HEP Phenomenology·hep-ph

Tue·Aug 25, 2026Tuesday·August 25, 2026

55 papers—42 primary·13 cross-listed

01
A Hydrogen-Like Model for Pion and Kaon Masses Based on Dirac Quark-Hamiltonians and Numerical Methods
Zhenhua Ning🇨🇳 · A. S. Davuluru🇺🇸 · H. Raposo🇺🇸 · Jong-Ping Hsu🇺🇸
We consider a relativistic hydrogen-like model for meson mass spectra. The model is based on a Lagrangian with a new general Yang-Mills symmetry. The strong interactions involve a fourth-order field equation that generates a linear confining potential. Notably, this model for meson masses requires quarks to carry only a single `confining charge' $f_{c}$ rather than three color charges. We classify meson mass spectra into sub-spectra defined by isospin, G-parity, total angular momentum and parity. By applying a numerical solver to the Dirac Hamiltonians--incorporating two short-range confining potentials, we obtain energy eigenvalues in natural units. The model has three coupling constants and one parameter. It provides a robust fit of 31 pions and kaons masses (from $\approx 140 M e V$ to $\approx 2, 300 M e V$ ) to within $\approx 18%$ of relative percentage error. The model suggests that the confining charge $f_{c}$ =0.045/MeV = 8.87 fm plays the role of the basic length in the quark interactions.
hep-phnucl-th0 citations
02
Know What You Don't Flow
Anja Butter🇩🇪 · Sascha Diefenbacher🇺🇸 · Tilman Plehn🇩🇪 · Lorenz Vogel🇩🇪
Calibrated learned uncertainties are a key requirement also for generative neural networks in LHC physics. For a toy model with an explicit likelihood we show how a heteroscedastic and a Bayesian normalizing flow learn the systematic and statistical uncertainties on the underlying phase space density. Without an explicit likelihood we train the heteroscedastic loss on a classifier-reweighted approximate generative network. We illustrate our comprehensive approach for top pair events and show how a conditional heteroscedastic flow propagates calibrated uncertainties to all phase space directions.
hep-ph0 citations
03
Electroweak and Single Top-Quark Conspiracy in Current LHC Data
Christoph Englert🇬🇧 · Roman Kogler🇩🇪 · Michael Spannowsky🇩🇪
Recent LHC measurements of electroweak single top-quark and top-quark associated Higgs boson production show a number of rate shifts, while related multiboson channels remain close to their Standard Model predictions. Gauge symmetry relates these processes such that deviations can be organised as the low-energy imprint of a common ultraviolet origin. A Standard Model Effective Field Theory (SMEFT) analysis of these rates together with $Z$ -pole observables identifies the pattern: a weak top dipole and a triple-gauge deformation carry the largest pulls, accompanied by a positive left-handed top-quark current. An acceptable fit is also obtained with the pure triple-gauge coefficient set to zero. We then ask whether a gauge-invariant model can produce this set of operators and still pass the numerous constraints from experimental data. Within weakly coupled renormalisable matching, no single scalar, vector or vector-like-quark multiplet is sufficient to reproduce the full pattern. A minimal possibility is a multi-threshold vector-like-quark sector (a singlet, a doublet and two triplets) whose currents arise at tree level, while the dipole requires additional loop dynamics that the current sector does not fix. A representative realisation, confronted with direct, indirect and flavour constraints, points to correlated measurements of electroweak single top-quark production, improved $t H$ and $t t ˉ H$ sensitivity, and updated searches for vector-like quarks.
hep-phhep-ex0 citations
04
Disentangling Charged-Current Scalar NSI from the Solar Sector at JUNO
Adriano Cherchiglia🇧🇷 · Pietro Chimenti🇧🇷 · Christiane Frigerio Martins🇧🇷 · Guilherme A. Nogueira🇧🇷 · Pedro Pasquini🇧🇷 · Orlando L.G. Peres🇧🇷
We constrain charged-current scalar non-standard interaction with reactor antineutrinos within a quantum field theory framework of neutrino oscillations. We derive an analytical expression up to $O (ε^{4})$ for the electron antineutrino survival probability including scalar NSI contributions, and show that these effects induce spectral distortions that admit a large mixing angle solution for $θ_{12}$ . Using the 59.1-day and preliminary 207.2-day JUNO datasets, we obtain the first neutrino-oscillation determination of NSI parameters individually, rather than in a flavor-summed combination, from reactor experiments. Assuming one year of data taken, we show that the only solar sector analysis breaks the degeneracy with the solar mixing angle at $3 σ$ of C.L.
hep-ph0 citations
05
Photon production from gluon splitting and fusion induced by a magnetic field of arbitrary strength in relativistic heavy-ion collisions
Alejandro Ayala🇲🇽 · Santiago Bernal-Langarica🇲🇽 · José Jorge Medina-Serna🇲🇽 · Ana Julia Mizher🇧🇷
We compute the yield and elliptic flow coefficient for photons produced during the pre-equilibrium stage of semi-central relativistic heavy-ion collisions from the gluon fusion and splitting processes induced by the presence of a magnetic field. The calculation is performed for arbitrary values of the field strength. The pre-equilibrium gluon distribution is modeled with a glasma-inspired Bose-Einstein occupation factor, as well as with an anisotropic distribution that accounts for the rapid initial expansion along the beam axis. In both cases, we find a very good agreement between the calculation and the experimental data from PHENIX. Most notably, the shape and strength of the elliptic flow coefficient are described quite well, representing a step towards solving the outstanding photon puzzle.
hep-phnucl-exnucl-th0 citations
06
Textures of dimension-six operators in the SMEFT with non-invertible selection rules
Tatsuo Kobayashi🇯🇵 · Hajime Otsuka🇯🇵 · Morimitsu Tanimoto🇯🇵 · Kei Yamamoto🇯🇵
We investigate the flavor structures of dimension-six operators in the Standard Model Effective Field Theory (SMEFT) subject to non-invertible selection rules. In particular, we classify the flavor textures of all baryon-number-conserving dimension-six SMEFT operators and determine the resulting constraints on their Wilson coefficients. The selection rules determine not only the texture zeros but also the allowed tensor structures of the Wilson coefficients, which can be expressed analytically in terms of a reduced number of independent parameters. We also find that the flavor structures of higher-dimensional operators are not necessarily aligned with those of the Yukawa couplings, in contrast to the Minimal Flavor Violation hypothesis, in which the Yukawa couplings govern the flavor structure of higher-dimensional operators. It turns out that the resulting flavor and chirality patterns differ from those typically obtained in SMEFT with conventional flavor symmetries, providing characteristic predictions for $B$ -meson observables and charged-lepton-flavor-violating radiative decays.
hep-phhep-th0 citations
07
Thermal width shift of $Δ^{++}$ in a pion gas
Ying Zhang🇨🇳 · Peng-Yu Niu🇨🇳 · Xin-yue Hu🇨🇳 · Kai-Jia Sun🇨🇳 · Qian Wang🇨🇳
We compute the thermal width shift of the $Δ^{++}$ resonance induced by a pion gas within a nonrelativistic effective field theory framework. The $Δ^{++}$ self-energy is evaluated from pion-forward-scattering diagrams with intermediate proton and $Δ$ states, weighted by the thermal pion distribution. Analytical expressions for the imaginary part of the self-energy yield the temperature-dependent width correction $δ Γ (T)$ . The width increases with temperature, reaching approximately $6$ ~MeV at $T \approx 160$ ~MeV. When the temperature-dependent $Δ$ and nucleon masses from an NJL-model chiral restoration scenario are incorporated, the width shift becomes non-monotonic, peaking near $T \approx 140$ ~MeV---a consequence of the competition between collisional broadening and the shrinking $Δ \to N π$ phase space as the $N$ -- $Δ$ mass gap closes. Applying our formalism to STAR data for $Δ^{++}$ in d+Au collisions at $s_{N N} = 200$ ~GeV, we extract a temperature $T \approx 300$ ~MeV at $p_{t} = 900$ ~MeV, consistent with the experimental extraction within errors. This value significantly exceeds the hadronic-phase temperature, explicitly demonstrating that the observed $Δ^{++}$ width shift is not solely of pion-gas origin---genuine hot-medium and collective-flow contributions must be substantial.
hep-ph0 citations
08
Direct renormalization of flavor-changing currents in vNRQCD for $B_{c}^{(*)}$ decays
Jichen Pan🇨🇳
We present a direct vNRQCD calculation of the two-loop anomalous dimensions of the leading flavor-changing nonrelativistic currents that govern the leptonic decays of the $B_{c}$ and $B_{c}^{*}$ mesons. The calculation is performed at the matching scale $ν = 1$ , where the anomalous dimensions are the ultraviolet counterterms required to cancel the residual infrared poles of the full-QCD short-distance coefficients. In contrast to the conventional extraction from those infrared poles, we determine the current renormalization constants directly in the effective theory. The pseudoscalar and vector channels are obtained from one spin-unified formula, with the spin dependence entering through $S (S + 1)$ . We also clarify the role of ultrasoft-induced mixing operators in the unequal-mass theory: they are essential for the full velocity running below $ν = 1$ , but their Wilson coefficients vanish at the matching point and do not alter the fixed-order current anomalous dimensions reported here. The results agree with the known matching calculations and reduce smoothly to the equal-mass quarkonium limits.
