HEP Phenomenology·hep-ph

Mon·Sep 21, 2026Monday·September 21, 2026

33 papers—23 primary·10 cross-listed

01
All-Order Helicity Selection Rules in Effective Field Theories
Luigi C. Bresciani · Nudzeim Selimovic
Using on-shell methods, we derive an all-order non-renormalization theorem for general four-dimensional effective field theories, relying on Poincaré invariance and unitarity. Each operator $O$ is assigned the weights $(w, w ˉ) = (ℓ - h, ℓ + h)$ , where $ℓ$ and $h$ are the number of particles and total helicity of its minimal configuration. At $L$ loops, the mixing $O_{j} \to O_{i}$ vanishes when $ℓ_{j} - ℓ_{i} = L - 1$ and either $w_{i} < w_{j} - 2 (L - 1)$ or $w ˉ_{i} < w ˉ_{j} - 2 (L - 1)$ , in the absence of non-holomorphic Yukawa couplings. These zeros follow entirely from tree-level data and are scheme independent under finite renormalizations that preserve the operator-length selection rule. For operators of dimensions five through eight, we identify broad classes of previously unknown zeros at higher loop orders, with particular emphasis on two loops, where the theorem provides direct checks on current calculations, as in the Standard Model Effective Field Theory.
hep-phhep-th
02
Entropy Dilution Mechanism and Dark Matter Isocurvature
Miha Nemevšek · Yue Zhang
We explore dark matter isocurvature perturbations in cosmological scenarios with entropy dilution resulting from a late decaying massive state that temporarily dominates the universe before big-bang nucleosynthesis. The dilution mechanism features a non-standard scaling window of the radiation energy density, which allows for a new way to derive the entropy dilution factor. On super-horizon scales, the same scaling window also governs the evolution of isocurvature, and we present an analytic approach to solving the perturbation equations. We characterize various regimes where dark matter isocurvature survives and is subject to constraints from the cosmic microwave background observations. For cosmologically viable scenarios, we find that dark matter is dominantly produced from its dilutor decay, and the isocurvature is suppressed by the entropy dilution factor to the $4/3$ power. Our work demonstrates the complementarity between isocurvature and collisionless damping of dark matter as powerful probes of the entropy dilution mechanism.
hep-ph
03
AutoTherm: Automated Thermal Field Theory rates for cosmology
Killian Bouzoud · Jacopo Ghiglieri · Greg Jackson
AutoTherm is a modular code automating the determination of thermal production and interaction rates for cosmology from Thermal Field Theory. This first release computes fully automatically the leading-order contribution from ultrarelativistic $2 \leftrightarrow 2$ processes to the production rate of an off-equilibrium $ϑ$ particle coupled to a thermal bath. It takes as input a FeynRules model file describing the Lagrangian of the bath- $ϑ$ system. The AutoTherm program consists of a Wolfram package, which utilises FeynArts/FormCalc, together with a few Python modules for symbolic and numerical routines. Their combined usage leads from the model file to the rate, but each component can also be used in a standalone manner. The main strength of this release is the automated, model-independent handling of Hard Thermal Loop resummation, which is necessary whenever a $2 \leftrightarrow 2$ process is mediated by a $t$ -channel massless mediator. Developments in Thermal Field Theory reduce the apparently large model dependence to the determination of the thermal mass of the mediator, which we automate successfully. They further allow us to provide three leading-order-equivalent implementations of HTL resummation. Their spread provides a first estimate of the theory uncertainty from higher-order thermal corrections. We showcase the strength of our AutoTherm framework by successfully reproducing or correcting a host of results in the literature, such as the thermal production rate of ultrarelativistic right-handed neutrinos, of gravitons and gravitinos, of axions and of dark photons.
hep-phastro-ph.CO
04
Thermal gravitino and axino rate from AutoTherm
Killian Bouzoud · Jacopo Ghiglieri · Greg Jackson
If ultrarelativistic supersymmetric particles are thermally produced in the early universe they would influence big-bang nucleosynthesis, dark matter and reheating constraints. While the basic framework for thermal gravitino and axino production is well established, the calculation is not completely settled. In this work, we revisit the problem using AutoTherm, a new tool which automates the computation of thermal rates from first-principles Thermal Field Theory, with control over the inherent theory uncertainty in Hard Thermal Loop resummation schemes. We demonstrate that the strict leading-order (LO) scheme, while unambiguous for hard momenta, can yield unphysical negative rates when extrapolated to soft momenta. To address this, we introduce a tuned scheme that ensures positivity and agreement with strict LO at high momenta, while avoiding gauge-dependent pathologies. We compare our results with existing parametrizations in the literature, identifying discrepancies and providing new, reliable fits for the gauge and Yukawa contributions to the gravitino and axino production rates. The choice of resummation scheme gives a theory uncertainty by a factor of $\sim 1.5$ ... $3$ depending on the temperature, which has been underappreciated until now. This residual spread should be taken into account in precision cosmological analyses of gravitino/axino abundancies.
