Wed·Mar 4, 2026Wednesday·March 4, 2026

1. 01*

   Open system approach to neutrinos propagating in an ultralight scalar background

   Lua F. T. Airoldi🇧🇷 · Gustavo F. S. Alves🇺🇸 · Pedro A. N. Machado🇺🇸 · Peter Vander Griend🇺🇸

   We examine decoherence in neutrino oscillations induced by an ultralight scalar field coupled to neutrinos. The scalar induces time- and position-dependent shifts in the neutrino mass matrix. Neutrinos sample different field configurations throughout an experimental data-taking period, which leads to damping effects in the oscillation pattern in the form of decoherence. By recasting the neutrino-scalar dynamics within the open quantum systems framework, we establish a mapping between a complete model and phenomenological decoherence approaches. We find that the parameter driving decoherence scales as $L^2/E^2$, where $L$ is the baseline and $E$ is the neutrino energy, as opposed to $L/E$ typically assumed in phenomenological studies of open system approaches to neutrino oscillations.

   hep-phhep-exPRD(2026)·2 citations
2. 02*

   Radiative Corrections in Supergravity Models of Inflation

   John Ellis🇬🇧 · Tony Gherghetta🇺🇸 · Kunio Kaneta🇯🇵 · Wenqi Ke🇺🇸 · Keith A. Olive🇺🇸

   Supergravity provides the natural supersymmetric framework for early universe cosmology. A broad class of inflationary models in no-scale supergravity yields tree-level predictions for cosmic microwave background (CMB) observables that closely resemble those of the Starobinsky $R+R^2$ model. Using results from global supersymmetry and supergravity, we analyze radiative corrections in models with canonical and non-canonical kinetic terms, focusing particularly on Starobinsky-like no-scale supergravity models. We derive conditions on the superpotential that keep the gravitino mass finite during inflation and ensure that loop-induced corrections to the Kähler potential remain either finite or subdominant relative to the tree-level potential. We show that in some models, most notably the original no-scale supergravity model with a Wess-Zumino superpotential, radiative corrections grow at large inflaton field values and can dominate the inflationary dynamics, rendering unreliable the model predictions for CMB data. However, we identify a class of no-scale Starobinsky-like models, including the Cecotti model, in which radiative corrections remain very small for inflaton field values $\lesssim 8$ (in Planck units), preserving the agreement of the tree-level predictions with Planck CMB data.

   hep-phastro-ph.COgr-qchep-thJHEP(2026)·9 citations
3. 03*

   Constraints on the odderon amplitude in the CGC framework

   Michael Roa🇨🇱 · Marat Siddikov🇨🇱 · Yanil Gentile🇨🇱 · Ivan Zemlyakov🇨🇱

   In this manuscript we analyzed the elastic $pp$ and $p\bar{p}$ cross-section in the Color Glass Condensate framework, treating them as a dilute-dense system, and derived the phenomenological constraints (upper bounds) on the odderon-mediated part of the dipole scattering amplitude $\mathcal{O}(Y,\mathbf{r},\mathbf{b})$. For our analysis we used the experimental data available from TOTEM-D0 and ISR collaborations and construct an observable defined as a combination of the cross-sections which allows us to suppress possible uncertainties associated with charge-parity even part of the amplitude. We analyzed two phenomenological parametrizations of odderons and demonstrated that after minor adjustments to the global normalization, they can describe the experimental data reasonably well, although due to large experimental uncertainties the odderon amplitude remains loosely constrained. Our results indicate that existing data provide limited sensitivity to the odderon and emphasize the need for improved precision and complementary observables.

   hep-phPRD(2026)·1 citation
4. 04*

   Probing Planck-Scale Physics with High-Frequency Gravitational Waves

   Stefano Profumo (University of California, Santa Cruz)🇺🇸

   We develop a framework for testing quantum gravity through the stochastic gravitational-wave background produced by evaporating near-Planck-mass primordial black holes. Because gravitons free-stream from the emission region without rescattering, they preserve a direct spectral record of the black-hole temperature--mass relation $T(M)$, a relation that is erased for all other Hawking-radiated species by rapid thermalization. We translate six representative phenomenological beyond-semiclassical frameworks (the generalized uncertainty principle, loop quantum gravity, noncommutative geometry, asymptotic safety, string/Hagedorn physics, and tunneling backreaction) into distinct $T(M)$ parametrizations and compute the resulting gravitational wave spectra numerically. Modifications that suppress $T(M)$ shift the spectral peak by up to ten decades in frequency, in some cases into the sensitivity bands of next-generation interferometers or resonant-cavity detectors, while models imposing a hard evaporation cutoff produce distinctive peak morphologies that discriminate between quantum-gravity scenarios. We further discuss the impact of different choices for post-inflationary conditions in the very early universe. We find that the relative spectral displacement between the standard Hawking prediction and any modified model is cosmology-independent, hence spectral shape rather than absolute peak frequency provides the cleanest probe of Planck-scale physics.

   hep-phastro-ph.HEgr-qchep-thPRD(2026)·1 citation
5. 05*

   JIMWLK on a quantum computer

   Anjali A. Agrawal🇺🇸 · Evan Budd🇺🇸 · Alexander F. Kemper🇺🇸 · Vladimir V. Skokov🇺🇸 · Andrey Tarasov🇺🇸 · Shaswat Tiwari🇺🇸

