeta }_{\perp }/T^3$ and ${\zeta }_{\parallel }/T^3$, initially rise from small values, reach a maximum, and then gradually decrease toward zero. We find that the bulk viscosity is highly sensitive to the longitudinal and transverse components of the sound velocity, particularly at high magnetic fields, indicating that its quantitative values should be interpreted with caution. We also calculate an additional cross viscosity, which is negative and whose magnitude increases with the magnetic field strength. Finally, we discuss the physical implications of these magnetoviscosity results in the contexts of magnetar physics and the strongly magnetized quark-gluon plasma produced in heavy-ion collisions.

    hep-phnucl-th0 citations
43. 43*

    An Excited Dark Matter Solution to the MeV Galactic Center Excesses

    Shyam Balaji🇬🇧 · Damon Cleaver🇬🇧 · Pedro De la Torre Luque🇪🇸

    Recent COMPTEL data analysis reveals a $\sim$ 2 MeV continuum excess whose spatial distribution closely matches the long-standing 511 keV line observed by INTEGRAL/SPI, indicating a common population of low-energy positrons that is difficult to reconcile with known astrophysical sources or standard thermal dark matter (DM). We show that a minimal Excited Dark Matter (XDM) model naturally explains these features. In this scenario a DM particle $\chi$ is inelastically upscattered into an excited state ${\chi }^{\ast }$, followed by de-excitation ${\chi }^{\ast }\to \chi e^{+}{e}^{-}$ producing $\sim$2 MeV positrons that reproduce the 511 keV line morphology and the COMPTEL MeV continuum. Using a full cosmic-ray (CR) propagation treatment, we obtain an excellent fit for $m_{\chi }\simeq$ 1.5 TeV DM particle with mass-splitting $\Delta m=m_{{\chi }^{\ast }}-m_{\chi }\simeq$ 4 MeV for an inelastic geometric scattering cross section of ${\sigma }_{\text{mr}}=3-4\times 10^{-23}{\text{cm}}^2$. The same positrons supply a substantial, radially flat contribution to the anomalous Central Molecular Zone (CMZ) ionization rate. This is the first unified treatment of XDM-induced positrons across all three observables, yielding correlated MeV signatures testable by upcoming missions targeting the Galactic MeV band.

    hep-phastro-ph.HEApJL(2026)·2 citations
44. 44*

    Neutrino Constraints on Scalar-Tensor Gravity

    Arturo de Giorgi🇬🇧 · Ivan Martinez Soler🇬🇧 · Sergio Sevillano Muñoz🇬🇧

    In this work, we derive novel constraints on scalar-tensor theories from neutrino physics. Spatial variations of the background scalar field effectively generate density and position-dependent Standard Model masses, including neutrinos. Neutrinos are a unicum in the SM due to their ability both to propagate over galactic distances and to traverse dense media such as Earth. This makes them an ideal probe of the background scalar field, which can in turn alter flavour oscillations and supernova time delays. As we enter the era of precision neutrino physics, we are compelled to explore such a scenario. We derive expressions for the relevant observables and obtain new bounds on a broad class of scalar-tensor models. We finally map the bounds to popular screening mechanisms models, such as the Symmetron and Chameleon.

    hep-phastro-ph.COgr-qc3 citations
45. 45*

    Unveiling a Hidden Epoch: Impact of Mediator Induced Matter Domination in Freeze-in Dark Matter

    Partha Konar🇮🇳 · Sudipta Show🇮🇳

    Freeze-in dark matter has recently garnered significant attention as a promising framework due to its feeble interactions, which are consistent with the null results from dark matter experiments. While previous studies have extensively investigated the production of dark matter through the decay of heavy particles, they overlook the cosmological role of the decaying mediator without justifying this assumption. We emphasize that the mediator can dominate the energy budget of the early universe during its decay, leading to an unavoidable early matter-dominated era. This intrinsic matter-dominated phase influences dark matter production in two key ways: (i) dark matter production occurs in both the early radiation and induced matter-dominated phases; specifically, considerable production occurs in the matter-dominated phase and stops when the mediator decays fully, and (ii) it causes dilution in dark matter abundance due to entropy injection before its saturation. Furthermore, this effect significantly alters the gravitational wave signature associated with the production of freeze-in dark matter through graviton emission during the mediator's decay. Specifically, it enhances the gravitational wave spectrum, making it viable for future high-frequency gravitational wave experiments.

