Measurement of CP Violation in B0 → φK0, and of Branching Fraction of and CP Violation in B0 → f0(980)KS0

The authors measure the time-dependent CP asymmetry parameters in B0 → K+K-K0 based on a data sample of approximately 277 million B-meson pairs recorded at the Υ(4S) resonance with the BABAR detector at the PEP-II B-meson Factory at SLAC. They reconstruct two-body B0 decays to φ(1020)Ks0 and φ(1020)KL0. Using a time-dependent maximum-likelihood fit, they measure sin2βeff(φK0) = 0.48 ± 0.28 ± 0.10, and C(φK0) = 0.16 ± 0.25 ± 0.09, where the first error is statistical, and the second is systematic. They also present measurements of the CP-violating asymmetries in the decay B0 → f0(→ π+π-)Ks0. The results are obtained from a data sample of 209 x 106 Υ(4S) → B(bar B) decays, also collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. From a time-dependent maximum-likelihood fit they measure the mixing-induced CP violation parameter S(f0(980)KS0) = - sin 2βefff0(980)KS0 = -0.95-0.23+0.32 ± 0.10 and the direct CP violation parameter C(f0(980)KS0) = - 0.24 ± 0.31 ± 0.15, where the first errors are statistical and the second systematic. Finally, they present a measurement of the branching fraction of the decay B0 → f0(→ π+π-)KS0. From a time-dependent maximum likelihood fit to a data sample of 123 x 106 Υ(4S) → B(bar B) decays they find 93.6 ± 13.6 ± 6.4 signal events corresponding to a branching fraction of Β(B0 → f0(980)(→ π+π-)K0) = (6.0 ± 0.9 ± 0.6 ± 1.2) x 10-6, where the first error is statistical, the second systematic, and the third due to model uncertainties