Journal of High Energy Physics最新文献

We study the collider phenomenology of leptophilic axion-like particles (ALPs), i.e. pseudoscalar particles that couple only to charged leptons. Loops of charged leptons induce effective interactions of the ALPs with photons, which depend on the momenta of the interacting particles and differ between pseudoscalar and derivative lepton couplings. We systematically discuss the form of the interaction with photons for general external momenta and identify the regimes when it can be safely approximated by an effective coupling constant. We use these results to derive novel constraints from LEP and calculate state-of-the-art limits from E137 and NA64 for four different scenarios, in which the ALPs couple either to a single lepton generation or universally to all, for both pseudoscalar and derivative lepton couplings. We collect complementary bounds from astrophysics, flavour, and other laboratory experiments to chart the allowed parameter space of leptophilic ALPs in the MeV-GeV mass range.

Conformal 3-point correlators of conserved currents play important roles in numerous directions. These correlators are fixed by conformal symmetry up to a few parameters, which are known only at leading order in perturbative expansions. The major challenges come from the multi-loop Feynman integrals with three external momenta. In this work, we employ the method of subgraphs to compute the subleading order corrections to the conformal current 3-point correlators in the large N expansion. We show that the method of subgraphs generates diagrammatic expansions for the conformal 3-point correlators, and that it is closely related to the operator product expansions in momentum space. We verify the subgraph expansions of conserved current 3-point correlators using exact results in 3D. We demonstrate that multi-loop 3-point Feynman integrals can be significantly simplified by taking the subgraph expansions. Due to constraints from conformal symmetry, it suffices to keep only the first few terms in the subgraph expansions to completely fix the subleading order corrections. We apply this method to compute the 1/N corrections to current correlators 〈JJJ〉 in the critical O(N) vector model and the Gross-Neveu-Yukawa model. We also compute the 1/N corrections to the coefficients in the current-current-scalar correlators 〈JJσ_T〉 and 〈JJσ〉 in the critical O(N) vector model. We compare the perturbative results with the bootstrap data and discuss their application to conductivity near the quantum critical point.

Realising F -term slow-roll inflation in supergravity is non-trivial due to the well-known η-problem. The common strategy to solve the problem is to impose a shift symmetry on the Kähler potential, but this often leads to a negative potential in the large-field regime. To avoid negative potentials, an additional superfield called the stabiliser is usually added with a desired interaction. An alternative mechanism in supergravity, avoiding the use of a stabiliser superfield, was earlier proposed by two of us in the setup with a single chiral superfield having inflaton and goldstino amongst its field components. In this work, we extend that alternative mechanism to multi-superfield models of inflation, thereby providing a generic framework for embedding a wide class of single- and multi-field inflation models into supergravity. We illustrate our approach by several concrete examples of multi-field inflation and clarify the conditions required to avoid tachyonic instabilities during multi-field evolution. Our proposal significantly broadens the theoretical landscape of F -term inflation models in supergravity.

Following our previous paper “Quantum noncommutative ABJM theory: first steps” [JHEP 1804 (2018) 070)], in this article we investigate one-loop 1PI four- & six-point functions by using the component formalism in the Landau gauge and show that they are UV finite and have well-defined θ^μν → 0 limit. Those results are also valid for all one-loop functions being UV finite by power-counting. In summary, taking into account results from previous [JHEP 1804 (2018) 070)] and this paper we conclude that, at least at the 1-loop order, the NCABJM theory is free from the noncommutative UV and IR instabilities, and that in the limit θ^μν → 0 it flows to the ordinary ABJM theory.

We investigate the quantum dynamics of a closed bosonic string in the curved spacetime of an AdS₅-Schwarzschild black hole. Starting from the Polyakov action, we perform a canonical quantization of the string and formulate its quantum mechanical equation of motion in the Schrödinger (string coordinate) representation. This framework facilitates in obtaining quantum mechanical wave equation governing the radial and angular modes of the string. A central result of our analysis is the emergence of a trapping radius in the exterior region of the black hole. Near this radius, the radial motion of the string is governed by an effective potential that supports small, quantized oscillations, akin to a quantum harmonic oscillator. This behavior indicates a localization of the string at the trapping surface, where it becomes dynamically confined. The angular sector of the wave function is found to be governed by the confluent Heun equation, yielding confluent Heun functions as the angular part of the wave function. The emergence of a trapping surface is analogous to the stretched horizon proposed by Susskind in the context of black hole complementarity. The quantized harmonic oscillation of the string at the trapping radius complements with the Planck’s black body whence the string can emit black-body radiation. Thus, the quantum dynamics of strings in black hole spacetimes offers a novel path to probing the quantum origin of Hawking radiation.

