HEP Phenomenology·hep-ph

Mon·Jul 27, 2026Monday·July 27, 2026

26 papers—18 primary·8 cross-listed

01
Scattering Amplitudes as Programs: Self-Evolving Search for Theory and Event Generation
Yi Gu🇬🇧 · Sven Krippendorf🇬🇧
By viewing scattering amplitudes as computer programs, we connect two goals: exposing useful analytic structure and constructing efficient numerical evaluators for collider phenomenology. Equivalent programs can differ sharply in multiplicity scaling, arithmetic complexity, cancellation, and runtime. Amplitude calculation therefore defines a structured search problem over analytic representations, recursive algorithms, colour and helicity organisation, and reuse of intermediate objects. We embed repository-scale coding agents inside an external generate-evaluate-select loop with frozen evaluators and objectives, and study three optimisation targets. A scaling search moves from BCFW recursion to a specialised fixed-k split-helicity transfer algorithm, reaching an 805x geometric-mean speed-up on the scored grid. A structural search reorganises NMHV terms into R-invariant-style cells and glued supercells, reducing inter-term cancellation. Across twenty QCD and electroweak processes, an exact-operation search reduces counted arithmetic by 47.7x and gives a 5.9x post-hoc Python runtime improvement. In matched pure-gluon component tests from n=4 to n=6, the evolved engine's speed advantage over the tested Sherpa-Comix exact-sum call grows from 10x to 277x, while its gap to process-specialised MadGraph5_aMC@NLO Fortran compiled at -O3 narrows from 77.7x to 13.7x. The searches move between mathematical representations and combine recursion, symmetry, basis reduction, dynamic programming, and shared computation into hybrid amplitude programs. They provide initial evidence that parts of amplitude optimisation can be made systematic through self-evolving program search, while leaving native generator integration and end-to-end event throughput as future tests. The generator comparison is an isolated exact matrix-element call, not a modification of MadGraph or Sherpa.
hep-phhep-th2 citations
02
Higher-order chiral Lagrangians with vector meson nonet in different representations
Wei Guo🇨🇳 · Qin-He Yang🇨🇳 · Shao-Zhou Jiang🇨🇳
In this paper, chiral Lagrangians with vector meson nonet are constructed across multiple representations, including those to the next-to-leading order in the vector-field representation, as well as to the next-to-next-to-leading order in the tensor-field and hidden local symmetry representations. For the next-to-leading order octet, redundant terms in the other literature are also identified in both the tensor-field and hidden local symmetry representations. Additionally, the equivalence between the tensor-field and hidden local symmetry representations is examined.
hep-ph0 citations
03
Formation and scaling of $Z_{N}$ strings for global $SU (N) / Z_{N}$ symmetry
Masaki Yamada🇯🇵
We numerically investigate networks of global $Z_{N}$ strings with multi-string junctions in a scalar field model whose vacuum manifold is $PSU (N) = SU (N) / Z_{N}$ . The construction of the model is motivated by the Higgs vacua of mass-deformed $N = 4$ supersymmetric Yang-Mills theory, commonly known as $N = 1^{*}$ theory, and provides a tractable effective description of string networks with baryon-vertex-like junctions. We perform classical lattice simulations of the formation and evolution of these networks in a radiation-dominated universe. For $N = 2, 3, 4, 5,$ and $8$ , we find that the networks approach a scaling regime rather than becoming frustrated. The normalization of the string density grows in proportion to the dimension of the adjoint representation, $N^{2} - 1$ , while non-minimal-charge components remain subdominant. These results imply that, at least for $N ≲ 8$ , the amplitude of the gravitational-wave energy density generated by the cosmic-string network scales as $Ω_{GW} \propto μ^{2} (N^{2} - 1)^{2}$ , where $μ$ is the tension of a unit-charge string.
