arXiv subjects

Giuseppe Bevilacqua

Publications and source records attributed to Giuseppe Bevilacqua.

At least 19 recordsLinked to original sources

arXiv2026

SMEFT everywhere: a NLO study of $\boldsymbol{pp \to t\bar{t}H}$ with decaying tops

We present the computation of the next-to-leading order QCD corrections to the $pp\to t\bar{t} H+X$ process in the di-lepton channel at the LHC, including relevant dimension-6 operators $({\cal O}_{tϕ}, \, {\cal O}_{ϕG},\, {\cal O}_{tG}, \, {\cal O}_{tW})$ from the Standard Model Effective Field Theory. In our studies, higher-order corrections and effective operators are consistently included in the production part of the process as well as in the top-quark decays. We perform a detailed study of linear, cross, and quadratic contributions and their uncertainties, including renormalisation group effects. Our findings are presented at the integrated and differential cross-section level for the LHC Run III center-of-mass energy of $\sqrt{s}=13.6$ TeV. Finally, we provide predictions for $pp\to t\bar{t} H+X$ with stable top quarks and compare them with the results in which top quarks are reconstructed from their decay products. We show that kinematic cuts, as well as higher-order effects and SMEFT operators in top-quark decays, are important and should be consistently considered together, because they have a significant impact on the shape of the standard observables measured for the $pp\to t\bar{t}H+X$ process at the LHC.

hep-ph↗

arXiv2026

Data-driven synthesis of high-fidelity triaxial magnetic waveforms for quantum control

We present a system for generating arbitrary, triaxial magnetic waveforms with a spectral content spanning from DC to tens of kHz, a critical capability for quantum control and spin manipulation. To compensate for amplifier-coil dynamics, we implement a data-driven approach to identify a numerical compensation model. The method parametrizes the system response using a Finite Impulse Response (FIR) filter calibrated on the specific waveform to be generated. The application of a driving signal designed via frequency-domain inversion of the identified model enables the synthesis of complex field sequences with sharp transitions between static and single- or multi-frequency temporal segments. The work is validated with experimental results demonstrating waveform fidelity and transient performance, thereby showcasing the precision and feasibility of the method.

physics.ins-det↗

arXiv2025

Towards numerical two-loop integrand reduction

We present a method for the integrand-level reduction of two-loop helicity amplitudes in both $d=4-2ε$ and $d=4$ dimensions. The amplitude is expressed in terms of a set of Feynman integrals and their coefficients that depend on the external kinematics. The analysis presented in this paper, in conjunction with the ongoing development of the computational framework $\text{HELAC-2LOOP}$, paves the road for the construction of an automated program for two-loop amplitude calculations for arbitrary scattering processes.

hep-ph↗

arXiv2025

Multipassage Landau-Zener tunneling oscillations in transverse/longitudinal dual dressing of atomic qubits

We investigate the time evolution of a non-resonant dressed-atom qubit in an XZ original configuration. It is composed of two electromagnetic fields, one oscillating parallel and the other orthogonal to the quantisation magnetic static field. The experiments are performed in rubidium and caesium atomic magnetometers, confined in a magneto-optical trap and in a vapour cell, respectively. Static fields in the $μ$T range and kHz oscillating fields with large Rabi frequencies are applied. This dual-dressing configuration is an extension of the Landau-Zener multipassage interferometry in the presence of an additional dressing field controlling the tunneling process by its amplitude and phase. Our measurement of the qubit coherence introduces additional features to the transition probability readout of standard interferometry. The coherence time evolution is characterized by oscillations at several frequencies, each of them produced by a different quantum contribution. Such frequency description introduces a new picture of the qubit multipassage evolution. Because the present low-frequency dressing operation does not fall within the standard Floquet engineering paradigm based on the high-frequency expansion, we develop an ad-hoc dressing perturbation treatment. Numerical simulations support the adiabatic and non-adiabatic qubit evolution.

