HEP Phenomenology·hep-ph

Tue·Sep 29, 2026Tuesday·September 29, 2026

35 papers—27 primary·8 cross-listed

01
Impact of Helicity-Isospin Convention Matching on the Extraction of $α$ from $B^{0} \to (ρ π)^{0}$
Radek Žlebčík
We show that the $ρ \to π π$ helicity convention used in the time-dependent Dalitz-plot measurements of $B^{0} \to (ρ π)^{0}$ decays does not match the convention assumed in the subsequent isospin analysis. Once corrected, the tension between the direct determination of the unitarity-triangle angle $α$ from these decays and its indirect determination from global fits decreases from $2.9 σ$ to $2.1 σ$ . Combined with the $B \to π π$ and $B \to ρρ$ modes, the direct determination becomes $α = (87. 0_{- 4.7}^{+ 11.8})^{\circ}$ , compared with the original world average $(84. 1_{- 3.0}^{+ 3.7})^{\circ}$ .
hep-phhep-ex
02
Neutrino Direct Simulation Monte Carlo: Accurate modeling of out-of-equilibrium decaying cosmological relics
Kensuke Akita · Miguel Escudero · Oleksii Ihnatenko · Maksym Ovchynnikov
We consider nonstandard cosmologies in which decaying relics inject energy at MeV temperatures, driving neutrinos out of equilibrium. The subsequent neutrino evolution shapes predictions for the cosmic radiation density and primordial light element abundances. Earlier work introduced Neutrino Direct Simulation Monte Carlo ( $ν$ DSMC), which describes neutrino transport through Monte Carlo sampling of particle interactions. Here, we extend this method by jointly evolving the relic population, neutrino spectra, electromagnetic plasma, and cosmic expansion, and coupling this evolution to Big Bang nucleosynthesis. The framework includes direct and inverse decays of the relic, neutrino flavor conversion, quantum statistics, and pion production by energetic neutrinos. To reveal the physical impact of these effects and independently test $ν$ DSMC, we compare several approaches to neutrino evolution across a range of nonstandard cosmological scenarios. We find excellent agreement with independent solutions of quantum kinetic or quasi-classical Boltzmann equations. Compared with these calculations, $ν$ DSMC includes a broader range of physical processes and is substantially faster for strongly nonthermal neutrino populations. This makes broad, robust parameter scans for nonstandard cosmologies practical. We show that when departures from thermal equilibrium are large, approximations that average over neutrino momenta can give qualitatively incorrect predictions, including the wrong sign of the change in the effective number of neutrino species and substantially incorrect primordial nuclear abundances. We conclude that the extended $ν$ DSMC framework enables reliable cosmological tests of new physics by following neutrino thermalization and its observable consequences.
hep-phastro-ph.CO
03
Disentangling $V_{u d}$ from New Physics in Beta Decays with the FCC-ee
Lemonia Gialidi · Elie Hammou · Kamil Laurent · Vaisakh Plakkot · Juan Rojo · Jordy de Vries
Superallowed nuclear $β$ -decays enable the most precise determination of the CKM element $V_{u d}$ , but they are only sensitive to an effective combination of $V_{u d}$ and New Physics contributions to left-handed charged currents, which low-energy data alone cannot disentangle. Here we determine $V_{u d}$ simultaneously with the relevant Wilson coefficients of the Standard Model Effective Field Theory (SMEFT) by combining, within the SMEFiT framework, a dedicated likelihood for superallowed transitions, including radiative and nuclear-structure uncertainties, with LEP and LHC world data and HL-LHC and FCC-ee projections. Current collider data and HL-LHC projections only partially lift the degeneracy between $V_{u d}$ and possible New Physics effects. Instead, the FCC-ee fully decouples $V_{u d}$ from New Physics, recovering SM-level precision while significantly tightening the constraints on the SMEFT Wilson coefficients. This conclusion is robust against variations in flavour assumptions and theory uncertainties. Our results highlight the complementarity between future colliders and low-energy experiments, and pave the way towards a SMEFT-consistent interpretation of first-row CKM unitarity tests and the Cabibbo angle anomaly.
hep-ph
04
Milky Way White Dwarfs as Inelastic Dark Matter Detectors
Javier F. Acevedo
We show that white dwarfs in the Galactic Center are a sensitive probe of inelastic dark matter (IDM) annihilation. IDM particles traversing a white dwarf may become gravitationally captured without fully settling in its interior if their energy drops below the kinematic threshold for inelastic scattering. In this regime, a fraction of the incoming particles remains bound on long-lived orbits that extend beyond the white dwarf's volume, enabling annihilation to partially proceed outside of the object. Some of the annihilation products subsequently escape, rather than being absorbed by the stellar material, producing a potentially detectable signal. We estimate the collective gamma-ray flux from the external annihilation sourced by these systems, as a function of the IDM parameters, and compare it to H.E.S.S. observations within the central degree of the galaxy. From this comparison, we derive tentative limits on the IDM scattering cross-section at the TeV mass scale, under largely conservative assumptions for the IDM density in this region. As a concrete application, we map these results into specific parameter constraints for dark photon-mediated and higgsino models with mass splittings at the MeV scale.
