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Giuseppe Bozzi

Publications and source records attributed to Giuseppe Bozzi.

At least 19 recordsLinked to original sources
arXiv2026

A first extraction of gluon TMDs from Higgs data at the LHC

We present the first extraction of the unpolarised gluon transverse-momentum-dependent (TMD) parton distribution from Higgs-boson production data at the LHC within the framework of TMD factorisation. The analysis is based on the currently available set of ATLAS and CMS measurements of the Higgs $q_T$ distribution at $\sqrt{s} = 8$ and $13$ TeV in the diphoton and four-lepton decay channels, restricted to the small-$q_T$ region where TMD factorisation is applicable. Theoretical predictions are computed up to N$^3$LL accuracy, with the contribution of the linearly polarised gluon TMD $h_1^{\perp g}$ accounted for. Fiducial selections are consistently incorporated for both two- (diphoton) and four-body (four-lepton) final states. The fit reproduces both the shape and the normalisation of the experimental data, and yields a moderate sensitivity to the nonperturbative content of gluon TMDs. We further assess the convergence of the perturbative expansion and the stability of the extracted distribution under variations of the $q_T$ cut. This analysis provides a baseline for future extractions combining LHC Higgs measurements with other gluon-sensitive processes spanning a broader range of hard scales.

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arXiv2025

Status of the W boson mass and the future of the electroweak fit in the next decades

A precise determination of the W boson mass is an essential test for the Standard Model of particle physics: the comparison of experimental value and theoretical prediction allows to probe the internal consistency of the electroweak sector and could possibly highlight signals of New Physics. We provide a concise and up-to-date summary of past and recent measurements at lepton and hadron colliders, a discussion of the known perturbative and non-perturbative theoretical ingredients used to provide predictions for the relevant observables, and an overview of future prospects to reduce systematic uncertainties and to compare different measurements in a consistent way. We conclude with a brief discussion on the relevance of the global electroweak fit at present and future colliders.

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arXiv2024

Perturbative RGE systematics in precision observables

QCD calculations for collider physics make use of perturbative solutions of renormalisation group equations (RGEs). Ambiguities related to these solutions can contribute significantly to systematic uncertainties of theoretical predictions for physical observables. We propose a general method to estimate these systematic effects using techniques inspired by soft-gluon and transverse-momentum resummation approaches. We first discuss the cases of the evolution of strong coupling $\alpha_s$, collinear parton-distribution functions (PDFs), and transverse-momentum-dependent distributions (TMDs). We then study the implications for precision observables in hadron-collider processes, such as the deep-inelastic scattering structure functions and the transverse-momentum distribution of the lepton pair in Drell-Yan production.

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arXiv2024

Flavor dependence of unpolarized quark Transverse Momentum Distributions from a global fit

We present an extraction of the unpolarized transverse-momentum-dependent parton distribution and fragmentation functions that takes into account possible differences between quark flavors and final-state hadrons. The extraction is based on experimental measurements from Drell-Yan processes and semi-inclusive deep-inelastic scattering, whose combination is essential to distinguish flavor differences. The analysis is carried out at N$^3$LL accuracy. The extracted flavor-dependent distributions give a very good description of the data ($\chi^2/N_{\rm dat} = 1.08$). The resulting uncertainties take fully into account also the uncertainties in the determination of the corresponding collinear distributions.

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arXiv2023

The case for an EIC Theory Alliance: Theoretical Challenges of the EIC

We outline the physics opportunities provided by the Electron Ion Collider (EIC). These include the study of the parton structure of the nucleon and nuclei, the onset of gluon saturation, the production of jets and heavy flavor, hadron spectroscopy and tests of fundamental symmetries. We review the present status and future challenges in EIC theory that have to be addressed in order to realize this ambitious and impactful physics program, including how to engage a diverse and inclusive workforce. In order to address these many-fold challenges, we propose a coordinated effort involving theory groups with differing expertise is needed. We discuss the scientific goals and scope of such an EIC Theory Alliance.

