HEP Phenomenology·hep-ph

Fri·Sep 11, 2026Friday·September 11, 2026

10 papers—9 primary·1 cross-listed

01
Nonthermal Solar Stalling of an Inelastic Scalar Signal in Xenon
XinXin Qi · Hao Sun
The LUX-ZEPLIN experiment has reported one nuclear-recoil candidate at $248 \kev$ in an extended-energy search. We construct an anomaly-free $U (1)_{B - 3 L_{τ}}$ model in which an $840 \gev$ complex scalar undergoes an endothermic transition with splitting $320 \kev$ . A $160 \mev$ vector with dark charge $Q_{χ} = 1$ gives $0.958$ accepted events in a public LZ-response reconstruction while scalar annihilation yields $Ω h^{2} = 0.1200$ . The physical nucleon ratio $f_{n} / f_{p} = - 0.86985$ suppresses solar iron capture, leaving $C_{⊙} = 1.09 \times 1 0^{19} s^{- 1}$ . We then evolve captured particles in energy, angular momentum, and internal state, including finite collision rates, thermal nuclear velocities, and the excited-state decay. The distribution stalls at an equivalent radius $r_{eff} = 0.194$ -- $0.198 \rsun$ , for which $Γ_{ann} = (1.33$ -- $1.38) \times 1 0^{15} s^{- 1}$ , below a model-specific IceCube public-data proxy by more than three orders of magnitude. The benchmark also lies below the dedicated NA64 $B - L$ limit. Thus solar-neutrino bounds on electroweak inelastic dark matter do not transfer model-independently to light-mediator scalar realizations.
hep-ph
02
Implications of Inelastic Dark Matter for Primordial Dark-Star Evolution: Kinematic Thresholds and Nonthermal Capture
Qinxun Li · Shengyi Liu
The recent 248-keV nuclear recoil candidate reported by LUX-ZEPLIN has renewed interest in endothermic inelastic dark matter, motivating us to examine its capture in primordial dark stars. Relative to the conventional elastic-capture picture in dark star evolution, endothermic capture adds two qualitative features. First, it opens only after the growing star crosses a compactness threshold, expressed as a kinematic radius $R_{kin} \propto μ_{χ} M_{⋆} / δ$ set by the stellar mass, the dark-matter--nucleus reduced mass and the mass splitting. The accreting growth carries the star through the threshold, and the capture rate turns on quadratically above it. Second, although newly captured particles generically begin on nonthermal bound orbits, endothermic kinematics can keep this normally transient population spatially extended, turning it into a persistent reservoir rather than an intermediate step toward a thermal core. Following complete chains of state-changing collisions, we find that the reservoir compacts sharply and then stalls, because a ground state particle below a compactness-dependent orbital energy has no allowed up-scatter anywhere in the star. A percent-level radius contraction reopens the relaxation. These kinematic results do not depend on whether the excited state decays promptly or is long-lived. As a result, inelastic capture does not replenish a thermal annihilation core. The captured population forms an evolving orbital distribution that sets up the co-evolutionary dynamics between the star and the dark matter in the core and the reservoir, which we develop in a companion paper.
hep-phastro-ph.COastro-ph.GAastro-ph.HE+1
03
The Dark Dimension and Majorana Neutrinos
Arturo de Giorgi · Dhruv Pasari
Recent developments in the Swampland program motivate the existence of a mesoscopic Dark Dimension of size $0.1 - 10 μ$ m with bulk Majorana fermions in the $1 - 10$ keV range. Motivated by this, we derive terrestrial constraints on Majorana bulk neutrinos as a function of the compactification radius. After determining the mass spectrum and mixing structure, we confront the model with Daya Bay neutrino-oscillation data, the KATRIN beta-decay bound, and the KamLAND-Zen neutrinoless double beta decay limit. For the latter, we obtain a closed-form expression for the effective Majorana mass and show that the Kaluza-Klein tower efficiently screens neutrinoless double beta decay when the nuclear momentum exceeds the compactification and Majorana scales. In the Dark-Dimension window, beta decay provides the strongest constraint, pushing the allowed Yukawa couplings down to $O (1 0^{- 3})$ . Oscillation and neutrinoless double beta decay searches remain complementary, probing smaller and larger Majorana masses, respectively. For completeness, outside the Dark-Dimension assumptions, we investigate how hierarchical Majorana masses can weaken the constraints.