hep-phastro-ph.HE
05
Prompting Particle Physics: Tokenized Multi-modal Foundation Models for Combinatorially Many Tasks
Nilotpal Kakati · Daniel Murnane · Baran Hashemi · Samuel Klein · Jeffrey Krupa · Eilam Gross · Lukas Heinrich · Michael Kagan
Reconstruction and simulation at a collider experiment are long chains of specialised algorithms, each tuned to a single step. We explore how one model can serve many of those steps at once, while still producing the intermediate objects (tracks, calorimeter cells, clusters, particles and jets) that make the chain interpretable. To do so, we represent every object in a jet in a single shared token vocabulary and train one model to map any subset of these modalities to any other. A task is then only a choice of which modalities to provide and which to request: particle flow, detector simulation and charged energy subtraction are all directions through the same set of weights. We train over all modality combinations, with a decoder emitting tokens either autoregressively or in parallel. With tokenisation, both architectures train stably with little tuning. In evaluations, both models produce realistic reconstruction and simulation objects, with the autoregressive model particularly faithful to output from Geant4. The autoregressive model also outperforms a state-of-the-art particle flow algorithm on many typical jet reconstruction metrics.
hep-phcs.LGhep-exphysics.data-an
06
The era of charmed resonance searches at the LHC
Daniel Whiteson
The LHC dijet program has searched extensively for resonances decaying to inclusive jets and, more recently, to bottom-quark jets, where the sensitivity enhancement from suppression of the background outweighs the loss of signal efficiency in bottom-quark tagging. However, no dedicated search for dijet resonances containing charm-tagged jets has been performed. We study the charm-tagging performance required to make such searches competitive with the inclusive dijet search. Using the ATLAS 13 TeV dijet mass spectrum with 139 fb $^{- 1}$ , we predict the expected charm-tagged spectra from simulated jet-flavor fractions and parameterized charm-, bottom-, and light-jet tagging efficiencies, and estimate the sensitivity of a profile-likelihood search in exclusive one- and two-tag categories. At the loosest working point of the current tagger, charm-tagged searches improve the expected sensitivity to a resonance decaying to two charm quarks across the full resonance mass range considered, although the quantitative sensitivity depends on the poorly constrained high- $\pt$ behavior of charm-tagging efficiencies and on the simulated heavy-flavor composition of the dijet background. These results provide performance targets for charm taggers and motivate the development of dedicated charm-tagged dijet resonance searches at the LHC.
hep-ph
07
Beam-polarization-enabled witness of four-dimensional entanglement in $Ω^{-} Ω ˉ^{+}$ pairs
Qiu-Yan Zhang · Peng-Cheng Hong · Wei-Min Song
We study the entanglement structure of $Ω^{-} Ω ˉ^{+}$ pairs produced in $e^{+} e^{-} \to ψ (3686)$ , focusing on whether the entanglement requires the full four-dimensional spin space of each spin- $3/2$ baryon. Beam polarization controls the parent-state populations and coherence, thereby modifying helicity interference. Using the negativity criterion $\Neg > 1$ and the measured BESIII helicity parameters, we find critical polarizations of about $0.65$ per beam for equal transverse polarization and $0.57$ per beam for equal-and-opposite longitudinal polarization. Full transverse polarization gives a near-maximal peak negativity, $\Neg_{peak} ≃ 1.50$ , with a production-rate-weighted angular fraction of $0.60$ satisfying the witness. At the optimal production directions, destructive interference removes the unequal-helicity channels, while the near equality of the relevant equal-helicity amplitudes yields nearly equal Schmidt coefficients. Constituent-quark benchmarks further show that the angular extent of the witness is more sensitive to relative phases than the peak negativity. These results link polarization-controlled helicity interference to four-dimensional entanglement in high-spin baryon production.
hep-ph
08
Escaping Solar Capture: Majoron mediated Elastic Dark Matter for the LZ 248~keV Event
Salvador Centelles Chuliá · Ayan Chattaraj · Rahul Srivastava · Surabhi Srivastava
We interpret the $248 ke V_{nr}$ nuclear-recoil candidate reported by LZ through elastic dark matter scattering mediated by a light Majoron. The Majoron provides a natural origin for the required pseudoscalar interaction: it is the pseudo Nambu-Goldstone boson associated with spontaneous lepton number breaking, directly connecting the recoil signal to neutrino mass generation. After a model independent analysis of this idea, we present a concrete realization in a scotogenic ultraviolet completion in which the lightest singlet Majorana fermion is dark matter and acquires both its mass and Majoron coupling from the symmetry breaking dynamics. A vector like up type quark and a type-I Dirac seesaw in quark sector communicate the Majoron interaction to the up quark. At low energies, the resulting portal generates the nonrelativistic operator $O_{6}$ , whose momentum dependence reproduces the high-recoil event without overpopulating the lower energy bins. Its spin structure removes the dominant heavy element solar capture channels, while capture on hydrogen is suppressed by poor kinematic matching and small momentum transfer. This construction simultaneously reproduces the LZ recoil spectrum and the observed thermal relic abundance while strongly suppressing solar capture.
hep-phgr-qchep-ex
09
Wide-Mass-Scanning-Range Setup and Phase-Resolved Protocol for Axion Dark Matter Detection
A. Cottet · T. Kontos
We propose a paradigm for quantum enhanced axion dark matter search, which does not rely on power measurements. We propose to measure directly the axion amplitude and phase in an interferometric protocol at the quantum limit, using a non-linear cavity. In addition, we introduce gyromagnetic modes as wide mass range transducers for axion signals compatible with standard haloscope designs. We expect this scheme to offer an improvement of at least 4 orders of magnitude in figure of merit and at least 2 orders of magnitude in mass window with respect to standard haloscopes. Owing to its generality, our proposed protocol has the potential to speed up axion search but also the search for dark photons or other cosmological objects, such as galactic masers.