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arXiv2022

Unpolarized Transverse Momentum Distributions from a global fit of Drell-Yan and Semi-Inclusive Deep-Inelastic Scattering data

We present an extraction of unpolarized transverse-momentum-dependent parton distribution and fragmentation functions based on more than two thousands data points from several experiments for two different processes: semi-inclusive deep-inelastic scattering and Drell-Yan production of lepton pairs. The baseline analysis is performed with a Monte Carlo replica method resumming large logarithms at N3LL accuracy. The resulting description of the data is very good ($\chi^2/N_{\rm dat} = 1.06$). For semi-inclusive deep-inelastic scattering, predictions for multiplicities are normalized by factors that cure the discrepancy with data introduced by higher-order perturbative corrections.

hep-ph↗
arXiv2020

Transverse-momentum-dependent parton distributions up to N$^3$LL from Drell-Yan data

We present an extraction of unpolarised Transverse-Momentum-Dependent Parton Distribution Functions based on Drell-Yan production data from different experiments, including those at the LHC, and spanning a wide kinematic range. We deal with experimental uncertainties by properly taking into account correlations. We include resummation of logarithms of the transverse momentum of the vector boson up to N$^3$LL order, and we include non-perturbative contributions. These ingredients allow us to obtain a remarkable agreement with the data.

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arXiv2020

DYTurbo: Fast predictions for Drell-Yan processes

Drell-Yan lepton pair production processes are extremely important for Standard Model (SM) precision tests and for beyond the SM searches at hadron colliders. Fast and accurate predictions are essential to enable the best use of the precision measurements of these processes; they are used for parton density fits, for the extraction of fundamental parameters of the SM, and for the estimation of background processes in searches. This paper describes a new numerical program, DYTurbo, for the calculation of the QCD transverse-momentum resummation of Drell-Yan cross sections up to next-to-next-to-leading logarithmic accuracy combined with the fixed-order results at next-to-next-to-leading order ($\mathcal{O}(α_{\mathrm{S}}^2)$), including the full kinematical dependence of the decaying lepton pair with the corresponding spin correlations and the finite-width effects. The DYTurbo program is an improved reimplementation of the DYqT, DYqT and DYNNLO programs, which provides fast and numerically precise predictions through the factorisation of the cross section into production and decay variables, and the usage of quadrature rules based on interpolating functions for the integration over kinematic variables.

hep-ph↗
arXiv2019

Azimuthal asymmetries in unpolarized SIDIS and Drell-Yan processes: a case study towards TMD factorization at subleading twist

We consider the azimuthal distribution of the final observed hadron in semi-inclusive deep-inelastic scattering and the lepton pair in the Drell-Yan process. In particular, we focus on the $\cos ϕ$ modulation of the unpolarized cross section and on its dependence upon transverse momentum. At low transverse momentum, for these observables we propose a factorized expression based on tree-level approach and conjecture that the same formula is valid in transverse-momentum dependent (TMD) factorization when written in terms of subtracted TMD parton distributions. Our formula correctly matches with the collinear factorization results at high transverse momentum, solves a long-standing problem and is a necessary step towards the extension of the TMD factorization theorems up to the subleading twist.

hep-ph↗
arXiv2019

Difficulties in the description of Drell-Yan processes at moderate invariant mass and high transverse momentum

We study the Drell-Yan cross section differential with respect to the transverse momentum of the produced lepton pair. We consider data with moderate invariant mass Q of the lepton pair, between 4.5 GeV and 13.5 GeV, and similar (although slightly smaller) values of the transverse momentum q_T. We approach the problem by deriving predictions based on standard collinear factorization, which are expected to be valid toward the high-q_T end of the spectrum and to which any description of the spectrum at lower q_T using transverse-momentum dependent parton distributions ultimately needs to be matched. We find that the collinear framework predicts cross sections that in most cases are significantly below available data at high q_T. We discuss additional perturbative and possible non-perturbative effects that increase the predicted cross section, but not by a sufficient amount.

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arXiv2019

Non-perturbative uncertainties on the transverse momentum distribution of electroweak bosons and on the determination of the $W$ boson mass at the LHC

In this contribution we present an overview of recent results concerning the impact of a possible flavour dependence of the intrinsic quark transverse momentum on electroweak observables. In particular, we focus on the $q_T$ spectrum of electroweak gauge bosons produced in proton-proton collisions at the LHC and on the direct determination of the $W$ boson mass. We show that these effects are comparable in size to other non-perturbative effects commonly included in phenomenological analyses, and should thus be included in precise theoretical predictions for present and future hadron colliders.

