Publications by Luca Rottoli

Parton distributions with theory uncertainties: general formalism and first phenomenological studies NNPDF Collaboration


RA Khalek, RD Ball, S Carrazza, S Forte, T Giani, Z Kassabov, RL Pearson, ER Nocera, J Rojo, L Rottoli, M Ubiali, C Voisey, M Wilson

Higgsstrahlung at NNLL ' plus NNLO matched to parton showers in GENEVA

PHYSICAL REVIEW D 100 (2019) ARTN 096016

S Alioli, A Broggio, S Kallweit, MA Lim, L Rottoli

A first determination of parton distributions with theoretical uncertainties


RA Khalek, RD Ball, S Carrazza, S Forte, T Giani, Z Kassabov, ER Nocera, RL Pearson, J Rojo, L Rottoli, M Ubiali, C Voisey, M Wilson

The transverse momentum spectrum of weak gauge bosons at N 3 LL + NNLO.

The European physical journal. C, Particles and fields 79 (2019) 868-

W Bizoń, A Gehrmann-De Ridder, T Gehrmann, N Glover, A Huss, PF Monni, E Re, L Rottoli, DM Walker

We present accurate QCD predictions for the transverse momentum ( p⊥ ) spectrum of electroweak gauge bosons at the LHC for 13TeV collisions, based on a consistent combination of a NNLO calculation at large p⊥ and N 3 LL resummation in the small p⊥ limit. The inclusion of higher order corrections leads to substantial changes in the shape of the differential distributions, and the residual perturbative uncertainties are reduced to the few percent level across the whole transverse momentum spectrum. We examine the ratio of p⊥ distributions in charged- and neutral-current Drell-Yan production, and study different prescriptions for the estimate of perturbative uncertainties that rely on different degrees of correlation between these processes. We observe an excellent stability of the ratios with respect to the perturbative order, indicating a strong correlation between the corresponding QCD corrections.

Constraints on the quartic Higgs self-coupling from double-Higgs production at future hadron colliders


W Bizon, U Haisch, L Rottoli

Towards small-x resummed parton distribution functions

Proceedings of Science 2017-April (2017)

L Rottoli, M Bonvini

© 2017 Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). We present preliminary results for fits of parton distribution functions (PDFs) which include the resummation of small-x logarithms at NLLx accuracy, performed in the NNPDF framework. We observe an improvement in the description of DIS data at small values of Bjorken x when resummation effects are included. The improvement is more marked when comparing NNLO+NLLx fits to NNLO ones, and is particularly noticeable for small-x and small-Q 2 HERA inclusive structure functions. The main effect of the resummation is an enhancement of the gluon and singlet PDFs at small-x, which persists at high scales.

Momentum-space resummation for transverse observables and the Higgs p perpendicular to at (NLL)-L-3+NNLO


W Bizon, PF Monni, E Re, L Rottoli, P Torrielli

Parton distributions with small-x resummation: evidence for BFKL dynamics in HERA data


RD Ball, V Bertone, M Bonvini, S Marzani, J Rojo, L Rottoli

Fiducial distributions in Higgs and Drell-Yan production at (NLL)-L-3+NNLO


W Bizon, X Chen, A Gehrmann-De Ridder, T Gehrmann, N Glover, A Huss, PF Monni, E Re, L Rottoli, P Torrielli

Charged hadron fragmentation functions from collider data: NNPDF Collaboration.

The European physical journal. C, Particles and fields 78 (2018) 651-

V Bertone, NP Hartland, ER Nocera, J Rojo, L Rottoli

We present NNFF1.1h, a new determination of unidentified charged-hadron fragmentation functions (FFs) and their uncertainties. Experimental measurements of transverse-momentum distributions for charged-hadron production in proton-(anti)proton collisions at the Tevatron and at the LHC are used to constrain a set of FFs originally determined from electron-positron annihilation data. Our analysis is performed at next-to-leading order in perturbative quantum chromodynamics. We find that the hadron-collider data is consistent with the electron-positron data and that it significantly constrains the gluon FF. We verify the reliability of our results upon our choice of the kinematic cut in the hadron transverse momentum applied to the hadron-collider data and their consistency with NNFF1.0, our previous determination of the FFs of charged pions, kaons, and protons/antiprotons.

Parton distributions from high-precision collider data


RD Ball, V Bertone, S Carrazza, L Del Debbio, S Forte, P Groth-Merrild, A Guffanti, NP Hartland, Z Kassabov, JI Latorre, ER Nocera, J Rojo, L Rottoli, E Slade, M Ubiali, NNPDF Collaboration

Pseudo-scalar Higgs boson production at (NLOA)-L-3+(NLL)-L-3 '