hep-phcond-mat.mes-hallquant-phNew J. Phys. 28 024504 (2026)
10
Dissecting the moat regime at low energies II: Correlations
Fabian Rennecke · Shi Yin
We study the effects of the moat regime on meson and quark correlation functions and the quark-antiquark potential in low-energy QCD, building on the two-flavor quark meson model in a random-phase approximation. We investigate the relation between the moat regime and Friedel oscillations in the quark-antiquark potential at large density and zero temperature. As it turns out, oscillations from the moat regime are a distinct phenomenon, arising from poles on unphysical Riemann sheets in this region. Furthermore, we find that in addition to pions and the sigma meson, also other mesons, including vector mesons and the eta, are sensitive to the moat regime. This leads in particular to an enhancement of the meson spectral function in the spacelike region. The quarks, on the other hand, appear to be essentially insensitive. This can have far-reaching consequences for the phase diagram, as for example the chiral phase boundary, including the location of the critical endpoint, can be affected in the moat regime even in absence of inhomogeneous instabilities.
hep-phhep-thnucl-th
11
Identification of $D_{s 1} (2933)$ as the $2 P_{1}$ state in the quark model
Jun Wang · Qiang Zhao
We investigate the internal structure of the newly observed charm-strange meson $D_{s 1} (2933)^{+}$ , which was reported by the LHCb Collaboration in $B^{0} \to D^{+} D^{-} K^{+} π^{-}$ , in the quark model by treating it as the $2 P_{1}$ state of the $c s ˉ$ system. The coupled-channel corrections to the $^{1} P_{1}$ -- $^{3} P_{1}$ mass matrix are evaluated through the two-point self-energy loops involving the $D K^{*}$ , $D^{*} K$ , $D^{*} K^{*}$ , $D_{s} ϕ$ , $D_{s}^{*} ϕ$ and $D_{s}^{*} η$ intermediate channels. Requiring the corrected eigenvalue to reproduce the measured mass yields a cutoff scale of about $0.82 GeV$ , a $2 P_{1}^{'}$ partner state at $3012 MeV$ , and a mixing angle of $- 12. 9^{\circ}$ that deviates significantly from the heavy-quark ideal-mixing angle. Moreover, the predicted three-body branching ratio fraction $R_{th} = 1.98$ for $D_{s 1} (2933) \to D^{+} K^{+} π^{-}$ via the $D K^{*}$ and $D_{2}^{*} K$ intermediate states is consistent with the experimental value $R_{exp} = 1.2 7_{- 0.95}^{+ 1.29}$ within uncertainties. These results support the assignment of $D_{s 1} (2933)$ as the $2 P_{1}$ excited state of the $c s ˉ$ system with final state interactions.
hep-ph
12
Landscape of pentaquark bound states with neural-network Variational Monte Carlo
Jing-Zhe Song · Wei-Lin Wu · Shi-Lin Zhu
We present a systematic study of the ground states of pentaquark systems using the neural network variational Monte Carlo method within the constituent quark potential model. We investigate all manifestly exotic pentaquark systems with negative parity, which cannot mix with the conventional baryons through the creation and annihilation of light or strange quark pair. We exhaust 387 color, spin, and isospin configurations and identify 21 pentaquark bound state candidates with binding energies ranging from $2$ to $15$ MeV. A striking observation is that all of the bound states are shallowly bound molecular states, and a deeply bound pentaquark state does not exist. The $QQq q Q ˉ$ , $ss q q Q ˉ$ , $Q s q q Q ˉ$ and $Qq q q Q ˉ$ bound states are composed of a heavy vector meson and a baryon, while the $QQq q s ˉ$ and $Qq q q s ˉ$ bound states are composed of a $K$ meson and a heavy baryon. As a cross-validation, the ground-state energies of the unbound systems converge to the baryon--meson thresholds from above, which are consistent with the S-wave scattering states and provide a reliable baseline for the bound-state criterion. Especially, we reproduce the lowest scattering states $η_{c} N$ and $η_{c} Λ$ in the $q q q c c ˉ$ and $q q sc c ˉ$ channels respectively, where the hidden-charm pentaquark resonances were observed experimentally. We also find that all fully heavy pentaquark states are unbound. Our results provide valuable guidance for future pentaquark searches at LHCb, Belle II, and other experiments.
