We show that multiparticle contributions to amplitudes of weak decays of the generic topology (heavy quark hits some intermediate point of the propagator line joining the end-points from which momenta $\textit{q}$ and $$q'$$ are emitted) is given in the heavy quark limit and at the leading order in $$\alpha _s$$ by the convolution of (i) hard kernel composed of highly virtual propagators of light degrees of freedom and (ii) the $\textit{B}$-meson multiparticle wave function, $$\langle 0|\phi (x)\phi (x_1)\cdots \phi (x_n)\phi _b(0)\phi (x'_{n'})\cdots \phi (x'_1)\phi (x')|B(p)\rangle $$ , in a $\textit{double-collinear}$ light-cone configuration: the coordinates $$x,x_1,\ldots ,x_n$$ are ordered and aligned along the light-like 4-vector $$a_\mu $$ , $$a^2=0$$ , $$q_\mu \propto a_\mu $$ , while the coordinates $$x',x_1',\ldots ,x'_{n'}$$ are ordered and aligned along the light-like 4-vector $$a'_\mu $$ , $$a'^2=0$$ , $$q'_\mu \propto a'_\mu $$ , $$a'a\ne 0$$ . Corrections to this factorization formula are suppressed by powers of $$\Lambda _\textrm{QCD}/M_B$$ .

Russia

Austria

Dmitri Melikhov

Factorization of multiparticle contributions to amplitudes of $\textit{B}$-meson weak decays

We investigate thermodynamics of a non-interacting quantum field in a static black hole background. The horizon divergences are regulated by the brick wall method, which consists of subjecting the quantum field to Dirichlet boundary conditions on a surface (the brick wall) just outside the horizon. Using heat kernel and Mellin transform methods, we derive high-temperature expansions for the free energy and entropy and study the boundary and higher-order geometric effects on the horizon divergences induced by the brick wall. We consider real scalar, complex scalar, and Dirac fields in Schwarzschild, Reissner–Nordström and dilatonic black hole backgrounds, as well as in their near-horizon geometries. By evaluating the high-temperature expansion of the entropy (up to a certain order) at the Hawking temperature, we show that, for a given field type, the leading horizon divergence is the same for all the metrics considered. Moreover, we show that the different orders in the high-temperature expansion become comparable at the Hawking temperature and compare our findings with existing results in the literature. We derive an explicit formula for the sub-leading horizon divergence expressed in terms of the field mass, surface gravity, horizon area, and dilaton parameter, which is applicable to all the exact metrics considered. We also consider the possibility of using Neumann boundary conditions to regularize the horizon divergences.

Türkiye

Emine Ertuğrul

Birses Debir

Levent Akant

Boundary effects on the thermodynamics of quantum fields near a static black hole

In this work I study the finite temperature Casimir effect caused by a complex and massive scalar field that breaks Lorentz invariance in a CPT-even, aether-like manner. The Lorentz invariance breaking is caused by a constant space-like vector directly coupled to higher order field derivatives. This vector needs to be space-like in order to avoid non-causality problems that will arise with a time-like vector. I investigate the two scenarios of the scalar field satisfying either Dirichlet or mixed boundary conditions on a pair of flat parallel plates. I use the generalized zeta function technique that enables me to obtain the Helmholtz free energy and the Casimir pressure when the Casimir plates are in thermal equilibrium with a heat reservoir at finite temperature. I investigate two different directions of the unit vector, parallel and perpendicular to the plates. I examine both scenarios for both types of boundary conditions and, in both cases and for the two different boundary conditions, I obtain simple analytic expressions of the Casimir energy and pressure in the three asymptotic limits of small plate distance, high temperature, and large mass, examining all combinations of boundary conditions, unit vector direction, and asymptotic limits.

United States

Andrea Erdas

Finite temperature Casimir effect of a Lorentz-violating scalar with higher order derivatives

In this paper we present the first measurement of a Gallium Arsenide (GaAs) crystal as a scintillating calorimeter with dual heat and light readout within the DAREDEVIL project. The experimental setup features a 4.3 g GaAs ( GaAs-1) crystal, operated at approximately 10 mK coupled with a Neutron Transmutation Doped (NTD) thermal sensor for phonon detection and an auxiliary calorimeter for the detection of scintillation light. For the GaAs-1 crystal, a baseline resolution of 121 ± 2 eV has been achieved. While, with a 3.5 g GaAs (GaAs-2) crystal an even better baseline resolution of 44.5 ± 0.8 eV was achieved. Alpha and X-ray calibration sources were used to study the scintillation light response to different types of interacting radiation. The GaAs crystal exhibits a strong particle discrimination capability based on the emitted scintillation light, featuring a light yield (LY) of 0.9 ± 0.2 keV/MeV for $$\alpha $$ induced events and 0.07 ± 0.01 keV/MeV for $$\beta $$ / $$\gamma $$ events, both measured at 1 MeV. The unusual luminescence behavior, i.e. more light being produced under irradiation by $$\alpha $$ particles warrants further investigation, particularly due to its potential to enhance sensitivity to low-energy nuclear recoils from light dark matter scattering.

