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 preliminary measurements of branching fractions and direct CP violating asymmetries in charmless two-body B decays, obtained with the BABAR detector using a sample of 227M {Upsilon}(4S) {yields} B{bar B} decays. We report the first observation of B{sup 0} {yields} K{sup 0}{bar K}{sup 0} and the first observation of direct CP violation in B{sup 0} {yields} K{sup +}{pi}{sup -} decays.

We present improved measurements of CP-violation parameters in the decays B° →??−, B° → K+?−, and B° →?°?°, and of the branching fractions for B° →?°?° and B° → K°?°. The results are obtained with the full data set collected at the?(4S) resonance by the BABAR experiment at the PEP-II asymmetric-energy B factory at the SLAC National Accelerator Laboratory, corresponding to 467 ± 5 million B{bar B} pairs. We find the CP-violation parameter values and branching fractions S{sub?+?−} = -0.68 ± 0.10 ± 0.03, C{sub?+?−} = -0.25 ± 0.08 ± 0.02,?{sub K−?+} = -0.107 ± 0.016{sub -0.004}{sup +0.006}, C{sub?°?°} = -0.43 ± 0.26 ± 0.05,?(B° →?°?°) = (1.83 ± 0.21 ± 0.13) x 10−6,?(B° → K0?°) = (10.1 ± 0.6 ± 0.4) x 10−6, where in each case, the first uncertainties are statistical and the second are systematic. We observe CP violation with a significance of 6.7 standard deviations for B° →?+?− and 6.1 standard deviations for B° → K+{pi}{sup -}, including systematic uncertainties. Constraints on the Unitarity Triangle angle? are determined from the isospin relations among the B → {pi}{pi} rates and asymmetries. Considering only the solution preferred by the Standard Model, we find? to be in the range [71{sup o}, 109{sup o}] at the 68% confidence level.

The authors present improved measurements of the branching fractions and CP asymmetries in the two-body decays B° 2!?°?°, B° 2!K°?° and B° 2!K?− as well as the quasi two-body B° 2!K1(1270)+?− and B° 2!K1(1400)+?− decays. These updated measurements are made using the complete set of BABAR data taken at the Y(4S) resonance, collected between 1999 and 2007 at the PEP-II collider at SLAC.

A summary of recent results of searches for direct CP Violation and measurements of charmless B-meson decay branching fractions with the BABAR detector is presented.