quant-ph↗

arXiv2025

Tri-axial time-dependent magnetic field calibrated in-situ by harmonic analysis of adiabatically evolving atomic spins

We introduce a methodology to calibrate in situ a set of coils generating bi- or tri-axial magnetic fields, at frequencies where a calibration performed under static conditions would be inaccurate. The methodology uses harmonic analysis of one component of the magnetization of an atomic sample whose spins adiabatically follow an ad hoc applied time-dependent field. The procedure enables the identification of phases and amplitudes of the coil currents required to produce a dynamic magnetic field with the assigned polarization. This determines coil constants that can be subsequently used to produce arbitrary three-dimensional time-dependent fields.

physics.ins-det↗

arXiv2024

LASS, the numerics

We summarize our efforts to create a numerical implementation of the Local Analytical Subtraction Scheme (LASS) for obtaining NNLO QCD predictions in electron-positron collisions. We focus on the regularization of double-real radiation contributions, which are typically the most computationally intensive part of NNLO calculations. We describe the structure of the subtraction terms in LASS and our approach to numerically validate them. Using arbitrary precision arithmetic, we demonstrate the proper convergence of individual subtraction terms, overlap removal terms, and spurious singularity cancellations in various singular limits. We show results for the specific case of three-jet production in $e^+e^-$ collisions. Our results validate the correctness of both the LASS formalism and our numerical implementation, setting the stage for full NNLO calculations using this method.

hep-ph↗

arXiv2024

Analysis of $(n+1)$ and $n$-parton contributions for computing QCD jet cross sections in the local analytic subtraction scheme

We analyze and implement the Local Analytic Sector Subtraction (LASS) scheme for handling infrared singularities in next-to-next-to-leading order (NNLO) calculations in perturbative QCD. We examine the key aspects of the scheme including sector function construction, singular limit parametrization, subtraction counterterm derivation, and integration techniques. As a proof-of-concept, we numerically implement LASS for the process $e^+e^- \rightarrow 3$ jets. In this study we examine the limiting behavior of subtraction terms for real-virtual contribution and explicitly demonstrate the pole cancellation of the double-virtual contribution. Differential cross sections are computed for several event shape observables, showing the stability and efficiency of LASS scheme. This work lays the foundation for developing an automated tool for NNLO QCD calculations using this promising scheme.

hep-ph↗

arXiv2024

Two-Loop Amplitude Reduction with HELAC

We discuss recent progress towards extending the Helac framework to the calculation of two-loop amplitudes. A general algorithm for the automated computation of two-loop integrands is described. The algorithm covers all the steps of the computation, from the generation of loop topologies up to the construction of recursion relations for two loop integrands. Finally, first steps towards the formulation of a new approach for reducing two-loop amplitudes to a basis of master integrals are discussed.

hep-ph↗

arXiv2023

Modelling uncertainties and prompt b-jet identification in $t\bar{t}b\bar{b}$ production with dilepton signatures at the LHC

As one of the primary backgrounds to $pp \to t\bar{t}H(H\to b\bar{b})$, the QCD process of $t\bar{t}b\bar{b}$ hadroproduction demands very accurate theoretical predictions and estimates of uncertainties. On top of that, the capacity of properly identifying prompt $b$-jets is beneficial for many analyses. In this contribution we discuss state-of-the-art predictions for $t\bar{t}b\bar{b}$ production with dilepton decays at the LHC, as obtained from full off-shell NLO QCD calculations. We evaluate the dominant uncertainties of the calculation and the impact of the off-shell effects on fiducial cross sections. Furthermore, we explore a kinematic prescription for the categorisation of prompt $b$-jets.