    hep-ph4 citations
46. 46*

    X-ray Evolution of Young Stars: Early Dimming and Coronal Softening in Solar-Mass Stars with Implications for Planetary Atmospheres

    Konstantin V. Getman (1)🇺🇸 · Eric D. Feigelson (1,2)🇺🇸 · Vladimir S. Airapetian (3,4)🇺🇸 · Gordon P. Garmire (5) ((1) Pennsylvania State University, (2) Center for Exoplanets and Habitable Worlds, (3) American University, (4) NASA/GSFC/SEEC, (5) Huntingdon Institute for X-ray Astronomy)🇺🇸

    X-ray and ultraviolet (XUV) emission from young stars plays a critical role in shaping the evolution of planetary atmospheres and the conditions for habitability. To assess the long-term impact of high-energy stellar radiation, it is essential to empirically trace how X-ray luminosities and spectral hardness evolve during the first ~<1 Gyr, when atmospheric loss and chemical processing are most active. This study extends the X-ray activity-mass-age analysis of <25 Myr stars by Getman et al. (2022) to ages up to 750 Myr, using Gaia-based cluster memberships, new Chandra observations of five rich open clusters (~45--100 Myr), and archival ROSAT and Chandra data for three older clusters (~220--750 Myr). We find a mass-dependent decay in X-ray luminosity: solar-mass stars undergo a far more rapid and sustained decline, accompanied by coronal softening and the disappearance of hot plasma by ~100 Myr, compared to their lower-mass siblings. These trends in solar-mass stars are likely linked to reduced magnetic dynamo efficiency and diminished ability to sustain large-scale, high-temperature coronal structures. The trends are significantly stronger than predicted by widely used XUV-rotation-age relations. The revised trends imply systematically lower rates of atmospheric mass loss and water photolysis, as well as altered ionization environments and chemical pathways relevant to the formation of prebiotic molecules, for planets in close orbits around solar analogs. These effects persist throughout at least the ~<750 Myr interval probed in this study.

    ↳ astro-ph.SRastro-ph.EPhep-phApJ(2026)·0 citations
47. 47*

    Constraining the dark matter origin of the halo-like 20 GeV $\gamma$-ray excess with the AMS-02 antiproton data

    Xiao Wang🇨🇳 · Kai-Kai Duan🇨🇳

    Very recently, a significant $\sim 20$ GeV gamma-ray excess in the Milky Way halo has been reported and a dark matter origin has been suggested. The inferred dark matter parameters are $m_{\chi }\sim 0.5-0.8$ TeV and $⟨\sigma v⟩\sim (5-8)\times 10^{-25}\mathrm{c}{\mathrm{m}}^3{\mathrm{s}}^{-1}$ for the $b\bar{b}$ channel. If correct, prominent antiproton emission is produced and can be directly tested by the AMS-02 data. In this work we calculate the corresponding antiproton emission and show that the expected flux at $\sim 100$ GeV is already above the AMS-02 observation. A proper treatment on the antiproton background resulting from the high energy cosmic ray propagation would suggest an annihilation cross section of $<2\times 10^{-26}\mathrm{c}{\mathrm{m}}^3{\mathrm{s}}^{-1}$, which is a few$\times 10$ times lower than that needed to interpret the potential signal. We therefore conclude that the $\sim 20$ GeV gamma-ray excess in the Milky Way halo is not a viable dark matter signal.

    ↳ astro-ph.HEastro-ph.COhep-phJCAP(2026)·5 citations
48. 48*

    Relativistic Dispersion Spectra across Lorentz boosted frames: Spurious modes and the enigma of causality

    Sayantani Bhattacharyya🇬🇧 · Sukanya Mitra🇮🇳 · Shuvayu Roy🇮🇳 · Rajeev Singh🇷🇴

    The analysis of excitation spectra in gradient-expanded relativistic fluid theories frequently leads to pathologies under Lorentz boosts. However, extracting the dispersion modes in a Lorentz boosted inertial frame can be nontrivial. Motivated by this problem, we develop a general framework for deriving the linearized dispersion spectra in Lorentz boosted frames using only information from the local rest-frame dispersion structure, particularly its mode-expansion coefficients. We observe that, under a Lorentz transformation from the local rest frame, additional boosted solutions may appear that conflict with the causality of the theory; we refer to these as "spurious modes." The key developments presented here are: (i) a convenient method for obtaining dispersion spectra across inertial frames, bypassing the traditional procedure of solving the boosted polynomial, and (ii) the establishment of a direct connection between mode conservation and the causality of a theory, supported by a detailed proof.

