HEP Phenomenology·hep-ph

Mon·Sep 28, 2026Monday·September 28, 2026

17 papers—8 primary·9 cross-listed

01
Metastable Neutron Stars as Transient-Rate Detectors of Heavy Dark Matter
Ziwen Yin · Hong-Yi Zhang
Metastable neutron stars can undergo catastrophic conversion to quark-containing stars when a localized energy deposition nucleates a critical bubble. We show that dark-matter-induced conversions can be constrained by the present transient rate of the neutron star population, rather than by the survival of any individual hadronic star as often assumed in previous literature. Population depletion makes the present transition rate nonmonotonic: weak triggering produces few transitions, whereas sufficiently rapid triggering predominantly converts stars formed in the past. Consequently, transient observations can exclude a finite interval of interaction rates, qualitatively different from conventional one-sided survival bounds. Using the beaming-corrected short gamma ray burst rate as a benchmark, we derive constraints on dark matter annihilation, decay, inelastic particle scattering, and elastic scattering of macroscopic dark matter, including parameter space not covered by existing probes. Transient demographics thus provide a new population level probe of dark sector interactions and the phase structure of ultradense matter.
hep-phastro-ph.COastro-ph.HE
02
Optimizing Cell-Based Negative Weight Mitigation with Optimal Transport
Lauren Hay · Rishabh Jain · Matt LeBlanc · Jennifer Roloff
As the accuracy of experimental results in high energy physics (HEP) increases, so does the demand for precision Monte Carlo (MC) simulation. Higher-accuracy event generation at next-to-leading order (NLO) and beyond brings with it negatively weighted events. These negatively weighted events reduce the statistical power of samples, increasing the number of events that need to be produced and straining already limited computational resources. We present a post-hoc reweighting scheme that employs cell-based resampling using an IRC-safe metric to define the cell radii. An optimal metric embeds kinematically similar events within the same cells, minimizing bias when reweighted. This motivates our exploration of a Optimal Transport (OT) based distance metrics. We compare the performance of the reweighting algorithm with different choices of metric, and explicitly demonstrate the performance on simulated Z+jets events produced at NLO accuracy.
hep-phphysics.data-an
03
Hybrid Partial Dressing: Correct Effective Potentials at All Temperatures
Raphaël Berthiaume · David Curtin · Michael Luke · Andrija Rasovic · Jyotirmoy Roy
We develop Hybrid Partial Dressing (HPD), a simple diagrammatic resummation scheme for finite-temperature effective potentials in scalar field theory which is valid at all temperatures. HPD improves on earlier resummation schemes such as Daisy Resummation and Partial Dressing by being two-loop exact at all temperatures and free of the overlapping momentum problem. Renormalization group improvement is straightforward to implement. We illustrate the scheme in multi-scalar theories with a spontaneously broken $Z_{2}$ symmetry, and compare it against existing approaches, showing in particular that it reproduces the two-loop Dimensional Reduction (DR) potential exactly in the high-temperature regime where DR applies, while remaining valid at all temperatures. This makes HPD suitable for the general study of strong first order phase transitions beyond the Standard Model, as we demonstrate through gravitational wave predictions from HPD and its RG-improved version, RGHPD.
hep-phastro-ph.CO
04
A Phase-Space Inclusive Figure of Merit Based in Optimal Transport for Validating Monte Carlo Reweightings
Rishabh Jain · Lauren Hay · Matt LeBlanc · Jennifer Roloff
Validating whether the underlying physics of a model has been retained after a full phase-space reweighting poses a unique challenge. Often, validation relies on comparing histograms of 1D observables; however, this can mask correlations and biases in the complete prediction. We present a novel, unbinned approach to comparing the performance of such reweighting schemes based on the "Cross-Section-Mover's Distance", an application of Optimal Transport that quantifies the work required to transform one theoretical prediction into another and enables an interpretation of results in terms of metric spaces. We demonstrate its utility when benchmarking various reweighting schemes that mitigate the effects of negative weights in a Monte Carlo simulation. This approach can be broadly applied in other scenarios where biases in full phase-space reweighting schemes should be studied in an unbinned way.