hep-phastro-ph.CO
05
Prospects for testing Lorentz symmetry with highly charged ions
Arnaldo J. Vargas
We investigate the prospects for testing Lorentz symmetry using highly charged ions. We derive the Lorentz-violating energy shifts relevant to Zeeman and Zeeman-hyperfine transitions within the ground state of H-like ions and to Zeeman and Zeeman-fine transitions within the ground state of B-like ions. The resulting signals include sidereal variations through the first harmonic of the sidereal frequency for H-like ions and through the third harmonic for B-like ions. For certain SME coefficients whose contributions scale with the fourth power of the electron momentum, the large electron momentum in H-like ions can provide sensitivity competitive with the best existing bounds at the precision achievable in H-like-ion spectroscopy. We also find that B-like-ion spectroscopy can provide competitive sensitivity to certain SME coefficients.
hep-ph
06
Endothermic Z'-Portal Dark Matter: LZ-LHC Complementarity
Nobuchika Okada · Digesh Raut
Motivated by the $2.6 σ$ high-energy recoil event recently reported by the LUX-ZEPLIN (LZ) Collaboration, we consider an endothermic $Z^{'}$ -portal Majorana dark matter framework and discuss the complementarity between the LZ event and LHC searches for a $Z^{'}$ resonance. As a concrete realization, we consider a gauged U(1) $B - L$ extension of the Standard Model. The phenomenology of the framework is essentially controlled by two free parameters: the U(1) $B - L$ gauge coupling $g_{B L}$ and the $Z^{'}$ boson mass $m_{Z^{'}}$ . For a fixed $m_{Z^{'}}$ , the observed dark matter abundance requires the dark matter mass to be near the $Z^{'}$ resonance, $m_{DM} \sim m_{Z^{'}} /2$ , and sets a lower bound on $g_{B L}$ . Complementarily, LHC searches for a $Z^{'}$ resonance set an upper bound on $g_{B L}$ . The parameter space allowed by the dark matter abundance and LHC constraints can account for the recent LZ event. The synergy between future $Z^{'}$ resonance searches at the High-Luminosity LHC and the LZ experiment may provide a test of this framework.
hep-phastro-ph.COhep-exhep-th
07
Interacting Boson System at Finite Temperature: The treatment of the lattice calculations
D. Anchishkin · V. Gnatovskyy · D. Zhuravel · V. Karpenko
We study interacting relativistic charged bosons at finite temperature and isospin density in a thermodynamically consistent mean-field approach with repulsive phi-4 and phi-6 interactions. The thermodynamics is formulated in an Extended Canonical Ensemble, in which the conserved isospin density, not the chemical potential, is the independent variable. This is essential in the condensed phase, where mu_I is fixed by condensation. With one constant fitted to the lattice pressure at T=122 MeV, the model reproduces the lattice isospin density, energy density, and trace anomaly, phi-6 being more accurate.
hep-phhep-latnucl-th
08
Probing the Effective HZ $γ$ Coupling via H $γ$ Production at FCC-ee
Lena Herrmann · Sara Aumiller · Ken Mimasu · Louis Portalès · Michele Selvaggi
This work presents the first dedicated study of the $e^{+} e^{-} \to H γ$ production mode at the FCC-ee. The analysis exploits all foreseen FCC-ee running scenarios at and above the WW threshold. This study demonstrates that the $e^{+} e^{-} \to H γ$ process provides a novel and direct handle on the effective $H γ γ$ and $H Z γ$ couplings through production, complementary to measurements based on Higgs decays. By combining measurements of multiple Higgs decay channels and center-of-mass energies, we show that an overall precision of 15% is achievable on the effective $H Z γ$ coupling. In addition, unlike decay observables, this process is also sensitive to the relative sign of the coupling and allows a full resolution of the corresponding sign ambiguity. We compare the expected sensitivity to the projected bounds from direct measurements of the $γ γ$ and $Z γ$ branching ratios at the HL-LHC and FCC-ee, as well as projections from global fits in the SMEFT framework.
hep-phhep-ex
09
Jet transport coefficients associated with fermionic two-point correlators in a weakly-coupled plasma
Shay Duddy · Lukas Opitz · Amit Kumar · Gojko Vujanovic
A new set of jet-medium transport coefficients stemming from jet-medium exchanges involving Glauber quarks encoded in $F^_{i}$ [Phys. Rev. C 111, 054913 (2025), Phys. Rev. C 113, 055207] are obtained by computing the tree-level leading-order $2 \to 2$ scattering rates and their moments using the approach developed in Refs. [arxiv 2608.17160, arxiv 2608.17161]. Sizeable deviations away from the leading logarithmic dependence of jet-medium transport coefficients and scattering rate are observed here, as previously mentioned in Refs.[arxiv 2608.17160, arxiv 2608.17161]. A closed-form expression for $F^_{i}$ accurate to $≲ 10$ \% or better is obtained, enabling our approach to be used within Monte Carlo simulations of jet-medium interactions. Monte Carlo simulations incorporating $F^_{i}$ are sensitive to flavor hydrodynamization dynamics as the medium created in nucleus-nucleus collisions transitions from the early-time Glasma dynamics to the quark-gluon plasma fluid.