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arXiv2018

Effect of flavor-dependent partonic transverse momentum on the determination of the $W$ boson mass in hadronic collisions

Within the framework of transverse-momentum-dependent factorization, we investigate for the first time the impact of a flavor-dependent intrinsic transverse momentum of quarks on the production of $W^{\pm}$ bosons in proton-proton collisions at $\sqrt{s}$ = 7 TeV. We estimate the shift in the extracted value of the $W$ boson mass $M_W$ induced by different choices of flavor-dependent parameters for the intrinsic quark transverse momentum by means of a template fit to the transverse-mass and the lepton transverse-momentum distributions of the $W$-decay products. We obtain $-6\leq ΔM_{W^+} \leq 9$ MeV and $-4\leq ΔM_{W^-} \leq 3$ MeV with a statistical uncertainty of $\pm 2.5$ MeV. Our findings call for more detailed investigations of flavor-dependent nonperturbative effects linked to the proton structure at hadron colliders.

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arXiv2018

Parton distributions and lattice QCD calculations: a community white paper

In the framework of quantum chromodynamics (QCD), parton distribution functions (PDFs) quantify how the momentum and spin of a hadron are divided among its quark and gluon constituents. Two main approaches exist to determine PDFs. The first approach, based on QCD factorization theorems, realizes a QCD analysis of a suitable set of hard-scattering measurements, often using a variety of hadronic observables. The second approach, based on first-principle operator definitions of PDFs, uses lattice QCD to compute directly some PDF-related quantities, such as their moments. Motivated by recent progress in both approaches, in this document we present an overview of lattice-QCD and global-analysis techniques used to determine unpolarized and polarized proton PDFs and their moments. We provide benchmark numbers to validate present and future lattice-QCD calculations and we illustrate how they could be used to reduce the PDF uncertainties in current unpolarized and polarized global analyses. This document represents a first step towards establishing a common language between the two communities, to foster dialogue and to further improve our knowledge of PDFs.

hep-ph↗
arXiv2015

Prospects for improving the LHC W boson mass measurement with forward muons

Measurements of the $W$ boson mass are planned by the ATLAS and CMS experiments, but for the time being, these may be unable to compete with the current world average precision of 15~MeV, due to uncertainties in the PDFs. We discuss the potential of a measurement by the LHCb experiment based on the charged lepton transverse momentum $p_T^{\ell}$ spectrum in $W \to μν$ decays. The unique forward acceptance of LHCb means that the PDF uncertainties would be anti-correlated with those of $p_T^{\ell}$ based measurements by ATLAS and CMS. We compute an average of ATLAS, CMS and LHCb measurements of $m_W$ from the $p_T^{\ell}$ distribution. Considering PDF uncertainties, this average is a factor of 1.3 more precise than an average of ATLAS and CMS alone. Despite the relatively low rate of $W$ production in LHCb, we estimate that with the Run-II dataset, a measurement could be performed with sufficient experimental precision to exploit this anti-correlation in PDF uncertainties. The modelling of the lepton-pair transverse momentum distribution in the neutral current Drell-Yan process could be a limiting factor of this measurement and will deserve further studies.

hep-ex↗
arXiv2015

PDF uncertainties on the W boson mass measurement from the lepton transverse momentum distribution

We study the charged current Drell-Yan process and we evaluate the proton parton densities uncertainties on the lepton transverse momentum distribution and their impact on the determination of the W-boson mass. We consider the global PDF sets CT10, MSTW2008CPdeut, NNPDF2.3, NNPDF3.0, MMHT2014, and apply the PDF4LHC recipe to combine the individual results, obtaining an uncertainty on MW that ranges between +-18 and +-24 MeV, depending on the final state, collider energy and kind. We discuss the dependence of the uncertainty on the acceptance cuts and the role of the individual parton densities in the final result. We remark that some PDF sets predict an uncertainty on MW of O(10 MeV); this encouraging result is spoiled, in the combined analysis of the different sets, by an important spread of the central values predicted by each group.

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arXiv2008

Higgs at LHC

An overview of recent theoretical results on the Higgs boson and its discovery strategy at ATLAS and CMS will be presented, focusing on the main Higgs analysis effective with low integrated luminosity (less than 30 fb^-1).

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arXiv2007

Soft-gluon resummation for Higgs differential distributions at the Large Hadron Collider

We study the transverse-momentum (q_T) and rapidity (y) distributions of the Higgs boson in perturbative QCD, including the most advanced theoretical information presently available: fixed-order perturbation theory at Next-to-Leading Order (NLO) in the large-q_T region (q_T ~ M_H, being M_H the Higgs mass), and soft-gluon resummation at the Next-to-Next-to-Leading Logarithmic accuracy (NNLL) in the small-q_T region (q_T << M_H). We present numerical results for the doubly-differential (q_T and y) cross section for the production of a Standard Model Higgs boson at the Large Hadron Collider (LHC).

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