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This dissertation describes a measurement of the direct CP asymmetry between inclusive b {yields} s{gamma} and {bar b} {yields} {bar s}{gamma} decays. This asymmetry is expected to be less than 0.01 in the Standard Model, but could be enhanced up to the order of 0.10 by non-Standard Model contributions. We use a sample of 89 million B{bar B} pairs recorded with the BABAR detector at PEP-II, from which we reconstruct a set of 12 exclusive b {yields} s{gamma} final states containing one charged or neutral kaon and one to three pions. We measure an asymmetry of A{sub CP} (b {yields} s{gamma}) = 0.025 {+-} 0.050(stat.) {+-} 0.015(syst.), corresponding to an allowed range of -0.06
We perform a measurement of direct CP violation in b to s+gamma Acp, and the measurement of a difference between Acp for neutral B and charged B mesons, Delta A_X_sgamma, using 429 inverse femtobarn of data recorded at the Upsilon(4S) resonance with the BABAR detector. B mesons are reconstructed from 16 exclusive final states. Particle identification is done using an algorithm based on Error Correcting Output Code with an exhaustive matrix. Background rejection and best candidate selection are done using two decision tree-based classifiers. We found A_cp = 1.73%+-1.93%+-1.02% and Delta A_X_sgamma = 4.97%+-3.90%+-1.45% where the uncertainties are statistical and systematic respectively. Based on the measured value of Delta A_X_sgamma, we determine a 90% confidence interval for Im C_8g/C_7gamma, where C_7gamma and C_8g are Wilson coefficients for New Physics amplitudes, at -1.64
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.
The presented study of the radiative electroweak "penguin"--Decay B->K*(892)gamma, proceeding by the b->sgamma "loop"-transition, provides an important test of the Standard Model and a candidate of the search for New Physics. The used data sample has been recorded at the Y(4S) resonance with the BABAR detector at the asymmetric electron-positron- collider PEP-II of the Stanford Linear Accelerator Center (SLAC) in California. The B->K*gamma branching fractions are measured in four K*-decay modes. A search for direct CP-violation in the B->K*gamma mode has also been carried out.
We report the measurement of the Cabibbo-Kobayashi-Maskawa CP-violating angle? through a Dalitz plot analysis of neutral D meson decays to K{sub S}°??− and K{sub S}° K+K− produced in the processes B{sup {-+}} → DK{sup {-+}}, B{sup {-+}} → D* K{sup {-+}} with D* → D?°, D?, and B{sup {-+}} → DK*{sup {-+}} with K*{sup {-+}} → K{sub S}°?{sup {-+}}, using 468 million B{bar B} pairs collected by the BABAR detector at the PEP-II asymmetric-energy e+e− collider at SLAC. We measure? = (68 ± 14 ± 4 ± 3){sup o} (modulo 180{sup o}), where the first error is statistical, the second is the experimental systematic uncertainty and the third reflects the uncertainty in the description of the neutral D decay amplitudes. This result is inconsistent with? = 0 (no direct CP violation) with a significance of 3.5 standard deviations.
We describe a measurement of the direct CP asymmetry between inclusive b 2!s[gamma] and {bar b} 2!{bar s}[gamma] decays. This asymmetry is expected to be less than 0.01 in the Standard Model, but could be enhanced up to about 0.10 by new physics contributions. We use a sample of 89 million B{bar B} pairs recorded with the BABAR detector at PEP-II, from which we reconstruct a set of 12 exclusive b 2!s[gamma] final states containing one charged or neutral kaon and one to three pions. We measure an asymmetry of A{sub CP} (b 2!s[gamma]) = 0.025 ± 0.050(stat.) ± 0.015(syst.), corresponding to an allowed range of -0.06