hep-phnucl-exnucl-th
10
FIMP dark matter in the scotogenic model at low-reheating temperatures
Robinson Longas · Andrés Rivera · David Suarez
The scotogenic model offers an attractive framework that explains light neutrino masses while accommodating a viable dark matter candidate. In this work, we study the phenomenology of singlet fermion dark matter, $N_{1}$ , produced via the freeze-in mechanism characterized by an instantaneous low reheating temperature, $T_{rh}$ . We explore the model's viable parameter space, incorporating current bounds from lepton flavor violation ( $μ \to e γ$ ) and direct detection limits. We show that low-reheating scenarios significantly reshape the viable region for $N_{1}$ dark matter, improving prospects for testing the scotogenic model in the FIMP scenario while keeping it consistent with current lepton flavor violation and cosmological bounds.
hep-ph
11
Endpoint anatomy of the baryon--meson sum rule in $b \to s ν ν ˉ$
Syuhei Iguro
Baryon-meson sum rules enable cross-checks among exclusive mesonic and baryonic measurements. Unlike their heavy-to-heavy counterparts, analogous heavy-to-light relations lack an explicit heavy-quark-symmetry origin. We investigate their origin in the $b \to s ν ν ˉ$ system by studying the relevant helicity amplitudes at the two kinematic endpoints. Although the sum rule follows algebraically from the simple short-distance structure, its coefficient depends nontrivially on the hadronic dynamics. At maximum recoil, the coefficient for the daughter baryons $B = Λ, Ξ$ is consistent with the approximate value $1/2$ within current form-factor uncertainties. At zero recoil, by contrast, a kinematic helicity projection enforces its exact vanishing. The fully integrated coefficients are numerically close to $1/4$ . However, unlike the one-quarter coefficient in the heavy-to-heavy system, they are not local symmetry coefficients but integrated quantities shaped by the behavior between the two endpoints. This understanding may guide the construction of baryon-meson sum rules in more general heavy-to-light decays.
hep-phhep-ex
12
Anomalous Matter Potentials in Earth's Inner Core: A Phenomenological Probe of Dark Matter and Light Sterile Neutrinos
Bipin Singh Koranga · Vivek Kumar Nautiyal
Standard treatments of Earth matter effects in neutrino oscillation experiments assume that the coherent forward scattering potential experienced by propagating neutrinos is sourced entirely by the Standard Model electron density predicted by the Preliminary Reference Earth Model (PREM). We examine how an anomalous matter potential localized in Earth's inner core, motivated by gravitationally captured dark matter or resonant mixing of active neutrinos with a light (eV-scale or lighter) sterile state, would distort the vu survival and vutove appearance probabilities relative to the Standard Model PREM expectation. Using a full three-flavor matrix-exponentiation propagation code with a four-shell PREM density profile, we parametrize the new-physics contribution as a fractional enhancement ecore of the electron-sector potential confined to the inner core (r<1221 km) and compute oscillation probabilities for near-vertically upgoing atmospheric neutrinos (L=8000to12742km). Trajectories that do not cross the inner core (L<=12500km) are essentially insensitive to ecore, reproducing the Standard Model expectation to better than 0.1%. In contrast, near-antipodal trajectories crossing the inner core (L>=12505km, corresponding to nadir angles within roughly half a degree of the vertical) show significant effects. The muon-neutrino survival probability is displaced by tens of percent for ecore=0.05to0.15 and by more than 100% at particular energies for the {\nu}{\mu} to {\nu}e appearance channel, with a pronounced neutrinoantineutrino asymmetry that mimics, but is physically distinct from, intrinsic CP violation. These results indicate that percent-level new-physics potentials confined to the inner core are within the discovery reach of high-statistics atmospheric neutrino telescopes such as IceCube Upgrade, KM3NeT/ORCA, and next-generation megaton-scale detectors.
hep-ph
13
The high-velocity dark matter halo of the Milky Way in light of the LZ 248 keV event
Ciaran A. J. O'Hare
The interpretation of high-energy nuclear recoil events in direct-detection experiments can depend sensitively on the poorly understood high-speed tail of the Galactic dark matter velocity distribution. This fact has been brought into sharper focus recently by an anomalous nuclear-recoil event at $E_{R} \approx 248 keV$ observed by the LZ experiment. If interpreted as caused by a dark-matter-induced recoil, kinematic constraints on many models imply this particle would have to emerge from the high-speed tail. Here, we re-assess this astrophysical uncertainty using Milky Way analogues from the IllustrisTNG and FIRE simulations. We find that the maximum laboratory-frame DM speed on June 16, when the event was observed, is $792. 7_{- 95.6}^{+ 82.9} km/s$ (median and 95\% containment across simulations), with a median very close to the fiducial SHM value. Modelling the tail of the velocity distribution in three dimensions is complicated by the fact that these simulated dark matter halos are anisotropic and are generically seen to spin in the same direction as the baryonic disk. However, we find that this does not reduce the maximum laboratory-frame DM speed because the approximately Gaussian azimuthal velocity distribution is negatively skewed by this co-rotation, rather than shifted by it. We illustrate these results in the context of an inelastic dark matter interpretation of the LZ event.
