Time Dependent CP Asymmetries and Branching RatioMeasurements in Charmless Three Body B Decays at BABAR

Abstract

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 → 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 → 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: B0 → ΦK0 and B0 → K$0\atop{s}$K$0\atop{s}$K$0\atop{s}$ β$eff\atop{SM}$ = 0.379. We examined the former with a completely new approach with respect to the past: the study of CP violation in the whole K+K-K0phase space through a time-dependent Dalitz plot analysis. With this approach, we simultaneously measured the CP-violating asymmetries of the ΦKJ0, f0(980)K0 resonant and K+K-K0 non-resonant contributions, avoiding one of the largest uncertainties which affected the previous measurements of B0 → ΦK0. We find β eff(B0 → ΦK0) = 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 B0 → K$0\atop{s}$K$0\atop{s}$K$0\atop{s}$ decays. The mixing-induced CP parameter S in the Standard Model should be equal to sin 2β parameter, which is measured with high precision in B → [c$\bar{c}$]K0 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 → s sector is shown in Fig. 9.8 A naive average of the b → s penguins, which does not account for the correlations existing among ΦK0, f0(980)K0 and K+K-K0, and that includes also modes with larger theoretical uncertainties, shows that -ηCP x S is lower than sin 2β. 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.