hep-ph0 citations
09
Baryon Asymmetry Transfer to Majorana Dark Matter from a Colored Partner
Wei Huang🇨🇳 · Hongjian Du🇨🇳 · Feng Luo🇨🇳 · Michihisa Takeuchi🇨🇳
We propose a mechanism in which a primordial baryon asymmetry determines the relic abundance of self-conjugate dark matter through a heavier partner sector. In a simplified model with a Majorana fermion $χ$ and a colored scalar partner $q ~$ , QCD annihilations deplete the symmetric partner population while a residual asymmetric component survives as a temporary reservoir. For feeble portal couplings, this asymmetry is transferred to $χ$ at late times, after dark matter freeze-out. The final relic abundance is controlled by the amount of surviving asymmetry, the timing of its transfer, and the subsequent dark matter annihilation. Solving the coupled Boltzmann equations with the relevant chemical-potential effects, we find that an intermediate range of portal couplings can reproduce the observed relic abundance without requiring a compressed mass spectrum. The qualitative mechanism remains robust against variations in the mass hierarchy, dark matter annihilation mode, and lepton asymmetry. The small portal couplings also make the colored partner potentially long lived, allowing LHC searches for heavy long-lived particles to constrain part of the viable parameter space.
hep-ph0 citations
10
Phase-constrained $Σ^{*}$ spectroscopy in the pure- $I = 1$ reactions $K_{L} p \to π^{+} Σ^{0}$ and $K_{L} p \to π^{+} Λ$
Dan Guo🇨🇳 · Marshall B. C. Scott🇺🇸 · Igor Strakovsky🇺🇸 · Fu-Rong Xu🇨🇳 · Bing-Song Zou🇨🇳
Low-energy $K ˉ N$ scattering provides direct access to strange-baryon spectroscopy, but conventional charged-kaon reactions mix the $I = 0$ and $I = 1$ amplitudes. Motivated by the isospin-selective nature of the $K_{L} p$ reactions, we present, to our knowledge, the first simultaneous analysis of the pure- $I = 1$ reactions $K_{L} p \to π^{+} Σ^{0}$ and $K_{L} p \to π^{+} Λ$ in which a common set of resonance parameters and a fixed relative-phase convention are imposed on both final states. Within an effective-Lagrangian model, a joint fit of available differential cross sections and recoil polarizations yields $χ^{2} / d.o.f. = 1.604$ . We find clear channel complementarity: the $t$ -channel $K^{*}$ exchange is more important in $K_{L} p \to π^{+} Λ$ , especially at forward angles, whereas $K_{L} p \to π^{+} Σ^{0}$ is more sensitive to the contribution of $Σ (1620) 1/ 2^{-}$ . At the same time, $Σ (1660) 1/ 2^{+}$ remains important through interference effects in both channels. These results demonstrate the importance of multichannel, phase-constrained analyses for establishing the $I = 1$ hyperon spectrum and provide timely phenomenological input for future high-precision measurements by the KLF program at JLab. Once the pure $I = 1$ amplitudes are reliably determined, they will also enable the separation of the $I = 0$ component in the much more abundant $K^{-} p \to π^{\pm} Σ^{\mp}$ data, opening a path toward a more quantitative study of the $Λ^{*}$ spectrum.
hep-phnucl-th0 citations
11
Integrating Heisenberg uncertainty and maximum entropy principles verses statistical approach to nucleon structure
A. Mirjalili🇮🇷 · S. Khosravi Kia🇮🇷 · S. Atashbar Tehrani🇮🇷
There are many methods to calculate the parton distributions. In this work, we are trying to determine the unknown parameters of valence quark and gluon densities, taking into account some constraints simultaneously. For this purpose, we consider two different approaches. At first approach, a parameterized form for the valence densities are assumed. Using the constraints imposed by the Heisenberg uncertainty and maximum entropy principles and also considering the quark number and momentum sum rules, the unknown parameters of the parton distributions are determined. In second approach, we attribute a statistical distributions to quark, anti-quarks and gluon densities which are including temperature T, volume V and chemical potential, $μ$ , as thermodynamic parameters. In this case, using only the maximum entropy principle and the quark number together with momentum sum rules, the parton distributions in terms of thermodynamic parameters are extracted. The results for valence quark densities in both approaches and additionally the gluon density in second approach are in {satisfactory match} with results from some parametrization models. By evolving these densities to the desired energy scales, we are able to calculate the nucleon $x F_{3}$ structure function and also the ratio of valence quark densities.
hep-ph0 citations
12
Axion-like particle production from kaon decays within U(3) chiral theory
Jinbao Wang🇨🇳 · Zhihui Guo🇨🇳 · Haiqing Zhou🇨🇳
Kaon decays provide important constraints on the axion-like particle (ALP), particularly through the $K \to π a$ processes. In this work, we compute the $K \to π a$ decay amplitudes, as well as the $K \to π π$ decay amplitudes, at leading order within U(3) chiral perturbation theory. The $π π$ final-state interaction effects in both processes are implemented by employing the chiral unitarization approach. The relevant weak low-energy constants are determined by fitting to the experimental data on $K \to π π$ decays. Our numerical analysis shows that the explicit $η_{0}$ contribution to the $K \to π a$ amplitudes is small, whereas the new weak operator unique to the U(3) theory can give a sizable contribution. The $π π$ final-state interactions are found to be insignificant in the $K^{\pm} \to π^{\pm} a$ decays, but give pronounced effects in the $K^{0} / K ˉ^{0} \to π^{0} a$ channels. Constraints on the ALP couplings are derived from the most recent NA62 upper limit on the $K^{+} \to π^{+} + in v i s ib l e$ decay. For completeness, we also include constraints from the KOTO search for $K_{L} \to π^{0} + in v i s ib l e$ , the NA62 measurement of $K^{+} \to π^{+} γ γ$ , and the NA48 measurement of $K_{S} \to π^{0} γ γ$ .
hep-ph0 citations
13
Theoretical description of the $D^{+} \to K ˉ^{0} π^{+} π^{0} π^{0}$ reaction
Zi-Ying Yang🇨🇳 · Wen-Hao Jia🇨🇳 · Dao-Chong Lin🇨🇳 · Wei-Hong Liang🇨🇳 · Chu-Wen Xiao🇨🇳 · Raquel Molina🇪🇸 · Qi-Fang Lü🇨🇳 · Eulogio Oset🇪🇸
We study the $D^{+} \to K ˉ^{0} π^{+} π^{0} π^{0}$ reaction, which shows two clear structures: the $K ˉ^{* 0}$ and $ρ^{+}$ in the $K ˉ^{0} π^{0}$ and $π^{+} π^{0}$ mass distributions, respectively. The study is done starting from the quark level with external and internal emission and hadronizing a pair of quarks to produce a vector and two pseudoscalars. We also consider another mechanism, which does not require hadronization of quark pairs: the direct production of $K ˉ^{* 0}$ and $ρ^{+}$ . With the help of six unknown parameters which are fitted to the data, we are able to get a very good agreement with experimental data for the $K ˉ^{0} π^{0}$ and $π^{+} π^{0}$ mass distributions and a qualitative one for the rest of mass distributions which do not show any particular structure experimentally.
hep-ph0 citations
14
Down-Type Jet Identification in Fully Hadronic $t t ˉ$ Events
Jinhui Guo🇨🇳 · Chenhao Peng🇨🇳
Fully hadronic $t t ˉ$ events carry the largest branching fraction and provide the down-type quark as a near-maximal spin analyzer ( $β_{d} ≃ 1$ ), yet they are rarely used for spin-correlation and entanglement studies because the down-type jets must be extracted from a difficult jet-to-parton reconstruction in the presence of a large QCD multijet background. We develop a two-stage machine-learning reconstruction for this channel: a GNN+Transformer network assigns all reconstructed jets into a legal six-jet top-pair candidate, and a second hybrid classifier resolves the four down/up hypotheses inside the two hadronic $W$ decays. The second stage combines an assignment scorer with an auxiliary conditional diffusion head; we find that the diffusion assignment score can rank hypotheses only when trained with a margin ranking objective, while standard denoising objectives leave it at the random baseline, and the two objectives are largely decoupled. We evaluate the method against a calibrated QCD background and an unmatched $t t ˉ$ component using both reconstruction and spin observables. Compared with a ST1 only benchmark with random down/up labels, the learned ST2 classifier improves both the effective spin-analysis factor and the purity-weighted six-parton exact fraction at fixed event selection. A direct check of the standard spin-correlation coefficient $D$ further gives an ML-reconstructed value compatible with the truth-level value within the resampled spread. These results show that down/up identification can retain useful spin-correlation information in the all-hadronic channel.