hep-ph↗

arXiv2023

A Wearable Wireless Magnetic Eye-Tracker, in-vitro and in-vivo Tests

A wireless, wearable magnetic eye tracker is described and characterized. The proposed instrumentation enables simultaneous evaluation of eye and head angular displacements. Such a system can be used to determine the absolute gaze direction as well as to analyze spontaneous eye re-orientation in response to stimuli consisting in head rotations. The latter feature has implications to analyze the vestibulo-ocular reflex and constitutes an interesting opportunity to develop medical (oto-neurological) diagnostics. Details of data analysis are reported together with some results obtained in-vivo or with simple mechanical simulators that enable measurements under controlled conditions.

physics.med-ph↗

arXiv2023

A study of additional jet activity in top quark pair production and decay at the LHC

We report on the calculation of the NLO QCD corrections to top quark pair production in association with two hard jets at the LHC. We take into account higher-order effects in both the production and decays of the top-quark pair. The latter are treated in the narrow width approximation and $t\bar{t}$ spin correlations are preserved throughout the calculation. This is the first time that such a complete study for this process is conducted at NLO in QCD. We present results for fiducial cross sections at the integrated and differential level. Furthermore, we investigate kinematic properties of the additional light jets and their distribution in the $pp\to t\bar{t}jj$ process. We examine jets in production and top-quark decays as well as the mixed contribution, where the two hardest non-$b$ jets are present simultaneously in the production and decay processes.

hep-ph↗

arXiv2022

$t\bar{t}b\bar{b}$ at the LHC: On the size of off-shell effects and prompt $b$-jet identification

We investigate full off-shell effects in $t\bar{t}b\bar{b}$ production in the dilepton channel at the LHC with the center-of-mass energy $\sqrt{s} = 13$ TeV. Specifically, we compute NLO QCD corrections to the $pp \to e^+ ν_e μ^- \barν_μb \bar{b} b \bar{b} + X$ process and provide a prescription for $b$-jet identification to distinguish prompt $b$ jets from $b$ jets originating from the decay of the top quarks. As an important irreducible background to $pp \to t\bar{t}H (H\to b\bar{b})$, $t\bar{t}$ production in association with two prompt $b$ jets is a primary source of uncertainty in the measurement of $t\bar{t}H (H\to b\bar{b})$. In quantifying full off-shell effects, we perform comparisons between the state-of-the-art full off-shell computation and the calculation in the narrow width approximation. The former includes all double-, single- and non-resonant Feynman diagrams, interferences as well as finite-width effects of the top quarks and $W$ gauge bosons. The latter restricts the unstable top quarks and $W$ gauge bosons to on-shell states and includes for the first time NLO QCD corrections to both production and decays. We observe that full off-shell effects are subdominant compared to the scale uncertainties for the integrated fiducial cross section and for the majority of differential observables in the phase-space regions that we investigated. However, for a number of observables related to beyond the Standard Model searches, full off-shell effects are significant. Furthermore, with our $b$-jet labelling prescription, the prompt $b$ jets and the $b$ jets from top-quark decays can be successfully disentangled.

hep-ph↗

arXiv2022

Report of the Topical Group on Top quark physics and heavy flavor production for Snowmass 2021

This report summarizes the work of the Energy Frontier Topical Group on EW Physics: Heavy flavor and top quark physics (EF03) of the 2021 Community Summer Study (Snowmass). It aims to highlight the physics potential of top-quark studies and heavy-flavor production processes (bottom and charm) at the HL-LHC and possible future hadron and lepton colliders and running scenarios.

hep-ph↗

arXiv2022

Tutorial notes for the evaluation of thermoelectric quantum bounds in ideal nanostructures