hep-phastro-ph.COhep-th0 citations
04
Direct constraints on the agnostic $ν$ SMEFT from heavy-neutrino searches at the LHC
Luc\'ıa Duarte🇺🇾 · Agust\'ın Guillenea
The observation of neutrino oscillations and masses motivates extensions of the Standard Model containing right-handed neutrinos. If additional new physics exists at scales beyond the direct reach of present experiments, its effects can be systematically described within the neutrino Standard Model Effective Field Theory ( $ν$ SMEFT). In this framework, heavy neutral leptons provide a promising target for collider searches. In this work, we reinterpret a CMS search for heavy Majorana neutrinos in the same-sign dimuon plus two jets final state to constrain the parameter space of the dimension-six $ν$ SMEFT. Using a detailed recast of the experimental analysis, we present results for both a pure-agnostic benchmark and a benchmark incorporating neutrinoless double-beta-decay bounds. For heavy-neutrino masses in the range $200 GeV \leq m_{N} \leq 15 TeV$ , the observed upper limits on the effective coupling strength range from $5.8 \times 1 0^{- 7} GeV^{- 2}$ to $2.3 \times 1 0^{- 6} GeV^{- 2}$ . These results constitute the first experimental exclusion limits on the agnostic $ν$ SMEFT parameter space obtained from a dedicated recast of an LHC heavy-neutrino search.
hep-phhep-ex0 citations
05
ALP pair production at the LHC
Ilaria Brivio🇮🇹 · Simone Meoni🇮🇹 · Davide Pagani🇮🇹
We study axion-like particle (ALP) pair production at the LHC, investigating its sensitivity to the simultaneous presence of dimension-5 and dimension-6 ALP interactions. Focusing on the signature with four isolated photons, we analyze for the first time the non-resonant process $g g \to aa$ , finding that it can constrain significantly ALP interactions, already at an integrated luminosity of 300 fb $^{- 1}$ . Particular attention is paid to the multidimensional nature of the ALP parameter space. To this end, we present a re-interpretation of a search for the Higgs-resonant process $g g \to h \to aa$ by the ATLAS Collaboration, recasting their results within a three-parameter space. We find that the multi-dimensional constraints resulting from both non-resonant and Higgs-resonant ALP pair production exhibit non-trivial features, that are expected to extend to other searches in which the ALPs decay into Standard Model particles.
hep-phhep-ex1 citation
06
Probing Lorentz invariance via diphoton decays of the Higgs boson
Alan Kostelecky🇺🇸 · Connor A. Petway🇺🇸 · Nathaniel Sherrill🇩🇪
The prospects for observing small departures from Lorentz invariance are studied using effective interactions of the Higgs boson with photons. A single operator of mass-dimension five suffices to describe all leading signatures of Lorentz violation in the diphoton decay channel. Comparison of the theoretical modified decay rates with observed signal strengths measured by the ATLAS and CMS Collaborations at the Large Hadron Collider indicates an estimated attainable sensitivity to the corresponding coefficients for Lorentz violation of order $1 0^{- 4}$ GeV $^{- 1}$ .
hep-ph0 citations
07
Revisiting Quark Confinement in the Proton through the Force on Quarks
Ji-Xin Yu🇨🇳 · Ao-Sheng Xiong🇨🇳 · Ji Xu🇨🇳 · Fu-Sheng Yu🇨🇳 · Yong Zheng🇨🇳
Quark confinement, the fact that colored quarks are permanently bound inside color-neutral hadrons and have never been observed as isolated particles, remains one of the central issues of the Standard Model. Recently, Ji et al.\,\cite{Ji:2026lyj} proposed a framework to define and measure the force on quarks in the proton, obtaining strong evidence for a net confining force and thus opening a new perspective on the study of confinement. In this work, we improve this analysis by incorporating light-cone QCD sum rule results to supplement the limited experimental and lattice QCD information in the large- $∣ q^{2} ∣$ region. We further formulate the reconstruction of the quark force as a regularized inverse problem, thereby reducing the model dependence associated with the prescribed functional parametrizations used before. The resulting quark force provides a complementary, less parametrization-dependent determination and remains consistent with that implied by a linear QCD potential, which also supports the robustness of the framework proposed in Ref.\,\cite{Ji:2026lyj}. We also show that improved future inputs can substantially reduce the uncertainty in the reconstructed quark force.