hep-ph0 citations
15
Effects of RG running in breaking $μ - τ$ reflection symmetry, conventional versus minimal seesaw
Chandan Kumar Borah🇮🇳 · Chandan Duarah🇮🇳
The $μ$ -- $τ$ reflection symmetry has attracted considerable attention owing to its prediction of a maximal atmospheric mixing angle and a Dirac CP-violating phase $δ = 3 π /2$ , consistent with indications from the T2K and NO $ν$ A experiments. Since current neutrino oscillation data exhibit small but significant deviations from the exact symmetry predictions, understanding the origin of its breaking has become an important problem. In this work, we investigate the radiative breaking of $μ$ -- $τ$ reflection symmetry within the framework of the minimal seesaw model through the renormalization group (RG) evolution of neutrino parameters. Assuming the symmetry to be exact at the flavor symmetry (seesaw) scale, we examine whether the observed low-energy neutrino oscillation data can be reproduced after RG evolution. Owing to the rank-two structure of the minimal seesaw model, one light neutrino mass eigenvalue vanishes, reducing the number of independent high-energy neutrino parameters from five to four. We perform a systematic numerical analysis to determine the allowed high-energy parameter space capable of reproducing the current experimental constraints at low energies. Furthermore, a comparative study between the conventional Type-I seesaw and the minimal seesaw frameworks is carried out by analyzing the RG evolution of the solar and atmospheric mass-squared differences.
hep-ph0 citations
16
Light Dark Matter from Self-cooling Dark Sectors
Esau Cervantes🇵🇱 · Andrzej Hryczuk🇵🇱 · Stefan Lederer🇵🇱
Light thermally produced dark matter is subject to strong bounds stemming from its free-streaming impact on suppressing structure formation. In this paper we show that these limits are significantly alleviated if the dark sector undergoes self-cooling, a new mechanism for lowering the temperature of the dark sector plasma through cannibal self-interactions during freeze-in production. We find that the Lyman- $α$ bounds can be modified by a few orders of magnitude in the sub-MeV region and frozen-in dark matter saturating the observed energy density can be as light as $\approx$ 1.9 (0.7) keV, compared to the $\approx$ 5.7 (1.9) keV warm dark matter limits determined from simulations. Interestingly, a secondary phase of cooling due to simultaneously efficient inverse cannibal- and decay-processes can dominate the modifications of Lyman- $α$ bounds, rather than self-thermalization via cannibal-reactions itself.
hep-ph0 citations
17
Long-range scalar interactions in the effective field theory approach to $0 ν β β$
Fahim Ahmed🇺🇸
As a lepton-number-violating process whose observation would establish the Majorana nature of neutrinos, neutrinoless double-beta decay ( $0 ν β β$ ) is an important low-energy nuclear probe of beyond-the-Standard-Model physics. Effective field theory (EFT) provides a general, model-independent description, and interference among effective mechanisms is essential for disentangling their contributions to the total decay rate. We focus on scalar-type terms of the long-range Lagrangian in the EFT approach to $0 ν β β$ . We simultaneously retain the two scalar interactions involving a common $(S + P)$ leptonic current coupled either to an $(S - P)$ or an $(S + P)$ hadronic current. Their coherent contribution produces mutual interference between the two scalar mechanisms, controlled by the relative complex phase of their couplings, in addition to their separate interference with the standard mass mechanism. We give a compact half-life expression, the explicit scalar--scalar interference coefficient in terms of scalar nuclear-matrix-element ratios and integrated phase-space factors, and a positivity bound on that coefficient. The calculation uses the closure and single-nucleon impulse approximations, retains the dominant scalar recoil subset, and includes the $s_{1/2}$ and $p_{1/2}$ Coulomb waves of the outgoing electrons. The resulting dimensionally explicit formulation provides a basis for correlated analyses of the two scalar coefficients.
hep-phnucl-th0 citations
18
Testing a Flavor-Singlet Radial-Hybrid Interpretation of the $X (2370)$ : Glueball Ambiguity and Discriminating Amplitude Measurements
Jianlong Lu🇸🇬
The nature of the pseudoscalar $X (2370)$ remains unresolved: glueball, hybrid, conventional $q q ˉ$ , and mixed configurations are all viable at the level of present information. We test a flavor-singlet $J^{P C} = 0^{-+}$ radial-hybrid interpretation using a channel-dependent one-node overlap surrogate at $m_{X} = 2.359 GeV$ and a separate flavor-singlet radiative production factor. The resulting decay template naturally suppresses $K^{*} K ˉ$ and can be conditionally normalized to the measured width, although its dominant scalar and tensor channels remain model dependent. Reproducing the inferred central $J / ψ \to γ X$ rate requires an effective singlet-production amplitude about $4.4$ times the fixed- $V (0)$ continuation of the available $N_{f} = 2$ lattice anchor. In a common-nuisance screening comparison, the hybrid-mixed-glueball integrated-score difference is $- 1.29$ , $+ 0.04$ , and $+ 0.41$ for tight, baseline, and wide nuisance settings, respectively; these values constitute a conditional-score tie rather than a composition measurement. We identify coherent amplitudes in $f_{0} (980) η$ , $a_{0} (980) π$ , and $K_{0}^{*} (1430) K ˉ$ as particularly informative. Under the stated proxy forecast covariance, including theory uncertainty for both templates, their joint separation is $Δ χ^{2} ≃ 6.5$ from the shared glueball template and $≃ 7.6$ from the radial- $q q ˉ$ surrogate. A flavor-singlet radial hybrid is therefore compatible with current data but remains indistinguishable from a mixed-glueball interpretation; a coherent amplitude analysis can test the competing decay patterns.
hep-ph0 citations
19
Analytical Solution of the Sudakov--BFKL Interpolation Equation for Small- $x$ Gluon TMDs
Yanbing Cai🇨🇳 · Wenchang Xiang🇨🇳 · Mengliang Wang🇨🇳 · Daicui Zhou🇨🇳
We analytically solve the evolution equation for small- $x$ gluon transverse-momentum-dependent distributions, which describes the interpolation between the Sudakov and BFKL regimes. We first derive its two limiting forms: the BFKL equation for $ξ = α σ s z^{2} /4 ≪ 1$ and the Sudakov equation for $ξ ≫ 1$ . The analytical solutions in these limits are obtained through Mellin-space diagonalization of the BFKL kernel and direct integration of the Sudakov evolution equation, respectively. We then solve the full interpolation equation using a Mellin-space diagonalization ansatz, in which the evolution factor $F (Y, ξ)$ describes the nontrivial $ξ$ -dependent modification of a Mellin eigenfunction of the BFKL kernel. This procedure reduces the original two-dimensional integral to a one-dimensional form and permits an analytical evaluation of the resulting evolution kernel. The obtained solution interpolates consistently between the BFKL and Sudakov regimes through an exponential factor $exp [H (ξ, γ)]$ . An analysis of the structure of $H (ξ, γ)$ allows a quantitative estimation of the transition region between the two dynamical regimes. Our calculation implies a potential matching point in the range of $ξ^{*} ≃ 0.04 - 0.15$ , which is substantially smaller than the naive evaluation value.
hep-ph0 citations
20
Eikonal Expansion for Classical Gluon Fields: from Weak to Strong
Shane Brown🇺🇸 · Alex DeBrizzi🇺🇸 · Alex Kovner🇺🇸
We develop a formal procedure of eikonal expansion for classical fields in gluodynamics. We show that in the weak field limit the expansion is straightforward and determines the eikonal components of vector potentials in terms of eikonal components of color currents via classical equations motion. We demonstrate that the recently proposed Born-Oppenheimer high energy evolution yields the ground state wave function interpretable in terms of the classical fields. The relevant classical field is indeed consistent with the eikonal expansion, and contains the leading eikonal and subeikonal components. For strong fields we find that the naive eikonal expansion is inconsistent, as nonlilearities in equations of motion lead to mixing of eikonal orders. Thus the effect of subeikonal components on the leading eikonal component is not suppressed by the eikonality parameter. We show that this problem can be rectified by classically "integrating out" high longitudional momentum components of gluon fields. This leads to a classical action for the low momentum components with small self interaction, but strongly renorlamized currents, which contain contribution due to high momentum modes.