hep-phphysics.data-an
05
Probing the Validity of EFT Approaches in Higgs + Jet Production at $s = 13$ TeV
Shubham Yadav · Prashant Shukla
The production of a Higgs boson with a jet is one of the most important processes studied at the LHC. It serves as a sensitive probe of high-energy dynamics and provides a powerful testing ground for the Standard Model, while also offering sensitivity to possible new physics effects. In this work, we perform a phenomenological study of Higgs + jet production in proton-proton collisions at 13 TeV center of mass energy, using the MadGraph5_aMC@NLO framework. We compare predictions obtained from the full loop induced Standard Model with those derived within the HEFT and SMEFT frameworks. Taking the Higgs transverse momentum as a probe, we study normalized distributions and ratio spectra to test the effective field theories. Our results show that effective approaches successfully reproduce the Standard Model behavior in the low transverse-momentum region. However, sizable deviations emerge at high pT, signaling the breakdown of the effective approximation. These findings highlight the importance of carefully accounting for kinematic effects when applying EFT-based methods to precision Higgs studies and provide a quantitative estimate of their range of validity.
hep-ph
06
Improving predictions for the $pp \to t t ˉ W^{+}$ process at the LHC with the MINLO method
Nikolaos Dimitrakopoulos
We compare the standard NLO and $MiNLO$ approaches for the full off-shell $pp \to t t ˉ W^{+} + X$ process at the LHC, at both the integrated and differential cross-section levels. Contrary to NLO, in the $MiNLO$ approach, which is now also available within the HELAC-NLO framework, renormalization and factorization scales are dynamically extracted and Sudakov form factors are incorporated. Results are particularly presented for the $pp \to t t ˉ W^{+} j$ process at NLO accuracy in perturbative QCD using two different scale choices. Merged predictions up to two jets to improve the overall modeling of the full off-shell $pp \to t t ˉ W^{+} + X$ process are also discussed.
hep-ph
07
Natural Saturation Of The Sterile Neutrino Dark Matter Resonant Production By a High Lepton Flavor Asymmetry In Primordial Plasma
Dmitry Gorbunov · Dmitry Kalashnikov
Sterile neutrinos remain a well-motivated dark-matter candidate whose cosmological abundance can be enhanced by resonant active--sterile conversion in the presence of a lepton asymmetry in primordial plasma. In the standard picture, a larger initial asymmetry increases the matter potential and can therefore promote resonant production. However, the same increase also shifts the resonance to later stages of the cosmological evolution when the plasma temperature is lower. We show that this delayed production epoch can overlap with the onset of active neutrino oscillations, which redistribute the flavor asymmetries and may substantially reduce, or in some cases nearly erase, the lepton asymmetry needed for a successful resonant sterile-neutrino production. This interplay provides a natural saturation mechanism for the final sterile-neutrino abundance: beyond a certain range of initial asymmetries, increasing the primordial asymmetry no longer leads to a proportional increase in the produced dark-matter density. We identify this effect as an additional constraint on resonant sterile-neutrino production at large lepton asymmetry and discuss its dependence on the flavor structure of the initial asymmetry and on the background cosmological evolution. Our numerical results reveal two order of magnitude range in sterile-active neutrino mixing parameter $sin^{2} (2 θ)$ presently consistent with the resonant mechanism of the dark matter sterile neutrino production. It must be investigated by the next generation X-ray telescopes to fully explore this mechanism and corresponding minimal models suggesting sterile neutrinos as viable dark matter. We also consider pion condensation at large flavor lepton asymmetries, which may lead to a first-order QCD phase transition and associated gravitational-wave production in the early Universe.
hep-phastro-ph.CO
08
Renormalized perturbation theory in an intense background electromagnetic field
Misha A. Lopez-Lopez · Giulio Audagnotto · Antonino Di Piazza
Quantum electrodynamics in strong background electromagnetic fields or strong-field QED (SFQED) has been investigated in great detail at the tree level. The study of SFQED at higher loops has not been carried out in a correspondingly systematic way, with the notable exception of strong background atomic fields. Here, we investigate the renormalization of SFQED by writing the standard unrenormalized SFQED Lagrangian density, which differs from the vacuum-QED Lagrangian density by the additional interaction term of the Dirac four-current density with the background four-vector potential, in terms of renormalized quantities and counterterms. Within this framework, we confirm the necessity of renormalizing the background field as an electric charge rather than as a photon field. We compare this approach with an alternative one which features a different renormalized Lagrangian density and we show that they are physically equivalent. As a byproduct, it will become clear that the renormalizability of SFQED directly derives from the renormalizability of vacuum QED. Also, we obtain that the renormalized SFQED Lagrangian density features a new counterterm as compared to the vacuum Lagrangian density. This counterterm is necessary to renormalize the electron self energy, which undergoes a new contribution as compared to vacuum QED, physically due to the electromagnetic field produced by the four-current density induced in the vacuum by the background electromagnetic field. The vacuum-induced electromagnetic field diverges and needs to be renormalized. We show how the renormalization of the vacuum-induced electromagnetic field is implemented explicitly at one loop and at two loops. The renormalization at all loops is shown to be more easily deduced at the level of the Lagrangian density. Finally, some subtleties concerning the renormalization procedure in the case of a free background field.