hep-phhep-exhep-latnucl-ex0 citations
08
Polarization fractions and helicity-dependent CP asymmetries in $B_{(s)} \to ρρ, ρ K^{*}$ and $K^{*} K^{*}$ decays
Jian Chai🇨🇳 · Shan Cheng🇨🇳 · Feng-Qing Hu🇨🇳 · Ya Li🇨🇳 · Jin-Yang Shen🇨🇳 · Da-Cheng Yan🇨🇳
In this paper, we present a phenomenological analysis of $B_{(s)} \to ρρ, ρ K^{*}$ and $K^{*} K^{*}$ decays using state-of-the-art perturbative QCD (pQCD) calculations. Our study is primarily motivated by recent polarization measurements from the LHCb and Belle II collaborations, which have significantly improved the precision of polarization fractions and enabled the first full determination of polarization-dependent CP asymmetries. This work extends the comprehensive pQCD study of charmless two-body $B$ decays reported in our previous paper [Chin. Phys. C 46 (2022) 123103], with a particular focus on polarization observables, especially the CP asymmetries in each helicity state, which reflect distinct orbital angular momentum configurations between the two vector mesons. Our predictions for the branching ratios and longitudinal polarization fractions in the $B^{0} \to K^{* 0} K ˉ^{* 0}$ and $B^{+} \to ρ^{0} K^{*+}$ modes are in good agreement with the new experimental data. However, the calculated longitudinal polarization fraction for $B_{s} \to K^{* 0} K ˉ^{* 0}$ is significantly larger than the LHCb measurement. Moreover, the predicted (helicity-dependent) CP asymmetries in $B^{+} \to ρ^{0} K^{*+}$ are about $30%$ smaller than the observed values. These discrepancies point to a rich interplay between different topological amplitudes, highlighting the need for further theoretical investigation to resolve the long-standing polarization puzzle in two-body $B$ decays into vector mesons.
hep-ph1 citation
09
Updated E141 constraints on a long-lived $X_{17}$ vector boson
A. Celentano🇮🇹 · A. Marini🇮🇹 · L. Marsicano🇮🇹
Since its first observation by the ATOMKI experiment in 2018, the $^{*} Be$ anomaly has attracted considerable interest within the dark sector community as it may indicate the existence of a new fundamental particle with a mass of about 16.9 MeV, the $X_{17}$ . However, the minimal model describing $X_{17}$ as a new vector boson is severely constrained by null results from legacy beam-dump experiments. Among these, the E141 experiment at SLAC places stringent limits on the $X_{17}$ coupling to electrons $ε_{e}$ in the $5.1 \times 1 0^{- 5} ≲ ε_{e} ≲ 1.7 \times 1 0^{- 4}$ region. This excludes the possibility of a long-lived $X_{17}$ , potentially in contrast with the preliminary estimate of the particle lifetime recently reported by the ATOMKI collaboration. The E141 limits commonly adopted in the literature rely on reinterpretations of the original analysis under solid but simplifying assumptions. While these studies provide a reliable estimate of the experiment's reach, they rely on approximations that were well justified when the boson mass was largely unconstrained. With the $X_{17}$ mass now confined to a narrow region by recent experimental observations, a more refined treatment of the E141 sensitivity becomes necessary. In this work, we revisit the E141 exclusion limits in the $X_{17}$ scenario by performing a dedicated reanalysis that incorporates a more accurate treatment of the experimental setup and signal prediction. We quantify the impact of these refinements on the excluded parameter space and discuss their implications for the compatibility between the E141 constraints and the vector boson interpretation of the ATOMKI anomalies.
