Measurements of inclusive low-Pt jets cross-section and azimuthal angle decorrelation of jets with large rapidity separation using run 1 cms data

Measurement of the inclusive jet cross section in proton-proton collisions at s = 8 TeV based on data collected by the CMS detector within an integrated luminosity of 5.6 pb-1 is presented in this thesis. The measurement was performed using the anti-kT clustering algorithm with a distance parameter R = 0.7 in the rapidity region of |y| < 4.7 for jet transverse momenta 21 < pT < 74 GeV/c. The measured jet cross-section is compared to predictions of next-to-leading order (NLO) QCD calculations. Measurement of the decorrelation in the azimuthal angle between the most forward and the most backward jets (MN jets) in data collected in pp collisions with the CMS detector at s = 7 TeV is presented in this thesis, too. The measurement is presented in the form of distributions of azimuthal-angle differences, ∆φ, between the MN jets, the average cosines of (π − ∆φ), 2(π − ∆φ), and 3(π − ∆φ), and ratios of these cosines. The jets are required to have transverse momenta, pT, in excess of 35 GeV and in the rapidity of |y| < 4.7. The results are presented as a function of the rapidity separation, ∆y, between the MN jets, reaching ∆y up to 9.4 for the first time and compared to predictions of various Monte Carlo event generators and to analytical predictions based on the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) and Balitsky-Fadin-Kuraev-Lipatov (BFKL) parton evolution schemes.