    ↳ hep-thgr-qchep-phnucl-thJHEP(2026)·4 citations
49. 49*

    Readdressing the contribution of photonuclear reactions to the muon content of extensive air showers: a heuristic approach

    Nickolay S. Martynenko🇷🇺

    The indirect ground-based observations of cosmic rays through extensive air showers in modern experiments typically involve the use of Monte Carlo simulations to determine the characteristics of the primary particles. These simulations necessitate assumptions about particle interactions at energies that have not yet been experimentally probed, which introduces systematic uncertainties in key observables, particularly the number of muons. Current research on this uncertainty primarily focuses on hadronic interaction models, the dominant source of muon production. This study presents an approach that takes into account another significant mechanism for muon generation: photonuclear reactions. A robust heuristic technique has been developed to estimate the contribution of these interactions to the total number of muons over a wide range of extensive air shower parameters (including primary particle type, energy, and slant atmospheric depth) and photonuclear interaction models, with an absolute percentage error on the order of $10\%$ in the estimated number of muons. Furthermore, several potential applications of the suggested method in relation to modern challenges in extensive air shower physics are discussed.

    ↳ astro-ph.HEhep-phPRD(2026)·0 citations
50. 50*

    Emergence of thermal recoil jets in high-energy heavy-ion collisions

    Peng Jing🇨🇳 · Yichao Dang🇨🇳 · Yang He🇨🇳 · Shanshan Cao🇨🇳 · Li Yi🇨🇳 · Xin-Nian Wang🇨🇳

    In the established paradigm of jet quenching in relativistic heavy-ion collisions, jets from initial hard parton scatterings are suppressed due to their interaction with the quark-gluon plasma (QGP) as they traverse the hot medium, serving as crucial tomographic probes of QGP properties. The QGP is also capable of absorbing and reprocessing energy deposited by the hard jets into emergent jet-like objects, providing a novel production mechanism of thermal recoil jets. These emergent thermal recoil jets exhibit distinct transverse momentum ($p_{\mathrm{T}}$) and jet-size ($R$) dependencies different from the hard jets, and naturally explain the puzzling observation of the enhanced yields of hadron or photon triggered jets at large azimuthal angle and solely at small $p_{\mathrm{T}}$ and large $R$. These thermal recoil jets are predicted to have unique substructures, such as their jet shape that increases with the radius and the thermal-like distribution of their constituents, which can be verified in future experimental analyses.

    ↳ nucl-thhep-phnucl-exPRL(2026)·4 citations
51. 51*

    Relation between leading divergences in nonrenormalizable $4D$ supersymmetric theories

    Ali Lakhal🇫🇷 · Konstantin Stepanyantz🇷🇺

    We consider an $\mathcal{N}=1$ nonrenormalizable supersymmetric gauge theory with the superpotential quartic in the chiral matter superfields. With the help of the Slavnov's higher covariant derivative regularization it is demonstrated that (in the lowest nontrivial order) the leading power divergent quantum correction to the gauge coupling constant is given by an integral of double total derivatives with respect to the loop momenta. The result obtained after calculating this integral turned out to be proportional to the corresponding quantum correction to the kinetic term of the matter superfields. More exactly, in the considered approximation the quadratically divergent contributions to the gauge coupling and to the kinetic term of the chiral matter superfields are related by an equation analogous to the exact NSVZ $\beta$-function for the renormalizable case.

    ↳ hep-thhep-phEPJC(2026)·4 citations
52. 52*

    Improving the electromagnetic form factor of the pion at large $Q^2$ using the Feynman-Hellmann theorem

    K. U. Can🇦🇺 · J. A. Crawford🇦🇺 · R. Horsley🇬🇧 · J. J. McKee🇦🇺 · P. E. L. Rakow🇬🇧 · I. van Schalkwyk🇦🇺 · G. Schierholz🇩🇪 · H. Stüben🇩🇪 · R. D. Young🇦🇺 · J. M. Zanotti🇦🇺

