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The authors present measurements of the CP-violation parameters S and C for the radiative decays B° →?°K{sub S}°? and B° →?K{sub S}°?; for B →?K? they also measure the branching fractions and for B →?K+? the time-integrated charge asymmetry A{sub ch}. The data, collected with the BABAR detector at the SLAC National Accelerator Laboratory, represent 467 x 106 B{bar B} pairs produced in e+e− annihilation at the PEP-II collider. In this summary they present an updated measurement of the time-dependent CP asymmetry in B° →?°K{sub S}°? decay mode and the first measurement of the time-dependent CP asymmetry in B° →?K{sub S}°? decay mode. Hadronic corrections in B° →?°K{sub S}°? decay mode might permit S to be as large as ± 0.1. Such corrections and NP effects could depend on m(?°K{sub S}°), so they split the data into two parts: the K*(892) region with 0.8
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 article summarizes measurements of time-dependent CP asymmetries in decays of neutral B mesons to charm final states using data collected by the BABAR detector at the PEP-II asymmetric-energy B factory. All results are preliminary unless otherwise stated.
The BABAR experiment at SLAC provides an opportunity for measurement of CP violation in B decays. A measurement of time-dependent CP violating asymmetries using exclusive B meson decays where the b quark decays to c{bar c}d (including B° 2!D*D*− and B° 2!D*{sup ±}D{sup {-+}} decays) is presented here. This is the first measurement of CP violation in a mode sensitive to the Unitarity Triangle parameter sin2[beta] outside of decays containing charmonium. It provides a comparison to measurements of sin2[beta] using b 2!c{bar c}s, and permits an observation into potential new physics sources of CP violation, such as supersymmetry, via differences between these measurements and those of B° 2!J/[psi] K{sub S}° as statistics of reconstructed neutral B decays to D{sup (*)+} D{sup (*)-} increase. The measured value of the time-dependent CP violating asymmetries are: S = 0.38 ± 0.88(stat) ± 0.12(syst) and C = -0.30 ± 0.50(stat) ± 0.13(syst) for B° 2!D*− D; S = -0.43 ± 1.41(stat) ± 0.23(syst) and C = 0.53 ± 0.74(stat) ± 0.15(syst) for B° 2!D*+ D−; and S = -0.05 ± 0.45(stat) ± 0.05(syst) and C = 0.12 ± 0.30(stat) {+-} 0.05(syst) for B° 2!D*− D+; where S corresponds to CP violation in the interference of mixing and decay and C corresponds to CP violation in decay.
In this work we presented measurements of CP violation and decay rates of B decays in final states not involving a charm quark in the final state. In particular, the time-dependent CP asymmetries of decays which proceed through b 2!s elementary transition is a particularly sensitive probe of physics beyond the Standard Model. In fact, even if the precise measurements of CP conserving and CP violating processes show the success of the CKM picture of the flavour physics, the sector of b 2!s transitions is still not strongly constrained and leaves room for new physics contributions. In particular, we considered the decays which have the cleanest theoretical prediction within the Standard Model: B° 2![phi]K° and B° 2!K{sub s}°K{sub s}°K{sub s}° [beta]{sub eff}{sup SM} = 0.379. We examined the former with a completely new approach with respect to the past: the study of CP violation in the whole KK−K° phase space through a time-dependent Dalitz plot analysis. With this approach, we simultaneously measured the CP-violating asymmetries of the [phi]KJ°, f0(980)K° resonant and KK−K° non-resonant contributions, avoiding one of the largest uncertainties which affected the previous measurements of B° 2![phi]K°. We find [beta]{sub eff}(B° 2![phi]K°) = 0.06 ± 0.16 ± 0.05, which is lower than the Standard Model expectation, but it is consistent with it within two standard deviations. Moreover, only a recently developed experimental technique, which allows the determination of the position of B decay vertex when no charged tracks are originating from it, has made possible the measurement of the time-dependent CP asymmetry in B° 2!K{sub s}°K{sub s}°K{sub s}° decays. The mixing-induced CP parameter S in the Standard Model should be equal to sin 2[beta] parameter, which is measured with high precision in B 2![c{bar c}]K° decays by the B-factories. This statement is true, in the Standard Model, with excellent approximation for the decays studied in this work. The summary of the measurements in the b 2!s sector is shown in Fig. 9.8 A naive average of the b 2!s penguins, which does not account for the correlations existing among [phi]K°, f0(980)K° and K+K−K°, and that includes also modes with larger theoretical uncertainties, shows that -[eta]{sub CP} x S is lower than sin 2[beta]. This is not an evidence of physics beyond the Standard Model, but the systematic deviation from the expected value is an hint that there is room for it. More compelling evidence for new physics could be obtained measuring significant deviation in each decay channel from Standard Model prediction. Currently all the measurement are statistically limited and therefore an increase in accumulated statistics will shed more light into this quest for New Physics.
We present new measurements of CP asymmetries in B° → (c{bar c})K{sup 0(*)} decays recorded by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC between 1999 and 2004. We determine sin2[beta] from decay-time distributions of 7730 signal events in a data sample of approximately 227 x 106 [Upsilon](4S) → B{bar B} decays. The measured value of sin2[beta] = 0.722 ± 0.040(stat) ± 0.023(syst) is in agreement with the value expected from the Standard Model. In a separate time-dependent angular analysis of B → J/[psi] K*° (K*° → K{sub S}°[pi]°) decays we measure cos 2[beta] to be positive at 86% CL.
We report on preliminary measurements of time-dependent CP asymmetries in neutral B decays to CP eigenstates with transition amplitudes that are dominated by penguin-type loops. The results are obtained from a data sample of up to 227 million {Upsilon}(4S) {yields} B{bar B} decays collected with the BABAR detector at the PEP-II asymmetric-energy B-meson Factory at SLAC. The amplitudes of the effective mixing-induced CP asymmetries, sin2{beta}{sub eff}, are derived from decay-time distributions of events in which one neutral B meson is fully reconstructed in a final state without charm and the other B meson is determined to be either a B{sup 0} or {bar B}{sup 0} from its decay products.
The BABAR detector at the PEP-II asymmetric B Factory at SLAC collected a sample of 23 x 10[sup 6] B[bar B] pairs in the years 1999 and 2000. Using this data sample, we measure the amplitude of the time-dependent CP-violating asymmetry in neutral B decays to the CP eigenstates J/[psi] K[sub S][sup 0], [psi](2S) K[sub S][sup 0] and J/[psi] K[sub L][sup 0]. We find a value of sin2[beta]= 0.34[+-] 0.20(stat)[+-] 0.05(syst). We also present preliminary measurements of the B[sup 0][bar B][sup 0] oscillation frequency and of the lifetimes of charged and neutral B mesons.
We report the observation of CP violation in the B[sup 0] meson system. Using a novel technique for time-dependent measurements, we measure a non-zero value for the CP-violating amplitude sin2[beta] at the 4.1[sigma] level. We also report on precision measurements of the B[sup+] and B[sup 0] lifetimes and the B[sup 0][bar B][sup 0] mixing frequency[Delta]m[sub d] obtained with the same technique, and on a first measurement of the time-dependent CP-violating amplitude in B[sup 0][yields][pi][sup+][sup -] decays.