Normalised multi-differential cross sections for top quark pair (t tbar) production are measured in proton-proton collisions at a centre-of-mass energy of 13 TeV using events containing two oppositely charged leptons. The analysed data were recorded with the CMS detector in 2016 and correspond to an integrated luminosity of 35.9 fb^-1. The double-differential t tbar cross section is measured as a function of the kinematic properties of the top quark and of the t tbar system at parton level in the full phase space. A triple-differential measurement is performed as a function of the invariant mass and rapidity of the t tbar system and the multiplicity of additional jets at particle level. The data are compared to predictions of Monte Carlo event generators that complement next-to-leading-order (NLO) quantum chromodynamics (QCD) calculations with parton showers. Together with a fixed-order NLO QCD calculation, the triple-differential measurement is used to extract values of the strong coupling strength alphaS and the top quark pole mass (mt_pole) using several sets of parton distribution functions (PDFs). The measurement of mt_pole exploits the sensitivity of the t tbar invariant mass distribution to mt_pole near the production threshold. Furthermore, a simultaneous fit of the PDFs, alpha_S, and mt_pole is performed at NLO, demonstrating that the new data have significant impact on the gluon PDF, and at the same time allow an accurate determination of alpha_S and mt_pole. The values alpha_S(mZ)=0.1135-0.0017+0.0021 and mt_pole=170.5+-0.8 GeV are extracted, which account for experimental and theoretical uncertainties, the latter being estimated from NLO scale variations. Possible effects from Coulomb and soft-gluon resummation near the t tbar production threshold are neglected in these parameter extractions. A rough estimate of these effects indicates an expected correction of mt_pole of the order of +1 GeV, which can be regarded as additional theoretical uncertainty in the current mt_pole extraction.

Measurement of t tbar normalised multi-differential cross sections in pp collisions at sqrt(s)=13 TeV, and simultaneous determination of the strong coupling strength, top quark pole mass, and parton distribution functions

Meridiani P.;Amapane N.;Argiro S.;Bellan R.;Cappati A.;Costa M.;Covarelli R.;Kiani B.;Migliore E.;Monaco V.;Monteil E.;Obertino M. M.;Pacher L.;Angioni G. L. P.;Romero A.;Sacchi R.;Salvatico R.;Shchelina K.;Sola V.;Solano A.;Soldi D.;Rumerio P.;Ravera F.;
2020-01-01

Abstract

Normalised multi-differential cross sections for top quark pair (t tbar) production are measured in proton-proton collisions at a centre-of-mass energy of 13 TeV using events containing two oppositely charged leptons. The analysed data were recorded with the CMS detector in 2016 and correspond to an integrated luminosity of 35.9 fb^-1. The double-differential t tbar cross section is measured as a function of the kinematic properties of the top quark and of the t tbar system at parton level in the full phase space. A triple-differential measurement is performed as a function of the invariant mass and rapidity of the t tbar system and the multiplicity of additional jets at particle level. The data are compared to predictions of Monte Carlo event generators that complement next-to-leading-order (NLO) quantum chromodynamics (QCD) calculations with parton showers. Together with a fixed-order NLO QCD calculation, the triple-differential measurement is used to extract values of the strong coupling strength alphaS and the top quark pole mass (mt_pole) using several sets of parton distribution functions (PDFs). The measurement of mt_pole exploits the sensitivity of the t tbar invariant mass distribution to mt_pole near the production threshold. Furthermore, a simultaneous fit of the PDFs, alpha_S, and mt_pole is performed at NLO, demonstrating that the new data have significant impact on the gluon PDF, and at the same time allow an accurate determination of alpha_S and mt_pole. The values alpha_S(mZ)=0.1135-0.0017+0.0021 and mt_pole=170.5+-0.8 GeV are extracted, which account for experimental and theoretical uncertainties, the latter being estimated from NLO scale variations. Possible effects from Coulomb and soft-gluon resummation near the t tbar production threshold are neglected in these parameter extractions. A rough estimate of these effects indicates an expected correction of mt_pole of the order of +1 GeV, which can be regarded as additional theoretical uncertainty in the current mt_pole extraction.
2020
80
7
658
765
Sirunyan A.M.; Tumasyan A.; Adam W.; Ambrogi F.; Asilar E.; Bergauer T.; Brandstetter J.; Dragicevic M.; Ero J.; Del Valle A.E.; Flechl M.; Fruhwirth ...espandi
File in questo prodotto:
File Dimensione Formato  
epjc7917-7.pdf

Accesso aperto

Descrizione: Articolo principale
Tipo di file: PDF EDITORIALE
Dimensione 4.93 MB
Formato Adobe PDF
4.93 MB Adobe PDF Visualizza/Apri

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/1774468
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 72
  • ???jsp.display-item.citation.isi??? 54
social impact