    At large momentum transfer, it becomes increasingly difficult to access the form factor of the pion $F_{\pi }(Q^2)$ using lattice QCD simulations. Two of the limiting factors include the increased computational cost of adding more statistics to overcome gauge noise, as well as suppressed overlap with the ground state of the boosted pion. Here we apply two noise reduction techniques, all-mode averaging (AMA) and momentum smearing, to the computation of $F_{\pi }(Q^2)$ at high momentum transfers using the Feynman-Hellmann (FH) theorem. First, we show that all-mode averaging by itself produces good improvement compared to previous results, at an equal computational cost. We also implement a momentum smearing technique to further reduce statistical uncertainties. In contrast to conventional smearing approaches, our Feynman-Hellmann method requires combining back-to-back momentum states, and hence we adapt a version of smearing involving a superposition of back-to-back smearing operations. This method is then implemented to compute $F_{\pi }(Q^2)$ at $Q^2=6.6\mathrm{Ge}{\mathrm{V}}^2$, demonstrating good improvement over the regular smeared counterpart. Finally both all-mode averaging and momentum smearing are combined to determine $F_{\pi }(Q^2)$ at $Q^2=6.6\mathrm{Ge}{\mathrm{V}}^2$ showing an excellent preliminary improvement over previous calculations.

    ↳ hep-lathep-phPoS(2025)·0 citations
53. 53*

    Gauge Theory Amplitudes from Cubic Scalar Feynman diagrams

    Roji Pius🇮🇳

    Feynman diagrams are the foremost tool in the perturbative study of quantum field theory. In gauge theories, the full potential of this tool is revealed when it is combined with the Slavanov-Taylor identities associated with the local gauge symmetry. Hence, it is desirable to have perturbative expansion of scattering amplitudes that combine the graphical nature of Feynman diagram expansion and the reations among various diagrams due to the Slavanov-Taylor identities. In a remarkable paper, motivated by the similarity between graph homology and the gauge theory BRST homology, Kreimer, Sars and van Suijlekom found such an expansion. The implication of this expansion is that the amplitudes in a generic non-abelian gauge theory can be constructed by transmuting the renormalised integrands of trivalent Feynman diagrams in a scalar quantum field theory. In this paper, we show that this surprising connection naturally emerges from Witten's open string field theory in the field theory limit.

    ↳ hep-thhep-phmath-phmath.MP0 citations
54. 54*

    Constraints on dark matter annihilation from a nearby subhalo candidate

    Ben-Yang Zhu🇨🇳 · Yun-Feng Liang🇨🇳 · Xiaoyuan Huang🇨🇳

    A recent analysis of pulsar timing data has reported evidence for a massive ($\sim 6\times 10^7{M}_{\odot }$) dark matter subhalo located only $\sim 0.8$ kpc from Earth. This candidate implies an exceptionally large $J$-factor of $\sim 10^{23}\mathrm{Ge}{\mathrm{V}}^2\mathrm{c}{\mathrm{m}}^{-5}$, exceeding that of known classical dwarf spheroidal galaxies by orders of magnitude and rivaling the Galactic Center. In this work, we utilize more than 17 years of $\text{Fermi}$-LAT data to search for gamma-ray emission from this subhalo. We identify a tentative excess in the region with ambiguous origin. Adopting a conservative strategy, we retain this excess without modeling additional astrophysical components, treating it instead as unmodeled background to derive upper limits on the dark matter annihilation cross-section for the $b\bar{b}$ and ${\tau }^{+}{\tau }^{-}$ channels. Despite this conservative treatment, the resulting limits remain stringent due to the exceptionally large $J$-factor. Subject to the dynamical confirmation of the subhalo, these constraints are potentially orders of magnitude stronger than those obtained from combined analyses of dwarf spheroidal galaxies and blind subhalo searches.

