Correlations of jets with other objects in 13 TeV proton proton collisions at CMS experiment

The physics motivation, detector design, triggers, calibration, and overall performance of the very forward CASTOR calorimeter of the CMS experiment are reviewed. Due to the position of the detector in the very forward phase space, it is possible to probe down to very low-x values of the proton momentum fraction. The CASTOR Cherenkov sampling calorimeter is located very close to the LHC beamline, at a radial distance of about 1 cm from the beam pipe and 14.4 m from the CMS interaction point, covering the pseudorapidity range of -6.6 < η<-5.2. The CASTOR detector was designed to withstand both high ambient radiation and strong magnetic fields. The performance of the CASTOR detector in the measuring of the very forward jets is reviewed using data collected in proton-proton collisions at the LHC at 13 TeV. The new work in this thesis is that we combine both the CASTOR and HF detectors to cover the very forward area by applying the condition Divides ηDivides<4.25, The de correlation in the azimuthal angle between the most forward and the most backward jets (Mueller-Navelet jets) was measured using data collected in pp collisions at the CMS detector at the LHC at √s = 13 TeV.