Searcharxiv⌕ Search

arXiv subjects

Giovanni Pelliccioli

Publications and source records attributed to Giovanni Pelliccioli.

44 records · Page 3Linked to original sources
arXiv2020

Polarized electroweak bosons in ${\bf \text{W}^+\text{W}^-}$ production at the LHC including NLO QCD effects

The measurement of polarization fractions of massive gauge bosons at the LHC provides an important check of the Standard Model and in particular of the Electroweak Symmetry Breaking mechanism. Owing to the unstable character of $\text{W}$ and $\text{Z}$ bosons, devising a theoretical definition for polarized signals is not straightforward and always subject to some ambiguity. Focusing on $\text{W}$-boson pair production at the LHC in the fully leptonic channel, we propose to compute polarized cross-sections and distributions based on the gauge-invariant doubly-resonant part of the amplitude. We include NLO QCD corrections to the leading quark-induced partonic process and also consider the loop-induced gluon-initiated process contributing to the same final state. We present results for both an inclusive setup and a realistic fiducial region, with special focus on variables that are suited for the discrimination of polarized cross-sections and on quantities that can be measured experimentally.

hep-ph↗
arXiv2020

VBSCan Mid-Term Scientific Meeting

This document summarises the talks and discussions happened during the VBSCan Mid-Term Scientific Meeting workshop. The VBSCan COST action is dedicated to the coordinated study of vector boson scattering (VBS) from the phenomenological and experimental point of view, for the best exploitation of the data that will be delivered by existing and future particle colliders.

hep-ph↗
arXiv2019

Polarized vector boson scattering in the fully leptonic WZ and ZZ channels at the LHC

Isolating the scattering of longitudinal weak bosons at the LHC is an important tool to probe the ElectroWeak Symmetry Breaking mechanism. Separating polarizations of $W$ and $Z$ bosons is complicated, because of non resonant contributions and interference effects. Additional care is necessary when considering $Z$ bosons, due to the $γ/Z$ mixing in the coupling to charged leptons. We propose a method to define polarized signals in $Z\!Z$ and $W^+\!Z$ scattering at the LHC, which relies on the separation of weak boson polarizations at the amplitude level in Monte Carlo simulations. After validation in the absence of lepton cuts, we investigate how polarized distributions are affected by a realistic set of kinematic cuts (and neutrino reconstruction, when needed). The total and differential polarized cross sections computed at the amplitude level are well defined, and their sum reproduces the full results, up to non negligible but computable interference effects which should be included in experimental analyses. We show that polarized cross sections computed using the reweighting method are inaccurate, particularly at large energies. We also present two procedures which address the model independent extraction of polarized components from LHC data, using Standard Model angular distribution templates.

hep-ph↗
arXiv2019

VBSCan Thessaloniki 2018 Workshop Summary

This document reports the first year of activity of the VBSCan COST Action network, as summarised by the talks and discussions happened during the VBSCan Thessaloniki 2018 workshop. The VBSCan COST action is aiming at a consistent and coordinated study of vector-boson scattering from the phenomenological and experimental point of view, for the best exploitation of the data that will be delivered by existing and future particle colliders.

hep-ph↗
arXiv2019

Local Analytic Sector Subtraction at NNLO

We present a new method for the local subtraction of infrared divergences at next-to-next-to-leading order (NNLO) in QCD, for generic infrared-safe observables. Our method attempts to conjugate the minimal local counterterm structure arising from a sector partition of the radiation phase space with the simplifications following from analytic integration of the counterterms. In this first implementation, the method applies to final-state massless particles. We show how our method compactly organises infrared subtraction at NLO, we deduce in detail the general structure of the subtraction terms at NNLO, and we provide a proof of principle with a complete application to a simple process at NNLO.

hep-ph↗
arXiv2018

Factorisation and Subtraction beyond NLO

We provide a general method to construct local infrared subtraction counterterms for unresolved radiative contributions to differential cross sections, to any order in perturbation theory. We start from the factorised structure of virtual corrections to scattering amplitudes, where soft and collinear divergences are organised in gauge-invariant matrix elements of fields and Wilson lines, and we define radiative eikonal form factors and jet functions which are fully differential in the radiation phase space, and can be shown to cancel virtual poles upon integration by using completeness relations and general theorems on the cancellation of infrared singularities. Our method reproduces known results at NLO and NNLO, and yields substantial simplifications in the organisation of the subtraction procedure, which will help in the construction of efficient subtraction algorithms at higher orders.

hep-ph↗
arXiv2018

$W$ boson polarization in vector boson scattering at the LHC

Measuring the scattering of longitudinally-polarized vector bosons represents a fundamental test of ElectroWeak Symmetry Breaking. In addition to the challenges provided by low rates and large backgrounds, there are conceptual issues which need to be clarified for the definition of a suitable signal. Since vector bosons are unstable and can only be observed through their decay products, the polarization states interfere among themselves. Moreover, already at tree level, there are diagrams which cannot be interpreted as production times decay of EW bosons but are necessary for gauge invariance. We discuss a possible way to define a cross section for polarized $W$'s, dropping all non resonant diagrams, and projecting on shell the resonant ones, thus, preserving gauge invariance. In most cases, the sum of polarized distributions reproduces the full results. In the absence of cuts, the ratios of the polarized cross sections to the full one agree with the results of a standard projection on Legendre polynomials. While the latter cannot be employed in a realistic environment, a comparison of the data with the shapes of the angular distributions for polarized vector bosons allows the extraction of the polarization fractions in the presence of selection cuts on the charged leptons.

hep-ph↗