hep-phnucl-th0 citations
21
Amplitude analysis and branching fraction calculations of $B_{c}$ meson decays into $B_{s} π$ , $D K π$ and $D_{s} K K$ final state mesons
Elnaz Amirkhanlou🇮🇷 · Behnam Mohammadi🇮🇷
In this study, several newly observed decay modes of the $B_{c}^{+}$ meson of the form $B_{c}^{+} \to D h^{+} h^{-}$ , where $D$ denotes a charmed meson and $h^{\pm}$ represents a charged pion or kaon, have been investigated. The decay channels $B_{c}^{+} \to D^{+} K^{+} π^{-}$ , $B_{c}^{+} \to D^{*+} K^{+} π^{-}$ and $B_{c}^{+} \to D_{s}^{+} K^{+} K^{-}$ were observed for the first time. The LHCb Collaboration has measured their branching fractions relative to the reference decay $B_{c}^{+} \to B_{s}^{0} π^{+}$ , and reported experimental values including $R^{e x p} (B_{c}^{+} \to D^{+} K^{+} π^{-}) = (1.96 \pm 0.23 \pm 0.08 \pm 0.10) \times 1 0^{- 3}$ , $R^{e x p} (B_{c}^{+} \to D^{*+} K^{+} π^{-}) = (3.67 \pm 0.55 \pm 0.24 \pm 0.20) \times 1 0^{- 3}$ and $R^{e x p} (B_{c}^{+} \to D_{s}^{+} K^{+} K^{-}) = (1.61 \pm 0.35 \pm 0.13 \pm 0.07) \times 1 0^{- 3}$ . In this regard, by performing precise calculations using the factorization approach, we have computed similar branching ratio values, including $R (B_{c}^{+} \to D^{+} K^{+} π^{-}) = (1.70 \pm 0.08) \times 1 0^{- 3}$ , $R (B_{c}^{+} \to D^{*+} K^{+} π^{-}) = (3.63 \pm 0.45) \times 1 0^{- 3}$ and $R (B_{c}^{+} \to D_{s}^{+} K^{+} K^{-}) = (1.09 \pm 0.08) \times 1 0^{- 3}$ . The obtained theoretical results show good consistency with the recent experimental measurements reported by the LHCb collaboration, confirming the effectiveness of the factorization formalism in describing these $B_{c}^{+}$ decay modes.
hep-ph0 citations
22
Relic Density of Asymmetric Dark Matter with Breit-Wigner Enhancement
Fangyu Liu🇨🇳 · Hoernisa Iminniyaz🇨🇳 · Qiquan Li🇨🇳
The Breit-Wigner Enhancement mechanism provides a novel interpretation for the ``enhancement factor'' derived from data of the PAMELA, ATIC, and PPB-BETS experiments, and we further extends this research to the case of asymmetric Dark Matter. We investigate the impact of resonance mechanism to the asymmetric Dark Matter case and constrain the resonance model parameters to satisfy the ``enhancement factor" and the asymmetric dark matter model parameters to meet the upper bound requirement imposed by the astronomical experiment.
hep-ph0 citations
23
Three-Technology Ultra-High-Energy Neutrino Flavor Measurement
Alba Burgos-Mondéjar🇺🇸 · William G. Thompson🇺🇸 · Carlos A. Argüelles🇺🇸
Ultra-high-energy (UHE) neutrinos, with energies above $100 PeV$ , are powerful probes of fundamental physics, offering unique opportunities to test and constrain models beyond the Standard Model. A central challenge is achieving sensitivity to their flavor composition, which encodes information about production mechanisms at the source as well as potential new physics during propagation. We propose, for the first time, a three-technology strategy to measure the flavor composition of UHE neutrinos by leveraging the complementary strengths of planned and existing experiments. This approach integrates in-ice radio (ARA, ARIANNA, RNO-G, the IceCube-Gen2 radio array), Earth-skimming (TAMBO, POEMMA, Trinity, AUGER, GRAND200k), and in-ice optical Cherenkov detectors (the IceCube-Gen2 optical array). We demonstrate the potential to achieve unprecedented sensitivity to UHE neutrino flavors. The method can be used to probe an energy-dependent neutrino flavor transition at the source across energies ranging from TeV to EeV. As such, this article highlights the discovery potential of a coordinated, multi-technology program for advancing both high-energy and ultra-high-energy neutrino astrophysics.
hep-ph0 citations
24
Charmonia at Finite Momentum and Spatial Correlators in Quark-Gluon Plasma
Thomas Hardin🇺🇸 · Ralf Rapp🇺🇸
Spatial correlation functions of quarkonia in the quark-gluon plasma are available from finite- temperature lattice-QCD with good precision. However, their interpretation in terms of microscopic spectral functions has been challenging due to a highly oscillating momentum integral in their Fourier transform and the need for a reliable evaluation of their 3-momentum dependence. Utilizing the thermodynamic T-matrix approach we first obtain a Lorentz-covariant scattering equation by taking advantage of a separable-potential approximation. Medium effects are included through state-of-the- art heavy-quark selfenergies and a potential screening which we constrain by euclidean correlators from lattice QCD. In addition to the usual two-particle cut in the scattering equation we also include particle-hole excitations, also referred to as zero mode. We find that both the increase of euclidean correlators with 3-momentum and the suppression of the spatial correlators found in lattice-QCD can be qualitatively reproduced, with the zero mode playing an essential role for the former but not for the latter.
hep-phnucl-th0 citations
25
On the Four-Loop Higgs--Gluon Form Factor in Nonlocal Quantum Field Theory
E. J. Thompson🇨🇦
In particle physics the virtual N $^{3}$ LO contribution to gluon-fusion Higgs production in the Standard Model requires four-loop multi-scale QCD amplitudes that in dimensional regularization are dominated by singular integral reduction and difficult master-integral evaluations. In this note we show that a nonlocal UV completion makes each fixed-order four-loop Feynman diagram fully convergent in four dimensions while keeping the analytic structure needed for Lehmann-Symanzik-Zimmermann (LSZ) reduction formula. For gluon-fusion $g g \to H$ we derive a closed form Schwinger-parameter representation where all loop-momentum integrals are performed analytically and thus leaving finite parameter integrals viable for direct numerical evaluation without needing the usual UV subtractions. This method heps to isolate the collider-hard contribution as a convergent four-loop form factor. The strong coupling then is defined by a finite normalization condition in the entire-function regularization scheme and it is related to the $MS$ coupling by finite matching where after this matching, the regulator-dependent corrections decouple in the local limit $E_{M} \to \infty$ .
hep-phgr-qchep-thquant-phNPB(2026)·0 citations
26
Toward a Unified Axion Cosmology
Takeshi Fukuyama🇯🇵
We explore a unified axion framework connecting grand unification, string-inspired axion-like particles (ALPs), and cosmology. Starting from the QCD axion associated with Peccei--Quinn symmetry in supersymmetric SO(10) GUT, we consider the broader spectrum of ultralight ALPs motivated by heterotic string theory. Within this multi-axion structure, we focus on two ultralight scales selected by cosmological requirements. A mode of order $1 0^{- 22}$ eV is assumed to constitute the dominant dark-matter component and can form a Bose--Einstein condensate whose attractive self-interaction leads to nonlinear collapse, providing possible seeds for high-redshift supermassive black holes. A lighter eigen-direction with a characteristic dynamical scale of order $1 0^{- 28}$ eV can transiently increase the pre-recombination expansion rate and reduce the sound horizon. An order-of-magnitude estimate shows that addressing the Hubble tension requires a sound-horizon-weighted axion fraction of order 0.1, corresponding, for a large initial displacement, to an effective decay constant of order $1 0^{18}$ GeV. We show that a multi-axion--multi-instanton system can in principle provide both the required aligned light direction and a higher-order effective potential that makes the $1 0^{- 28}$ eV contribution transient. The framework links theoretically motivated axionic degrees of freedom to the distinct scales required by dark-matter, early-black-hole, and Hubble-tension phenomenology.
hep-ph0 citations
27
Orbital Angular Momentum as a Transverse Probe of Elliptic Small- $x$ Gluon Tomography
Wei Kou🇨🇳 · Xurong Chen🇨🇳
We propose a new way to probe elliptic small- $x$ gluon geometry in hard diffractive dijet deep inelastic scattering: a localized lepton wave packet carrying orbital angular momentum is used as a tunable transverse analyzer of the target. Unlike the conventional plane-wave setup, where the probe provides a fixed transverse projection, the OAM mode supplies additional radial and azimuthal structure while leaving the target dipole matrix element unchanged. We characterize the resulting elliptic response through $S_{M} = D_{M} - C_{M}$ and find finite-yield response nodes whose origin depends on the OAM channel. In the present benchmark, the $M = 1$ crossing is associated mainly with a zero of the direct response, whereas the $M = 3$ channel exhibits a nontrivial cancellation $D_{3} = C_{3} \neq = 0$ . Signed transverse response densities show that this node results from a spatial cancellation rather than from a disappearance of the underlying scattering strength, and its position can be shifted by changing the beam--target offset. The specific sensitive value of $M$ depends on the analyzer profile and kinematics; the broader result is that localized OAM wave packets provide a controllable probe-side degree of freedom for small- $x$ gluon tomography.
hep-phhep-th0 citations
28
Revisiting the $Λ (1405)$ pole structure with convolutional neural networks
Julius B. Pagayon🇵🇭 · Vince Angelo A. Chavez🇵🇭 · Denny Lane B. Sombillo🇵🇭
We revisit the long-standing ambiguity surrounding the complex pole structure of the $Λ (1405)$ resonance by reframing it as a classification problem for convolutional neural networks (CNNs). By training our models to recognize subtle geometric variations on nearly degenerate lineshapes using targeted differential feature on empirical CLAS data, we establish a data-driven consensus on large inference samples. Our results show that the analytic structure characterized by two poles on the $[b t]$ sheet and additional pole on the $[bb]$ sheet globally dominates. The inference-guided pole parameter extraction reveals that the $Λ (1405)$ is a two-state system, characterized by a molecular state sitting below the $K ˉ N$ threshold and a non-molecular state lying above the $Σ π$ threshold.