hep-phhep-ex1 citation
10
Resolving Lorentz-Violating New Physics at ESSnuSB Using High-Statistics Complementarity with T2HK
Himanshu Bora🇮🇳 · Debajyoti Dutta🇮🇳 · Monjowara Khatun🇮🇳 · Abinash Medhi🇮🇳
A primary objective for next-generation long-baseline neutrino facilities is the search for Planck-scale Lorentz Invariance Violation (LIV). In this work, we explore the capabilities of the proposed ESSnuSB and T2HK experiments to constrain isotropic, CPT-violating LIV parameters ( $a_{α β}$ ). The modifications to oscillation probabilities induced by these LIV parameters can introduce parameter degeneracies with the atmospheric mixing angle $θ_{23}$ and the Dirac CP-violating phase $δ_{C P}$ , which can potentially result in incorrect determination of the said standard oscillation parameters if we do not account for LIV effects. Through detailed GLoBES simulations, we find that while the second-oscillation-maximum configuration of ESSnuSB yields good constraints on the exact phase of $δ_{C P}$ , its intrinsic neutrino-antineutrino statistical asymmetry persistently leads to wrong octant fake solutions for $θ_{23}$ . By synergizing ESSnuSB's 360 km and 540 km baselines with the complementary, high-statistics measurements from first-maximum configuration of the T2HK's 295 km baseline, we show that the degeneracies are resolved for most LIV parameters. Our analysis reflects how complementarity between ESSnuSB and T2HK provides an effective, matter-independent framework to break LIV-induced degeneracies and establish bounds on Planck-scale LIV physics.
hep-phJ.Subatomic Part.Cosmol.(2026)·0 citations
11
Statistical validation of template-based parameter extraction from toy thrust distributions for future FCC-ee studies
Fatih ilgin🇷🇺
A statistically reliable parameter-extraction procedure should be validated independently of the physical and detector models to which it will eventually be applied. A template-based inference framework is developed and tested using controlled toy thrust distributions as a methodological benchmark for future FCC-ee event-shape studies. The model contains two-jet-like and three-jet-like event components whose relative contribution is governed by a continuous control parameter. Three extraction strategies are compared: a discrete Pearson-type $χ^{2}$ distance, a discrete multinomial negative-log-likelihood estimator, and a likelihood estimator based on linearly interpolated templates. Their performance is quantified with 10,000 pseudo-experiments for samples containing 200--2000 events. Off-grid recovery, histogram-binning variations, template-statistics variations, and a model-mismatch test based on modified momentum smearing are also studied. The multinomial likelihood consistently outperforms the simple uncorrelated Pearson-type baseline used here. For an input parameter of 0.30, the correct-template fraction increases from $0.467 \pm 0.005$ for 200 events to $0.934 \pm 0.002$ for 2000 events. Interpolation reduces off-grid discretization effects, with a maximum absolute mean bias of approximately 0.003 in the tested configuration. Model mismatch nevertheless produces measurable biases, demonstrating that nominal closure alone is insufficient to establish robustness. This study does not determine the physical strong coupling constant. It provides a controlled framework for comparing estimators, quantifying statistical resolution, and diagnosing model dependence before application to realistic parton-shower simulations, hadronization models, detector effects, and FCC-ee data.
hep-phhep-ex0 citations
12
SMEFT-Pheno-Agent: a natural-language-driven AI agent for machine-learning-assisted Standard Model Effective Field Theory phenomenology
Yu-Chen Guo🇨🇳 · Jie Wang🇨🇳 · Ji-Chong Yang🇨🇳
We present SMEFT-Pheno-Agent, a Python workflow guided by a natural-language AI agent to perform machine-learning-assisted Standard Model Effective Field Theory (SMEFT) phenomenology at high-energy colliders. The software coordinates twelve automated execution phases spanning configuration intake, environment validation, event generation, machine-learning selection, statistical inference, and final audit. At each phase boundary, the agent interprets natural-language intent to generate runnable parameter files and adapter invocations required for subsequent execution. Once the detector-level events are written, the agent automatically proposes key kinematic observables alongside candidate machine-learning algorithms suited to the specific data structure and analysis objectives. All numerical calculations are delegated strictly to validated domain tools, with MadGraph5_aMC@NLO, Pythia, Delphes generating collider simulations, and MLAnalysis extracting features. The agent cannot modify physical parameters outside the locked configuration, and all LLM-produced artifacts, including parameter files, observable choices, algorithm selections, and prose drafts, are documented in machine-readable phase manifests prior to execution. These manifests establish complete reproducibility and audit traceability for SMEFT phenomenology studies.
