Search for resonances in $b$-jets final states with the CDF II and the LHCb experiments

Abstract

This thesis describes the search for resonances decaying into a pair of b-jets performed with the datasets collected by the CDF II experiment at the Tevatron and the LHCb at the LHC. The unique characteristics of these particle detectors, which are highlighted through the thesis with a constant comparison between the two experiments, give the opportunity to search also in the low dijet invariant mass region, unaccessible to the other general purpose detectors at the LHC. A dataset corresponding to 5.4 $fb^{-1}$ of data collected at CDF II is used to measure the cross section of the inclusive $Z\to b\bar{b}$ process, which turns out to be in agreement with the theory prediction, together with the data-simulation energy scale factor for b-jets. With the same event selection and background modeling then, the limit on inclusive $H\to b\bar{b}$ process is set. At this point, the study on inclusive $H\to b\bar{b}$ channel is extended with a sensitivity study by using 1.6 $fb^{-1}$ of data collected in 2016 at the LHCb. The future prospects for this search are reported. Finally, the search for a beyond Standard Model Higgs-like particle produced in association with b-jets and decaying into a pair of b-jets, with the CDF II dataset, is described. No evidence of its production has been seen in the data, hence is set a 95\% Confidence Level upper limit on its production cross section as a function of the particle invariant mass in the range from 100 to 300 GeV/$c^{2}$.