    ↳ astro-ph.HEhep-ph2 citations
55. 55*

    Standardizing reverberation-mapped H$\beta$ active galactic nuclei using time-averaged radius$-$luminosity relations with 5100\,Å\,, broad H$\beta$, and narrow \OIII\ luminosities

    Shulei Cao🇺🇸 · Amit Kumar Mandal🇵🇱 · Michal Zajaček🇨🇿 · Bharat Ratra🇺🇸

    Active galactic nuclei (AGN) have been studied as alternate probes in cosmology due to their large and stable luminosities and broad redshift range. Previously it was shown that higher-redshift AGN that were reverberation-mapped (RM) using broad Mg\,\textsc{ii} and C\,\textsc{iv} lines are standardizable and yield weak cosmological constraints that are consistent with those from better-established probes. In contrast, lower-redshift AGN that were reverberation-mapped using the broad H$\beta$ line exhibited tensions with the standard cosmological model, in particular they preferred currently decelerating cosmological expansion. Here we study the standardizability of a homogeneous RM H$\beta$ sample of $\sim 100$ AGN (over redshifts $0.00308\le z\le 0.8429$), whose H$\beta$ time delays and three luminosity tracers (at 5100\,Å\,, broad H$\beta$, and narrow [O\,\textsc{iii}]) are averaged over several epochs. We find that this averaged sample is standardizable using three $R-L$ relations. While for luminosities corresponding to 5100\,Å\, and the broad H$\beta$ line the cosmological constraints prefer currently decelerating cosmological expansion, the cosmological parameters for the narrow [O\,\textsc{iii}] luminosity are more consistent with those from better-established probes and they are in agreement with currently accelerating cosmological expansion. This demonstrates for the first time that narrow-line region [O\,\textsc{iii}] can be utilized for AGN standardization and cosmological constraints. Selecting proper photoionizing flux proxies for the broad-line region is thus crucial in studies of RM AGN standardizability.

    ↳ astro-ph.GAastro-ph.COgr-qchep-ph+10 citations
56. 56*

    PSR J0537-6910: Exponential recoveries detected for 12 glitches

    E. Zubieta🇦🇷 · C. M. Espinoza🇨🇳 · D. Antonopoulou🇬🇧 · W. C. G. Ho🇺🇸 · L. Kuiper🇳🇱 · F. García🇦🇷 · S. del Palacio🇦🇷

    Pulsar glitches are unresolved increments of the rotation rate that sometimes trigger an enhancement of the spin-down rate. On occasions, the augmented spin-down decays gradually in an exponential manner, particularly after the largest glitch events. The young pulsar PSR J0537-6910 exhibits the highest known glitching rate, with 60 events detected in nearly 18 years of monitoring. Despite most PSR J0537-6910 glitches being large, only one exponential recovery has been reported, following its first discovered glitch. This is puzzling, as pulsars of similar characteristics typically present significant exponential recoveries. We aim to determine whether this reflects an intrinsic difference in PSR J0537-6910 or a detectability issue, for example due to its high glitch frequency. The full dataset, including recent NICER observations, was systematically searched for exponential relaxations. Each glitch was tested for evidence of a recovery over a broad range of trial timescales. Promising candidates were investigated further by comparing recovery models with and without an exponential term using Bayesian evidence. We discovered six new glitches, bringing the total to 66. Our criteria strongly indicates the presence of 11 previously undetected exponential recoveries. We presente updated glitch and timing solutions. Exponential recoveries are detected only for the largest glitches, though not all of them. The inferred timescales range from 4 to 37 d, with the decaying frequency increment generally below $1\%$ of the total. We find that $\ddot{\nu }$ can remain stable across several glitches, with persistent changes associated with only some events. In particular, it tends to be lowest after glitches with exponential recoveries, yielding inter-glitch braking indices between 6 and 9. Following glitches without recoveries, $\ddot{\nu }$ is higher, leading to braking indices between 10 and 35.

    ↳ astro-ph.HEhep-phAstron.Astrophys.(2026)·3 citations
57. 57*

    Extending Weinberg's EFT: effective scalar-tensor theories up to sixth order

    Eugeny Babichev🇫🇷 · Sukŗti Bansal🇦🇹 · Maria Mylova🇯🇵 · Antonio Padilla🇬🇧

    We present a systematic construction of the six-derivative effective scalar-tensor theories, extending the four-derivative framework previously developed by Steven Weinberg. The on-shell effective field theory comprises five parity-even and three parity-odd independent six-derivative scalar-tensor interactions, representing all inequivalent deformations consistent with general covariance. We further confirm this operator counting through an independent analysis using the scattering amplitude formalism in four-dimensional flat spacetime. The six-derivative Lagrangian constructed here provides the next-to-leading-order extension of scalar-tensor gravity, furnishing a robust framework for exploring quantum or stringy corrections, parity-violating interactions, and strong-curvature effects in cosmology, black hole physics and gravitational wave observations.