   We propose a method for solving the Jalilian-Marian-Iancu-McLerran-Weigert-Leonidov-Kovner (JIMWLK) evolution equation on quantum computers. Our approach exploits the reformulation of the JIMWLK equation as a Lindblad master equation governing the rapidity evolution of the hadronic density matrix, as established in prior work. To render the problem tractable for quantum simulation, we introduce several approximations: the two-dimensional transverse plane is reduced to a one-dimensional radial lattice by assuming azimuthal symmetry of the jump operators; the gauge group is restricted to $\mathrm{SU}(2)$; and the infinite Wilson lines of the JIMWLK equation are replaced by finite Wilson links along the light-cone direction. The resulting bosonic Hilbert space is truncated using the electric field basis familiar from Hamiltonian lattice gauge theory, with states restricted to angular momenta $j\le j_{\max }$. We derive the matrix elements of the JIMWLK Lindblad jump operators in this basis. As a benchmark, we demonstrate rapid convergence of the fundamental dipole expectation value with $j_{\max }$ for both pure and mixed Gaussian initial density matrices. For the simplest truncation, $j_{\max }=1/2$, we implement the Lindblad evolution using a quantum simulation algorithm verified with the Qiskit statevector simulator by decomposing the non-unitary evolution operator into a linear combination of unitaries. This work establishes a concrete pathway toward quantum simulation of high-energy QCD evolution equations, with direct relevance to the physics program of the Electron-Ion Collider.

   hep-phPRD(2026)·2 citations
6. 06*

   Nonlinear physics of axion inflation

   Oleksandr Sobol🇩🇪 · Richard von Eckardstein🇩🇪 · Elias Koch🇩🇪 · Svetlana Gurevich🇩🇪 · Uwe Thiele🇩🇪 · Kai Schmitz🇩🇪

   An axion-like field coupled to an Abelian gauge field provides one of the simplest inflationary models that is free from the eta problem and possesses an efficient reheating mechanism. For sufficiently large coupling, this system enters a regime of strong gauge-field backreaction, exhibiting rich and intricate dynamics. In this work, we employ a semi-analytical method, the gradient-expansion formalism, to perform a comprehensive parameter scan and determine the precise conditions under which backreaction sets in. Previous studies have shown that the Anber-Sorbo solution, in which the potential-gradient force acting on the axion is balanced by Hubble friction and gauge-field backreaction, is unstable. Here, we broaden the parameter space and identify a new region in which the Anber-Sorbo solution remains stable despite strong backreaction. Although our analysis is restricted to a homogeneous axion field and to perturbations that depend only on time, we expect that this stability property can be extrapolated to generic time- and space-dependent perturbations. This newly identified region therefore represents a distinct type of backreaction - stable backreaction - which may not be accompanied by the rapid growth of perturbations. We further investigate the nonlinear behavior of solutions in the backreaction regime in a toy model (de Sitter, constant potential slope, no axion gradients), identifying a supercritical Hopf bifurcation at the onset of instability, a nontrivial limit cycle in the unstable regime, and burst-like oscillatory dynamics. Finally, we present a more stringent criterion for the onset of (unstable) backreaction, based on crossing the instability threshold, and apply this criterion to two benchmark inflationary models.

   hep-phastro-ph.COhep-thnlin.PSJHEP(2026)·5 citations
7. 07*

   Nature of $K^{\ast }(1680)$ and $q\bar{q}$-hybrid mixing as the SU(3) partner of ${\eta }_1(1855)$ in the strange sector

   Samee Ullah🇨🇳 · Ye Cao🇨🇳 · Ming-Xiao Duan🇨🇳 · Hai-Bing Fu🇨🇳 · Qiang Zhao🇨🇳

   We presents an investigation of the $K^{\ast }(1680)$ state in its strong decays into two-body finial states within the flux-tube model and quark pair creation model. Since the charge conjugation parity is not conserved in the strange sector, the conventional $q\bar{q}$ states of $J^{P(C)}=1^{-(-)}$ can mix with the lowest hybrid states with $J^{P(C)}=1^{-(+)}$. Our analysis of the $K^{\ast }(1680)$ two-body strong decays indicates that the decay pattern of $K^{\ast }(1680)$ cannot be explained by the conventional $q\bar{q}$ scenario. Meanwhile, strong evidence shows the $q\bar{q}$-hybrid mixing mechanism in the strange sector. The phenomenological consequences of such a mixing are also discussed. Our study can provide a guidance for the future search for hybrid multiplets in experiment at BESIII, LHCb, and Belle-II.

   hep-ph0 citations
8. 08*

   Sommerfeld enhancement from unstable final-state particles in dark matter annihilation

   Tomohiro Abe🇯🇵 · Ryosuke Sato🇯🇵 · Takumu Yamanaka🇯🇵

   We study the Sommerfeld enhancement of the annihilation cross section of dark matter into heavier unstable particles. In this process, the annihilation products become non-relativistic near the kinematical threshold. If they experience long-range interactions with each other, their wave function is distorted from a plane wave, and the annihilation cross section can be significantly enhanced. When evaluating the Sommerfeld enhancement from the long-range interactions between the annihilation products, the decay of the products needs to be taken into account. We treat this issue by including the decay width in the Schrödinger equations of the two-body wave function of the annihilation products. We find that bound states of the annihilation products with a narrow decay width enhance the annihilation cross section through a resonant effect. At the same time, this formulation automatically includes the annihilation process with off-shell final state particles, which is relevant for a wide decay width. We show that the resonant effect significantly affects the prediction of the dark matter relic abundance.