hep-ph
09
MAGGIE: A Magnetic Gravitational Wave Induction Experiment
Jasper Jödicke · Marios Maroudas · Toma-Stefan Cezar · Dieter Horns
Gravitational waves (GWs) can induce effective electromagnetic currents when interacting with external electric and magnetic fields, as described by linearized gravity modifications to Maxwell's equations. This coupling enables a novel detection approach for high-frequency gravitational waves (HFGWs) using axion haloscope experiments. Here we present the MAGnetic Gravitational wave Induction Experiment (MAGGIE), the first lumped-element HFGW detector proposed in Europe, designed to probe HFGWs in the kHz-MHz regime by leveraging a 14 T solenoidal magnet at the University of Hamburg. The GW-induced magnetic flux is captured by a custom-designed pickup loop optimized for the expected symmetry of the effective current. A figure-8-shaped geometry, oriented to break the azimuthal symmetry, is implemented, together with a blind-loop configuration, for real-time noise rejection and calibration. The readout scheme is tailored for continuous signals and time-domain transient searches, using waveform templates for primordial black hole (PBH) mergers. The expected experimental reach in terms of strain spectral noise density at the 40 MHz high-frequency end is projected to reach $\sim 4 \times 1 0^{- 16} / Hz$ for transient searches, and in terms of strain, projected to reach $\sim 1 0^{- 19}$ for 1 year of continuous search. This allows MAGGIE to constrain currently unexplored regions of the HFGW parameter space.
↳ gr-qcastro-ph.IMhep-exhep-ph
10
Physics-Informed Neural Networks for Static Black-Hole Exterior Metrics: Charge and Cosmological-Constant Sweeps
Huan Jin · Fei Wu · Fei Xue
We apply physics-informed neural networks (PINNs) to recover the time-time component of static, spherically symmetric black-hole exterior metrics from a reduced ordinary differential equation (ODE). Inspired by recent work on solving Einstein field equations with deep learning~\cite{Li2023}, we encode the vacuum/charged exterior through a residual loss and an asymptotic boundary constraint---not by embedding analytic metric terms such as $2 M / r$ directly into the network output. Unlike the distributed PINN (DPINN) strategy of Ref.~\cite{Li2023}, which partitions the radial domain into subdomains with separate networks, we employ a \emph{unified} fully connected network over the entire interval $[r_{m i n}, r_{m a x}]$ , avoiding spurious jumps at subdomain interfaces. Moreover, whereas Ref.~\cite{Li2023} restricts training to $r \in (10, 300)$ ---well outside the steep $1/ r$ and $1/ r^{2}$ curvature of the inner exterior---we begin at $r_{m i n} = 1 0^{- 2} M$ , spanning three decades in radius and covering the strongly varying region that DPINNs sidestep by domain truncation. Holding the mass fixed at $M = 1$ , we sweep electric charge $Q \in {0, 0.5, 1.0, 1.1}$ at $Λ = 0$ and sweep $Λ \in {0, 0.1, - 0.1}$ at $Q = 0.5$ . All configurations achieve relative $L_{2}$ errors below $6%$ against the analytic reference. For the representative case $Q = 0.5$ , $Λ = 0.1$ , three independent trainings with fixed seeds yield relative errors of $3.89%$ , $1.08%$ , and $2.76%$ (mean $2.58%$ , standard deviation $1.41%$ ), demonstrating robustness of the mesh-free approach without labeled field data.