    ↳ hep-thastro-ph.COgr-qchep-phJHEP(2026)·1 citation
58. 58*

    The Serendipitous Axiodilaton: A Self-Consistent Recombination-Era Solution to the Hubble Tension

    Adam Smith🇬🇧 · Maria Mylova🇯🇵 · Carsten van de Bruck🇬🇧 · C.P. Burgess🇨🇦 · Eleonora Di Valentino🇬🇧

    Axio-dilaton cosmology provides a minimal benchmark model for both Dark Matter (DM) and Dark Energy (DE) that is well motivated by fundamental physics. The axion and dilaton arise as pseudo-Goldstone modes of symmetries that predict particle masses depend on the dilaton, and therefore to evolve cosmologically, leading to correlated modifications of recombination physics, the sound horizon, and late-time expansion and growth histories. We confront this model with Planck 2018 temperature, polarisation, and lensing data, SPT-3G high-$\ell$ measurements, DESI DR2 BAO, and Pantheon$+$ supernovae, assuming that the axion makes up all of the dark matter and that the dilaton plays the role of a dark energy field. We find that it fits the data somewhat better than $\Lambda$CDM cosmology, with the ${\chi }^2$ lowered by $\simeq 7$ for three additional parameters, and significantly raises the inferred Hubble constant to $H_0\simeq 69.2\mathrm{km}{\mathrm{s}}^{-1}\mathrm{Mp}{\mathrm{c}}^{-1}$, reducing the Hubble tension to $\lesssim 3\sigma$ and thereby allowing a joint fit of CMB and SH0ES data. The model fits this enlarged data set as well as the $w_0{w}_a$ model with an electron mass modified by hand at recombination, though it does so with calculable dynamics. Axio-dilaton self-interactions robustly fake a phantom equation of state in DESI measurements. There is a sting: cosmology prefers dilaton-matter couplings $|\mathbf{g}|\sim 10^{-2}$-$10^{-1}$, which are large enough to have been detected in solar-system tests of General Relativity. These results show how axio-dilatons can provide a viable cosmology preferred by current data at surprisingly large couplings, within a framework that links dark energy, dark matter, and time-dependent particle masses in a coherent way. They suggest both new observable signals and new theoretical directions, aimed at resolving the apparent inconsistency with non-cosmological observations.

    ↳ astro-ph.COgr-qchep-phhep-th16 citations
59. 59*

    Two-point correlators in de Sitter-prepared states with bra-ket wormholes

    Sunghoon Jung🇰🇷 · Minju Kum🇺🇸 · Junghwan Lee🇰🇷

    Motivated by the finiteness of de Sitter (dS) horizon entropy, we study how "bra-ket wormholes" modify correlation functions in gravitationally prepared states. Euclidean wormhole saddles in gravitational path integrals can generate non-factorizing contributions to correlation functions, as in replica-wormhole explanation of the Page curve and bra-ket-wormhole restoration of strong subadditivity. By defining 'time' variables and computing observables in a flat region attached to the dS boundary, we evaluate bra-ket wormhole contributions to scalar two-point functions and find late-time transitions in the dominant saddle, accompanied by the ramp-and-plateau behavior of correlations and the characteristic timescale comparable to the fast scrambling. Each observable is consistent with `complementarity', in the sense that wormhole effects are distinguishable only at late respective times. Consistencies are based upon the interplay of (i) inflationary horizon exit and re-entry, (ii) enhancement of correlations at small comoving momentum by wormhole contributions, (iii) a competition between mode counting and topological suppression that drives a transition to wormhole dominance, which naturally yields the fast scrambling timescale, and (iv) irreducible errors by cosmic variance in early CMB-like observations. To clearly interpret in terms of entropy and chaotic nature of dS, one needs a more complete mechanism of wormhole stabilization.