   hep-phastro-ph.CO1 citation
9. 09*

   Weinberg Angle, Neutron Abundance in BBN, and Lifetime

   Cheng Tao Yang🇺🇸 · Johann Rafelski🇺🇸

   We present state of the art kinetic theory determination of the neutron abundance available for the Big-Bang nucleosynthesis (BBN). Our work is motivated by the study of the neutron lifespan measured in the laboratory and the unknown strength of weak interactions coupling constant $G_{\mathrm{F}}$ at finite temperature in the primordial Universe. We draw attention to the relevant dependence of $G_{\mathrm{F}}$ on the symmetry breaking Weinberg angle $s_{\mathrm{W}}^2$, a free parameter in the standard model of particle physics. We establish how the value of $s_{\mathrm{W}}^2$ by way of $G_{\mathrm{F}}$ modification influences neutron abundance available for BBN and neutron lifetime.

   hep-phastro-ph.COnucl-thParticles(2026)·0 citations
10. 10*

    Radiative decays of hadronic molecules: From confusion to inspiration

    Feng-Kun Guo🇨🇳 · Christoph Hanhart🇩🇪 · Alexey Nefediev🇩🇪

    Radiative decays of hadronic states provide an essential source of information that can facilitate deciphering their nature and properties. However, a lot of confusion concerning radiative decays of hadronic molecules and their interpretation can be found in the literature. In this paper, we briefly review several types of such decays and pinpoint similarities and essential differences between them. In particular, we emphasise the crucial role played by the hierarchy of the scales relevant to the studied system and the resulting necessity of employing an approach that considers them appropriately. We illustrate the situation with several instructive examples.

    hep-phhep-exParticles(2026)·2 citations
11. 11*

    Electroweak Higgs boson pair production: Updated inclusive cross sections

    Ramona Gröber🇮🇹 · Alexander Karlberg🇨🇭 · Mathieu Pellen🇩🇪 · Gioia Sacchi🇮🇹 · Michael Spira🇨🇭

    We present updated inclusive cross sections for electroweak Higgs boson pair production for energies of relevance to the LHC and High-Luminosity phase of the LHC. The cross sections are presented at N${}^3$LO QCD+NLO EW for vector-boson fusion and NNLO QCD for associate production with a vector boson. We compute the cross sections using the most up-to-date theory inputs, both in the Standard Model and for a few anomalous values of the trilinear Higgs self-coupling.

    hep-phhep-exSciPost Phys.Comm.Rep.(2026)·1 citation
12. 12*

    Triply polarized $WWW$ at the LHC: first glimpse at LO

    Van Cuong Le🇻🇳 · Duc Ninh Le🇻🇳 · Thi Nhung Dao🇻🇳

    We present first results for triply polarized $WWW$ events at the LHC. The calculation is performed at leading order for fully leptonic decays using the Standard Model (SM). Employing an inclusive kinematic cut setup, we found that the triply-transverse polarization fraction is about $51\%$, while the triply-longitudinal (LLL) fraction is smallest with $1.4\%$ for the $W^{-}{W}^{+}{W}^{+}$ process. The interference between different polarization amplitudes amounts to $+1.8\%$. Results for the $W^{+}{W}^{-}{W}^{-}$ case are similar. On the technical side, a new general on-shell mapping for multi-resonance processes, being a crucial element of polarized cross-section calculation, is also presented. Finally, comparisons with the results of MoCaNLO and Sherpa are provided, showing good agreements.

    hep-phhep-exEPJC(2026)·2 citations
13. 13*

    Scattering and Femtoscopic Correlation Functions of the ${\Sigma }_c^{++}{\pi }^{+}$, ${\Sigma }_c^0{\pi }^{-}$ and ${\Sigma }_b^{+}{\pi }^{+}$ Systems

    Mikel F. Barbat🇪🇸 · Juan Nieves🇪🇸 · Laura Tolos🇪🇸

    We present predictions for scattering observables and femtoscopic correlation functions (CFs) of the $I=2$ ${\Sigma }_c^{++}{\pi }^{+}$, ${\Sigma }_c^0{\pi }^{-}$ systems and its heavy-flavor counterpart ${\Sigma }_b^{+}{\pi }^{+}$. In both heavy-quark sectors, the strong interaction is formulated within two distinct theoretical frameworks, each constrained to reproduce the lowest-lying odd-parity isoscalar spin-$1/2$ resonances, ${\Lambda }_c(2595)$ and ${\Lambda }_b(5912)$, respectively. While the ${\Sigma }_c^0{\pi }^{-}$ pair is governed solely by the strong interaction, electrostatic contributions are included in the other two channels involving charged particles through relativistic Coulomb wave functions. We show that the differences observed in the scattering observables between the two strong-interaction models arise mainly from the specific ultraviolet regularization schemes employed. The inclusion of Coulomb effects induces only a very small increase in both the scattering length and the effective range. The resulting CFs in the charm and bottom sectors display analogous global features, in agreement with expectations from heavy-quark flavor symmetry. Both, the ${\Sigma }_c^{++}{\pi }^{+}$ and ${\Sigma }_b^{+}{\pi }^{+}$ CFs, when computed including only the strong interaction, exhibits substantial discriminating power among the different models. However, once Coulomb effects are incorporated, the CFs become largely affected by the repulsive electrostatic interaction, which diminishes their sensitivity to the details of the underlying strong dynamics, thereby reducing the capability to differentiate between theoretical descriptions. Thus, the ${\Sigma }_c^0{\pi }^{-}$ CF-being free from Coulomb effects-provides the most suitable observable for constraining the strong dynamics of the isotensor ${\Sigma }_c\pi$ system.