hep-phastro-ph.COastro-ph.GA
14
Localized CP violation driven by cross-channel interference between $K_{0}^{*} (1430)^{0}$ and $ρ (770)^{0}$ in $B^{\pm} \to K^{\pm} π^{+} π^{-}$ decays
Jin-Zhao Guo · Gang Lü
For the charmless three-body decay $B^{\pm} \to K^{\pm} π^{+} π^{-}$ , a CP asymmetry sign reversal typically occurs in the low- $m_{π π}$ region. However, experimental data reveals a localized anomaly in the specific phase space region $0.4 GeV^{2} < m_{π π}^{2} < 0.8 GeV^{2}$ and $1.5 GeV^{2} < m_{K π}^{2} < 2.5 GeV^{2}$ , where the regular pattern is broken by a rightward tilt. In this work, we investigate the dynamical origin of this phenomenon by employing a quasi-two-body factorization scheme that integrates short-distance perturbative QCD (PQCD) hard kernels with long-distance $S$ -wave LASS and $P$ -wave relativistic Breit--Wigner(RBW) line shapes. Our results demonstrate that the localized anomaly is driven by cross-channel interference between the scalar $K_{0}^{*} (1430)^{0}$ and vector $ρ (770)^{0}$ resonances, which exhibit an orthogonal geometric topology on the Dalitz plot. Crucially, we show that the rapid variation of the relative strong phase within the intersection region induces coherent interference effects alternating between the charge-conjugated channels, significantly reshaping the local CP asymmetry profile. This cross-channel dynamics framework provides a self-consistent theoretical benchmark for overlapping resonance regions, offering valuable insights for upcoming high-luminosity experiments at Belle II and the HL-LHC.
hep-ph
15
Discriminating baryonium and final-state-interaction interpretations of $X (2356)$
Bing-Dong Wan · Sheng-Qi Zhang
We revisit the $X (2356)$ enhancement observed by BESIII in $e^{+} e^{-} \to Λ Λ ˉ η$ from the viewpoint of near-threshold dynamics. Motivated by the possibility of light $Λ Λ ˉ$ baryonium, we compare this interpretation with final-state-interaction (FSI) explanations within a minimal FSI-dressed pole framework. Fits of the pure-FSI, baryonium-like-pole, and mixed pole--continuum scenarios to the digitized BESIII spectrum identify the energy-dependent FSI description as providing the best balance between fit quality and model complexity. The extracted pole positions depend strongly on the amplitude parametrization, demonstrating the sensitivity of the baryonium interpretation to the treatment of the continuum. We discuss how decay channels, spin observables, and partner searches can provide complementary constraints on the dynamics underlying the enhancement.
hep-phhep-ex
16
Leptogenesis and Planck-scale black hole remnants in a Pati-Salam cosmology
Arnab Chaudhuri · Erdenebulgan Lkhagvadorj · Satyabrata Mahapatra
We study leptogenesis and Planck-scale remnant dark matter from primordial black hole (PBH) evaporation in a minimal Pati-Salam cosmology, with the gauge symmetry broken before inflation so that magnetic monopoles are diluted away. A singlet inflaton with a near-inflection potential enhances the curvature power spectrum on small scales, producing a narrow black hole population that briefly dominates the energy density. The Pati-Salam embedding ties the right-handed neutrino masses to the SU(2)_R breaking scale, and cosmological consistency forces both the scalar-sector Yukawa coupling and the heavy neutrino mass well below that scale. Two regimes emerge, depending on whether the black holes are hot enough to emit the lightest right-handed neutrino. Lighter PBHs drive non-thermal leptogenesis, while heavier ones require a thermal asymmetry and also affect it through entropy dilution. If quantum gravitational backreaction halts evaporation at the Planck scale, each PBH leaves a stable remnant whose present abundance scales as the inverse five-halves power of the initial mass. Suppressing remnants requires heavier black holes, but the lighter PBHs needed for non-thermal leptogenesis overproduce remnant dark matter. Thus, remnant dark matter and non-thermal leptogenesis are mutually exclusive. When the thermal contribution is included, a single initial PBH mass near 10^6 g accommodates the observed dark matter abundance, the heavy neutrino mass required by the baryon asymmetry, and the Pati-Salam breaking scale. The scenario predicts a stochastic gravitational wave background from Poisson fluctuations of the black hole distribution, within reach of future experiments, alongside high-frequency graviton emission constrained by future measurements of the effective number of relativistic species.
hep-ph
17
AGN and DSNB Neutrino Oscillation in Dark Matter Background
Po-Yan Tseng · Yu-Min Yeh
The neutrino-matter interaction cause the final flavor compositions deviating from those expected in vacuum. In this work we consider neutrinos interact with ultra-light scalar dark matters $ϕ$ ( $m_{ϕ} ≪ 1 eV$ ). When the neutrinos emitted from a distant source and propagate through the dark matter medium, the MSW potential in the Hamiltonian is replaced by the hypothetical $ν ϕ$ effective potential. Two types of neutrino sources are adopted in our calculations. The first is point-like neutrino source, the Active Galactic Nuclei (AGN), which produce $O (TeV)$ neutrinos primarily through charged pion decay, yielding an initial flavor ratio of ( $ν_{e}, ν_{μ}, ν_{τ}$ )=( $1 : 2 : 0$ ). We focus on two specific AGNs, NGC 1068 and TXS 0506+056 in our analysis, whose distances from Earth are much larger than the neutrino oscillation lengths. We consider the range of $ν ϕ$ coupling constant such that the adiabatic condition and mean free path can be satisfied. Hence, by assuming neutrinos are produced randomly from their corona regions, we compute the averaged flavor ratio at Earth with $m_{ϕ} = 10, 1, 0.1 peV$ and $m_{ϕ} = 1, 0.1, 0.01 feV$ , generate the ternary plots of neutrino flavors, and compare the results with the IceCube present and future sensitivities. The second source considered is the Diffuse Supernova Neutrino Background (DSNB), it is an isotropic neutrino source with energy $O (MeV)$ . Applying the core-collapse simulation neutrino temperatures to the DSNB flux, we repeat the similar analysis for the DSNB with $m_{ϕ} = 1 0^{- 22} eV$ , and we estimate different neutrino flavors lies in the HK/DUNE/JUNO combined sensitivities limit.