hep-ph3 citations
13
Simultaneous extraction of top quark mass, strong coupling, effective mixing angle, and proton PDFs using inclusive DIS and proton-proton collision data
Mikel Mendizabal Morentin🇩🇪 · Katerina Lipka🇩🇪 · Giovanni Limatola🇩🇪 · Efstathios Agrafiotis🇩🇪 · Oleksandr Zenaiev🇩🇪 · XiaoMin Shen🇨🇳 · Sven Olaf Moch🇩🇪
We present the first simultaneous determination of the proton parton distribution functions (PDFs) together with the strong coupling, the top quark pole mass, and the effective weak mixing angle. The analysis is performed at next-to-next-to-leading order in QCD using the xFitter framework, based on inclusive deep-inelastic scattering measurements at HERA and precise measurements of jet, electroweak boson, and top quark-antiquark pair production in proton-proton collisions at the LHC. Non-relativistic QCD effects in top quark-antiquark pair production are considered at next-to-leading order, and combined with next-to-leading logarithmic soft-gluon resummation. Simultaneously with PDFs and Standard Model (SM) parameters, relevant top quark SM effective-field-theory (SMEFT) operators are constrained. The precision of the obtained SM parameters is competitive with the state-of-the art individual extractions and accounts for the correlations among those parameters and PDFs. This work paves the way for future global interpretation of the LHC data in terms of QCD, SM and SMEFT.
hep-ph0 citations
14
Non-Markovian heavy-quark equilibration and equilibrium correlation function in a thermal medium
Monisha Nair🇮🇳 · Juan Torres-Rincon🇪🇸 · Santosh K. Das🇮🇳
We compute the charm-quark current-current correlation function within the Langevin framework and extract the heavy-quark diffusion coefficient using the Green--Kubo formula. The formalism is further extended to evaluate the correlation function using a generalized Langevin equation that incorporates memory effects via an exponentially decaying memory kernel. We find that while memory effects qualitatively modify the transient structure of the current correlations, the value of the transport coefficient remains unchanged in the non-relativistic limit. In addition, we investigate heavy-quark thermalization in the presence of memory and compare the non-equilibrium solution of a generalized Fokker--Planck equation with the one obtained from the generalized Langevin equation in the non-relativistic limit. We also consider the relativistic version of the correlated noise case and observe that memory effects can give rise to a damped, oscillatory equilibration of the heavy quark in a non-Markovian bath.
hep-phcond-mat.stat-mech1 citation
15
Hot and Dense Medium Effects on the $B_{s}^{*}$ and $B^{*}$ Multiplets
K. Azizi🇮🇷 · N. Er🇹🇷 · J.Y. Süngü🇹🇷
We present an extensive analysis of the in-medium masses and decay constants of the $B_{s}^{*} (5415)$ and $B^{*} (5325)$ multiplets, including both particles and antiparticles, using QCD sum rules at finite temperature and density. The OPE incorporates the full temperature- and density-dependent contributions from the quark, gluon, and mixed condensates. Computing the strange ( $B_{s}^{* 0}$ , $B ˉ_{s}^{* 0}$ ), charged ( $B^{*\pm}$ ), and neutral ( $B^{* 0}$ , $B ˉ^{* 0}$ ) doublet properties allows us to study the effects of flavor symmetry breaking, strangeness, and heavy-quark decoupling on the beauty vector mesons in the medium. Our results indicate that the mass is remarkably resistant to the medium across the entire multiplet: no state loses more than $\sim 13%$ of its vacuum value, even at $T = T_{c}$ and $n = 5 n_{0}$ , the extreme conditions explored here. The decay constant is far more sensitive, losing up to $\sim 78%$ at the same point. Baryon density clearly dominates the medium response, while temperature plays a secondary role until the system approaches the deconfinement crossover. At zero density, every state loses almost the same fraction of its mass and decay constant: mass shifts lie between $- (0.5$ - $1.1) %$ and decay-constant shifts between $- (3.9$ - $5.3) %$ , regardless of charge or flavor, so temperature alone does not distinguish a particle from its antiparticle. At finite baryon density, a clear particle-antiparticle asymmetry emerges: at $T = 0$ and $n = 5 n_{0}$ , the $B ˉ^{* 0}$ mass decreases by $12.9%$ , whereas the $B^{* 0}$ mass shifts by only $6.1%$ , a gap of nearly seven percentage points driven entirely by the vector self-energy. This provides a theoretical basis for the future heavy-ion collision program at RHIC, LHC, FAIR, and NICA.