    hep-phnucl-thPLB(2026)·2 citations
14. 14*

    Magnetic monopoles and high frequency gravitational waves from quasi-stable strings

    Rinku Maji🇰🇷 · Qaisar Shafi🇺🇸

    The spontaneous breaking of $SO(10)$ via flipped $SU(5)$ to the Standard Model yields a novel scenario in which the superheavy topologically stable GUT monopole carrying a single unit ($2\pi /e$) of Dirac magnetic charge emerges from the merger of a confined but topologically distinct monopole-antimonopole pair that are pulled together by a string. The $SO(10)$ breaking via the subgroup $SU(4{)}_c\times SU(2{)}_L\times SU(2{)}_R$, following a similar reasoning, produces a topologically stable monopole that carries two units ($4\pi /e$) of Dirac charge. We explore the cosmological consequences of this scenario by assuming that the monopoles and strings experience a limited number of inflationary $e$-foldings, before re-entering the horizon and ultimately forming a network of quasi-stable strings bounded by monopole-antimonopole pairs. We identify regions of the parameter space that yield an observable number density of the GUT monopole from the collapse of the appropriate string segments. The gravitational waves emitted by these quasi-stable cosmic strings lie in the Hz to kHz range, which can be tested in a number of proposed and ongoing experiments.

    hep-phastro-ph.COhep-thPRD(2026)·5 citations
15. 15*

    A new methodology for direct detection of heavy dark matter at intense particle beam facilities

    A. Acar🇬🇧 · M. Bashkanov🇬🇧 · D.P. Watts🇬🇧

    We propose new concepts for experiments in which intense high energy photon or muon beams are employed parasitically to detect scattering by cosmic heavy weakly interacting dark matter (DM) particles. We show that the scattering cross-sections are sizeable enough to potentially observe beam scattering on heavy dark matter particles at high beam intensities for typically inferred near-Earth DM densities of ${\rho }_{\chi }\sim 0.3GeV/c{m}^3$. The predicted effect is particularly large in the case of a proposed muon collider Higgs factory, especially in the heavy (and poorly constrained) DM scenarios of WIMPZilla's. Current photon facilities such as at Jefferson Laboratory are predicted to require intensity and energy upgrades to reach detectable rates.

    hep-ph0 citations
16. 16*

    Momentum-projected hadron entanglement from lattice-QCD replica correlators

    Kiminad A. Mamo🇺🇸

    We define a finite-volume lattice-QCD density-matrix observable for the vacuum-subtracted spatial R'enyi response of a source-sink-prepared, momentum-projected hadron. At fixed regulator, integer R'enyi index $n>1$, spatial region $B_R$, spin projection, gauge-theory cut prescription $\mathcal{C}$, and after the usual double-sided source-sink projection, the central result is an exact source-sink replica identity: the response is obtained from the logarithm of a replicated hadron correlator on the cut geometry normalized by the corresponding power of the ordinary one-sheet correlator. This identity makes the natural first numerical target the two-sheet $n=2$ measurement of the replicated source-sink correlator ratio, together with a finite-volume test of whether the response scales as $L^{-3}$ at fixed physical $R$. The exponent is a lattice output to be tested, not an input theorem for the nonlinear R'enyi functional. The construction is prescription-defined in gauge theory, and full QCD requires the replicated sea-quark determinant and valence contractions on the replicated cut graph; quenched and partially quenched calculations are therefore pilots. Large-$N_c$ two-dimensional QCD provides an interacting benchmark in which the matched one-meson response is suppressed by the inverse spatial volume, with the short-interval coefficient controlled by light-front PDF moments.

    hep-phhep-lathep-thnucl-th2 citations
17. 17*

    Heavy-quark box-loop corrections to $q\bar{q}\to Z\gamma$ at two loops in QCD

    Dario Kermanschah🇨🇭 · Matilde Vicini🇨🇭

    We numerically compute the two-loop QCD corrections to $Z\gamma$ production at the LHC mediated by light- and heavy-quark box loops. The calculation employs the pipeline of refs. arXiv:2407.18051 and arXiv:2510.18801, which performs Monte Carlo integration over spatial loop momenta after local subtraction of infrared, ultraviolet, and threshold singularities. We validate our results for partonic squared matrix elements with massless-quark loops against known benchmarks, extend them to include heavy-quark contributions, and compute the double-virtual corrections to $pp\to Z\gamma$ by performing the loop and phase space integrations simultaneously. This computation demonstrates the flexibility of the approach in handling both massless and massive final-state bosons, as well as additional mass scales in the loop.

    hep-ph1 citation
18. 18*

    Axial triangles in $q\bar{q}\to Z\gamma$ at two loops in QCD directly in four dimensions

    Dario Kermanschah🇨🇭 · Matilde Vicini

    We numerically evaluate the two-loop QCD squared matrix element for in $q\bar{q}\to Z$ and $q\bar{q}\to Z\gamma$ with heavy top and bottom quarks circulating in a triangular fermion loop, by simultaneously subtracting infrared, ultraviolet, and threshold singularities directly in loop momentum space. This computation serves as an explicit demonstration that axial couplings can be included in the final state within the framework of arXiv:2510.18801. By formulating the entire calculation in four spacetime dimensions, with anomaly cancellation realised locally in loop momentum space, we bypass the complications associated with treating ${\gamma }^5$ in dimensional regularisation.

