Publications
2024
- , Niccolò Laurenti, .NNPDF4.0 aN3LO PDFs with QED corrections. 31st International Workshop on Deep-Inelastic Scattering and Related Subjects, 2024 Conference
[ InspireHEP, ArXiv, Abstract ]We review recent progress in the global determination of the collinear parton distributions (PDFs) of the proton within the NNPDF framework. This progress includes NNPDF4.0 variants with QED effects and with missing higher order uncertainties (MHOUs) via the theory covariance matrix formalism, as well as PDFs based on QCD calculations at approximate N\(^3\)LO (aN\(^3\)LO) accuracy. We present the combination of these theoretical developments resulting into NNPDF4.0 aN\(^3\)LO variants accounting for QED corrections and with a photon PDF. We compare these aN\(^3\)LO QED PDFs with analogous results obtained by the MSHT group, and briefly quantify their implications at the level of representative LHC cross-sections.@inproceedings{Barontini:2024dyb, author = {Andrea Barontini and Niccolò Laurenti and Juan Rojo}, title = { {NNPDF4.0 aN3LO PDFs with QED corrections} }, booktitle = {31st International Workshop on Deep-Inelastic Scattering and Related Subjects}, year = {2024} } - , , Niccolò Laurenti, , .LO, NLO, and NNLO Parton Distributions for LHC Event Generators. Journal of High Energy Physics, 2024 Paper
[ InspireHEP, ArXiv, Abstract ]We present NNPDF4.0MC, a variant of the NNPDF4.0 set of parton distributions (PDFs) at LO, NLO and NNLO, with and without inclusion of the photon PDF, suitable for use with Monte Carlo (MC) event generators, which require PDFs to satisfy additional constraints in comparison to standard PDF sets. These requirements include PDF positivity down to a low scale \(Q \sim 1\) GeV, smooth extrapolation in the very small and large \(x\) regions, and numerically stable results even in extreme regions of phase space for all PDFs. We compare the NNPDF4.0MC PDFs to their baseline NNPDF4.0 counterparts, and to the NNPDF2.3LO set entering the Monash tune of the Pythia8 event generator. We briefly assess the phenomenological impact of these PDFs on the cross-sections for hard and soft QCD processes at the LHC.@article{Cruz-Martinez:2024cbz, author = {Juan Cruz-Martinez and Stefano Forte and Niccolò Laurenti and Tanjona R. Rabemananjara and Juan Rojo}, title = { {LO, NLO, and NNLO Parton Distributions for LHC Event Generators} }, journal = {Journal of High Energy Physics}, year = {2024} } - .The Path to N3LO Parton Distributions. European Physical Journal C, 2024 Paper
[ InspireHEP, ArXiv, Abstract ]We extend the existing leading (LO), next-to-leading (NLO), and next-to-next-to-leading order (NNLO) NNPDF4.0 sets of parton distribution functions (PDFs) to approximate next-to-next-to-next-to-leading order (aN\(^3\)LO). We construct an approximation to the N\(^3\)LO splitting functions that includes all available partial information from both fixed-order computations and from small and large \(x\) resummation, and estimate the uncertainty on this approximation by varying the set of basis functions used to construct the approximation. We include known N\(^3\)LO corrections to deep-inelastic scattering structure functions and extend the FONLL general-mass scheme to \(\mathcal{O}(\alpha_s^3)\) accuracy. We determine a set of aN\(^3\)LO PDFs by accounting both for the uncertainty on splitting functions due to the incomplete knowledge of N\(^3\)LO terms, and to the uncertainty related to missing higher corrections (MHOU), estimated by scale variation, through a theory covariance matrix formalism. We assess the perturbative stability of the resulting PDFs, we study the impact of MHOUs on them, and we compare our results to the aN\(^3\)LO PDFs from the MSHT group. We examine the phenomenological impact of aN\(^3\)LO corrections on parton luminosities at the LHC, and give a first assessment of the impact of aN\(^3\)LO PDFs on the Higgs and Drell-Yan total production cross-sections. We find that the aN\(^3\)LO NNPDF4.0 PDFs are consistent within uncertainties with their NNLO counterparts, that they improve the description of the global dataset and the perturbative convergence of Higgs and Drell-Yan cross-sections, and that MHOUs on PDFs decrease substantially with the increase of perturbative order.@article{NNPDF:2024nan, author = {The NNPDF collaboration}, title = { {The Path to N3LO Parton Distributions} }, journal = {European Physical Journal C}, year = {2024} } - .Determination of the theory uncertainties from missing higher orders on NNLO parton distributions with percent accuracy. European Physical Journal C, 2024 Paper
[ InspireHEP, ArXiv, Abstract ]We include uncertainties due to missing higher order corrections to QCD computations (MHOU) used in the determination of parton distributions (PDFs) in the recent NNPDF4.0 set of PDFs. We use our previously published methodology, based on the treatment of MHOUs and their full correlations through a theory covariance matrix determined by scale variation, now fully incorporated in the new NNPDF theory pipeline. We assess the impact of the inclusion of MHOUs on the NNPDF4.0 central values and uncertainties, and specifically show that they lead to improved consistency of the PDF determination with an ensuing moderate reduction of PDF uncertainties at NNLO.@article{NNPDF:2024dpb, author = {The NNPDF collaboration}, title = { {Determination of the theory uncertainties from missing higher orders on NNLO parton distributions with percent accuracy} }, journal = {European Physical Journal C}, year = {2024} } - .Photons in the proton: implications for the LHC. European Physical Journal C, 2024 Paper
