Title: Some aspects of hadron-hadron collisions in high energy interactions (B$0\atop{s}$ mixing oscillations in semileptonic decay at D0 experiment)
Abstract: In this thesis, we report the study on one such particle called the B$0\atop{s}$ meson made up of a bottom and a strange quark. B$0\atop{s}$ mesons are currently produced in a great numbers only at the Tevatron and we report a study done to measure the mixing parameter Δms between the B$0\atop{s}$ meson and its anti-particle $\bar{B}$$0\atop{s}$. Mixing is the ability of a very few neutral mesons to change from their particle to their antiparticle and vice versa. Until recently there existed only a lower limit on this measurement, here we report an upper bound and a most probable value for the mixing parameter. In the following chapter, we discuss the theoretical motivation behind this study. The measurement technique and the different factors that effect the measurement are also given. In Chapter 3, we provide an overview of the experimental setup needed to perform the study. In Chapter 4, we present a new initial state flavor tagging algorithm using electrons and measurement of the B$0\atop{d}$ mixing parameter Δmd with the new technique. Details of the combined initial state tagging used in the B$0\atop{s}$ mixing study are also given. A detailed description of the B$0\atop{s}$ mixing analysis and the results are covered in Chapter 5. And finally the results from all the three channels and a bound on the mixing parameter are presented in Chapter 6.