hep-phhep-exhep-th
04
Ultralight Axial Dark Matter
Anson Hook · Junwu Huang · Kevin Zhou
Ultralight dark matter could be an axial vector field, a simple possibility which motivates new experiments. Couplings to fermions, through an axial vector current or a dark electric dipole moment operator, lead to enhanced spin torques compared to axion dark matter. An axial vector also has an analogue of the axion-photon coupling, though its consistent realization requires a photon mass. Under this "axial-photon" coupling, the effect of a background magnetic field is suppressed, and the strongest experimental probes involve polarimetry, electric fields in superconducting cavities, and the cosmic microwave background. Since a massive axial vector is dual to a massive two-form, our results also apply to "Kalb-Ramond" dark matter motivated by string theory.
hep-phastro-ph.COgr-qc
05
On the Numerical Integration of One-Loop Cosmological Collider Signals
Michael Borinsky · Aidan Herderschee · Qianshu Lu
In a broad class of inflationary models, the leading non-Gaussian bispectrum arises from one-loop rather than tree-level processes. However, realistic one-loop contributions remain largely unexplored for phenomenologically relevant masses beyond the simplest bubble diagrams. This is insufficient for observational purposes because, for generic masses and couplings, triangle contributions need not be suppressed relative to their bubble counterparts. We present a numerical method for evaluating scalar one-loop in-in diagrams contributing to the inflationary bispectrum at fully general external momenta and masses. First, the Witten-Feynman parameterization reduces de Sitter loop integrals to generalized Euler-Mellin integrals governed by Symanzik graph polynomials. Unfortunately, the exponents of the polynomials in the integrand become complex for sufficiently heavy masses, leading to sign problems when evaluating the integral using standard numerical techniques. To remedy this problem, we introduce the reduced Schwinger method, which evaluates a highly oscillatory subintegral analytically to obtain a Gauss hypergeometric kernel, leaving the remaining integrals to standard numerical quadrature. We validate the algorithm by reproducing known analytic results for the tree-level bispectrum in terms of $_{3} F_{2}$ functions, and then apply it to the one-loop bubble and triangle contributions at general kinematics. This yields the first direct numerical evaluation of the complete one-loop bispectrum, valid across the full kinematic range. Using these numerical results, we construct bispectrum templates and compare them with CMB data.
hep-phastro-ph.COhep-th
06
Re-examining the sensitivity of JWST to decaying axion dark matter
Caleb Gemmell · Christopher Dessert · Andrea Caputo · Joshua W. Foster
An eV-scale QCD axion comprising the observed dark matter (DM) abundance is expected to generate a photon line at infrared energies that would be observable or near-observable in data collected by the James Webb Space Telescope (JWST), as might more general axion-like particles (ALPs) over a broader range of masses and couplings. This has motivated a number of efforts to either forecast JWST sensitivities to a QCD axion or realize them through analyses of publicly available datasets. At present, no consensus exists; leading analyses disagree by as much as an order of magnitude in terms of axion-coupling sensitivity, implying an orders-of-magnitude discrepancy in raw flux density sensitivity, and consistency between the analyses and prior forecasts is unclear. We address these outstanding discrepancies with a bespoke data reduction and flexible nonparametric inference procedure that lead to well-controlled and robust limits on the decay of eV-scale axion DM, consistent with previously forecasted sensitivities. We further demonstrate that the strongest previously claimed sensitivities exceed those attainable by any analysis of the datasets from which they were derived. We exclude QCD axion DM for masses between $500 meV$ and $2.5 eV$ using NIRSpec data, while setting limits on ALP DM complementary to other astrophysical constraints at masses between $100 meV$ and $500 meV$ . However, we find the sensitivities to be systematically limited, and therefore unlikely to be improved upon by ongoing data collection or re-analysis unless instrumental modeling and data reduction pipelines improve considerably.