The wave-like nature of electrons leads to the existence of upper bounds on the thermoelectric response of nanostructured devices [R. S. Whitney, Phys. Rev. Lett. 112, 130601 (2014); Phys. Rev. B 91, 115425 (2015)]. This fundamental result, not present in classical thermodynamics, was demonstrated exploiting a two-terminal device modelled by non-linear scattering theory. In the present paper, we consider non-linear quantum transport through the same type of device working both as thermal machine and as refrigerator. For both operations, starting from charge and heat current expressions, we provide analytic quantum bounds for power exchanged, thermal currents and device efficiencies. For this purpose, we adopt a transmission function that maximizes the engine efficiency for given power output. For the optimal boxcar- or theta function-transmission shapes, we provide in a tutorial way an explicit deduction of the quantum bound expressions reported in the above cited papers.

cond-mat.mes-hall↗

arXiv2022

NLO QCD corrections to full off-shell production of $t\bar{t}Z$ including leptonic decays

Motivated by ongoing new physics searches in the top-quark sector at the Large Hadron Collider we report on the calculation of NLO QCD corrections to the Standard Model $pp\to t\bar{t}Z+X$ process in the tetra-lepton decay channel. This calculation is based on the matrix elements for the $e^+ ν_e\, μ^-\barν_μ\, b\bar{b} \,τ^+τ^-$ final state and includes all resonant and non-resonant Feynman diagrams, interferences and off-shell effects of the top quark as well as the $W$ and $Z$ gauge bosons. Also incorporated are photon-induced contributions. As it is customary for such studies, we show theoretical predictions for both fixed and dynamical factorisation and renormalisation scale choices and different PDF sets. Furthermore, we study the main theoretical uncertainties that are associated with neglected higher-order terms in the perturbative expansion and with the parameterisation of the PDF sets. In order to investigate the size of off-shell effects and higher-order corrections in top-quark decays, we perform a second computation for this process, which is based on the narrow-width-approximation where the top quarks, $W$ and $Z$ gauge bosons are kept on-shell. Results are given for the integrated and differential fiducial cross sections for the LHC Run II center-of-mass energy of $13$ TeV.

hep-ph↗

arXiv2022

Bright and dark Autler-Townes states in the atomic Rydberg multilevel spectroscopy

We investigated the Autler-Townes splitting produced by microwave transitions between atomic Rydberg states explored by optical spectroscopy from the ground electronic state. The laser-atom Hamiltonian describing the double irradiation of such a multilevel system is analysed on the basis of the Morris-Shore transformation. The application of this transformation to the microwave-dressed atomic system allows the identification of bright, dark, and spectator states associated with different configurations of atomic states and microwave polarisation. We derived synthetic spectra that show the main features of Rydberg spectroscopy. Complex Autler-Townes spectra are obtained in a regime of strong microwave dressing, where a hybridisation of the Rydberg fine structure states is produced by the driving.

physics.atom-ph↗

arXiv2022

An innovative eye-tracker. Main features and demonstrative tests

We present a set of results obtained with an innovative eye-tracker based on magnetic dipole localization by means of an array of magnetoresistive sensors. The system tracks both head and eye movements with a high rate (100-200 Sa/s) and in real time. A simple setup is arranged to simulate head and eye motions and to test the tracker performance under realistic conditions. Multimedia material is provided to substantiate and exemplify the results. A comparison with other available technologies for eye tracking is drawn, discussing advantages (e.g. precision) and disadvantages (e.g. invasivity) of the diverse approaches, the presented method standing out for low cost, robustness and relatively low invasivity.

physics.med-ph↗

arXiv2022

Off-shell $t\bar{t}b\bar{b}$ production at the LHC: QCD corrections, theory uncertainties and $b$-jet definitions

We present state-of-the-art predictions for off-shell $t\bar{t}b\bar{b}$ production with di-lepton decays at the LHC with $\sqrt{s}=13$ TeV. Results are accurate at NLO in QCD and include all resonant and non-resonant diagrams, interferences and finite-width effects for top quarks and $W$ bosons. We discuss the impact of QCD corrections and assess theoretical uncertainties from scale and PDF dependence at the integrated and differential level. Additionally we investigate the size of contributions induced by initial-state $b$ quarks to the NLO cross section.

hep-ph↗