Italy

A. Melchiorre

D. Helis

A. Puiu

G. Benato

P. Carniti

I. Colantoni

A. Continenza

N. Marco

A. Ferella

C. Ferrari

F. Giannessi

C. Gotti

E. Monticone

S. Nagorny

France

E. Olivieri

L. Pagnanini

G. Pessina

C. Petrucci

S. Pirro

A. Prajapati

G. Profeta

M. Rajteri

P. Settembri

A. Shaikina

C. Tresca

D. Trotta

First measurement of GaAs as a scintillating calorimeter: achievements and prospects

Within the Bethe–Salpeter framework, we present a computation of space-like electromagnetic form factors for pseudoscalar mesons, including light and heavy-light systems. Our approach employs a flavour-dependent variation of the standard Taylor effective charge, which contains key contributions from the quark-gluon vertices. This effective interaction is a common ingredient of all relevant dynamical equations, and accommodates the crucial mass differences between the various quark flavours. Particular attention is paid to the nonperturbative determination of the quark-photon vertex. The computed electromagnetic form factors for the pion and the kaon mesons show excellent agreement with experimental determinations. In addition, the predictions for the charge radii of heavy-light systems are in overall good agreement with lattice QCD.

Spain

A. Miramontes

J. Papavassiliou

Germany

J. Pawlowski

Electromagnetic properties of heavy-light mesons

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 $\textit{b}$-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 $\textit{π}$/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 GCN excludes the $$ \mathcal{CP} $$ phase larger than 5$\textit{°}$ at 95$\textit{.}$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 $$ t\overline{t} $$ pair can be within reach of the High Luminosity Large Hadron Collider (HL-LHC), quantitatively surpassing the sensitivity of more traditional approaches.

Waleed Esmail

Japan

A. Hammad

South Korea

Adil Jueid

United Kingdom

Sweden

Stefano Moretti

Boosting probes of $$ \mathcal{CP} $$ violation in the top Yukawa coupling with Deep Learning

We point out that events with 6 or more top quarks may be observed at the LHC if certain particles exist at the TeV scale. In a model where a vectorlike quark of charge 2/3 decays into a top quark and a pseudoscalar particle, which subsequently decays into a top-antitop pair, the LHC production cross section for events with 6 top quarks may be above 10 fb. If the pseudoscalar is part of a complex scalar field, then longer cascade decays, involving the scalar partner, may lead to events with 8 or even 10 top quarks. We show that for a region of parameter space the dominant LHC signal in this model is 8 top quarks (i.e., four $$ t\overline{t} $$ pairs). The ensuing signals would be spectacular, including many leptons and $\textit{b}$ jets. A discovery in that case would allow several cross section measurements that may determine the masses of all three new particles.

Elias Bernreuther

Bogdan Dobrescu

Multi-top signals of vectorlike quarks at the LHC

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 ($\textit{d}$ + 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 $\textit{d}$ = 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.

Francesca Pacifico

Charlotte Sleight

Massimo Taronna

Conformal partial wave expansion of celestial correlators

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 $\textit{α}$ $\textit{→}$ 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.

Brazil

Max Guillen

Marcelo Santos

Eggon Viana

The pure spinor superparticle and 10D super-Yang-Mills amplitudes

We perform a detailed pseudodata study to estimate the expected theory uncertainty in the extraction of the strong coupling constant, $\textit{α}$ ($\textit{m}$ ), from a fit to the measured Drell-Yan transverse momentum ($\textit{q}$ ) spectrum at small $\textit{q}$ ≪ $\textit{m}$ . 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 $\textit{q}$ 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 $\textit{q}$ ≲ 10 GeV, from where most of the $\textit{α}$ sensitivity originates. The associated nonperturbative uncertainties on $\textit{α}$ when fitting only the $\textit{q}$ 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 $\textit{α}$ extraction from Drell-Yan data at small $\textit{q}$ . We also discuss the implications of our findings, calling into question a recent $\textit{α}$ extraction from the $\textit{Z q}$ spectrum by the ATLAS experiment.

Belgium

Thomas Cridge

Giulia Marinelli

Frank Tackmann

Theory uncertainties in the extraction of $\textit{α}$