CP Violation in Flavor Tagged $B_s \to J/\psi \phi$ Decays

Abstract

In this dissertation, we present the results of a time-dependent angular analysis of Bs → J/ΨΦ decays performed with the use of initial-state flavor tagging. CP violation is observed in this mode through the interference of decay without net mixing and decay with net mixing, that is, Bs → J/ΨΦ and Bs → $\bar{B}$s → J/ΨΦ . The time-dependent angular analysis is used to extract the decay widths of the heavy and light Bs eigenstates and the difference between these decay widths ΔΓs {triple_bond} ΓsL-ΓsH. Initial-state flavor tagging is used to determine the matter-antimatter content of the Bs mesons at production time. We combine flavor tagging with the angular analysis, which statistically determines the contributions of the CP-even and CP-odd components at decay time, to measure the CP-violating phase βs. The phase βs is expressed in terms of elements of the Cabibbo-Kobayashi-Maskawa matrix as βs {triple_bond} arg (-VtsV*tb/VcsV*cb), and is predicted by the Standard Model to be close to zero, βsSM = 0.02. In the measurement of ΔΓs, we use a dataset corresponding to 1.7 fb-1 of luminosity, collected at the CDF experiment from proton-antiproton collisions at a center of mass energy √s = 1.96 TeV. In the measurement of βs, we use a dataset corresponding to 1.3 fb-1 of collected luminosity. We measure ΔΓs = (0.071-0.059+0.064 ± 0.007) ps-1 using the time-dependent angular analysis. Combining the angular analysis with flavor-tagging, we find that assuming the Standard Model predictions of βs and ΔΓs, the probability of a deviation as large as the level of the observed data is 33%. We obtain a suite of associated results which are discussed in detail in this dissertation alongside the main results.