↳ gr-qchep-phphysics.comp-ph
11
Tracing out massive fields in cosmology
Guanhao Sun · Sam S.C. Wong
Cosmological correlators are calculated through the in-in formalism in (quasi-)de Sitter background. Its effective description is best represented by a reduced density matrix. In this work, we study how integrating out a massive field in de Sitter space determines the reduced density matrix of a light field at a finite observation time. Starting from a quasi-single-field model with non-linear couplings, we first evaluate the massive field wavefunctional at fixed final value and then trace over this value. The trace generates branch-mixing terms which are generally present in the Schwinger--Keldysh description. For a conformally coupled massive field, we show explicitly that the light field bispectrum from the effective description agrees with a full theory calculation. This example also shows that decay of a field at the future boundary does not by itself justify discarding its contribution to the trace. We discuss the differences between an exact nonlocal effective description and the local effective field theory obtained through a large mass expansion. We then identify which local cubic terms affect the late-time probability and which contribute only a wavefunctional phase. Finally, we organize the resulting kernels by response, noise, and Schwinger--Keldysh consistency conditions, and discuss the symmetry constraints on the reduced density matrix.
↳ hep-thastro-ph.COhep-ph
12
Point-cloud generative models for fast calorimeter simulation across particles and geometries
Thorsten Buss · Henry Day-Hall · Frank Gaede · Gregor Kasieczka · Katja Krüger · Anatolii Korol · Thomas Madlener · Peter McKeown · Martina Mozzanica · Lorenzo Valente
Detailed Geant4 simulation of calorimeter showers is the largest single computing cost of collider experiments, and the High-Luminosity LHC will need about ten times more simulated events than are currently produced. We summarise recent progress in generative point cloud fast simulation for highly granular calorimeters. CaloClouds3 generates photon (electromagnetic) showers, is geometry-independent, and runs on average about 120x faster than Geant4 on a single CPU. CaloHadronic uses transformer attention to extend the point cloud diffusion approach to pion (hadronic) showers spanning the electromagnetic and hadronic calorimeters. AllShowers unifies twelve particle types in a single model with far fewer parameters than the specialised baselines while matching or exceeding their fidelity. We close with cross-geometry transfer learning, which needs two to three orders of magnitude fewer training showers while preserving the generative performance.
↳ physics.ins-dethep-exhep-ph
13
Parnassus for the CLD Detector: A Generative Machine-Learning Surrogate for Detector Simulation and Reconstruction at the FCC-ee
Umar Sohail Qureshi · Benjamin Nachman · Caterina Vernieri
Detector simulation and event reconstruction will be computationally expensive for future $e^{+} e^{-}$ collider programs and are currently critical bottlenecks for accurate feasibility studies. To address this challenge, we build a Parnassus model for the CLD detector concept. Parnassus is a framework for automatically tuning a surrogate model, in our case, a conditional flow matching neural network, to emulate a full detector simulation and reconstruction. We train on $e^{+} e^{-} \to Z \to q q ˉ$ events at $s = 91.2$ GeV processed through a Geant4 simulation of the CLD detector concept and the Pandora particle-flow reconstruction and reproduce single-particle kinematics, particle-IDs, and impact-parameter distributions. We also examine jet- and event-level features, inclusively and split by flavor, and find excellent fidelity, significantly better than the parameterized program Delphes. Furthermore, we train a transformer-based flavor tagger on the reconstructed particle-flow constituents and show that the surrogate preserves the $b / c / s / q$ discrimination of the full CLD reconstruction. The Parnassus CLD model achieves a generation cost of about 1.2 ms (40 ms) per event on a single GPU (CPU), over three (two) orders of magnitude faster than full simulation and reconstruction. Our model is publicly available for feasibility and design studies.
↳ physics.ins-dethep-exhep-phphysics.data-an
14
Set Transformer inference of the neutron star equation of state from stellar observations
Márcio Ferreira · Valéria Carvalho · Michał Bejger · Constança Providência
We develop a permutation-invariant Set Transformer to reconstruct the equation of state (EoS) of dense matter from variable-size, unordered sets of neutron star (NS) observations. The model takes stellar masses together with radii, tidal deformabilities, or both, and predicts either the pressure $P (n)$ or the sound speed $c_{s}^{2} (n)$ on a fixed density grid, along with density-dependent uncertainties. Nothing in the architecture prescribes which star informs which density: self-attention couples all observations nonlinearly, and each density point reads the full set through its own learnable query, so the star-to-density mapping is learned from the data. Trained on independent piecewise-polytropic and Gaussian-process EoS ensembles, the model provides well-calibrated predictions whose uncertainty increases in density regions that stable stars cannot probe. Reconstruction errors decrease with the number of observations, while tidal deformability generally improves accuracy at a fixed observation count, even when it carries its own measurement noise. Sensitivity analysis reveals a density-local mapping: in the pressure models, predictions at density $n$ depend most strongly on stars whose central densities are near $n$ . We also show that the sensitivity of the model to the inferred stellar compactness provides information on the minimum central density. These results demonstrate that set-based neural inference, in which the star-to-density mapping is learned rather than assumed, can extract physically interpretable EoS information with calibrated uncertainties.
