In this dissertation, we present the results of a time-dependent angular analysis of B s → 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, B s → J/ψφ and B s → B s → J/ψφ. The timedependent angular analysis is used to extract the decay widths of the heavy and light B s eigenstates and the difference between these decay widths ∆Γ s ≡ Γ L s − Γ H s . Initial-state flavor tagging is used to determine the matter-antimatter content of the B s mesons at production time. We combine flavor tagging with the angular analysis, which statistically determines the contributions of the CP-even and CPodd components at decay time, to measure the CP-violating phase β s . The phase β s is expressed in terms of elements of the Cabibbo-Kobayashi-Maskawa matrix as β s ≡ arg (−V ts V * tb /V cs V * cb ), and is predicted by the Standard Model to be close to zero, β SM s = 0.02. In the measurement of ∆Γ s , 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 β s , we use a dataset corresponding to 1.3 fb −1 of collected luminosity. We measure ∆Γ s = (0.071 +0.064 −0.059 ± 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 β s and ∆Γ s , 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.Thesis Supervisor: Christoph M.E. Paus Title: Associate Professor
AcknowledgmentsExperimental particle physics is a fundamentally collaborative effort, and the work presented in these pages would not have been possible without the guidance, assistance, and support of my colleagues at MIT and at the CDF experiment. My time as a Ph.D. student was also made infinitely more enjoyable by the personal relationships I have been lucky to forge during these years.I am the eleventh student to have the privilege to call Christoph M.E. Paus his Ph.D. advisor. His intuition and skill as a physicist, his dedication, his indefatigability and leadership are all evident in the contributions he has made to our field. These qualities need not my reiteration; they form the natural basis for the admiration shared by all those who know him well. Eleven of us have been lucky to know the qualities that make Christoph stand out as an unmatched mentor and advisor. He manages to give his students generous support while simultaneously granting them the essential independence necessary to develop their own skills. He knew when to trust that my approach was the right one, or when to let me find out that it was the wrong one, and when to step in to correct my course. And finally, perhaps most importantly, he knew how to guide me through ch...