    hep-ph1 citation
19. 19*

    Unitarity and Unitarization

    Alexandre Salas-Bernárdez🇪🇸

    This article reviews unitarization methods essential for extending Effective Field Theories (EFTs) beyond their perturbative limits, particularly in hadronic and electroweak (EW) sectors. Perturbative EFTs, like Chiral Perturbation Theory (ChPT), often violate unitarity bounds at higher energies, a breakdown observed in phenomena such as $\pi \pi$ scattering resonances. To overcome this, non-perturbative techniques including the Inverse Amplitude Method (IAM), $K$-matrix formalism, and N/D approach are detailed. The IAM and the N/D methods resum perturbative series while preserving fundamental $S$-matrix principles: unitarity, analyticity, and causality, dynamically generating resonant behavior. The article emphasizes the unique role of dispersive frameworks, especially the Roy equations, which rigorously incorporate analyticity and crossing symmetry. It highlights their potential for future application in the electroweak sector, offering a powerful tool to constrain the Standard Model and interpret collider data.

    hep-phEur.Phys.J.ST(2026)·3 citations
20. 20*

    Higgs Boson Production in Association with a Single Top Quark as a Probe of the Top Yukawa Coupling

    Tetiana Obikhod🇺🇦 · Ievgenii Petrenko🇺🇦

    This paper provides a detailed analysis of the associated production of the Higgs boson with a single top quark ($tH$) in proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$ and $14\mathrm{TeV}$. Based on the ATLAS search, we have employed innovative modeling approaches to improve the sensitivity to new physics and improve Standard Model constraints. The major goals are to optimize the data selection, statistical error estimation, determination of physical limits on the top quark Yukawa coupling (${\kappa }_t$), and future experimental projections for HL-LHC. Simulations with MadGraph5aMC@NLO at LO+MLM give cross-sections of ${\sigma }_{tHq}$ and ${\sigma }_{tWh}$ in SM, scaled by K-factors to simulate NLO accuracy. For inverted ${\kappa }_t=-1$ (ITC), positive enhancements are seen, consistent with constructive interference. Kinematic distributions ($H_T$, $p_T(h)$, $\eta [j]$, $\Delta R[t,h]$) are checked against ATLAS expectations, confirming the optimized approach to maximize signal extraction and suppress systematics.

    hep-phProb.Atomic Sci.Technol. (2026) 3(163), 9…·0 citations
21. 21*

    Unitarity bounds and sum rules in the SMEFT

    Luigi C. Bresciani🇮🇹 · Paride Paradisi🇮🇹 · Andrea Sainaghi🇮🇹

    We present a comprehensive reassessment of perturbative unitarity bounds in the dimension-six Standard Model Effective Field Theory, exploiting a new formalism based on spinor-helicity techniques to derive partial-wave unitarity bounds for generic $N\to M$ scattering amplitudes. We find that, in several cases, these theoretical constraints are already competitive with, or even stronger than, the corresponding experimental bounds for energy scales above a few TeV. This is especially the case for four-fermion operators under realistic flavor assumptions, where unitarity bounds can be further strengthened by exploiting sum rules.

    hep-ph4 citations
22. 22*

    The COSMIC WISPers White Paper: The physics case for Weakly Interacting Slim Particles

    Ariel Arza🇨🇳 · Deniz Aybas🇹🇷 · Shyam Balaji🇬🇧 · Reuven Balkin🇺🇸 · Kai Bartnick🇩🇪 · Charles F. A. Baynham🇬🇧 · Itay M. Bloch🇨🇭 · Claudio Bonati🇮🇹 · Dmitry Budker🇩🇪 · Clare Burrage🇬🇧 · Malte Buschmann🇳🇱 · Francesca Calore🇫🇷 and 115 other authors

    Axions and other very weakly interacting slim particles (WISPs), with masses below 1 GeV, arise naturally in many extensions of the Standard Model of particle physics. In particular, they could offer a new framework to explain the nature of dark matter and may help address a range of puzzling observations in astrophysics and particle physics. This review provides an overview of ongoing WISP searches and outlines the prospects for the next decade, spanning their theoretical motivation, indirect signatures in astrophysical observations, and dedicated laboratory experiments. It is based on the work carried on by the EU-funded COST Action ``Cosmic WISPers in the Dark Universe: Theory, astrophysics, and experiments'' (CA21106, https://www.cost.eu/actions/CA21106). This network plays a key role in coordinating and supporting WISP searches across Europe, while also contributing to the development of a roadmap aimed at securing European leadership in this research area. It is emphasized that Europe is currently pursuing a rich, diverse, and cost-effective experimental program, with the potential to deliver one or more transformative discoveries.

    hep-phastro-ph.HEhep-exhep-th41 citations
23. 23*

    Complementarity between atmospheric and super-beam neutrinos at ESSnuSB

    ESSnuSB: J. Aguilar🇪🇸 · M. Anastasopoulos🇸🇪 · D. Barčot🇭🇷 · E. Baussan🇫🇷 · A. K. Bhattacharyya🇸🇪 · A. Bignami🇸🇪 · M. Blennow🇸🇪 · M. Bogomilov🇧🇬 · B. Bolling🇸🇪 · E. Bouquerel🇫🇷 · F. Bramati🇮🇹 · A. Branca🇮🇹 and 81 other authors

    The ESSnuSB experiment aims to measure the leptonic CP phase ${\delta }_{CP}$ with an unprecedented resolution by probing neutrino oscillations at the second oscillation maximum. In the present work, the complementarity between the long-baseline neutrino program and atmospheric neutrinos is investigated for ESSnuSB. By simulating atmospheric neutrino events equivalent of 5.4 Mt$\cdot$year exposure, the resolution for ${\delta }_{\mathrm{CP}}^{}$ is found to improve from $7.5^{\circ }$ ($6.7^{\circ }$) to $7.1^{\circ }$ ($6.5^{\circ }$) at $1\sigma$~CL for ${\delta }_{\mathrm{CP}}^{}=-90^{\circ }$ ($+90^{\circ }$) with respect to super-beam neutrinos, resolving also the degeneracies arising from neutrino mass ordering. These findings highlight the synergies that exist between super-beam neutrinos and atmospheric neutrinos in ESSnuSB.