hep-phhep-exhep-latnucl-th
13
Quantum tomography at the Electron-Ion Collider
Michael Fucilla · Yuxun Guo · Yoshitaka Hatta
We initiate the study of quantum state tomography---the experimental reconstruction of the complete spin density matrix---of massless and massive quark-antiquark pairs produced at the future Electron-Ion Collider (EIC). We show that all components of the spin density matrix can be accessed through azimuthal angular correlations between hadron and dihadron pairs generated by the Collins and dihadron fragmentation functions. This enables the experimental investigation of a variety of quantum information properties at the EIC, such as entanglement and Bell-nonlocality. We predict that the recently discovered maximal entanglement in the heavy-quark sector is signaled by a strong modification of the usual Collins angular dependence $cos (ϕ + ϕ^{'})$
hep-phhep-exnucl-th
14
Machine learning for the LHC physics program: a 2025-2026 stocktake
Jesse Thaler
The first sentence of this abstract--and the introduction to these proceedings--was authored by a human, but the bulk of this document was generated by an agentic AI system. In this talk, I take stock of machine learning (ML) for the LHC physics program over the twelve months from May 2025 to May 2026. The corpus is the HEPML Living Review, split at May 2025 into 1,756 earlier papers and 569 later ones. An AI pipeline surveyed the 569 abstracts, ranked them by citations, recency, theme, and collaboration involvement, and read 103 papers in full (95 from after the split, plus 8 earlier baseline papers), producing a structured note for each. The notes were then synthesized into six claims about the state of the field, checked by independent reviewer agents, and re-verified against the source papers. The headline claim is that (1) ML for high-energy physics (HEPML) stopped being a research area that builds tools and became infrastructure that the LHC physics program depends on: ATLAS and CMS now publish physics results that depend on neural networks, and the archived ALEPH data have re-entered production. The other five claims are: (2) simulation-based inference and foundation models are two revolutions starting to merge; (3) AI agents are the genuinely new front, with 47 papers in twelve months and no adopted measurement yet; (4) "do we trust it?" is the fastest-growing agenda, with one recent paper in five about uncertainty, calibration, or interpretability; (5) what is slowing down is informative, since equivariance was absorbed into a tool and model-specific phenomenology ceded ground to model-agnostic searches; and (6) theory ML crossed a capability threshold in multiple research areas. I close with what is settled, what is incoming, and what is open, and briefly discuss the concerns raised by this way of working with AI.
hep-phcs.LGhep-ex
15
$K ˉ^{0} d$ Bound State and Correlation Function
M. Bayar · P. Encarnación · A. Feijoo · E. Oset
We study the $K ˉ^{0} d$ system using a new formulation of the fixed-center approximation that preserves elastic unitarity. The resulting scattering amplitude predicts a bound state below threshold, which can be interpreted as a $Λ (1380) N$ configuration complementary to the $K^{-} pp$ state associated with the higher $Λ (1405)$ pole. The interaction is attractive, with scattering parameters of the same order as recent $K^{-} d$ determinations. We further calculate the $K ˉ^{0} d$ correlation function, which exhibits a characteristic structure associated with the bound state and provides a Coulomb-free observable that can be tested in future ALICE measurements. Results obtained with two different $K ˉ N$ models are very similar, indicating the robustness of the predictions against the choice of the underlying interaction.
hep-phnucl-th
16
Resonantly-Enhanced Baryogenesis through Asymmetric Capture by Primordial Black Holes
Fayez Abu-Ajamieh · Xiaoyan Huo
Primordial black holes (PBHs) can generate the Baryon Asymmetry of the Universe (BAU) through asymmetric capture of baryon-charge-carrying particles, but previous realizations of this mechanism typically yield an asymmetry well below the observed value because the relevant CP-violating scattering asymmetry is loop suppressed. We show that this limitation can be overcome through resonant CP violation in a mixed system of two nearly degenerate unstable fermions, $Y_{1, 2}$ , whose mass splitting is comparable to their decay widths. Rare production of the coherent $Y_{1}$ -- $Y_{2}$ state, followed by CP-asymmetric return and loss decays, generates an $O (0.1)$ difference in integrated decay probabilities while preserving the global baryon charge at the Lagrangian level. Embedding this resonant source in the PBH-capture transport system yields the observed baryon asymmetry. We first reproduce the mechanism in a zero-temperature, sudden-evaporation treatment, which gives $η_{B}^{T = 0} ≃ 2.37 \times 1 0^{- 10} ≃ 2.72 η_{B}^{obs}$ . We find that after including thermal corrections and continuous PBH evaporation and entropy production, the resulting BAU becomes $η_{B} = 8.72 \times 1 0^{- 11}$ in agreement with the observed value. An interesting finding of the model is that even if PBH absorption remains active, we would still have BAU $η_{B}^{no evap} \sim 9.1 \times 1 0^{- 12} \sim 0.105 η_{B}^{obs}$ . We further investigate gravitational-wave signatures associated with the primordial fluctuations responsible for PBH formation. The corresponding scalar-induced gravitational-wave spectra peak at $f \sim 0.16 - 0.17 MHz$ , with $h^{2} Ω_{GW}^{peak} \sim (3 - 7) \times 1 0^{- 8}$ . Under idealized sensitivity assumptions, U-DECIGO can achieve signal-to-noise ratios above 10 for the benchmark spectra.
hep-ph
17
Stress in static force fields and the sign of the D-term
Adam Freese
The sign of the D-term is negative for a variety of hadrons, including the proton and pion. Speculation that this is the result of a mechanical stability condition has persisted despite counterexamples, including the positive D-term of the hydrogen atom. In this work, I explore how the sign of the D-term is influenced by the stress carried by static abelian force fields, finding the contributions from spin-even fields to be negative and the contributions from spin-odd fields (such as the electromagnetic field) to be positive. These contributions correlate with the signs of the D-terms of the fields' respective quanta. Since fields with different spin can produce identical potentials---thus resulting in equally-stable composite systems with identical wave functions---the sign of the D-term has nothing to do with stability. Since hadrons are bound by spin-one gluons, their negative D-terms appear atypical and require explanation. I briefly speculate on how color flux confinement could produce a negative hadronic D-term.