hep-ph
18
LUX-ZEPLIN's Stairway to Hea $ν$ en: limits on elastic scatters of dark matter from solar capture
Debajit Bose · Akash Kumar Saha · Nirmal Raj · Tarak Nath Maity · Ranjan Laha
The recent report of xenon recoiling with about 250 keV energy at the LUX-ZEPLIN (LZ) dark matter direct detection experiment was interpreted by the collaboration as either a momentum-dependent elastic scatter or an inelastic scatter. In this study, we take elastic operators listed by LZ that fit the datum to better than 3 $σ$ , and perform a log-likelihood analysis using the reported significances to reverse-engineer their best-fit Wilson coefficients. We then estimate for each operator the rate of dark matter capturing in the Sun, and assuming self-annihilations of the captured population to standard final states studied by IceCube, we place limits on them from measurements at IceCube and Super-Kamiokande of the fluxes of solar-direction and atmospheric neutrinos. We show that large ranges of dark matter masses around the weak scale that explain the LZ event are ruled out in this scenario, with the strongest limits placed by direct annihilations to neutrino-antineutrino final states.
hep-ph
19
ALP Distributions from Hadron Structure
Shuai Zhao
We investigate how hadron structure and quark-flavor couplings shape axion-like particle (ALP) radiation in hadron collisions. For the elastic pole, the virtuality integral is ultraviolet finite at fixed momentum fraction if the pseudoscalar form factor falls as a positive power of $1/ Q^{2}$ at large $Q^{2}$ , eliminating the point-particle beam-energy logarithm. Pion-pole and lattice-QCD isovector benchmarks suppress the process-weighted elastic contribution by roughly three orders of magnitude relative to the point-particle result. Two coefficient sets matched to the same leading low-energy nucleon source yield process-weighted resolved leading logarithms differing by four orders of magnitude, demonstrating the sensitivity of resolved ALP radiation to heavy-quark coupling configurations.
hep-ph
20
Searching for Axions from Atmospheric Kaon Decays
Tousif Raza
Cosmic-ray interactions in the Earth's atmosphere produce copious secondary mesons, providing a natural laboratory for searches for new physics. We investigate the atmospheric production of axions through the rare kaon decay $K^{+} \to π^{+} a$ . If sufficiently long-lived, these axions can reach large underground detectors such as Super-Kamiokande and IceCube and decay through the diphoton channel, $a \to γ γ$ . Using data from Super-Kamiokande and IceCube, we derive constraints on the axion decay constant $f_{a}$ for masses up to $m_{a} \sim 350 MeV$ . We demonstrate that atmospheric kaon decays provide a novel probe of axion parameter space, yielding constraints complementary to existing bounds.
hep-phhep-ex
21
Charged lepton flavor violating decays and $(g - 2)_{e_{a}}$ in an extended standard model with singlet and triplet leptoquarks
L.T. Hue · N.V. Hop · Vo Quoc Phong · N.H.T. Nha
We study the anomalous magnetic moments of charged leptons and their lepton flavor-violating decays in a Standard Model extension containing one $S U (2)_{L}$ singlet and one $S U (2)_{L}$ triplet scalar leptoquark. Our results reveal significant correlations among $Δ a_{e, μ}$ and the decay rates of $e_{b} \to e_{a} γ$ , and $h, Z \to e_{b}^{\pm} e_{a}^{\mp}$ . In particular, the branching ratios $Br (e_{b} \to e_{a} γ)$ and $Br (h, Z \to e_{b} e_{a})$ exhibit significant correlations. The model cannot simultaneously accommodate sizable values of $∣Δ a_{e} ∣ = O (1 0^{- 13})$ and $∣Δ a_{μ} ∣ = O (1 0^{- 10})$ . For $∣Δ a_{μ} ∣ = O (1 0^{- 10})$ and Br $(μ \to e γ) > 1 0^{- 15}$ , the decay rates are suppressed to Br $(τ \to e γ) < O (1 0^{- 12})$ and Br $(h \to τ e) < O (1 0^{- 6})$ , while the remaining ones can reach the forthcoming experimental sensitivities. Conversely, for $∣Δ a_{e} ∣ = O (1 0^{- 13})$ , one obtains the suppressed decay rates Br $(τ \to μ γ) < O (1 0^{- 11})$ and Br $(h \to τ μ) < O (1 0^{- 7})$ .