    ↳ hep-exhep-ph1 citation
24. 24*

    Emergent Gribov horizon kernel from replica symmetry breaking in Yang--Mills theories

    Rodrigo Carmo Terin🇪🇸

    We show that, in the replica-broken sector of the Serreau--Tissier (ST) gauge fixing, the expansion of the replica determinant in the regulator $\zeta$ induces a nonlocal bilinear gluonic kernel with the same color and Lorentz structure as the quadratic part of the BRST-invariant Gribov horizon functional. This establishes an effective leading-order correspondence with the refined Gribov-Zwanziger (RGZ) horizon sector, rather than a reconstruction of the full nonlinear functional $H(A^h)$. The induced scale satisfies ${\gamma }_{\mathrm{ind}}^4\propto \zeta$ at leading order, up to scheme-dependent normalization and higher-order corrections. Depending on the replica phase, the ST sector yields either a local Curci--Ferrari (CF) screening mass or an induced RGZ-type horizon kernel, avoiding double counting of infrared scales.

    ↳ hep-thhep-lathep-phnucl-thEPJC(2026)·2 citations
25. 25*

    Effects of isovector spin-orbit interaction on the charge-weak form factor difference in ${}^{48}$Ca, ${}^{208}$Pb, ${}^{90}$Zr and ${}^{62}$Ni

    Tong-Gang Yue🇨🇳 · Zhen Zhang🇨🇳 · Lie-Wen Chen🇨🇳

    The nucleon spin-orbit interaction is a cornerstone of nuclear structure theory, yet its isospin dependence remains insufficiently constrained within modern nuclear energy density functional (EDF) theory. It was recently shown that, within the framework of extended Skyrme EDFs, the charge-weak form factor difference $\Delta F_{\mathrm{CW}}$ in ${}^{48}$Ca exhibits remarkable sensitivity to the effective isovector spin-orbit (IVSO) interaction, whereas $\Delta F_{\mathrm{CW}}$ in ${}^{208}$Pb is much less sensitive to this channel. Extending this analysis to other nuclei, we find that ${}^{90}$Zr, with its ten spin-orbit unpaired $1{\mathrm{g}}_{9/2}$ neutrons, displays a $\Delta F_{\mathrm{CW}}$ sensitivity to the IVSO strength similar to that of ${}^{48}$Ca, arising from modifications to the central mean-field potential rather than the one-body spin-orbit potential. In contrast, ${}^{62}$Ni, like ${}^{208}$Pb, remains largely insensitive to the IVSO interaction. This structure-driven distinction suggests an experimental strategy: future parity-violating electron scattering measurements, e.g., the MREX experiment at the MESA facility, on ${}^{48}$Ca and ${}^{90}$Zr would help constrain the effective IVSO strength, while measurements on ${}^{208}$Pb and ${}^{62}$Ni can provide a cleaner probe of the density dependence of the symmetry energy with reduced IVSO sensitivity.

    ↳ nucl-thastro-ph.HEhep-phnucl-exParticles(2026)·0 citations
26. 26*

    From Reachability to Learnability: Geometric Design Principles for Quantum Neural Networks

    Vishal S. Ngairangbam🇬🇧 · Michael Spannowsky🇬🇧

    Classical deep networks are effective because depth enables adaptive geometric deformation of data representations. In quantum neural networks (QNNs), however, depth or state reachability alone does not guarantee this feature-learning capability. We study this question in the pure-state setting by viewing encoded data as an embedded manifold in $\mathbb{C}{P}^{2^n-1}$ and analysing infinitesimal unitary actions through Lie-algebra directions. We introduce Classical-to-Lie-algebra (CLA) maps and the criterion of almost Complete Local Selectivity (aCLS), which combines directional completeness with data-dependent local selectivity. Within this framework, we show that data-independent trainable unitaries are complete but non-selective, i.e. learnable rigid reorientations, whereas pure data encodings are selective but non-tunable, i.e. fixed deformations. Hence, geometric flexibility requires a non-trivial joint dependence on data and trainable weights. We further show that accessing high-dimensional deformations of many-qubit state manifolds requires parametrised entangling directions; fixed entanglers such as CNOT alone do not provide adaptive geometric control. Numerical examples validate that aCLS-satisfying data re-uploading models outperform non-tunable schemes while requiring only a quarter of the gate operations. Thus, the resulting picture reframes QNN design from state reachability to controllable geometry of hidden quantum representations.