hep-phnucl-th
18
Probing Solar Chameleons with XENONnT Ionization-Only Data
Guan-Wen Yuan
Screened scalar fields provide a possible connection between dark energy and laboratory-scale new physics while remaining compatible with existing fifth-force constraints. Solar production offers a direct probe of these models, and ionization-only measurements extend the sensitivity of liquid-xenon detectors into the sub-keV regime. We present the first search for solar chameleons using low-energy S2-only data, based on the 7.83 tonne-year XENONnT ionization-only data set. The predicted electronic-recoil spectrum is folded through the run-dependent detector response and tested directly in corrected-S2 (cS2) space. A joint binned likelihood combines the seven cS2 bins of science runs SR0, SR1, and SR2. We sample the five-dimensional parameter space ${β_{e}, β_{γ}, M_{e}, Λ, n}$ and derive posterior constraints on the conformal and disformal electron couplings. The data extend the recoil-energy reach to approximately $0.04 keV_{ee}$ , where the few-electron detector response and instrumental backgrounds must be modeled explicitly. In the disformal-dominated regime, the result is expressed in terms of $β_{eff} \equiv β_{γ} (eV / M_{e})^{4}$ . We obtain the upper limit $lo g_{10} β_{eff} < - 3.64$ . Although the present analysis reaches a lower energy threshold than our previous XENONnT electronic-recoil analysis, the resulting constraint is weaker, primarily because the disformal absorption rate decreases rapidly toward low recoil energies, where the background rate also becomes larger. This analysis establishes low-energy ionization data as a new experimental channel for testing solar chameleons and screened dark-energy models.
hep-phastro-ph.HEastro-ph.SR
19
Thermal masses in the Standard Model at three loops
Mikael Chala
We compute the Higgs thermal mass and the electroweak and colour Debye mass parameters to full $O (g^{6})$ in dimensional reduction, where $g$ represents a gauge coupling or the top Yukawa. We employ new methods to evaluate previously unknown mixed-signature sum-integrals.
hep-phhep-th
20
Mono-Z signal for dark matter searches at future lepton colliders and cosmological interpretation
Anupam Ghosh · Partha Kumar Paul · Abhik Sarkar · Rituparna Ghosh · Rachit Sharma · Subhaditya Bhattacharya
We investigate mono- $Z$ signature at the future electron-positron collider within the dark matter effective field theory (DMEFT) framework, considering operators up to dimension six for scalar, fermionic, and vector dark matter (DM) candidates. The operators are classified according to their underlying production mechanisms. We identify the phenomenologically viable parameter space by imposing the observed DM relic abundance together with direct and indirect detection constraints, Higgs invisible decay limits, and LHC mono- $Z$ bounds obtained through a recasting analysis. We study the discovery prospects of the surviving DM operators at the future $e^{-} e^{+}$ collider including initial and final state radiation, detector simulation, and the reconstruction of both leptonic and hadronic $Z$ -boson decay modes. We exploit missing energy, missing transverse momentum, recoil mass, $Z$ -boson pseudorapidity, together with beam polarization, which play a significant role to distinguish the signal from the Standard Model background. We find that fermionic dipole, scalar leptophilic, vector Higgs-portal, and gauge-portal DM operators offer robust mono- $Z$ discovery potential, probing multi-TeV effective scales.
hep-ph
21
Scheme Transformations in Non-Linear QCD Evolution: Towards a Stable NLO BK Equation
Renaud Boussarie · Paul Caucal · Piotr Korcyl · Yacine Mehtar-Tani
High-energy QCD evolution at NLO suffers from large collinear logarithms that make the perturbative expansion of the Balitsky-Kovchegov (BK) equation unstable. We develop a systematic scheme-transformation framework using the Doi-Peliti formalism to relate projectile ( $k^{+}$ ) and target ( $k^{-}$ ) factorization schemes. The transformation of high-energy operators and the evolution kernel generates NLO terms that cancel the problematic double collinear logarithm. The resulting NLO BK equation is free of this instability, with only single collinear and double anti-collinear enhancements remaining. Numerical solutions show stable evolution up to $Y = 10$ for both Golec-Biernat-Wusthoff and McLerran-Venugopalan initial conditions, providing a consistent path toward combining stable NLO evolution with rotated NLO impact factors.
hep-ph
22
Heavy Higgsino Dark Matter With Low Reheating in View of the LZ High-Recoil Event
C. Pallis
We show that a heavy higgsino $h ~$ with mass $m_{h ~} \sim 0.1 PeV$ , which can be made consistent with the recent LUX-ZEPLIN event avoiding constraints from direct and indirect detection, can account for the present cold dark matter abundance of the universe, if the reheating temperature is bounded as $T_{rh} ≲ 595 GeV$ . These values can be achieved by a possible out-of-equilibrium decay of a modulus $ϕ$ with mass $m_{ϕ} ≫ m_{h ~}$ and a non-vanishing branching ratio into $h ~$ 's which plays a decisive role in reducing $T_{rh}$ below its upper limit via the non-thermal $h ~$ production. The modulus $ϕ$ can be identified with the scalar component of the goldstino superfield which is involved in the generation of the $μ$ parameter of MSSM (with $μ ≃ m_{h ~}$ ) via the Giudice-Masiero mechanism.