hep-ph
22
Analytic results on the massive three-loop form factors: gluonic contributions
J. Blümlein · A. De Freitas · P. Marquard · J. Obrovsky · C. Schneider
We compute the gluonic contributions to the three-loop heavy-quark form factors for the vector, axial-vector, scalar, and pseudoscalar currents. In the low-energy limit, $q^{2} / m^{2} \to 0$ , we used guessing algorithms to derive closed-form difference and differential equations from the rational sequences associated with the multiple zeta values and other constants appearing in the expansion coefficients, which required up to 26000 coefficients in the most demanding cases. Part of the results are obtained analytically in terms of harmonic polylogarithms and square-root valued iterated integrals by solving the obtained differential equations. For the remaining contributions, arbitrarily deep series expansions around the singularities of the form factors can be obtained by matching local expansions at intermediate points and by exploiting the differential equations obeyed by the functions associated with each transcendental constant in the expansions around $s = q^{2} / m^{2} = 0$ . For all these calculations advanced computer algebra methods have been employed. By using analytic continuation methods for differential equations matching the expansions at different values of $s$ and using PSLQ, we derive analytic results in the high-energy limit, $q^{2} / m^{2} \to \infty$ . The expansion coefficients are expressed in terms of multiple zeta values up to weight $w = 6$ together with three additional constants, two related to sixth-root-of-unity letters and one associated with quadratic-form implied iterated integrals. We also derive deep expansions about the threshold and pseudo-threshold. Numerical results are presented in the whole kinematic range and compared to results in the literature.
hep-ph
23
Resurrecting Electroweak Dark Matter via Type-II Seesaw in light of recent LZ Event
Partha Kumar Paul · Sujit Kumar Sahoo · Narendra Sahu · Shashwat Sharma
The recent observation of the high-energy nuclear recoil event LZ230616 with a recoil energy around 248 keV provides an interesting possibility to probe inelastic doublet dark matter (iDM). However, the electroweak doublet DM scenarios face strong constraints from solar DM capture for DM masses around the TeV scale which give rise to correct thermal relic density. In this work, we revive the inelastic doublet DM (iDM) scenario via type-II seesaw. In particular, we consider an inert lepton doublet (ILD) DM. While the minimal ILD scenario gives the correct relic abundance around the TeV scale, it is strongly constrained by direct detection and solar DM capture. In the type-II seesaw, the presence of the scalar triplet generates the required mass splitting and provides additional annihilation channels, allowing the correct relic abundance for much larger DM masses. The larger DM mass also helps evade the solar capture and indirect detection constraints. Additionally, the scalar triplet gives sub-eV neutrino masses required by the oscillation data.
hep-phastro-ph.COhep-exhep-th
24
Calculating Axion-Matter Couplings in String Theory
Joshua N. Benabou · Naomi Gendler · Thomas R. Harvey · Jakob Moritz
In this work we calculate, for the first time, the dominant perturbative contributions to axion--matter couplings explicitly in string theory. Concretely, we compute these couplings in Calabi--Yau compactifications of heterotic string theory where the vector bundle is a sum of line bundles. They are expressed as overlap integrals requiring the Ricci-flat metric, the Hermitian Yang-Mills bundle metric, and the matter field harmonic forms. We compute these by solving the corresponding coupled differential equations with neural networks. Our results establish a characteristic hierarchy of four-dimensional couplings: axions couple to fermions as $L \supset c_{ψ} \frac{\partial _{μ} a}{f _{a}} ψ^{†} σ ˉ^{μ} ψ$ with $c_{ψ}$ an $O (1)$ function of Kähler moduli for the model-dependent axions, while the corresponding coupling for the model-independent axion is suppressed by $α_{YM}$ at the ultraviolet matching scale. The model-dependent axions thus couple to fermions similarly as DFSZ-like four-dimensional axions, whereas the model-independent axion's couplings are loop-suppressed as in KSVZ-like constructions. The methods developed here apply directly to the large class of heterotic line bundle models with realistic spectra, and can be adapted to type II constructions.
↳ hep-thhep-ph
25
Cosmological Correlators from Resurgence
Yuanzhao Li · Zhong-Zhi Xianyu
Integrating out heavy particles is generally viewed as an irreversible procedure that erases some physical information above the cutoff scale of the resulting effective theory. However, this does not preclude the possibility of recovering the heavy propagating degrees from the low-energy effective theory with appropriate boundary data supplied. A classic example is the recovery of Schwinger pair production from the resummed Euler-Heisenberg effective action. In this work, we perform a similar exercise in a cosmological setting. We show that it is possible to reconstruct the inflationary correlators with massive exchanges, for a discrete heavy spectrum and arbitrary tree topologies, from the low-energy effective theory together with unitarity and Bunch-Davies boundary conditions. The divergent EFT series is resummed in three ways: the boundary differential operators, spectral representation, and Borel resummation, and the exponentially suppressed cosmological collider signals are recovered via analytic continuation. Our construction provides a resurgent relation between the local EFT background and the nonanalytic heavy-particle production, and may also be viewed as an inverse problem for the dispersive bootstrap.
