A measurement of the dijet production cross section is reported based on proton-proton collision data collected in 2016 at s = 13 Te V by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of up to 36.3 fb - 1 . Jets are reconstructed with the anti- k T algorithm for distance parameters of R = 0.4 and 0.8. Cross sections are measured double-differentially (2D) as a function of the largest absolute rapidity | y | max of the two jets with the highest transverse momenta p T and their invariant mass m 1 , 2 , and triple-differentially (3D) as a function of the rapidity separation y ∗ , the total boost y b , and either m 1 , 2 or the average p T of the two jets. The cross sections are unfolded to correct for detector effects and are compared with fixed-order calculations derived at next-to-next-to-leading order in perturbative quantum chromodynamics. The impact of the measurements on the parton distribution functions and the strong coupling constant at the mass of the Z boson is investigated, yielding a value of α S ( m Z ) = 0.1179 ± 0.0019 .

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A measurement of the jet mass distribution in hadronic decays of Lorentz-boosted top quarks is presented. The measurement is performed in the lepton + jets channel of top quark pair production (tt¯) events, where the lepton is an electron or muon. The products of the hadronic top quark decay are reconstructed using a single large-radius jet with transverse momentum greater than 400GeV. The data were collected with the CMS detector at the LHC in proton-proton collisions and correspond to an integrated luminosity of 138fb-1. The differential tt¯ production cross section as a function of the jet mass is unfolded to the particle level and is used to extract the top quark mass. The jet mass scale is calibrated using the hadronic W boson decay within the large-radius jet. The uncertainties in the modelling of the final state radiation are reduced by studying angular correlations in the jet substructure. These developments lead to a significant increase in precision, and a top quark mass of 173.06±0.84GeV.

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• časopisecké články MeSH