hep-phastro-ph.COhep-th
23
Constraining Ultra-Light Vector Bosons via Solar Neutrino Oscillations: The Gauged $L_{μ} - L_{τ}$ Model and Prospects for JUNO and XLZD
Ilídio Lopes
We present an extension of the Standard Model based upon the gauged $U (1)_{L_{μ} - L_{τ}}$ symmetry, featuring an ultra-light vector boson that couples to the difference of muon and tau lepton numbers. This anomaly-free construction, historically motivated by the muon's anomalous magnetic moment, is employed here as an independent phenomenological framework for solar neutrino physics. Through kinetic mixing with the photon, the $Z^{'}$ boson generates an effective matter potential within the solar interior, thereby modifying neutrino flavour oscillations via the Mikheyev--Smirnov--Wolfenstein mechanism. Utilising recent solar neutrino measurements from Borexino, SNO, and Super-Kamiokande, together with an up-to-date standard solar model, we constrain the boson mass to be below $5.7 \times 1 0^{- 17} eV$ , a potential ultra-light dark matter candidate. The optimal model, with coupling parameter $η_{o} \approx - 2$ , yields $χ_{ν}^{2} = 2.7$ , compared with $χ_{ν}^{2} = 3.1$ for the standard three-flavour scenario. This best fit corresponds to an effective four-fermion coupling $g_{Z^{'}}^{2} ε / m_{Z^{'}}^{2} \approx 6.6 \times 1 0^{- 23} eV^{- 2}$ , approximately $5.7$ times the Fermi constant, equivalent for $ε \approx 1$ and a reference mediator mass of $1 eV$ to a gauge coupling $g_{Z^{'}} \approx 8 \times 1 0^{- 12}$ . We also present projections for forthcoming experiments: the Jiangmen Underground Neutrino Observatory (JUNO), operating since August 2025 with world-leading precision on oscillation parameters, together with the XLZD consortium, should substantially refine these constraints. Such ultra-light particles may address long-standing discrepancies in galaxy simulations within the cold dark matter paradigm, whilst terrestrial long-baseline neutrino experiments provide complementary probes of this parameter space.
hep-phastro-ph.SRhep-exhep-th
24
Gottfried-Jackson polarization filters for holographic dilaton and transverse-traceless gluon responses in near-threshold $J / ψ$ photoproduction
Arkadiy I. Syamtomov
Within the Hatta-Yang holographic graviton-dilaton amplitude for near-threshold $J / ψ$ photoproduction, we identify exact dilaton-null spin-projection channels in the Gottfried-Jackson basis. The $m = 0$ and $m = - λ_{γ}$ amplitudes receive no dilaton contribution; for photon polarization normal to the reaction plane the $m = 0$ channel further isolates $A_{g} (t) + B_{g} (t)$ and requires nucleon spin transfer. Standard beam-polarization spin-density-matrix elements then furnish TT-only controls and a bilinear containing linear dilaton-TT interference. A comparison with modern GlueX and CLAS12 cross sections shows that the original fixed-shape holographic amplitude cannot describe the full near-threshold data with one overall normalization, making the polarization filters tests of the production tensor rather than predictions of a globally validated reaction model.
hep-phhep-exhep-th
25
Sub-MeV gamma-ray lines from an endothermic interpretation of the LZ recoil candidate
Maíra Dutra · Jacinto P. Neto · Clarissa Siqueira
Endothermic upscattering of heavy dark matter offers a compelling interpretation of the high-energy nuclear-recoil candidate recently reported by LUX-ZEPLIN (LZ), with a characteristic recoil energy $E_{R} \propto δ$ , where $δ$ is the mass splitting between the dark matter states. Cosmological and experimental constraints motivate the depletion of the primordial heavier state, which can be regenerated in the Galactic halo. We show that, if the heavier state decays radiatively, the same mass splitting sets the energy of a gamma-ray line, $E_{γ} ≃ δ$ . For our benchmark, this leads to a sub-MeV line within the projected reach of the Compton Spectrometer and Imager (COSI), scheduled for launch in 2027. The confirmation of the LZ candidate event as a dark matter signal would therefore motivate dedicated searches for sub-MeV gamma-ray lines, with COSI providing a timely opportunity to test this interpretation.
hep-phastro-ph.HE
26
Finite-Size Effects on Symmetry Restoration in a Rotating Scalar Field
Jorge David Castaño-Yepes · Larry A. Cerón-Suárez
We investigate $Z_{2}$ symmetry restoration in a real $λ ϕ^{4}$ theory confined to a finite cylindrical region undergoing rigid rotation. The finite transverse extent is imposed through Dirichlet boundary conditions, resulting in a discrete Fourier-Bessel spectrum and an explicit radial dependence of the fluctuation propagator. Using the background-field method, we derive the one-loop effective potential while retaining the spatial structure induced by the finite geometry. At finite temperature, rotation enters through the angular-momentum-dependent shifts of the thermal mode energies, coupling the rotational state to the discrete transverse spectrum. The resulting coincident-point propagator defines a position-dependent thermal self-energy, which is incorporated into the effective potential through ring resummation. This yields a spatially resolved effective potential whose structure depends simultaneously on the background field, temperature, angular velocity, and transverse size. We then use its spatial average to determine the symmetry-restoration temperature and study its dependence on the rotational state and the finite-volume spectrum. The results show that the rotational modification of the transition temperature retains an explicit dependence on the transverse size, reflecting the spectral structure of the finite rotating system rather than solely the causal constraint associated with the light cylinder.