↳ hep-thastro-ph.COhep-ph
26
Systematic Uncertainties and Their Impact on Gamma-Ray Searches for Dark Matter in Dwarf Galaxies
Toni Bertólez-Martínez · Dan Hooper · Arifa Khatee Zathul
Gamma-ray observations of Milky Way dwarf galaxies provide some of the strongest constraints on dark matter annihilation and are approaching the sensitivity required to test dark matter interpretations of the Galactic Center Gamma-Ray Excess. The results, however, depend critically on the inferred dark matter distributions in these systems, conventionally described by their $J$ -factors and spatial profiles. We review several sources of systematic uncertainty in dwarf galaxy $J$ -factor determinations, including stellar membership, unresolved binaries, departures from equilibrium and spherical symmetry, and assumptions regarding the stellar and dark matter density profiles. Most $J$ -factor determinations reported in the literature neglect several of these uncertainties, and the resulting measurements are often more dispersed than their quoted uncertainties would suggest. This indicates uncertainties of order $Δ lo g_{10} J \sim 0.5$ or larger may be warranted for many of these systems. Using an ensemble of simulated Fermi-LAT observations of a stacked sample of 27 dwarf galaxies, we quantify how these unmodeled uncertainties affect the resulting constraints on the dark matter annihilation cross section. We find that adding an uncertainty of $Δ lo g_{10} J \sim 0.5$ or 1.0 in quadrature weakens the median upper limits of a stacked analysis by factors of 1.4 or 3.2, respectively. Furthermore, underestimating these uncertainties can cause such analyses to exclude the true annihilation cross section more frequently than the nominal confidence level would imply. Such undercoverage is especially pronounced in stacked analyses and persists even when the adopted and true $J$ -factor uncertainties agree. Mismodeling spatially extended halos as point sources, as is sometimes done, further strengthens the resulting limits and increases the probability that true signals will be incorrectly excluded.
↳ astro-ph.HEastro-ph.COhep-ph
27
The Galactic Dynamics of Free-Floating Planets: From Ejection Kicks to Microlensing
Zara Sayed · Stefano Profumo · Nolan Smyth
Free-floating planets (FFPs) may retain dynamical signatures of the mechanisms that eject them from their host systems. We integrate $1 0^{6}$ collisionless FFP test particles for $1 0^{8}$ ~yr in a static, phenomenological Galactic potential, comparing a mass-independent kick model with a mass-coupled prescription ( $σ_{CB} \propto M^{- 0.15}$ , $v_{PL} \propto M^{- 0.5}$ ) against a matched no-kick control. The imposed mass dependence is recovered at injection, with the combined-channel median coupled kick decreasing from $10.716$ to $0.708 km s^{- 1}$ across five mass bins---a factor of $\sim 15.1$ . A mass-dependent trend remains visible after $100$ ~Myr of Galactic propagation in the matched kicked-versus-control displacement, whose median decreases from $0.7001$ to $0.0539$ ~kpc across the same bins. The remaining numerical distinction is concentrated in this mass-resolved differential displacement rather than in the bulk phase-space moments: the final velocity dispersions of the null and coupled kicked populations are nearly identical, only a few percent of particles leave the adopted disk region, and the fraction of particles satisfying the formal Galactic-unbound criterion ( $E_{i} > 0$ ) remains negligible in every diagnostic we report. Comparing each kicked population against its matched no-kick control shows that much of the overall kinematic heating arises from the evolution of the initially warm, nonequilibrium disk rather than from the ejection kick itself, isolating the kick's smaller contribution.
↳ astro-ph.EPastro-ph.GAastro-ph.SRhep-ph
28
Self-Similar Mass Spectra of Hierarchical Black Hole Mergers
Liam Blum · Stefano Profumo · Ryan Schantz · Quoc Ha Tran
Black holes that merge repeatedly carry a record of that history in their mass distribution. We treat hierarchical merging as a coagulation problem, in which a single kernel encodes how the merger rate depends on the masses involved and on cosmic time, and we derive the late-time spectra that such populations approach. The framework yields closed scaling laws, an exactly solvable benchmark, and a classification of merger environments by a single exponent measuring how strongly mergers favor or suppress massive participants. Applying it to primordial black holes requires care in translating published merger rates into kernel form; done correctly, three of the four standard binary-formation channels map onto superlinear kernels and are therefore candidates for runaway growth, in which the heaviest objects would dominate and no steady mass-conserving spectrum exists; establishing physical gelation, however, requires the full population-dependent kernel and its finite coagulation history, neither of which we settle here. Only the early three-body channel maps into the nongelling regime and admits slow self-similar growth. Numerical solutions across thirteen suppressive, nongelling kernels show that the shape of the spectrum is not fixed by the scaling exponent alone, and that accounting for the energy radiated at each merger measurably changes the high-mass cutoff and drains the population's total black-hole mass.
↳ astro-ph.HEastro-ph.COgr-qchep-ph
29
On asymptotically and anomaly-free SU(N) chiral gauge theories for arbitrarily large N
Kort Beck · Patrick Draper
A large catalog of asymptotically free and anomaly-free SU(N) chiral gauge theories that admit a large-N limit was constructed by Eichten, Kang, and Koh. Here we compute the global structure of their symmetry groups and tabulate the 't Hooft anomalies of the faithful symmetries, including those that are visible only in backgrounds carrying fractional flux. Most theories in the catalog contain fundamentally charged matter and support no genuine one-form electric center symmetry. However, fractional fluxes still arise from the faithful quotient and contribute to the anomaly in the same way as a two-form background for a one-form symmetry. The anomalies are computed using two methods, first with the descent procedure, and second by placing the theory on a four-torus, which supports twisted fluxes for background gauge fields. We discuss a selection of candidate IR behaviors and present a general discussion of how matching the anomalies associated with fractional flux constrains these theories beyond the imposition of ordinary zero-form anomaly matching. Based on large-N reasoning, we formulate a new proposal for the IR behavior of a pair of models, consistent with the zero-form 't Hooft anomaly matching conditions. The matching condition involving fractional flux amounts to one additional test, which the scenario is shown to pass.