hep-phnucl-th0 citations
29
$Δ$ resonance contributions to QED radiative corrections in neutron and inverse beta decay
Oleksandr Tomalak🇨🇳 · Yi-Bo Yang🇨🇳
We incorporate the $Δ (1232)$ resonance into pion-induced QED radiative corrections to neutron decay and inverse beta decay (IBD). Within the framework of heavy-baryon chiral perturbation theory with explicit $Δ$ degrees of freedom, we compute additional contributions and study their impact on IBD cross sections and on the renormalization of the nucleon isovector vector and axial-vector charges. $Δ$ resonance does not renormalize the vector charge. For the axial-vector charge, including the $Δ$ resonance restores power counting and significantly reduces the QED radiative correction to the experiment-over-lattice-QCD ratio $g_{A} / (g_{A}^{QCD} g_{V})$ , bringing it to zero within radiative-correction uncertainties. $Δ$ resonance increases the pion-induced QED radiative corrections to IBD by a factor $1.2$ - $1.3$ .
hep-phhep-exhep-latnucl-ex+10 citations
30
Impact of Bubble Nucleation History and Friction on Primordial Black Hole Formation
Tathagata Ghosh🇮🇳 · Kousik Loho🇮🇳 · Sudip Manna🇮🇳
Cosmological first-order phase transitions (FOPTs) in the early Universe are an exciting prediction of many beyond the Standard Model scenarios. Owing to the stochastic nature of bubble nucleation, some causal patches may remain trapped in the false vacuum long after the surrounding regions have completed the transition and started to redshift. Under suitable conditions, these delayed patches can become sufficiently overdense to collapse into primordial black holes (PBHs). One therefore expects characteristic parameters, such as the PBH mass and PBH formation time to be sensitive to the underlying phase-transition dynamics. Here, we adopt a model-independent framework with a fixed mean bubble separation scale ( $R_{*}$ ) to directly compare the impact of exponential and Gaussian nucleation profiles on PBH formation. We further incorporate the effects of friction on the bubble walls arising from interactions with the surrounding plasma. We find that friction significantly modifies the bubble dynamics, leading to significant changes in the PBH mass and formation time for both nucleation histories. Moreover, the stochastic gravitational-wave spectrum generated by the FOPT can provide a complementary probe of the underlying dynamics, allowing the effects of friction on the bubble wall evolution to be distinguished from the frictionless case.
hep-phastro-ph.CO0 citations
31
Semileptonic Decay of $Λ_{b} \to N (1520) ℓ^{-} ν ˉ_{ℓ}$ from QCD Light-cone Sum Rules
Ke-Sheng Huang🇨🇳 · Ao-Sheng Xiong🇨🇳 · Hua-Yu Jiang🇨🇳 · Fu-Sheng Yu🇨🇳
We investigate the complete set of vector and axial-vector form factors for the charged-current transition $Λ_{b}^{0} \to N (1520)^{+}$ using QCD light-cone sum rules (LCSRs) based on the light-cone distribution amplitudes (LCDAs) of the $Λ_{b}$ baryon, with the hard-scattering kernels evaluated at tree level. In the hadronic representation of the correlation function, we include the pole contributions of both the negative-parity $N (1520)$ , with $J^{P} = 3/ 2^{-}$ , and the positive-parity $N (1720)$ , with $J^{P} = 3/ 2^{+}$ . By matching a selected set of Lorentz structures, we derive sum rules that separate the $N (1520)$ contribution from the $N (1720)$ contribution within the adopted two-pole hadronic ansatz. After extrapolating the large-recoil LCSR results over the physical $q^{2}$ region using a pole-improved $z$ expansion truncated at linear order, we predict the differential branching fractions, the lepton forward-backward asymmetry, the charged-lepton polarization, and the $N (1520)$ polarization in $Λ_{b}^{0} \to N (1520)^{+} ℓ^{-} ν ˉ_{ℓ}$ ( $ℓ = e, μ, τ$ ). The corresponding total branching fractions are $B_{e, μ, τ} = (12.4 \pm 10.5, 12.4 \pm 10.5, 5.0 \pm 4.3) \times 1 0^{- 5}$ . Within the stated approximations, these results may serve as theoretical benchmarks for future experimental studies of this channel.
hep-ph0 citations
32
Disentangling isospin violation in charmonia decaying into $Ξ Ξ$ pairs
Huan-Ran Wen🇨🇳 · Chun-Qiu Zhao🇨🇳 · Xu Cao🇨🇳 · Jian-Ping Dai🇨🇳
Based on a model-independent isospin decomposition, we perform a data-driven analysis of $J / ψ$ and $ψ (2 S)$ decays into $Ξ Ξ ˉ$ pairs by leveraging the full set of observables from high-statistics BESIII data. We find that the isospin-violating amplitudes are predominantly driven by the electric couplings, with magnitudes reaching approximately 10%, contrasting with the smaller magnetic contributions of about 3%. A partial-wave analysis further reveals that $S$ -wave isospin violation is comparable to the $D$ -wave contribution.
hep-ph0 citations
33
Neural Boltzmann Equations
Jonas Spinner🇬🇧 · Jack Shergold🇬🇧
The dynamics of particles in the early universe are described by Boltzmann equations, which involve high-dimensional phase-space integrals. Classical approaches use quadrature integration and evolve the system on a fixed momentum grid, which scales poorly to complicated systems and parameter scans, severely limiting the complexity of processes that can be studied. We introduce Neural Boltzmann Equations (NBEs), which combine three coupled concepts to overcome these limitations. First, particle properties are encoded in physics-inspired neural distribution functions, with parameters that can be predicted using neural networks, enabling efficient parameter scans. Second, phase-space integrals are evaluated with Monte Carlo, using importance sampling tools from collider physics. Third, we use the natural gradient method to evolve the system. After demonstrating the individual benefits of NBEs, we use the framework to perform a precision calculation of the effective number of relativistic neutrino degrees of freedom in the early universe.
hep-phcs.LGstat.ML0 citations
34
Integration-by-parts identities in the presence of measurement delta functions
Saimeng Zhou🇩🇪
We derive a convenient form of integration-by-parts (IBP) identities for dimensionally regulated loop integrals that include a measurement constraint imposed by a delta distribution $δ (ϕ (ℓ))$ , where $ϕ$ is a regular and generally non-linear function of the loop momentum. Non-trivial IBP relations can be generated directly by vectors tangent to the hypersurface $ϕ = 0$ , leaving the measurement delta as an overall factor and avoiding derivatives of distributions. This construction provides a systematic route to differential distributions within reverse unitarity for non-linear measurement functions, in particular, for transverse-momentum distributions. We implement the construction and validate it for transverse-momentum distributions in $t t ˉ H$ production at leading order and $t t ˉ$ production at next-to-leading order in QCD.
hep-ph0 citations
35
Search for Light Scalars in the Two Real Singlet Model at the LHC
Aman Desai🇦🇺 · Kristin Lohwasser🇬🇧 · Mohamed Ouchemhou🇭🇷 · Tania Robens🇭🇷 · Prasenjit Sanyal🇰🇷
We investigate exotic scalar decays $h_{2} \to h_{1} h_{1}$ in the Two Real Singlet Model (TRSM), focusing on light CP-even scalars with $20 \leq M_{1} \leq 60$ ~GeV and $20 \leq M_{2} \leq 120$ ~GeV. Unlike previous studies focused on gluon--gluon fusion or vector-boson fusion production, we explore associated production with electroweak gauge bosons, $pp \to V h_{2}$ {\sl( $V = W, Z$ )}, as a complementary and experimentally clean probe of light scalar cascades in the TRSM. The subsequent decay $h_{1} \to b b ˉ$ leads to final states containing four $b$ -jets accompanied by a charged lepton and missing transverse energy. We evaluate the sensitivity of the $4 b + ℓ ν_{ℓ}$ channel at $s = 13.6$ ~\TeV for the LHC Run~3 and the HL-LHC. For an integrated luminosity of $300 fb^{- 1}$ , the $W^{+} h_{2}$ channel provides the strongest sensitivity, reaching a significance of approximately $4 σ$ , while the $W^{-} h_{2}$ channel reaches approximately $3 σ$ . At the HL-LHC with $3000 fb^{- 1}$ , the corresponding significances increase to approximately $12 σ$ and $8 σ$ , respectively, highlighting the strong discovery potential of associated light-scalar production in the TRSM.
hep-ph0 citations
36
Radiative decays of the isoscalar $S$ -wave $D D ˉ$ molecule
Yuan-Jun Gao🇨🇳 · Gang Li🇨🇳 · Shi-Dong Liu🇨🇳 · Pan-Pan Shi🇪🇸
In the hadronic molecular picture, an isoscalar $S$ -wave $D D ˉ$ molecule is naturally expected as the spin-0 partner of $X (3872)$ . Assuming this state, denoted by $X_{0}$ , to be a pure $D D ˉ$ molecule with quantum numbers $J^{P C} = 0^{++}$ , we investigate its radiative decays $X_{0} \to γ V (V = ρ^{0}, ω)$ within an effective Lagrangian framework. The decay amplitudes are generated by intermediate charmed-meson loops, with electromagnetic gauge invariance consistently maintained throughout the calculation. We evaluate the partial decay widths and examine their dependence on the $X_{0}$ mass and the cutoff. Although the individual decay widths exhibit a sizable dependence on the cutoff, their ratio is remarkably stable. In particular, we obtain that the ratio for the decays $X_{0} \to γ ρ^{0}$ and $X_{0} \to γ ω$ is approximately 2.26, which is insensitive to the variation of the cutoff. This robust ratio provides a useful model-insensitive signature of the molecular structure of $X_{0}$ .
