This thesis describes a high-quality, high-precision method for the data analysis of an interesting elementary particle reaction. The data was collected at the Japanese B-meson factory KEKB with the Belle detector, one of the most successful large-scale experiments worldwide. CP violation is a subtle quantum effect that makes the world look different when simultaneously left and right and matter and antimatter are exchanged. This being a prerequisite for our own world to have developed from the big bang, there are only a few experimental indications of such effects, and their detection requires very intricate techniques. The discovery of CP violation in B meson decays garnered Kobayashi and Maskawa, who had predicted these findings as early as 1973, the 2008 Nobel prize in physics. This thesis describes in great detail what are by far the best measurements of branching ratios and CP violation parameters in two special reactions with two charm mesons in the final state. It presents an in-depth but accessible overview of the theory, phenomenology, experimental setup, data collection, Monte Carlo simulations, (blind) statistical data analysis, and systematic uncertainty studies.

This 2nd edition is an extensive update of "B Decays?. The revisions are necessary because of the extensive amount of new data and new theoretical ideas. This book reviews what is known about b-quark decays and also looks at what can be learned in the future.The importance of this research area is increasing, as evidenced by the approval of the luminosity upgrade for CESR and the asymmetric B factories at SLAC and KEK, and the possibility of experiments at hadron colliders.The key experimental observations made thus far, measurement of the lifetimes of the different B species, B0-B0 mixing, the discovery of ?Penguin? mediated decays, and the extraction of the CKM matrix elements Vub and Vcb from semileptonic decays, as well as more mundane results, are described in great detail by the experimentalists who have been closely involved with making the measurements. Theoretical progress in understanding b-quark decays using HQET and lattice gauge techniques are described by theorists who have developed and used these techniques.Synthesizing the experimental and theoretical information, several articles discuss the implications for the ?Standard Model? and how further tests can be done using measurements of CP violation in the B system.

The authors have studied the B{sup ±} → J/[psi][pi]{sup ±} and B{sup ±} → J/[psi]K{sup ±} decays using a 20.7 fb−1 data set collected with the BABAR detector. They observe a signal of 51 ± 10 B{sup ±} → J/[psi][pi]{sup ±} events and determine the ratio [Beta]({sup {+-}} → J/[psi][pi]{sup {+-}})/[Beta](B{sup {+-}} → J/[psi]K{sup {+-}}) to be [3.91 {+-} 0.78(stat.) {+-} 0.19(syst.)]%. The CP-violating charge asymmetries for the B{sup {+-}} → J/[psi][pi]{sup {+-}} and B{sup {+-}} → J/[psi]{sup {+-}}K{sup {+-}} decays are determined to be [Alpha]{sub {pi}} = 0.01 {+-} 0.22(stat.) {+-} 0.01(syst.) and [Alpha]{sub K} = 0.003 {+-} 0.030(stat.) {+-} 0.004(syst.).

The Belle II detector is situated at the asymmetric $e^{-}e^{+}$ collider SuperKEKB at KEK in Tsukuba in Japan, which operates with an energy slightly above the mass of the Y(4S) resonance. As a result, pairs of B mesons are predominantly produced. Due to the clean experimental environment, various measurements to test the Standard Model and precisely determine its parameters can be performed. This is e.g. the element $V_{ mathrm{cb}}$ of the CKM matrix among others, where one of the leading systematic uncertainties arises due to decays of the nature $B to D^{**} ell nu_{ ell}$ . This th...