hep-phhep-th
27
Pseudospectra in Holographic QCD Models
Luiz F. Ferreira
We investigate the spectral stability of quasinormal modes in nonconformal holographic QCD models using pseudospectral analysis. We first consider the soft-wall model, focusing on scalar and vector fields, and then extend the analysis to the analytic Improved Holographic QCD (IHQCD) model, where we study tensor glueball fluctuations. In both cases, the equations of motion are formulated as linear eigenvalue problems, allowing the instability of the quasinormal spectrum to small perturbations to be quantified through the pseudospectrum. We find that the spectral stability of the quasinormal modes exhibits a nontrivial dependence on temperature, reflecting the presence of intrinsic dimensionful scales in holographic QCD models. As the temperature increases, the magnitude of the imaginary part of the quasinormal frequencies grows, signaling an increasing decay rate and the progressive loss of coherence of the corresponding hadronic excitations. At sufficiently high temperatures, the quasinormal frequencies approach an approximately linear dependence on temperature, although this regime is reached only after the associated hadronic states have melted. We further compare the pseudospectral instability with the behavior of the corresponding spectral functions. Our results indicate that the growth of pseudospectral instability provides a complementary characterization of the loss of spectral stability and can serve as a useful diagnostic of hadronic dissociation and melting in holographic QCD.
hep-ph
28
Global equilibrium at order $O (ℏ^{2})$ : pseudo-gauge ambiguity, Maxwell relations, and thermodynamic consistency
Asaad Daher · David Wagner · Masoud Shokri · Dirk H. Rischke
We study massive spin- $1/2$ Boltzmann particles in global thermodynamic equilibrium with rotation and acceleration, consistently including quantum corrections up to order $O (ℏ^{2})$ . For such a system, the fluid velocity becomes an independent thermodynamic variable and fundamental thermodynamic relations have to be extended. Employing the Wigner-function formalism, we show that the standard mass-shell condition $k^{2} = m^{2}$ is modified at order $O (ℏ^{2})$ by contributions quadratic in the thermal vorticity. Incorporating this modified mass-shell constraint, we derive the (net) particle-number current, energy-momentum tensor, spin-current tensor, and associated thermodynamic quantities in the kinetic, canonical, and de Groot--van Leeuwen--van Weert (GLW) pseudo-gauges. We explicitly demonstrate that, while global quantities, like the total particle number or total energy, are independent of the choice of pseudo-gauge, local quantities, like the particle-number density or the energy density, are pseudo-gauge dependent. We then examine the thermodynamic relations in each pseudo-gauge and demonstrate that thermodynamic consistency requires that the thermodynamic Maxwell relations are satisfied. We find that these relations hold in the kinetic-theory pseudo-gauge, whereas they are in general violated in the canonical and GLW pseudo-gauges. These findings suggest a preference for using the kinetic-theory pseudo-gauge in applications such as spin hydrodynamics.
↳ nucl-thhep-phhep-th
29
Wormhole fragmentation and the axion Weak Gravity Conjecture
Puxin Lin · Gary Shiu
We derive the axion Weak Gravity Conjecture (aWGC) from the nonperturbative fragmentation of Euclidean wormholes into charged defects. Requiring fragmentation to lower the Euclidean action fixes the axion action-to-charge bound and its order-one coefficient. Without additional scalars, this coefficient coincides with that of the Imaginary Distance Bound (IDB), while additional scalars strengthen the bound. The aWGC in the presence of multiple axio-dilaton pairs is discussed, leading to geometric representations. Axions satisfying the aWGC render the corresponding wormholes unstable, potentially suppressing their proliferation and resolving associated factorization problems.
↳ hep-thgr-qchep-ph
30
Universality classes of sharp gravitational production of light particles
Kanta Ito · Yusuke Mikura · Shuichiro Yokoyama
We establish a classification of the gravitational production of light particles across sharp transitions connecting different asymptotic forms of the scale factor. A family of smooth scale factors with a transition duration $Δ η$ is characterized by its regularity in the sharp-transition limit $Δ η \to 0$ , leading to three qualitatively different universality classes: $C^{0}$ , $C^{1}$ , and $C^{2}$ -or-smoother. We find that the $C^{0}$ class exhibits a quadratic enhancement in the energy density of produced particles, $ρ \propto Δ η^{- 2}$ , while the $C^{1}$ class shows a logarithmic enhancement, $ρ \propto ln (1/Δ η)$ . No sharp-transition enhancement occurs for the $C^{2}$ -or-smoother class. Using a specific $C^{\infty}$ model of the scale factor, we derive the energy density analytically and confirm both the predicted quadratic scaling and its coefficient by numerically solving the mode equation. These results identify the regularity of the scale factor in the sharp limit as the key property controlling the sharp-transition enhancement.
↳ astro-ph.COgr-qchep-ph
31
LaMET-Agent: An Agent Framework for Large-Momentum Effective Theory Analysis
Jinchen He · Xiangyu Jiang · Fei Yao · Dian-Jun Zhao
Large-momentum effective theory (LaMET) provides a first-principles framework for computing the $x$ dependence of light-cone parton distributions from lattice QCD. Over the past decade, theoretical and numerical advances have established a mature multi-stage workflow for systematic calculation of parton physics, although its implementation still requires expert judgment and substantial repeated effort. We present lamet-agent, an open-source large language model (LLM) agent framework that organizes this workflow into an executable, reproducible, and inspectable analysis pipeline. The present release supports collinear quark distributions and implements correlator analysis, renormalization, Fourier transformation, perturbative matching, continuum, physical pion mass and infinite-momentum extrapolations, and automated result review. We validate it on four end-to-end analyses: pion parton distribution functions in the gauge-invariant and Coulomb-gauge formulations, and pion and kaon distribution amplitudes, obtaining results consistent with the published calculations. Extensions to transverse-momentum-dependent distributions, generalized transverse-momentum-dependent distributions, and gluonic distribution functions are planned for subsequent releases.
