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Study of double parton scattering in four-jet production at low transverse momentum in proton-proton collisions at √s = 13 TeV

Book - Dissertation

A study of inclusive four jet production in proton-proton collisions at a centre-of-mass energy of 13 TeV is presented. The data sample was collected in 2016 with the CMS detector at the LHC during a low intensity run, with an integrated luminosity of 0.042 pb-1. Differential cross sections are measured as a function of the jet transverse momentum, pseudorapidity, and several other observables that exploit angular correlations. The lowest jet transverse momentum cuts required in this paper are 35, 30, 25, and 20 GeV for the first, second, third and fourth leading jet respectively within |η| < 4.7, leading to a fiducial cross section of σ = 2.77 ± 0.02 (stat.)+0.68-0.55(syst.) μb. It is found that the data are very sensitive to different aspects of the underlying event, parton showers, and matrix element calculations. In particular the interplay between the de-correlations caused by parton showers and double parton scattering contributions is shown to be important. Models employing angular ordered parton showers, off-shell initial kinematics, as well as models with higher order matrix element calculations provide a better description of the data in certain observables, compared to standard leading-order models. The ΔS observable, which characterizes the azimuthal angular difference between the hard and soft jet pair, is used to extract a double parton scattering contribution by means of a template fit method. Model dependent values of sigma effective are calculated and compared to previous measurements. While all extracted values of the effective cross section show agreement with measurements performed at lower centre-of-mass energies, a strong model dependence of the double parton scattering contribution is found.
Number of pages: 233
Publication year:2020
Keywords:Doctoral thesis