New sets of CMS underlying-event parameters (''tunes'') arepresented for the pythia8 event generator. These tunes use the NNPDF3.1parton distribution functions (PDFs) at leading (LO), next-to-leading(NLO), or next-to-next-to-leading (NNLO) orders in perturbative quantumchromodynamics, and the strong coupling evolution at LO or NLO.Measurements of charged-particle multiplicity and transverse momentumdensities at various hadron collision energies are fit simultaneously todetermine the parameters of the tunes. Comparisons of the predictions ofthe new tunes are provided for observables sensitive to the event shapesat LEP, global underlying event, soft multiparton interactions, anddouble-parton scattering contributions. In addition, comparisons aremade for observables measured in various specific processes, such asmultijet, Drell-Yan, and top quark-antiquark pair production includingjet substructure observables. The simulation of the underlying eventprovided by the new tunes is interfaced to a higher-order matrix-elementcalculation. For the first time, predictions from pythia8 obtained withtunes based on NLO or NNLO PDFs are shown to reliably describeminimum-bias and underlying-event data with a similar level of agreementto predictions from tunes using LO PDF sets.

Extraction and validation of a new set of CMS pythia8 tunes from underlying-event measurements

Albergo, S.;Potenza, R.;Tricomi, A.;Tuve, C.;
2020-01-01

Abstract

New sets of CMS underlying-event parameters (''tunes'') arepresented for the pythia8 event generator. These tunes use the NNPDF3.1parton distribution functions (PDFs) at leading (LO), next-to-leading(NLO), or next-to-next-to-leading (NNLO) orders in perturbative quantumchromodynamics, and the strong coupling evolution at LO or NLO.Measurements of charged-particle multiplicity and transverse momentumdensities at various hadron collision energies are fit simultaneously todetermine the parameters of the tunes. Comparisons of the predictions ofthe new tunes are provided for observables sensitive to the event shapesat LEP, global underlying event, soft multiparton interactions, anddouble-parton scattering contributions. In addition, comparisons aremade for observables measured in various specific processes, such asmultijet, Drell-Yan, and top quark-antiquark pair production includingjet substructure observables. The simulation of the underlying eventprovided by the new tunes is interfaced to a higher-order matrix-elementcalculation. For the first time, predictions from pythia8 obtained withtunes based on NLO or NNLO PDFs are shown to reliably describeminimum-bias and underlying-event data with a similar level of agreementto predictions from tunes using LO PDF sets.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.11769/390539
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