hep-phhep-exhep-lat1 citation
16
Baryon-number-violating nucleon decays into a dark photon particle
Jin-Han Liang🇨🇳 · Yi Liao🇨🇳 · Xiao-Dong Ma🇨🇳 · Xiang Zhao🇨🇳
Baryon-number-violating (BNV) nucleon decays into a light new particle represent an exciting yet experimentally unexplored frontier. In this work, we systematically study nucleon decays into a dark photon using a low-energy effective field theory extended with a dark photon $X$ , referred to as $X$ LEFT. We first construct a complete set of leading-order BNV $X$ LEFT operators and then perform a systematic matching onto the chiral perturbation theory for operators involving light $u, d, s$ quarks that dominantly contribute to nucleon decays. Within the chiral framework, we derive general expressions for the decay widths of both two- and three-body nucleon decays and analyze the momentum distributions in the latter. Finally, we thoroughly reinterpret the existing experimental data on conventional two-body modes (into a lepton and a meson) to set lower bounds on partial lifetimes of the corresponding three-body modes involving an additional dark photon. These bounds allow us to further set stringent constraints on the $X$ LEFT operators and other correlated decay modes. Our results provide a toolkit for future experimental and theoretical studies of these exotic nucleon decays.
hep-ph0 citations
17
Nambu-Goldstone emissions from the cosmological evolution of global monopoles
Yukihiro Kanda🇯🇵 · Naoya Kitajima🇯🇵
We show the emission of the Nambu-Goldstone (NG) bosons from the cosmological evolution of global monopoles. The NG bosons are non-thermally produced from the dynamics of global monopoles such as the pair annihilation of monopole and anti-monopole. Our numerical lattice simulations demonstrate that the spectrum of NG bosons emitted from the scaling evolution of global monopoles has a peak around the horizon scale, as in the case with the global string and the semilocal string. We also estimate the abundance of the pseudo-Nambu-Goldstone (pNG) dark matter when one (or both) of the NG modes has a soft mass.
hep-phastro-ph.CO0 citations
18
Finite Formation Time Antenna Radiation: Color Spectators Break Single-Emitter BDMPS-Z
Fabio Domínguez🇪🇸 · Pablo Guerrero-Rodríguez🇪🇸 · Carlos A. Salgado🇪🇸
We compute the direct contribution to the squared matrix element for the in-medium soft gluon emission off a color-singlet quark-antiquark pair. To do this, we incorporate medium interactions that take place during the finite formation time of the antenna, thereby accounting for a largely neglected source of modifications with respect to the vacuum baseline. As a consequence, non-trivial correlations with the spectator (i.e.\ non-emitting) leg of the antenna emerge, greatly increasing the complexity of the result even at leading- $N_{c}$ order. The observed modifications entail a significant departure from the limit of instantaneous antenna formation, where the calculation effectively reduces to the well-known BDMPS-Z spectrum.
hep-phnucl-th0 citations
19
Light Antinuclei Coalescence: Femtoscopic Constraints via Neural-Flow Surrogates
M. Korwieser🇩🇪 · L. Fabbietti🇩🇪 · B. Hashemi🇩🇪 · L. Heinrich🇩🇪 · M. Mahlein🇩🇪 · D. L. Mihaylov🇧🇬 · C.S. Zeyn🇩🇪
Precise predictions of cosmic-ray antinuclei fluxes, a prime dark matter signature, are limited by the lack of data constraining production rates of antinuclei. We mitigate this bottleneck with a fast, differentiable normalizing-flow surrogate for the femtoscopic source model (CECA), fit to 49 ALICE proton-proton correlation functions, and extrapolated via scaling laws to the low-multiplicity domain relevant for cosmic rays. The surrogate reproduces CECA with sub-percent emulation fidelity, yielding data-constrained source functions that remove the dominant uncertainty in coalescence-based antinuclei production rates. The resulting uncertainties on the coalescence parameters $B_{2}$ and $B_{3}$ shrink from factors of 10-100 and $\sim$ 1000 to the few percent and ten-percent level, respectively, with an additional $\sim 15%$ wavefunction systematic for $B_{2}$ .