hep-phastro-ph.CO
07
Computationally Efficient Description of Medium Response to Jets in Heavy Ion Collisions
Jorge Casalderrey-Solana · José Guilherme Milhano · Daniel Pablos · Krishna Rajagopal · Xiaojun Yao
We develop an Efficient Wake procedure for computing the distribution of hadrons originating from jet wakes in heavy ion collisions - the hydrodynamic response of a droplet of quark-gluon plasma to the energy and momentum deposited in it by high-energy partons propagating through it. The procedure employs the linearity of linearized hydrodynamics and takes account of the effects of both longitudinal expansion and transverse radial flow on the hydrodynamic evolution of the wakes and on the resulting particle production at the freezeout hypersurface. It makes repeated use of template solutions to linearized hydrodynamics in a Bjorken flow background with no transverse flow, templates that need only be computed once, and uses suitable rotations and boosts to map fluctuations from these templates to fluctuations at a point on the freezeout hypersurface in a way that incorporates the effects of the radial flow. We benchmark this procedure by comparing its results to results obtained from full $(3 + 1)$ -dimensional nonlinear hydrodynamics calculations, find reasonable agreement, and find that our Efficient Wake procedure yields a much better description of the distribution of hadrons originating from jet wakes than does the older oversimplified procedure employed in the Hybrid Model. And, the Efficient Wake procedure is computationally efficient: it is at least tens of thousands of times faster than full nonlinear hydrodynamics calculations. Hence, we anticipate that when our new procedure is implemented in Monte Carlo analyses of jets in heavy ion collisions, for example in the Hybrid Model, it will greatly improve the description of the soft component of many jet and jet substructure observables as compared to experimental data.
hep-phnucl-th
08
Opening the Topological Portal to Dark Sectors with Colliders
Joe Davighi · Admir Greljo · Lia Schöneweiß · Nudzeim Selimovic
We study the phenomenology of the topological portal between QCD and pseudo-Nambu--Goldstone dark matter proposed in~\cite{Davighi:2024zip}. We construct a weakly coupled ultraviolet completion in which a vector mediator gauges a baryonic current of QCD for the light quark flavours, linking it to dark pions parametrizing the coset $S U (2)_{D} / U (1)_{D}$ . As a concrete anomaly-free realisation, we gauge the leptophobic combination $B_{1} + B_{2} - 2 B_{3}$ . This completion allows us to calculate thermal coannihilation beyond the regime of validity of the pion effective theory, including resonant mediator effects, and to test the resulting thermal target with boosted-dijet and monojet searches at the LHC, with LEP and bottomonium data, and with flavour observables. These collider signatures follow directly from the symmetry structure required by matching onto the topological portal. At low momentum transfer, the topological operator instead controls the decay of the heavier dark pion, which is long-lived. A future high-statistics $Z$ factory, such as FCC-ee, can probe the low-mass region where hadron-collider sensitivity deteriorates, providing complementary tests of the topological portal.
hep-phhep-th
09
EFT Approaches to Sommerfeld Enhancement and Bound States in Singular Potentials
Arindam Bhattacharya · Rashmish K. Mishra · Tracy R. Slatyer
The Sommerfeld enhancement (SE) from long-range interactions, and the related bound state formation rate, can be important non-perturbative inputs to dark matter (DM) annihilation signals. In the presence of singular interaction potentials, the conventional boundary conditions of the Schrödinger equation fail, obfuscating the computation of SE, its physical origin, and its relation to bound states in such potentials. In this work, we clarify the origin of SE in singular potentials in a two-fold manner: using the framework of velocity power counting in non-relativistic effective field theory (NREFT), and via position-space regularization of singular potentials at short distances to compute SE and bound states. We illustrate our findings through the case of pseudoscalar mediators interacting with massive Dirac DM. We find that when such a system arises from a UV-complete theory at weak coupling, no SE is generated. However, in the case of a derivatively coupled pseudoscalar, where the interaction is described by a higher-dimension operator in an effective theory, SE (and bound states) can occur for weak couplings if there is a large hierarchy between the cutoff scale of the effective theory and the dark matter mass. This SE is sensitive to the choice of the UV completion of the potential at short distances, but a non-negligible SE can persist even when the UV physics alone would not generate any SE; we elucidate the interplay of UV and IR physics in this case.
hep-phastro-ph.COhep-th
10
PBH runaway during reheating
Md Riajul Haque · Mathieu Gross · Mathieu Houlier · Yann Mambrini
The growth of primordial black holes through the absorption of the surrounding plasma has recently been shown to exhibit a critical behavior during radiation domination. We extend this analysis to the reheating era and derive analytical solutions for general reheating histories. We show that reheating modifies the critical condition for runaway absorption, making it dependent on both the reheating dynamics and the black-hole formation time. We identify two distinct regimes: runaway growth occurring during reheating, or being triggered after the onset of radiation domination by the mass accumulated during reheating. More generally, we derive a simple composition law describing how independent mass- growth mechanisms combine across successive cosmological eras. Applying it to radiation absorption and inflaton accretion, we obtain analytical results in excellent agreement with the full numerical evolution.
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