hep-phhep-exnucl-exnucl-th0 citations
37
Resonance-continuum interference with a possible tensor $X (6900)$ in radiative double-charmonium production at $s = 10.58 GeV$
Meng-Kun Jia🇨🇳 · Yi-Jie Li🇨🇳 · Guang-Zhi Xu🇨🇳 · Kui-Yong Liu🇨🇳
We study radiative double-charmonium production, $e^{+} e^{-} \to H H γ$ with $H = J / ψ$ and $η_{c}$ , at $s = 10.58 GeV$ , including a possible tensor contribution from the fully charmed state $X (6900)$ . The nonresonant amplitudes are calculated within the color-singlet non-relativistic QCD framework, while the $J^{P C} = 2^{++}$ resonance is combined coherently with the continuum. We find that continuum--resonance interference significantly modifies the invariant-mass distributions near $M_{H H} ≃ M_{X}$ . The $J / ψ J / ψ γ$ channel exhibits a pronounced phase-dependent resonant structure, with a near-resonance cross section of $0.038$ -- $0.111 fb$ . In contrast, the $η_{c} η_{c} γ$ channel is continuum dominated and shows only a localized interference effect with an extremely suppressed production rate, rendering its experimental observation extremely challenging. These channel-dependent features arise from the different effective decay structures and demonstrate the importance of an amplitude-level treatment of the $X (6900)$ contribution.
hep-ph1 citation
38
Probing Glueball content of X(2370) through heavy quarkonium radiative decays and electron-positron annihilation
Ruilin Zhu🇨🇳 · Qiang Zhao🇨🇳
In this paper, we first analyze the light-cone distribution amplitudes of the pseudoscalar Glueball and point out that the two-gluon and quark-antiquark pair contributions naturally mix at the quantum loop level. Based on the $η - η^{'} - G - η_{c}$ tetra-mixing scheme and existing experimental results, we analyze the branching ratio of $J / ψ \to P + γ$ with pseudoscalar meson $P$ and extract the mixing parameters of the tetra-mixing scheme. We then successfully predict the branching ratio of $ψ (2 S) \to P + γ$ , which is found to be in good agreement with experimental results. We also find that the branching ratios of $J / ψ \to X (2370) + γ$ and $ψ (2 S) \to X (2370) + γ$ are highly sensitive to the Glueball-charmonium mixing angle: the destructive mixing interference in the branching ratio of $J / ψ \to X (2370) + γ$ occurs at $ϕ_{g c} \approx 0.01$ , whereas that in $ψ (2 S) \to X (2370) + γ$ occurs at $ϕ_{g c} \approx 0.11$ . Moreover, the $J / ψ \to X (2370) + γ$ branching ratio exhibits constructive mixing interference when the mixing angle is larger than $ϕ_{g c} \approx 0.02$ . Finally, we also study the electroproduction cross sections of pseudoscalar mesons. After excluding the resonance contributions, the theoretical calculations agree with the experimental measurements in order of magnitude, and we also present theoretical predictions for the electroproduction cross section of the $X (2370)$ . These theoretical results can be readily tested by current BESIII and Belle-II experiments, and further experimental measurements will reveal the intrinsic nature of the $X (2370)$ .
hep-phhep-exhep-lat0 citations
39
Next-to-leading-order QCD corrections to $S$ - and $P$ -wave heavy quarkonium decay to $l^{+} l^{-} γ$
Zhi-Guo He🇨🇳 · Xu-Dong Huang🇨🇳
In this work, we comprehensively study the total and differential decay widths of the radiative Dalitz decays $H \to l^{+} l^{-} γ$ up to QCD next-to-leading order (NLO) accuracy within the framework of NRQCD factorization. Our calculation includes the decays of $S$ -wave states ( $η_{c}, η_{b}$ ) and the $P$ -wave triplets ( $χ_{c J}, χ_{b J}$ for $J = 0, 1, 2$ ) to both electron ( $l = e$ ) and muon ( $l = μ$ ) final states. To match realistic experimental detection thresholds, systematic kinematic cuts are implemented on the final-state photon energy. Our analysis of the lepton-pair invariant mass distribution shows distinct singular behaviors across the multiplets originating from the lepton-pair threshold region, which is regularized by the lepton mass, and the soft-photon region, respectively. For the $S$ -wave states, there is only one peak near the lepton-pair threshold region, while for the $J = 0$ and $J = 2$ $P$ -wave states, the peaks show up in both regions. However, for the $J = 1$ $P$ -wave states, the peak only appears in the soft-photon region. Such features provide a rich venue to probe the $γ^{*} \to l^{+} l^{-}$ form factor in heavy quarkonium decay. Integrating over the bounded phase spaces reveals a distinct hierarchy among the $χ_{Q J}$ states in the sensitivity of our theoretical predictions to the soft-photon energy cuts, ordered as $χ_{Q 1} > χ_{Q 2} > χ_{Q 0}$ . In the $χ_{c J} \to l^{+} l^{-} γ$ cases, as the energy cut increases from 100 $MeV$ , to 500 $MeV$ the theoretical predictions at QCD NLO are reduced by $6% (χ_{c 0})$ , $66% (χ_{c 1})$ , and $21% (χ_{c 2})$ for $l = e$ , and by $17% (χ_{c 0})$ , $66% (χ_{c 1})$ , and $39% (χ_{c 2})$ for $l = μ$ . Comparing our predictions with the upcoming high-precision experimental tests at BESIII will definitely deepen our understanding of the predictive power of perturbative calculations.
hep-ph0 citations
40
Imprints of nuclear shell structure in exclusive vector meson production
Arpita Mondal🇮🇳 · Arjun Kumar🇺🇸 · Debojit Sarkar🇮🇳
We report for the first time that, within the saturation framework, exclusive vector meson production at small $x$ is sensitive to the shell structure of the target nucleus. Self-consistent nuclear densities from occupied single-particle orbitals in the quark-meson coupling (QMC) model modify the coherent $∣ t ∣$ -differential cross section, enhancing secondary diffractive lobes in light nuclei and displacing the higher-order minima in intermediate-mass nuclei, whereas for heavy targets the shifts are weaker. Because the small $J / ψ$ dipole is insensitive to saturation, these features make coherent $J / ψ$ production a clean probe of nuclear shell structure, most favorably for intermediate-mass nuclei such as calcium isotopes. For the larger $ϕ$ dipole, shell structure must be included in the nuclear initial state before saturation effects can be isolated in differential observables at the Electron Ion Collider. Our results establish exclusive vector meson production as a probe of the mean-field nuclear structure at small $x$ and provide a baseline for isolating residual many-body correlations.
hep-phhep-exnucl-th0 citations
41
Generalized Chiral $U (1)_{B - L}$ : Towards a Less Constrained $Z^{'}$ and Dark Matter
Ranjeet Kumar🇰🇷 · Hemant Kumar Prajapati🇮🇳
Extensions of the Standard Model by a $U (1)_{X}$ gauge symmetry predict a new $Z^{'}$ boson, whose mass is severely constrained by high-mass dilepton resonance searches at the LHC. We show that these bounds can be relaxed by generalizing the chiral $(B - L)$ charge assignment while preserving gauge anomaly cancellation. The resulting $U (1)_{X}$ charges are parameterized by two independent parameters, and an appropriate choice of these parameters suppresses the $Z^{'}$ branching fraction into charged leptons, substantially weakening the dilepton constraints. The framework accommodates Dirac neutrino masses through a Dirac type-I seesaw mechanism and a stable singlet scalar DM candidate without requiring an additional discrete symmetry. We find that the modified charge assignment, although beneficial for collider phenomenology, introduces a tension between obtaining the observed relic abundance and satisfying direct detection limits when DM annihilation proceeds solely through the $Z^{'}$ portal. The inclusion of scalar-mediated annihilation channels resolves this tension and opens up a broad viable parameter space, with DM masses ranging from $M_{DM} ≃ 60 GeV$ to $10 TeV$ . The resulting parameter space is consistent with the observed relic density, direct detection, collider, and electroweak precision constraints, demonstrating that a generalized chiral charge structure can simultaneously accommodate a less constrained $Z^{'}$ sector, neutrino masses, and viable dark matter phenomenology.