    ↳ quant-phcs.LGhep-exhep-ph+10 citations
27. 27*

    An update on the HVP contribution to $g_{\mu }-2$ in isoQCD from ETMC

    Simone Bacchio🇨🇾 · Alessandro De Santis🇩🇪 · Antonio Evangelista🇨🇾 · Roberto Frezzotti🇮🇹 · Giuseppe Gagliardi🇮🇹 · Marco Garofalo · Lorenzo Maio🇮🇹 · Francesca Margari🇮🇹 · Ferenc Pittler🇨🇾 · Simone Romiti🇨🇭

    We present an update on the determination of the leading-order hadronic vacuum polarisation contribution to the muon anomalous magnetic moment in isospin-symmetric QCD by the Extended Twisted Mass Collaboration. The calculation is based on five $N_f=2+1+1$ gauge ensembles generated with Wilson-clover twisted-mass quarks at maximal-twist and near-physical pion masses, spanning four lattice spacings and two volumes. For the dominant quark-connected contributions, we employ two distinct valence-quark regularisations and present results for both the isovector and isoscalar components.

    ↳ hep-lathep-phPoS(2026)·2 citations
28. 28*

    Testing gravitational wave polarizations with LISA

    Shingo Akama🇵🇱 · Maxence Corman🇩🇪 · Paola C. M. Delgado🇨🇿 · Alice Garoffolo🇺🇸 · Macarena Lagos🇨🇱 · Alberto Mangiagli🇩🇪 · Sylvain Marsat🇫🇷 · Manuel Piarulli🇫🇷 · Gianmassimo Tasinato🇬🇧 · Jann Zosso🇩🇰 · Giuseppe Gaetano Luciano🇪🇸 · Nils A. Nilsson🇰🇷 and 7 other authors

    In this paper we quantify the ability of the Laser Interferometer Space Antenna (LISA) to test the presence of non-tensorial polarizations as well as modifications to the tensor ones in gravitational waves emitted from massive black hole binaries. We employ the Parametrized Post-Einsteinian (PPE) formalism to model deviations from General Relativity (GR) for tensor, vector, and scalar polarizations. Our PPE parametrization is inspired by post-Newtonian waveforms from four modified gravity theories: Horndeski, Einstein-aether, Rosen's bimetric, and Lightman-Lee. We consistently implement these modifications across the inspiral, merger, and ringdown phases, ensuring proper waveform alignment and tapering. Subsequently, we perform Fisher forecasts to derive expected constraints on deviations from General Relativity and map these constraints to the parameter spaces of the four gravity theories. For tensor polarizations, LISA achieves constraints on amplitude modifications ranging between $\sim 10^{-4}-10^{-2}$ precision level, depending on the frequency evolution of the modifications, for systems with $10^5-10^7{\mathrm{M}}_{\odot }$ at $z=1$. We find that LISA can distinguish breathing and longitudinal scalar polarizations only for relatively light binaries with $M\lesssim 10^4{\mathrm{M}}_{\odot }$, beyond which these modes become degenerate in the detector response. Importantly, constraints on vector polarizations are approximately 2-3 times more precise than for scalar polarizations. For both vector and scalar modes, amplitude measurements reach precisions ranging between $\sim 10^{-8}-10^{-2}$, depending on the frequency evolution of the modifications, for systems with $10^5-10^7{\mathrm{M}}_{\odot }$ at $z=1$. These results demonstrate LISA's potential to probe gravity in the strong-field regime via gravitational wave polarizations.

    ↳ astro-ph.COgr-qchep-phJCAP(2026)·5 citations
29. 29*

    The multiloop sunset to all orders

    Pierre Vanhove🇫🇷

    We derive exact, convergent representations of multiloop sunset Feynman integrals in two dimensions for arbitrary mass configurations and all loop orders valid for large Euclidean momentum. The integrals are expressed as sums of symmetric polynomials in logarithmic mass ratios, normalized by the external momentum squared, with coefficients determined by analytic series expansions. For the equal-mass case, we establish a dimension-lowering relation expressing the $L$ loop sunset integrals in $D+2$ as the one in $D$ dimensions acted on a differential operator of order $L-1$. These representations are free of complicated transcendental functions, making them well-suited to both formal analysis and high-precision numerical evaluation. The two-dimensional results serve as boundary conditions for dimension-shifting relations, enabling systematic reconstruction of four-dimensional sunset integrals via analytic continuation to $D=4-2ϵ$.

    ↳ hep-thhep-phmath-phmath.MP2 citations
30. 30*

    Probing Axions with Relativistic Jet Polarimetry

    Dashon Michel Jones · Richard Anantua🇺🇸 · Razieh Emami · Nate Lujan

    The prospect of identifying axion signals due to axion-photon coupling induced changes to the polarization has now become a reality in view of near-horizon polarimetric observations by the Event Horizon Telescope (EHT). Axion-like particles (ALPs), motivated as dark matter candidates by the strong CP problem, induce frequency-independent birefringence in linearly polarized radiation, producing observable rotations of the electric vector position angle. While previous studies have focused exclusively on axion signatures in near-horizon accretion disk emission, the relativistic jet of M87 -- extending from 10 gravitational radii to kiloparsec scales -- remains unexplored as an axion probe despite offering extended path lengths through the putative dark matter distribution. In this study, we investigate the effects of an axion cloud around the jet in M87 on the Stokes maps of relativistic jets using a stationary, axisymmetric, self-similar model for the jet and a coherent, homogeneous soliton core in M87's galactic center for the axion background. At 230 GHz, for representative couplings in range $g_{a\gamma }\sim 5\times 10^{-15}-5\times 10^{-14}Ge{V}^{-1}$, we find that axion masses in the $10^{-21}eV$ range produce degree-level to multi-degree EVPA rotations, in some cases exceeding typical EHT measurement uncertainties, whereas masses in the $10^{-22}eV$ range yield predominantly sub-degree rotations. We identify a suite of morphological diagnostics that together constitute a framework for distinguishing axion-induced birefringence from plasma Faraday rotation in resolved jet polarimetry.