↳ astro-ph.HEhep-ph0 citations
20
An Introduction to Bayesian and Frequentist Simulation-Based Inference with Machine Learning
Maximilian Dax🇩🇪 · Theo Heimel🇧🇪 · Gilles Louppe
Simulation-based inference (SBI) with machine learning is an increasingly important tool for solving inverse problems in science and engineering, including parameter inference and the inversion of detector effects. We provide an overview of the Bayesian and frequentist statistical frameworks, describe how machine-learning-based SBI methods, such as neural posterior estimation and neural likelihood estimation, can be used for parameter estimation within these frameworks, and show that the same methods can also be applied to Empirical Bayes or unfolding tasks. We also discuss how to validate inference results and the limitations of SBI with machine learning.
↳ cs.LGastro-ph.COastro-ph.GAhep-ex+22 citations
21
Lattice study of spin interactions between heavy quarks in the quark-gluon plasma
Dibyendu Bala🇩🇪 · Olaf Kaczmarek🇩🇪 · Sayantan Sharma🇮🇳 · Swagatam Tah🇮🇳
We calculate the spin-dependent potential, which is the $O (1/ M^{2})$ correction term to the thermal potential between a static quark-antiquark pair within non-relativistic QCD. At leading order in hard thermal loop perturbation theory, we show that this spin-dependent potential has an imaginary part which is different in magnitude for pseudoscalar and vector quarkonium states. For the first time, we extract the imaginary part non-perturbatively using lattice techniques, in the deconfined phase of quenched QCD at $T \sim 470$ MeV, after performing a continuum estimation and subsequent renormalization. We have found that the spin-dependent potential in the quark-gluon plasma phase is complex, and its imaginary part has a remarkably significant contribution over the thermal static potential for charmonium states. Consequences of this thermal spin-dependent potential on the quarkonium spectral functions are also discussed.
↳ hep-lathep-phnucl-exnucl-th0 citations
22
Dynamical Baryogenesis in Rainbow Cosmology
Surendra Kumar Gour🇮🇳 · Malay K. Nandy🇮🇳
We investigate baryogenesis in the framework of rainbow cosmology employing a complex scalar field with a softly broken global $U (1)$ -symmetry. The modified dispersion relation of rainbow cosmology leads to energy-dependent modification to the FLRW metric components, that modifies the Friedmann equation and the scalar field dynamics. We thereby obtain analytical solutions for the scalar field evolution in the radiation-dominated epoch, and show that baryon asymmetry is generated dynamically even from an initially baryon-symmetric state. We find that the baryon-to-photon ratio asymptotically approaches a constant value in the long-time limit, which is proportional to the symmetry-breaking coupling strength $λ$ , and scales with the scalar field mass as $M^{- 5/2}$ . Our results demonstrate that requiring consistency with the observed baryon asymmetry constrains the $λ$ and $M$ values within reasonable ranges, thus providing a viable dynamical mechanism for baryogenesis during the radiation-dominated era without invoking supersymmetry.
↳ gr-qchep-ph0 citations
23
Resonances at finite temperature from the lattice
Jakob Hoffmann🇩🇪 · Peter Lowdon🇩🇪 · Owe Philipsen🇩🇪
The properties of hadronic resonances at finite temperature constitute an important probe of the thermal QCD medium. In this work we use the concept of thermoparticles, which characterise thermally-modified but stable particle-like states, to define the notion of two-particle scattering at finite temperature, and establish a unitarity relation for the thermal scattering amplitude. We derive a finite-temperature generalisation of the vacuum two-particle quantisation condition via a skeleton expansion of the finite-volume correlation function. Solving this condition at the finite-volume energy levels of the system constrains the form of the thermal scattering amplitude, and hence the properties of resonances. In contrast to the vacuum case, the kinematic function containing the leading finite-volume corrections is finite at all energies, reflecting the fact that thermoparticles have broadened spectral peaks due to their interactions with the thermal medium. Since all lattice simulations involve a finite temporal extent, our approach can also be used to study finite-temporal size effects in vacuum analyses.