hep-ph0 citations
42
Two-loop renormalisation and Higgs phenomenology in the five-dimensional MSSM
Ammar Abdalgabar🇪🇬 · Alan S. Cornell🇿🇦 · Aldo Deandrea🇫🇷 · Howeida M. Esmaeil🇸🇩 · Mohammed Omer Khojali🇫🇷
The five-dimensional Minimal Supersymmetric Standard Model (5D MSSM) provides an attractive framework in which power-law renormalisation group evolution naturally generates a sizeable trilinear stop coupling, allowing the observed Higgs boson mass to be reproduced without requiring too heavy a supersymmetric spectra. In this work we present a comprehensive two-loop analysis of the 5D MSSM, deriving the complete renormalisation group equations governing the gauge, Yukawa and soft supersymmetry-breaking sectors and examining the perturbative consistency of the theory. Particular attention is given to the ultraviolet behaviour of the model, where we demonstrate that the potentially dangerous leading two-loop contributions cancel as a consequence of the underlying $N = 2$ supersymmetry, leaving a well-behaved perturbative expansion. Building upon this framework, we compute the radiatively corrected Higgs effective potential including the complete Kaluza-Klein (KK) contributions through KK resummation, and investigate the resulting implications for the Higgs sector. The phenomenological viability of the model is subsequently explored through detailed numerical studies of the Higgs boson mass, electroweak precision observables, Higgs coupling modifiers and signal strengths, allowing constraints on the compactification scale and supersymmetric parameter space to be established. We find that the inclusion of the two-loop corrections preserves the characteristic power-law behaviour of the five-dimensional theory while yielding a phenomenologically viable parameter space consistent with current collider and precision measurements.
hep-ph0 citations
43
What Neural Network Field Theory Can and Cannot Realise on a Computer
Thomas R. Harvey🇺🇸
One aim of neural network field theory is to put a quantum or effective field theory on a computer, with the network ensemble itself as the theory. We ask how far that aim can be pushed for a function class regular enough to be computed with. Our main result is a no-go theorem with assumptions that hold for standard network architectures. We use it to separate four versions of neural network field theory, according to whether the defining object is the finite width ensemble or its infinite width limit, and whether the target we want to compute is a quantum or an effective field theory. Neither finite width interpretation is straightforwardly consistent. For finite width ensembles with finite variance at each point, the QFT interpretation fails reflection positivity, while the EFT interpretation establishes no scale separation by which the positivity violation can be placed outside its domain of validity. Of the two limit versions, one can be simulated in full and the other only in part, as only its smeared correlators are computable with a controlled error. As such, at the level of a controlled numerical computation, the QFT and EFT versions cannot be distinguished. One dimension escapes the obstruction, yet reflection positivity is shown to still fail there at every finite width for the cosine network. Two escapes from the theorem remain, giving up either finite variance at a point or exact rotation invariance, and we discuss both of these possibilities.
↳ hep-thcs.LGhep-lathep-ph+21 citation
44
The Schwarzschild Black Hole in an External Gravitational Tidal Field: the Quasinormal Spectrum
Dimitrios Giataganas🇹🇼 · Alex Kehagias🇬🇷 · Antonio Riotto🇨🇭
A black hole need not ring down in isolation, since a nearby companion can subject it to an external gravitational tide. We calculate how a quadrupole tide modifies the Schwarzschild black hole resonances. Linearising the exact tidally distorted Schwarzschild solution in the tidal amplitude $A$ , we derive the diagonal odd- and even-parity perturbation equations on the deformed background and compute the formal first order displacements of analytically continued Schwarzschild resonances. Each diagonal first order shift factorises as $δ ω_{n ℓ m} = A c_{ℓ m} κ_{n ℓ}$ , giving one reduced complex coefficient for each $(n, ℓ)$ , expressed as a ratio of contour integrals, multiplied by a universal Zeeman-like pattern that splits the $2 ℓ + 1$ azimuthal multiplet. For the $ℓ = 2$ and $ℓ = 3$ sectors analysed explicitly, the odd- and even-parity shifts coincide, so Schwarzschild isospectrality survives at first order in the tidal amplitude. Quadratic tidal forces, by contrast, can break this degeneracy. Moreover, for a physical companion, the astrophysically dominant $(n, ℓ, m) = (0, 2, 2)$ mode oscillates faster and decays more slowly. Finally, we show that the eikonal shifts admit a geometric description in terms of the Penrose limit about the tidally deformed photon ring.
↳ gr-qcastro-ph.COhep-phhep-th1 citation
45
Bound and Resonant Spectra of Few-Lepton Coulomb Systems
Liang-Zhen Wen🇨🇳 · Yao Ma🇨🇳 · Zhi-He Shen · Shi-Lin Zhu🇨🇳
We present a unified calculation of bound and resonant states in purely leptonic Coulomb systems: $e^{-} e^{-} e^{+}$ ( $Ps^{-}$ ), $μ^{+} e^{-} e^{-}$ ( $Mu^{-}$ ), $μ^{+} μ^{+} e^{-}$ ( $Mu_{2}^{+}$ ), $e^{+} e^{+} e^{-} e^{-}$ ( $Ps_{2}$ ), and $μ^{+} μ^{+} e^{-} e^{-}$ ( $Mu_{2}$ ). Using an extended stochastic variational method combined with the complex scaling method, we resolve the natural-parity $S$ - and $P$ -wave spectra. Near their respective $n = 2$ thresholds, all three trilepton systems exhibit Gailitis--Damburg sequences generated by $2 S$ and $2 P$ Stark mixing and the resulting inverse-square attraction. Although microscopically distinct from the Efimov effect, this mechanism produces the same inverse-square asymptotics and geometric scaling. The $Ps^{-}$ and $Mu^{-}$ systems exhibit resonance sequences of comparable density, whereas the $Mu_{2}^{+}$ produces a much denser spectrum, with 20 resolved members in the $^{3} P^{o}$ channel. In $Mu_{2}^{+}$ , the deeper states follow molecular Born--Oppenheimer configurations, while the near-threshold spectrum is governed by the atomic $Mu (2) + μ^{+}$ structure. In $Ps_{2}$ , coupling between threshold-degenerate configurations is essential for a near-threshold bound state. In $Mu_{2}$ , the Born--Oppenheimer organization of the resonance spectrum is channel dependent.
↳ physics.atom-phhep-exhep-phnucl-ex0 citations
46
Searching for signatures of self-interacting dark matter in halos from full-physics simulations: From 3D structure to projected observables
Giovanni Y. Ferron · Antonio Ragagnin🇮🇹 · Lorenzo Pizzuti · Moritz S. Fischer🇩🇪
In this work we explore the imprints of self-interacting dark matter (SIDM) on the structure of simulated galaxy groups and clusters in view of future optical surveys. We find that both baryonic and projection effects lead to a significant alleviation of the SIDM core-forming behavior on the mass and density profiles, resulting in very small ( $≲ 5%$ ) deviations from standard collisionless dark matter. The opposite trend emerges for our most massive halos, where SIDM tends to significantly enhance the central density instead; we compare those halos with the observed dark matter profiles of two galaxy clusters, MACS J1206 and Abell S1063, finding that SIDM may leave potentially detectable imprints on cluster cores when considering the small observational uncertainty of current kinematic mass measurements. Finally, we find that weak lensing observations provide a promising tool for testing SIDM on cluster scales: in an idealized scenario where systematics are under control, weak lensing shear profiles exhibit up to $\sim 20%$ level deviations for $M_{200} ≳ 1 0^{13} M_{⊙}$ halos. Conversely, the projected concentration-mass relation is only slightly modified by our SIDM models. We also discuss the limitiations of our analysis and the impact of the simulation resolution, as well as possible extension of this work. Overall, our results provide a baseline for future SIDM studies: although line-of-sight projection and baryonic effects significantly reduce SIDM imprints on halo mass profiles, weak lensing and kinematic analyses in galaxy clusters may potentially allow for robust detection and constraining of dark matter self-interactions in massive structures from megaparsec down to kiloparsec scales.
↳ astro-ph.COhep-ph0 citations
47
On the fundamental group calculation associated to reverse-engineering an exotic CP ^2 #3 \overline{CP }^2 and CP ^2 #2 \overline{CP }^2
Paul Kirk
I provide a detailed exposition of the fundamental group calculations in the ``reverse engineering" construction of an exotic $\CP^{2} #3 \CP^{2}$ and of an exotic $\CP^{2} #2 \CP^{2}$ .
↳ math.GThep-ph0 citations
48
Holographic SU(3) color superconductivity at finite baryon chemical potential
Xin Zhao🇨🇳 · Zhang-Yu Nie🇨🇳 · Ya-Peng Hu🇨🇳
We present a holographic model of SU(3) color superconductivity (CSC) where a global color symmetry is spontaneously broken by a diquark condensate at finite baryon chemical potential. At $μ_{b} = 0$ , a systematic stability analysis over all SU(3) channels recovers the known SU(2) s+p competition. Based on that, the finite $μ_{b}$ further generalizes the s-wave order to an S1+iS2 structure. We find that $μ_{b}$ enhances the critical temperature of the S1+iS2 phase while suppressing the p-wave -- the latter vanishes beyond a certain $μ_{b}$ when backreaction is included. This opposite trend reshapes the phase diagram: with increasing $μ_{b}$ , the balanced S+ phase (S1=S2) takes over the entire color-superconducting region. Our non-Abelian framework provides a concrete holographic description of global SU(3) symmetry breaking, relevant for understanding color-superconducting phases in dense QCD and may offer new insights into the physics of neutron-star interiors.