    ↳ gr-qchep-phhep-th3 citations
60. 60*

    Electron-positron pair creation induced by multi-pulse train of electric fields: effect of randomness in time-delay

    Deepak Sah🇮🇳 · Manoranjan P. Singh🇮🇳

    We investigate the creation of electron-positron pairs (EPPs) in a sequence of alternating-sign, time-dependent electric field pulse trains by solving the quantum Vlasov equations. Specifically, we focus on Sauter-like pulse trains with random time delays between successive pulses, drawn from a Gaussian distribution wherein the extent of fluctuations is controlled by the standard deviation ${\sigma }_T$ of the distribution. We find that increasing ${\sigma }_T$ leads to a dramatic transformation in the longitudinal momentum spectrum. The well-known fringe pattern, akin to that in the multi-slit interference, gets significantly modified. The averaged spectra exhibit a robust Gaussian-like envelope with residual oscillations, which are much more prominent in the central momentum region. Notably, we find that in certain cases, stochastic time delays lead to a pronounced enhancement in the central peak of the distribution function for pulse train containing $N$ pulses. For example, for $N=20$ pulses, ${\sigma }_T\approx 31$ $[m^{-1}]$(about $17\%$ of the mean time delay) yields nearly a tenfold increase in the central peak, which for ${\sigma }_T\approx 50$ $[m^{-1}]$ (about $27\%$ of the mean time delay), scales up to $10^3.$ This may open up new possibilities for optimizing multi-pulse field configurations and guide future experimental designs aimed at maximizing EPPs creation.

    ↳ quant-phhep-phhep-thNPB(2026)·2 citations
61. 61*

    Resonances: Universality and Factorization on Higher Sheets

    Miguel Correia🇨🇦 · Celina Pasiecznik🇨🇦

    Most particles in nature are unstable, manifesting as resonances in scattering processes. Using analyticity and unitarity, we show nonperturbatively that resonances, defined as poles on higher Riemann sheets of scattering amplitudes, share basic properties with stable particles: (i) Universality, that a resonance generically appears in every S-matrix element; and (ii) Factorization, that amplitudes factorize on resonance poles. Our framework applies in any spacetime dimension and across arbitrarily many two-particle cuts, including cases where the kinematic Riemann surface becomes infinitely sheeted. Importantly, we find that resonance data (mass, width, couplings, and sheet index) are fully encoded on the physical sheet, where causality can impose additional constraints. These results are relevant for extending S-matrix bootstrap studies beyond elastic scattering.

    ↳ hep-thhep-phnucl-th4 citations
62. 62*

    Positivity with Long-Range Interactions

    B. Bellazzini🇫🇷 · J. Berman🇺🇸 · G. Isabella🇺🇸 · F. Riva🇨🇭 · M. Romano🇫🇷 · F. Sciotti🇪🇸

    We introduce infrared finite, analytic, crossing symmetric, Regge behaved, and Lorentz invariant amplitudes ${\mathcal{M}}_{\mathcal{E}}$, labeled by the experimental energy resolution $\mathcal{E}$ for detecting soft photons and gravitons. For $\mathcal{E}$ exponentially smaller than any hard scale, they also satisfy unitarity and their associated cross sections reproduce the inclusive, infrared-finite cross sections of ordinary amplitudes. These properties make ${\mathcal{M}}_{\mathcal{E}}$ suitable for deriving infrared-safe positivity bounds on effective field theories in the presence of long-range forces even in $D=4$. As an illustration, we present explicit bounds in the low-energy theory of pions coupled to electromagnetism and gravity.

    ↳ hep-thhep-phJHEP(2026)·21 citations
63. 63*

    The spectrum of Feynman-integral geometries at two loops

    Piotr Bargiela🇬🇧 · Hjalte Frellesvig🇨🇳 · Robin Marzucca🇨🇭 · Roger Morales🇺🇸 · Florian Seefeld🇩🇰 · Matthias Wilhelm🇩🇰 · Tong-Zhi Yang🇨🇭

    We provide a complete classification of the Feynman-integral geometries at two-loop order in four-dimensional Quantum Field Theory with standard quadratic propagators. Concretely, we consider a finite basis of integrals in the 't Hooft--Veltman scheme, i.e. with $D$-dimensional loop momenta and four-dimensional external momenta, which belong to 79 independent topologies, or sectors. Then, we analyze the leading singularities of the integrals in those sectors for generic values of the masses and momenta, using the loop-by-loop Baikov representation. Aside from the Riemann sphere, we find that elliptic curves, hyperelliptic curves of genus 2 and 3 as well as K3 surfaces occur. Moreover, we find a smooth and non-degenerate Del Pezzo surface of degree 2, a particular Fano variety known to be rationalizable, resulting in a curve of geometric genus 3. These geometries determine the space of functions relevant for Quantum Field Theories at two-loop order, including in the Standard Model.

    ↳ hep-thhep-phJHEP(2026)·10 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.