T Ahmed, M Bonvini, MC Kumar, P Mathews, N Rana, V Ravindran, L Rottoli

On the Higgs cross section at (NLO)-L-3+(NLL)-L-3 and its uncertainty


M Bonvini, S Marzani, C Muselli, L Rottoli

The prompt atmospheric neutrino flux in the light of LHCb

JHEP Springer Berlin Heidelberg 02 (2016) 130-

R Gauld, L Rottoli, J Rojo, S Sarkar, J Talbert

The recent observation of very high energy cosmic neutrinos by IceCube heralds the beginning of neutrino astronomy. At these energies, the dominant background to the astrophysical signal is the flux of `prompt' neutrinos, arising from the decay of charmed mesons produced by cosmic ray collisions in the atmosphere. In this work we provide predictions for the prompt atmospheric neutrino flux in the framework of perturbative QCD, using state-of-the-art Monte Carlo event generators. Our calculation includes the constraints set by charm production measurements from the LHCb experiment at 7 TeV, and has been recently validated with the corresponding 13 TeV data. Our results for the prompt flux are a factor of about 2 below the previous benchmark calculation, in general agreement with two other recent estimates, and with an improved estimate of the uncertainty. This alleviates the existing tension between the theoretical prediction and IceCube limits, and suggests that a direct direction of the prompt flux is imminent.

Intrinsic charm in a matched general-mass scheme

Physics Letters B Elsevier 754 (2016) 49-58

M Bonvini, RD Ball, V Bertone, S Forte, P Groth Merrild, J Rojo, L Rottoli

The FONLL general-mass variable-flavour number scheme provides a framework for the matching of a calculation in which a heavy quark is treated as a massless parton to one in which the mass dependence is retained throughout. We describe how the usual formulation of FONLL can be extended in such a way that the heavy quark parton distribution functions are freely parameterized at some initial scale, rather than being generated entirely perturbatively. We specifically consider the case of deep-inelastic scattering, in view of applications to PDF determination, and the possible impact of a fitted charm quark distribution on is assessed.

A determination of the charm content of the proton


RD Ball, V Bertone, M Bonvini, S Carrazza, S Forte, A Guffanti, NP Hartland, J Rojo, L Rottoli

Fitting EMC structure functions with intrinsic charm

XXIV International Workshop on Deep-Inelastic Scattering and Related Subjects, 11-15 April, 2016 DESY Hamburg, Germany Scuola Internazionale Superiore di Studi Avanzati (S I S S A) (2016)

L Rottoli

A detailed study of the impact of the data collected by the European Muon Collaboration (EMC) on the parton distribution function (PDF) of the charm quark is presented. The analysis is performed in the NNPDF framework, and the charm PDF is freely parametrized on equal footing as light quark and gluon distributions. We find that variations in the treatment of EMC data do not modify the charm PDF and do not affect our previous conclusion on the presence of an intrinsic component in the charm PDF.

Towards parton distributions with fitted charm

Nuclear and Particle Physics Proceedings Elsevier 270-272 (2016) 23-26

P Groth-Merrild, L Rottoli, RD Ball, V Bertone, L Del Debbio, S Carrazza, A Guffanti, S Forte, PN Hartland, Z Kassabov, IJ Latorre, J Rojo, M Ubiali

Modern parton distribution function fits require an accurate treatment of heavy quark mass effects. In this contribution, we discuss how the FONLL general-mass variable flavour number scheme can be extended to allow for the possibility of a fitted charm PDF. We present a first estimate of the impact of a fitted charm contribution in the FONLL structure functions, and we discuss the development towards including a fitted charm PDF in the NNPDF framework.

Charm in Deep-Inelastic Scattering


L Rottoli, RD Ball, M Bonvini

We show how to extend systematically the FONLL scheme for inclusion of heavy quark mass effects in DIS to account for the possible effects of an intrinsic charm component in the nucleon. We show that when there is no intrinsic charm, FONLL is equivalent to S-ACOT to any order in perturbation theory, while when an intrinsic charm component is included FONLL is identical to ACOT, again to all orders in perturbation theory. We discuss in detail the inclusion of top and bottom quarks to construct a variable flavour number scheme, and give explicit expressions for the construction of the structure functions $F^c_2$, $F^c_L$ and $F^c_3$ to NNLO.

Charm production in the forward region: constraints on the small-x gluon and backgrounds for neutrino astronomy

Journal of High Energy Physics Springer Verlag 2015 (2015) 1-46

R Gauld, J Rojo, L Rottoli, J Talbert

The recent observation by the IceCube experiment of cosmic neutrinos at energies up to a few PeV heralds the beginning of neutrino astronomy. At such high energies, the conventional neutrino flux is suppressed and the prompt component from charm meson decays is expected to become the dominant background to astrophysical neutrinos. Charm production at high energies is however theoretically uncertain, both since the charm mass is at the boundary of applicability of perturbative QCD, and also because the calculations are sensitive to the poorly-known gluon PDF at small-x. In this work we provide detailed perturbative QCD predictions for charm and bottom production in the forward region, and validate them by comparing with recent data from the LHCb experiment at 7 TeV. Finding good agreement between data and theory, we use the LHCb measurements to constrain the small-x gluon PDF, achieving a substantial reduction in its uncertainties. Using these improved PDFs, we provide predictions for charm and bottom production at LHCb at 13 TeV, as well as for the ratio of cross-sections between 13 and 7 TeV. The same calculations are used to compute the energy distribution of neutrinos from charm decays in pA collisions, a key ingredient towards achieving a theoretically robust estimate of charm-induced backgrounds at neutrino telescopes.