↳ hep-thhep-ph0 citations
49
Particle Dark Matter in the 1980s and 1990s
Michael S. Turner
In 1980, the Universe was made of stars, cosmology was the province of less than 100 astronomers, the Hubble constant was only known to within a factor of two, and the hot big bang was the ``the standard model of cosmology.'' Particle physics was a thriving enterprise concerned with the inner space of quarks, leptons and the strong, weak and electromagnetic interactions. The Standard Model was newly established and the aspirations were for a ``grand unification'' of the forces and particles. By 2000, the agendas of inner space and outer space were inextricably linked, and $Λ$ CDM with its inflation, particle dark matter and dark energy -- and a Hubble constant reliably known to better than 10\% -- was the new standard model. The big questions connecting inner space and outer space included the origin of ordinary matter, the identity of dark matter, the nature of dark energy, and an understanding of the origin of space, time and the Universe. Particle dark matter, the idea that the bulk of the mysterious dark matter is a new, long-lived or stable elementary particle, played a central in bringing together inner space and outer space, and today is still a hot topic in both fields.
↳ astro-ph.COhep-ph0 citations
50
Constraining Gravitational Waves from Superconducting Cosmic Strings with the Dark Ages $21$ -cm Signal
Adeela Afzal🇷🇺
Superconducting cosmic strings (SCSs) are characterized by three parameters: the dimensionless string tension $G μ$ , the current amplitude $Y$ , and the vector coupling, $e ~$ as recently explored in \cite{Rybak:2024our}. Using the Charge-Velocity-dependent One-Scale (CVOS) model, we compute the stochastic gravitational wave background (SGWB) emitted by current-carrying loops, including the suppression effect of vector radiation. While previous studies have shown that large $e ~$ suppresses the SGWB, allowing larger $G μ$ to evade pulsar timing array (PTA) bounds \cite{Rybak:2024our}, we demonstrate that this parameter space is definitively constrained by an independent, astrophysically clean probe: the Dark Ages global $21$ -cm signal. We recalculated the recently derived $21$ -cm bounds \cite{Si:2025vsj} into the generic $(e ~, Y, G μ)$ parameter space and find that at the threshold where vector radiation emission starts dominating, any coupling $e ~ ≳ 1 0^{- 7}$ and $Y ≃ 0.67$ and $G μ ≳ 1 0^{- 13}$ injects sufficient ionizing radiation to completely erase the $21$ -cm absorption signal at redshift $z ≃ 89$ . Greater current amplitudes impose more stringent constraints. This excludes a large parameter space considered viable. Our model-independent results highlight the complementarity between future lunar-based $21$ -cm experiments and gravitational wave (GW) observatories.
↳ astro-ph.COgr-qchep-phhep-th1 citation
51
Calculation of neutron electric dipole moment from Lattice QCD
Thomas Blum🇺🇸 · Fangcheng He🇺🇸 · Taku Izubuchi🇺🇸 · Luchang Jin🇺🇸 · Hiroshi Ohki🇯🇵 · Sergey Syritsyn🇺🇸
Experimental constraints on the neutron electric dipole moment (nEDM) may imply strong-CP problem in QCD, or unnatural smallness of the QCD theta angle. In this work, we present a novel determination of the neutron electric dipole moment (nEDM) $d_{n}$ sensitivity to theta term from nonperturbative QCD on a lattice with background electric field. Using Feynman-Hellmann theorem, we compute nEDM from the matrix element of local topological charge density between nucleon ground states spatially polarized by an electric field. These states have mixed spatial parity, and we construct them using variational analysis. We obtain statistically significant signal for the theta induced nEDM from lattices with 2+1 dynamical domain wall fermions corresponding to pion masses of 340, 420, and 576 MeV and lattice spacing $a \approx 0.11 fm$ . After extrapolating to the physical point, we obtain $d_{n} = - 0.0050 (4) (8) θ ˉ$ e $\cdot$ fm. Comparison with the current experimental bound on nEDM implies constraint $∣ θ ˉ ∣ ≲ 1 0^{- 11}$ , which confirms existence of the strong-CP problem in QCD. Our pioneering work demonstrates that neutron EDM can be reliably determined from the local density of topological charge with robust control of systematic effects, and can be directly extended to other CP-violating interactions.
↳ hep-lathep-exhep-ph1 citation
52
Differentiable Parametric Simulation and Reconstruction Models in Parnassus
Abdelrahman Elabd🇺🇸 · Eilam Gross🇮🇱 · Dmitrii Kobylianskii🇮🇱 · Runze Li🇺🇸 · Benjamin Nachman🇺🇸
Parnassus is a framework for fast detector simulation and reconstruction, directly mapping truth-level particles onto reconstructed objects. Such models can be built from deep generative networks trained on paired samples, which are fit automatically to a target detector, or from parametric prescriptions of the kind used by Delphes, which are constructed by hand. We remove this asymmetry by making the parametric models fully differentiable so that their parameters can be fit to a target sample by gradient descent. We demonstrate closure by fitting a parametric model to samples from a known configuration of itself, recovering the generating parameters and characterizing the degeneracies among them, and we present a first fit to CMS full simulation. The resulting models are interpretable, inexpensive, and run in the standard Parnassus pipeline which is fully Python based and GPU enabled.
↳ hep-exhep-phphysics.data-an0 citations
53
Open Quantum Systems Approaches for Heavy-Ion Collisions
Alexander Rothkopf🇰🇷
In this contribution to Strangeness in Quark Matter 2026, I review the open quantum systems approach, a modern theoretical framework for addressing the interaction of a quantum system with its environment, and highlight recent progress in its application to the understanding of in-medium heavy quarkonium in relativistic heavy-ion collisions.
↳ nucl-thhep-ph0 citations
54
Dynamics of Wave Structures in Multifield Fuzzy Dark Matter Halos
Yu-Ming Yang🇨🇳 · Xiao-Jun Bi🇨🇳 · Peng-Fei Yin🇨🇳
As a natural extension of the single-field fuzzy dark matter (FDM) model, multifield FDM has attracted increasing attention in recent years. This scenario is motivated both by the axiverse scenario predicted by string theory and by the possibility that multifield FDM may provide a better match to astrophysical observations than its single-field counterpart. In this work, we perform high-resolution numerical simulations to systematically investigate the dynamics of wave structures in multifield FDM halos. In particular, we study the oscillatory and stochastic motions of the central core, the evolution and statistical properties of granules, and the resulting dynamical heating of embedded stellar systems. We find that the frequency spectra of the core density oscillations develop multiple peaks and shift toward higher frequencies relative to the single-field case. The centers of different field components undergo nearly synchronized random walks, while subdominant components exhibit larger random-walk amplitudes. We further show that the suppression of granule density fluctuations with increasing number of fields is largely insensitive to the fractional abundance of each component over a broad parameter range. Moreover, using self-consistent simulations, we find that the dynamical heating induced by granules is progressively suppressed as the number of fields increases. However, once the contribution from the central core is taken into account, this trend would become much less pronounced.
↳ astro-ph.COastro-ph.GAhep-ph0 citations
55
Complex frequency evolution of direct waves from binary black hole mergers
Ling Sun🇦🇺 · Sizheng Ma🇨🇦 · Patrick P. Chen · Andrew Laeuger · Neil Lu🇦🇺 · Yanbei Chen🇺🇸
While no signal originating at a black hole's event horizon can reach future null infinity, information about the horizon and its immediate vicinity can be encoded in asymptotic properties of waves emitted by matter or field perturbations falling toward a growing/forming horizon. Within a response-filtered framework, "direct wave" denotes source-sensitive plunge and remnant-formation information revealed by filtering the black-hole response. Unlike a stationary damped sinusoid with a fixed complex frequency, the direct wave follows the evolving source and has an evolving instantaneous complex frequency tied at late times to the remnant horizon angular velocity $Ω_{H}$ and surface gravity $κ_{H}$ . Using rational filters, we remove quasinormal modes from numerical-relativity waveforms to study this evolution. Before numerical contamination, trajectories depend on remnant spin: the real frequency evolves toward $2 Ω_{H}$ from above for lower spins ( $χ_{f} ≲ 0.7$ ) and from below for higher spins ( $χ_{f} ≳ 0.7$ ), while the instantaneous decay rate increases toward $\sim 2 κ_{H}$ and, in some high-spin cases, beyond it. As in particle-plunge results, the horizon-controlled value is approached only at late times, as frame dragging controls near-horizon motion. For $χ_{f} \sim 0.7$ remnants of non-precessing, comparable-mass binaries, the early-time real frequency is close to $2 Ω_{H}$ because the binary orbital frequency transitions smoothly to the remnant horizon frequency. Finite-time deviations therefore carry information about merger/collapse dynamics rather than undermining the horizon connection. Full direct-wave evolution requires numerical-relativity calibration. We further show that approximate pole-zero pairing in the Kerr response motivates a spin-dependent minimal filter set that suppresses quasinormal-mode features while revealing source-trajectory information.
↳ gr-qcastro-ph.HEhep-ph3 citations

Affiliations

first authorsco-authorsvia INSPIRE