↳ hep-thhep-ph
30
Complex scalar field thick branes: stability of linear perturbation and evolution of scalar Kaluza-Klein modes coupled with gravity
Wang-Long Dong · Heng Guo · Qun Wei · Yong-Tao Lu
We investigate the stability and localization properties of Minkowski, de Sitter (dS), and anti-de Sitter (AdS) thick branes generated by a complex scalar field $Φ$ . The scalar self-interaction potential contains a temperature parameter $a$ . As $a$ approaches its critical value, the imaginary part of $Φ$ becomes double-kinked and the energy density splits into two peaks, indicating the formation of two sub-branes. The analysis of linear scalar, vector, and tensor perturbations shows no signs of instability in the scalar and vector sectors, while the factorization of the tensor perturbation equation excludes tachyonic tensor modes. The graviton zero mode is localized on the Minkowski and dS branes but is not normalizable on the AdS brane. We further study a real test scalar field $Ψ$ with a coupling function $F (R)$ between its kinetic term and the spacetime curvature. The scalar zero mode can always be localized on the Minkowski and dS branes, with a continuous gapless spectrum of scalar Kaluza--Klein (KK) modes. Massive scalar resonances emerge near the critical value of $a$ for suitable values of $β$ . Increasing $β$ produces more resonances and prolongs the lifetimes of the lower resonances, while their time evolution exhibits the characteristic decay of metastable modes. For the AdS brane, the scalar zero mode is also localized, whereas the divergent effective potential at the boundaries traps the massive scalar KK modes as bound states, yielding a discrete mass spectrum.
↳ hep-thgr-qchep-ph
31
21-cm Constraints on S-wave Dark Matter Annihilation with Subhalo-enhanced Effects
Zixuan Xu · Sibo Zheng
Observations of the 21-cm signal can probe energy injection into the intergalactic medium arising from dark matter annihilation during cosmic dawn and reionization. For s-wave annihilation, the annihilation rate depends on the squared dark matter density, making the 21-cm signal sensitive to dark matter halo substructure. In this work, we extend the numerical method of DM21cm to address spatially inhomogeneous s-wave annihilation including subhalo effects, using semi-analytical treatment of SASHIMI-C. Our numerical results show that the projected HERA limit for the $γ γ$ annihilation channel is stronger than the Leo~T bound within the dark matter mass range of $m_{χ} \leq 3 keV$ , whereas the projected HERA limit for the $e^{+} e^{-}$ annihilation channel is the strongest among the existing bounds for $m_{χ} \sim 0.1$ -- $1 GeV$ .
↳ astro-ph.COhep-ph
32
Sine-Gordon Model with Bosonic Tensor Networks: Continuum Matching and Soliton Scattering
Florian Hechenberger · Tommaso Rainaldi · Felix Ringer
We use bosonic tensor networks to connect the lattice sine-Gordon model in the Hamiltonian formulation quantitatively to its continuum theory. Matching the lattice vertex operator to its conformal normalization at the free-boson ultraviolet fixed point yields the exact relation between the bare lattice coupling and the renormalized continuum mass parameter. The soliton mass then approaches Zamolodchikov's exact continuum prediction throughout the studied parameter range, without adjustable parameters. Using uniform matrix product states and a quasiparticle ansatz, we also recover the relativistic soliton dispersion and the two lightest breather masses at the percent level. We simulate real-time collisions of Gaussian soliton-antisoliton wave packets near a reflectionless point and extract the Wigner spatial displacement. We compare this displacement with the exact continuum prediction obtained from the momentum derivative of the transmission phase, recovering its characteristic rapidity dependence. Our bosonic simulations provide a foundation for nonintegrable extensions, offer lessons for renormalization in other Hamiltonian lattice field theories, including gauge theories, and provide benchmarks for continuous-variable quantum simulations.
↳ quant-phhep-phhep-thnucl-th
33
Axial $U (1)$ Symmetry Breaking in Hot QCD: From Topology to the Chiral Phase Transition
Heng-Tong Ding
Heating matter can restore symmetries spontaneously broken at low temperature. The axial $U (1)$ symmetry of quantum chromodynamics (QCD) is different: it is present in the classical theory with massless quarks but is broken upon quantization by the axial anomaly. The anomaly persists at every temperature, yet its observable effects can weaken. Can hot matter nevertheless behave as though this symmetry were restored at long distances? Whether such effective axial $U (1)$ restoration occurs depends on how microscopic quark and gluon dynamics governs the strength and spatial range of axial breaking. This review brings together theoretical developments and first-principles lattice QCD calculations. We examine how gluon-field topology shapes the low-lying Dirac modes and their correlations, how these modes contribute to axial breaking at different spatial scales, and what this implies for the order and critical behavior of the chiral phase transition as quark masses approach zero.
↳ nucl-thhep-lathep-phhep-th