A novel definition of holographic correlation functions on the celestial sphere of Minkowski space was recently introduced in [1] as the extrapolation of bulk time-ordered correlation functions to the celestial sphere. In this work, focusing on theories of scalar fields iyn (d + 2)-dimensional Minkowski space, we show that in perturbation theory such celestial correlation functions admit a conformal partial wave expansion with meromorphic spectral density, and hence also an expansion into conformal blocks. This is achieved in the hyperbolic slicing of Minkowski space by extending the harmonic function (“spectral”) decomposition of AdS bulk-to-bulk propagators to the Minkowski Feynman propagator. We study the conformal partial wave expansion of celestial correlators for four-point contact and tree-level exchange diagrams, and extract the contributions to their conformal block expansions in the direct channel. When all scalar fields are massless, the tree-level exchange diagram takes a remarkably simple form and is given by a finite sum of conformal blocks (and, for d = 2, their derivatives as well). We also discuss the conformal partial wave expansion at the non-perturbative level, where Lorentz unitarity manifests as positivity of the spectral density.

An open question in AdS/CFT is how to reconstruct semiclassical bulk operators precisely enough that non-perturbative quantum effects can be computed. We propose a set of physically-motivated requirements for such a reconstruction map, and explicitly construct a map satisfying these requirements in Jackiw-Teitelboim (JT) gravity. Our map is found by canonically quantizing “action-angle” variables for JT gravity, which are chosen to ensure that the spectrum of the fundamental quantum theory matches known results from the gravitational path integral. We then study unitary quantum dynamics in this theory, and obtain analytical predictions for the dynamics of the wormhole length, including its quantum fluctuations, leveraging techniques from quantum ergodicity theory. Level repulsion in the non-perturbative JT spectrum implies that the average wormhole length is non-monotonic in time, that fluctuations in wormhole length are non-perturbatively suppressed until nearly the Heisenberg time, and that the late-time-evolved Hartle-Hawking state has a heavy-tailed distribution of lengths. We discuss the implications of our results for the “complexity = volume” conjecture.

We perform a detailed pseudodata study to estimate the expected theory uncertainty in the extraction of the strong coupling constant, α_s(m_Z), from a fit to the measured Drell-Yan transverse momentum (q_T) spectrum at small q_T ≪ m_Z. We consider two approaches to estimate the dominant perturbative uncertainties. We first discuss that the traditional approach based on varying unphysical scales is insufficient here because it cannot correctly account for bin-by-bin theory correlations in the q_T spectrum, which are critically important in this case. We then use this case as a nontrivial application of a new approach based on theory nuisance parameters (TNPs), which encodes the correct theory correlations by construction. Moreover, the TNPs can be profiled in the fit thereby allowing the data to constrain the theory uncertainties in a consistent manner. We furthermore discuss the interplay with nonperturbative effects in the peak region q_T ≲ 10 GeV, from where most of the α_s sensitivity originates. The associated nonperturbative uncertainties on α_s when fitting only the q_T spectrum are large. They can in principle be reduced by including additional constraints on the nonperturbative Collins-Soper kernel from lattice QCD calculations. We find that these improvements in the treatment of perturbative and nonperturbative uncertainties and their correlations will enable a competitive α_s extraction from Drell-Yan data at small q_T. We also discuss the implications of our findings, calling into question a recent α_s extraction from the Z q_T spectrum by the ATLAS experiment.

The precise measurement of the top-Higgs coupling is crucial in particle physics, offering insights into potential new physics Beyond the Standard Model (BSM) carrying ( mathcal{CP} ) Violation (CPV) effects. In this paper, we explore the ( mathcal{CP} ) properties of a Higgs boson coupling with a top quark pair, focusing on events where the Higgs state decays into a pair of b-quarks and the top-antitop system decays leptonically. The novelty of our analysis resides in the exploitation of two conditional Deep Learning (DL) networks: a Multi-Layer Perceptron (MLP) and a Graph Convolution Network (GCN). These models are trained for selected CPV phase values and then used to interpolate all possible values ranging from 0 to π/2. This enables a comprehensive assessment of sensitivity across all ( mathcal{CP} ) phase values, thereby streamlining the process as the models are trained only once. Notably, the conditional GCN exhibits superior performance over the conditional MLP, owing to the nature of graph-based Neural Network (NN) structures. Specifically, for Higgs top coupling modifier set to 1, with ( sqrt{s} ) = 13.6 TeV and integrated luminosity of 3 ab⁻¹ GCN excludes the ( mathcal{CP} ) phase larger than 5° at 95.4% Confidence Level (C.L). Our Machine Learning (ML) informed findings indicate that assessment of the ( mathcal{CP} ) properties of the Higgs coupling to the ( toverline{t} ) pair can be within reach of the High Luminosity Large Hadron Collider (HL-LHC), quantitatively surpassing the sensitivity of more traditional approaches.

We present a prescription for computing tree-level scattering amplitudes in 10D super-Yang-Mills (SYM) theory using the pure spinor worldline formalism. The pure spinor formalism has proven to be a powerful framework for studying supersymmetric field theories, providing manifestly covariant and BRST-invariant formulations of amplitudes. By incorporating the worldline approach, we construct a first-quantized representation of SYM amplitudes in 10D, where interactions are encoded through the insertion of vertex operators along the particle’s trajectory. We explicitly compute the N-point function, demonstrating an agreement with the α^′ → 0 limit of open superstring amplitudes and confirming that the kinematic numerators satisfy the expected BRST relations. Our results establish the pure spinor worldline formalism as a tool for studying scattering amplitudes and suggest further applications to 11D supergravity.