↳ hep-latcs.AIhep-ph
32
Exact Solutions for Chiral Gravitational Waves from Spin-2 Mixing
Mohammad Ali Gorji · Yuhang Zhu
A spectator spin-2 field can mix linearly with the metric tensor perturbations. We study the coupled tensor system in an inflationary background, including a parity violating effect parametrised by $θ$ . Without expanding in the linear mixing between the two fields, we solve the system exactly for arbitrary mass while treating the mixing strength nonperturbatively. The mode functions of both helicities are constructed by acting with an operator-valued Gauss hypergeometric function $_{2} F_{1}$ on Whittaker modes, and the late-time power spectrum of each graviton helicity is expressed in closed form in terms of the generalised hypergeometric function $_{3} F_{2}$ . We find that one helicity is exponentially enhanced, showing that strong mixing with a spectator spin-2 field can generate a large and highly chiral primordial gravitational wave spectrum. The degree of circular polarisation is bounded by $tanh (π θ)$ , independently of the spin-2 mass and the mixing strength. The same solution also gives the late-time power spectrum of the spectator field and its cross spectrum with the graviton. In the weak mixing limit, our exact result reproduces the perturbative Schwinger-Keldysh result. These solutions provide a nonperturbative framework for studying primordial gravitational waves sourced by additional tensor modes.
↳ gr-qcastro-ph.COhep-phhep-th
33
$β$ Recoil spectroscopy as a Beyond Standard Model laboratory
Leendert Hayen
We consider the nuclear recoil spectrum following allowed $β$ decay as a laboratory for Beyond Standard Model searches, and perform an exhaustive treatment of the Standard Model prediction. We consider final state interactions, nuclear structure corrections, kinematic corrections and radiative corrections, derive new results and show that the nuclear recoil spectrum is theoretically exceptionally clean. We construct a clean statistical framework and analyze the Fisher information for extracting exotic current constraints and testing Cabibbo-Kobayashi-Maskawa top-row unitarity, and consider a number of sterile neutrino scenarios. In addition, we find that for select isotopes separate measurement of the $β$ -asymmetry and recoil spectrum can achieve an increase in the statistical power of up to a factor 40.
↳ nucl-thhep-phnucl-ex
34
Accelerating systems as probes of Lorentz violation
Quentin G. Bailey · Nils A. Nilsson · Sawyer J. Star
We investigate the Fulling-Davies-Unruh effect in a local Lorentz-violating effective field theory, focusing on the quantum-field response of accelerated detectors. We canonically quantize a real scalar field exactly in the coefficients for Lorentz violation. The dispersion relation, Hamiltonian, and massless and massive Wightman functions are obtained. We determine the conditions under which the scalar dynamics preserves boost symmetry and distinguish these from the weaker conditions required for stationarity along a single accelerated worldline. The Wightman functions are used to construct the finite-time Unruh-DeWitt response for a uniformly accelerated detector. For generic coefficients the response is nonstationary and depends on both the duration and temporal location of the measurement. The spectrum, which is the resulting excitation rate as a function of the energy level difference in the detector, is obtained numerically. It shows discernable differences with the usual massive thermal spectrum for dimensionless coefficients on the order of $1 0^{- 7}$ . Experimental implications of the result are discussed. As an alternative viewpoint, we place Lorentz violation in the point-particle sector, derive the exact trajectory generated by a constant electric field, and study the proper-time Fourier response of a conventional scalar wave along the modified trajectory.
↳ hep-thgr-qchep-ph
35
Stochastic gravitational-wave background from self-interacting superradiant clouds
Yin-Da Guo · Richard Brito · Chen Yuan
Gravitational-wave (GW) observations offer a powerful probe of new fundamental fields. One well-motivated source is black hole (BH)--boson cloud systems, in which an ultralight scalar field forms a cloud around a rotating BH via superradiance and emits long-lived nearly monochromatic GWs. In this work, we compute the stochastic GW background (SGWB) from such systems, extending previous work by including scalar self-interactions, and discuss its detectability with next-generation ground-based GW detectors. We find that self-interactions can suppress the SGWB and thereby relax existing LIGO-Virgo-KAGRA constraints inferred from null searches. Namely, the LIGO detectors at design sensitivity are insensitive to a SGWB produced by scalar fields with a decay constant $f_{s} ≲ 3 \times 1 0^{17}$ GeV, independently of the scalar field mass. Looking ahead, we show that a moderately self-interacting cloud can still produce a detectable SGWB with next-generation detectors. Under conservative assumptions, for a decay constant $f_{s} = 1 0^{17}$ GeV, the Einstein Telescope (ET) will be sensitive to scalar masses in the range $\sim [1 0^{- 13.0}, 1 0^{- 11.8}]$ eV, while Cosmic Explorer (CE) will be sensitive to scalar masses in the range $\sim [1 0^{- 13.2}, 1 0^{- 11.7}]$ eV. We also find that the minimum decay constants that still yield a detectable SGWB for ET and CE are $f_{s} \sim 6 \times 1 0^{16}$ GeV and $\sim 3 \times 1 0^{16}$ GeV, respectively.
↳ gr-qcastro-ph.HEhep-ph