    ↳ astro-ph.HEastro-ph.COgr-qchep-ph1 citation
31. 31*

    Beyond thresholds: reconstructing UV physics from IR expansions

    Hiromasa Takaura🇯🇵 · Wen Yin🇯🇵

    We show that ultraviolet information can be extracted from low-energy expansion coefficients, assuming analyticity and the absence of massless singularities. By reorganizing the low-energy expansion through an inverse Laplace transform and a controlled coarse-graining procedure, we make ultraviolet behavior accessible beyond the cutoff of the effective field theory. In particular, we determine the sign of the beta function and the associated dynamical scale directly from the low-energy expansion of a physical observable below the mass thresholds in QED and QCD-like theories.

    ↳ hep-thhep-ph0 citations
32. 32*

    Neutrino mass limits and decaying dark matter: background evolution versus perturbations

    Thomas Montandon🇫🇷 · Vivian Poulin🇫🇷 · Thomas Rink🇩🇪 · Thomas Schwetz🇩🇪

    We revisit cosmological neutrino mass bounds when a fraction of dark matter is allowed to decay to massless dark radiation. By compensating the late-time increase in the matter density induced by neutrinos becoming non-relativistic, decaying dark matter (DDM) can render datasets solely sensitive to the background density effectively insensitive to neutrino masses. Using data from baryonic acoustic oscillations (BAO) and Type Ia supernovae together with a distance prior from the cosmic microwave background (CMB), we find that neutrino masses as large as $\mathcal{O}(1\mathrm{eV})$ are allowed without degrading the fit. Moreover, the combination of BAO data with the CMB distance prior yields a preference for a non-zero DDM fraction, and alleviates the need for dynamical dark energy with phantom crossing. However, the degeneracy introduced by DDM is decisively broken once perturbation observables are included. Incorporating the full $\text{Planck}$ CMB likelihood, and in particular CMB lensing, restores strong constraints on the neutrino mass in the DDM scenario, $\sum m_{\nu }\lesssim 0.079\mathrm{eV}$. In contrast, neutrino mass constraints in a smooth dark energy model described by the Chevallier-Polarski-Linder parametrization become merely $\sim 25\%$ stronger compared to background-only analyses. Our results highlight the essential role of structure-growth measurements in assessing extensions of the dark sector and to obtain robust cosmological neutrino mass bounds.

    ↳ astro-ph.COhep-phJCAP(2026)·4 citations
33. 33*

    The effects of non Bunch-Davies initial conditions on gravitationally produced relics

    Enrico Bertuzzo🇮🇹 · Gabriel M. Salla🇧🇷 · Andrea Tesi🇮🇹

    Typical gravitational production of relics from amplification of inflationary perturbations assumes Bunch-Davies initial conditions, i.e. a vacuum with initially no particles. In this paper we investigate the impact of non Bunch-Davies initial conditions to the final abundance of relics, with particular attention to the parameter space where the total dark matter abundance is reproduced. We present a general framework for any initial condition, through which we show their non-trivial effect on both spectrum and late-time abundance. We argue that for particles whose source of conformal symmetry breaking comes only from a mass term (spin-1/2 fermions and conformally coupled scalars), the choice of initial conditions has little impact on the mass range relevant to dark matter. For other particles, e.g. the longitudinal mode of spin-1, we see a large deviation from the standard computation. We exemplify and quantify our results with an initial thermal state and a two-stage inflation scenario, highlighting that the total dark matter can be obtained for a wide range of masses.

    ↳ gr-qcastro-ph.HEhep-phPRD(2026)·2 citations
34. 34*

    Parameter estimation of eccentric massive black hole binaries with LISA and its cosmological implications

    Jia-Hao Zhong🇨🇳 · Jin-Zhao Yang🇨🇳 · Tao Yang🇨🇳 · Xu-Heng Ding🇨🇳 · Xi-Long Fan🇨🇳 · Kai Liao🇨🇳 · Bei You🇨🇳

    Future space-based gravitational wave (GW) observatories such as LISA will detect massive black hole binaries (MBHBs), which are expected to be accompanied by electromagnetic counterparts, thereby providing bright standard sirens for cosmology. The orbital eccentricity of MBHBs can significantly improve the parameter estimation of GWs because the multiple harmonics induced by eccentricity provide additional information and help break down the degeneracies among waveform parameters. In this paper, we use the EccentricFD waveform and construct 5-year GW event catalogs for LISA under three population models (popIII, Q3d and Q3nod). For the three models, we find that an initial eccentricity of $e_0=0.4$ at $10^{-4}$ Hz yields improvements in sky localization and distance inference by a factor of $\mathcal{O}(10)$ in the best cases. As a consequence, the average number of bright sirens increases substantially: from 8 to 11 (PopIII), 6 to 12 (Q3d) and 13 to 24 (Q3nod). This increase in event number, together with enhanced localization and distance inference, leads to tighter cosmological constraints. In the $\Lambda$CDM model, for instance, the relative uncertainty on $H_0$ is reduced from $8.17\%$ to $4.35\%$ for the Q3d model, corresponding to an improvement of approximately $47\%$. We also investigate the improvement in constraints on the dark energy equation of state and modified GW propagation when combining bright sirens with the latest cosmic microwave background data. These results demonstrate that eccentricity is a remarkably significant feature in GW detection and parameter estimation, enabling more accurate measurements of the Universe with future space-based observatories.

    ↳ astro-ph.IMastro-ph.COgr-qchep-phPRD(2026)·2 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.