Amplitude Analysis and Measurement of the Time-Dependent CP Asymmetry of B⁰→K_S⁰K_S⁰K_S⁰ Decays

We present the first results on the Dalitz-plot structure and improved measurements of the time-dependent CP-violation parameters of the process B⁰→K_S⁰K_S⁰K_S⁰ obtained using 468×10⁶ BB̄ decays collected with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. The Dalitz-plot structure is probed by a time-integrated amplitude analysis that does not distinguish between B⁰ and B̅⁰ decays. We measure the total inclusive branching fraction ℬ(B⁰→K_S⁰K_S⁰K_S⁰)=(6.19 ± 0.48 ± 0.15 ± 0.12)×10⁻⁶, where the first uncertainty is statistical, the second is systematic, and the third represents the Dalitz-plot signal model dependence. We also observe evidence for the intermediate resonant states ʄ₀(980), ʄ₀(1710), and ʄ₂(2010). Their respective product branching fractions are measured to be (2.70_{-1.19}^{+1.25} ± 0.36 ± 1.17)×10⁻⁶, (0.50_{-0.24}^{+0.46 ± 0.04 ± 0.10)×10⁻⁶, and (0.54_{-0.20}^{+0.21} ± 0.03 ± 0.52)×10⁻⁶. Additionally, we determine the mixing-induced CP-violation parameters to be S = -0.94_{-0.21}^{+0.24 ± 0.06 and C = -0.17 ± 0.18 ± 0.04, where the first uncertainty is statistical and the second is systematic. These values are in agreement with the standard model expectation. For the first time, we report evidence of CP violation in B⁰→K_S⁰K_S⁰K_S⁰ decays; CP conservation is excluded at 3.8 standard deviations including systematic uncertainties.