↳ nucl-thastro-ph.HEhep-ph
15
Observational constraints on scalar-vector-tensor dark energy with phantom-divide crossing
Nandan Roy · Shinji Tsujikawa · Ying-li Zhang · Zejun Zhang
We constrain a scalar-vector-tensor (SVT) dark-energy model in which the vector sector drives the dark-energy equation of state below $- 1$ at earlier times, while a canonical scalar field subsequently drives it across $- 1$ toward a present-day value above $- 1$ . We confront the model with DES Year 5 supernovae, DESI DR2 baryon acoustic oscillations, and compressed cosmic microwave background information, and then include Gold-2017 redshift-space-distortion (RSD) measurements to probe structure growth. The background posterior assigns substantial weight to crossing histories and gives a better best fit than the flat $Λ$ -cold-dark-matter ( $Λ$ CDM) model. The RSD analysis preserves this qualitative background evolution, constrains the clustering amplitude, and increases the posterior support for the directional crossing criterion. Since the growth analysis also imposes additional perturbative support conditions, this increase cannot be attributed to the RSD likelihood alone. Matched PolyChord calculations give Bayes factors larger than unity for SVT relative to $Λ$ CDM under both prior-volume conventions considered here. The quantitative Bayes factor depends on the prior normalization assigned to the regular radiation-era branch and is larger in the RSD analysis under either convention. Overall, current expansion and structure-growth data are consistent with a stable dynamical crossing of the phantom divide in the SVT model.
↳ astro-ph.COgr-qchep-phhep-th
16
Thermodynamic geometry as the missing link: toward a unified framework for black hole first-order phase transitions
Shi-Hao Zhang · Jing-Fei Zhang · Xin Zhang
Black hole first-order phase transitions have been described by several seemingly independent frameworks, including local geometry, global topology, complex analysis, and thermodynamic geometry. While the first three have been unified, thermodynamic geometry has remained outside. We prove that the divergence points of the normalized Ruppeiner curvature scalar $R_{N}$ coincide exactly with the solutions of $T^{'} (r_{h}) = 0$ , where $r_{h}$ is the horizon radius. These solutions include extremal points (spinodal points) and stationary inflection points (thermodynamic critical points). Thus, the divergence of $R_{N}$ is a necessary but not sufficient condition for a first-order phase transition. This clarifies the mathematical origin of curvature divergence and why thermodynamic geometry can reliably indicate but not alone confirm phase transitions. Using the local geometric framework as a central framework, we incorporate Ruppeiner geometry into this unified picture; a similar analysis also applies to Weinhold geometry. Consequently, the four frameworks are unified within a single structure based on the local folding of the temperature function. This advances our understanding of the mathematical structure of black hole first-order phase transitions and provides clues for possible extensions to other types of phase transitions.
↳ gr-qchep-phhep-th
17
Suitability studies of exotic muon decay at the High Intensity heavy-ion Accelerator Facility
Lingzhi Dong · Jinning Li · Leyun Gao · Cheng-en Liu · Yu Xu · Xuecheng Zhang · Liangwen Chen · Qite Li · Chen Zhou · Qiang Li · Zhiyu Sun
We present a detailed feasibility study of exotic muon decay searches using the muon beam at the High Intensity heavy-ion Accelerator Facility (HIAF). For the decay channel mu to eX0, where X0 denotes a new boson featuring LFV couplings, the produced electron carries very low energy when the mass of X0 approaches the muon mass, making detection challenging. Nevertheless, the high-energy beam at HIAF can boost these electrons up to a measurable energy range. The detector system proposed here comprises front-end scintillators for particle identification (PID) and a main detector consisting of an RPC stack to track decay products and a scintillator for energy measurement. Leveraging the kinematic properties of low momenta and small emission angles of signal electrons, we employ optimized momentum and angular acceptance cuts on the RPC detector to efficiently suppress background events. With this strategy, we obtain an upper limit of 1e-5 on the branching ratio of the exotic muon decay at 95% confidence level, achieving state-of-the-art sensitivity.
↳ hep-exhep-phphysics.ins-det