[ InspireHEP, ArXiv, Abstract ]We construct a set of parton distribution functions (PDFs), based on the recent NNPDF4.0 PDF set, that also include a photon PDF. The photon PDF is constructed using the LuxQED formalism, while QED evolution accounting for \(\mathcal{O} (\alpha)\), \(\mathcal{O} (\alpha \alpha_s)\), and \(\mathcal{O} (\alpha^2)\) corrections is implemented and benchmarked by means of the \(\texttt{EKO}\) code. We investigate the impact of QED effects on NNPDF4.0, and compare our results both to our previous NNPDF3.1QED PDF set and to other recent PDF sets that include the photon. We assess the impact of photon-initiated processes and electroweak corrections on a variety of representative LHC processes, and find that they can reach the 5% level in vector boson pair production at large invariant mass.@article{NNPDF:2024djq, author = {The NNPDF collaboration}, title = { {Photons in the proton: implications for the LHC} }, journal = {European Physical Journal C}, year = {2024} }
- Niccolò Laurenti.Inclusion of QED corrections in PDFs fits. Nuclear and Particle Physics Proceedings, 2023 Conference
[ InspireHEP, doi, Abstract ]The need of percent precision in high energy physics requires the inclusion of QED effects in theoretical predictions, including the contribution of photon-initiated processes. In this contribution we present ongoing work towards extending the NNPDF4.0 NNLO determination of parton distribution functions (PDFs) with QED effects and a photon PDF. We study the impact of QED effects in the NNPDF4.0 fit, compare our results with NNPDF3.1QED and other recent QED PDF fits, and we assess the impact of the photon PDF for representative LHC processes.@inproceedings{LAURENTI2023, author = {Niccolò Laurenti}, title = { {Inclusion of QED corrections in PDFs fits} }, booktitle = {Nuclear and Particle Physics Proceedings}, year = {2023} }
- Niccolò Laurenti, , .Approximating missing higher-orders in transverse momentum distributions using resummations. 29th International Workshop on Deep-Inelastic Scattering and Related Subjects, 2022 Conference
[ InspireHEP, ArXiv, Abstract ]We present a more reliable approach to approximate the unknown next-to-next-to-next-to-leading order (N\(^3\)LO) transverse momentum distribution of colourless final states, namely the Higgs boson produced via gluon fusion and the lepton pair produced via Drell--Yan (DY) mechanism. The approximation we construct relies on the combination of various resummation formalisms -- namely threshold, small-pt and high energy resummations -- by exploiting the singularity structure of the large logarithms in Mellin space. We show that for the case of Higgs boson production, the approximate N3LO transverse momentum distribution amounts to a correction of a few percent with respect to the NNLO result with a reduction in the scale dependence.@inproceedings{Laurenti:2022wov, author = {Niccolò Laurenti and Tanjona R. Rabemananjara and Roy Stegeman}, title = { {Approximating missing higher-orders in transverse momentum distributions using resummations} }, booktitle = {29th International Workshop on Deep-Inelastic Scattering and Related Subjects}, year = {2022} }
- Niccolò Laurenti.Construction of a next-to-next-to-next-to-leading order approximation for heavy flavour production in deep inelastic scattering with quark masses. Master Thesis, 2021 MasterThesis
[ InspireHEP, ArXiv, Abstract ]The subject of this thesis is the construction of an approximation for the next-to-next-to-next-to leading order (N\(^3\)LO) deep inelastic scattering (DIS) massive coefficient function of the gluon for \(F_2\) in heavy quark pair production. Indeed, this object is one of the ingredients needed for the construction of any variable flavour number (factorization) scheme at \(\mathcal{O}(\alpha_s^3)\). The construction of such scheme is crucial for the improvement of the accuracy of the extraction of the parton distribution functions from the experimental data, that in turn will provide an improvement of the accuracy of all the theoretical predictions in high energy physics. Despite the function we are interested in is not known exactly, its expansion in some kinematic limits is available. In particular the high-scale limit (\(Q^2 \gg m^2\)), high-energy limit (\(z\rightarrow 0\), where \(z\) is the argument of the coefficient function) and threshold limit (\(z\rightarrow z_{max} = 1/(1+4m^2/Q^2)\)) of the exact coefficient function are all known, with the exception of some terms that we will provide in approximate form. Therefore, combining these limits in a proper way, we will construct an approximation for the unknown term of the N\(^3\)LO gluon coefficient function, that describes the exact curve in the whole range of \(z\). Since other approximations for the N\(^3\)LO gluon coefficient functions are present in the literature, we will conclude by comparing our final approximate coefficient functions with such approximations. We will show a comparison both for the NNLO, whose exact function is known, and for the N\(^3\)LO. With our approach, we expect our results to be more accurate than previous approximations, thus providing a sufficient precision for a complete description of DIS at N\(^3\)LO and the consequent determination of N\(^3\)LO PDFs.@article{Laurenti:2024anf, author = {Niccolò Laurenti}, title = { {Construction of a next-to-next-to-next-to-leading order approximation for heavy flavour production in deep inelastic scattering with quark masses} }, series = {Master Thesis}, year = {2021} }