↳ hep-lathep-phhep-thnucl-th0 citations
24
First Lattice QCD Determination of Lepton-Flavor-Universality Ratios in Light-Meson Leptonic Decays
Peter Boyle🇺🇸 · Norman H. Christ🇺🇸 · Xu Feng🇨🇳 · Taku Izubuchi🇺🇸 · Luchang Jin🇺🇸 · Christopher T. Sachrajda🇬🇧 · Xin-Yu Tuo🇺🇸
The ratio of electronic to muonic leptonic decay widths, $R_{e / μ}$ , for the light mesons $π$ and $K$ , provides a clean test of lepton flavor universality (LFU) and a sensitive probe of physics beyond the Standard Model. Its Standard-Model prediction is exceptionally precise, with the leading uncertainty associated with the structure-dependent (SD) radiative correction of $O (0.1%)$ . As experiments such as PIONEER and NA62 aim for unprecedented precision, this SD correction has become an essential ingredient in precision experiment--theory comparisons. We present the first lattice QCD $+$ QED calculation of this SD correction at the physical pion mass and in the continuum limit. We employ the infinite-volume reconstruction (IVR) method with Coulomb-gauge photons, significantly reducing both statistical errors and finite-volume effects. We obtain the Standard-Model predictions, $R_{e / μ} = 1.23501 (10) \times 1 0^{- 4}$ for $π$ and $R_{e / μ} = 2.47653 (34) \times 1 0^{- 5}$ for $K$ . Our results reduce the hadronic uncertainty in $R_{e / μ}$ , provide the most precise Standard-Model predictions to date, and establish first-principles benchmarks for future high-precision tests of LFU.
↳ hep-lathep-ph1 citation
25
Dilatonic states, phase transitions, and criticality in holography
Daniel Elander🇵🇹 · Maurizio Piai🇬🇧
The dilaton is the hypothetical scalar particle associated with spontaneous breaking of approximate scale invariance. It has been predicted to arise dynamically, as a bound state, in special extensions of the standard model of particle physics based on composite dynamics. In confining gauge theories, generic arguments suggest that the scale of explicit symmetry breaking coincides with the confinement scale, that governs also its spontaneous breaking, by setting the size of all the condensates, as well as the masses of bound states and their excitations. Whether a light dilaton can nevertheless exist in such a context is an open question in quantum field theory, answering which has potentially transformative implications from a conceptual viewpoint, besides having striking phenomenological ramifications. It has been suggested that the mass of the dilaton might be suppressed, in respect to the confinement scale, in the special case in which the underlying strongly coupled dynamics undergoes a zero-temperature (weak) phase transition. Identifying the special conditions under which this happens is the subject of ongoing investigations. A dedicated programme of exploration, carried out within the context of gauge-gravity dualities (holography), has been set up to test the viability of this mechanism. We review the relevant technology within holography, and the status of such a programme, by comparing results obtained in a survey of explicit examples. We do so both within the bottom-up, simplified version of gauge-gravity dualities, but also within the more refined, and complete, top-down approach to holography, in which the gravity theory is known to have a more fundamental origin. We highlight the first examples of confining theories in which a parametrically light holographic dilaton forms as a bound state in a region of parameter space in proximity to a critical point of the field theory.
↳ hep-thhep-ph1 citation
26
One-loop effective potential in Kalb-Ramond scalar electrodynamics
Pratik Chattopadhyay🇮🇱 · M. J. Neves🇧🇷
In this work, we study the effective potential at one loop for the Kalb-Ramond scalar electrodynamics. The model is based on a complex scalar field coupled to the electromagnetic field as usual, and also to the Kalb-Ramond field through the dual vector associated with the strength tensor of the $2$ -form gauge field. There is an additional topological coupling of the electromagnetic field and the Kalb-Ramond field. The quantum corrections generated by the Kalb-Ramond sector are computed using dimensional regularization, and the ultraviolet divergences are removed by introducing the appropriate counterterms, leading to a finite renormalized effective potential. We find that the effective potential at one-loop generates terms of the form $ϕ^{6}$ , which is not present in the original bare Lagrangian. As a result, we introduced new counter terms to eliminate such divergences. The theory thus considered is not closed under renormalization.
↳ hep-thhep-ph0 citations

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Mon·Jul 27, 2026Monday·July 27, 2026

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