Measurement of the Branching Fraction and Time-Dependent CP Asymmetry in the Decay B0->D*+D*-Ks

TL;DR

This paper measures the decay rate and CP asymmetry in B0->D*+D*-Ks decays, revealing significant resonant contributions and suggesting a positive cos2beta with high confidence, advancing understanding of CP violation.

Contribution

It provides the first measurement of the branching fraction and evidence for a resonant state in B0->D*+D*-Ks decays, along with a time-dependent CP asymmetry analysis.

Findings

Branching fraction B(B0->D*+D*-Ks) = (4.4 ± 0.4 ± 0.7) x 10^{-3}

Evidence for B0->D*- D+_{s1}(2536) with 4.6σ significance

Indicates cos2beta is positive at 94% confidence level

Abstract

We study the decay B0->D*+D*-Ks using (230 +/- 2) x 10^{6} BBbar pairs collected by the Babar detector at the PEP-II B factory. We measure a branching fraction B(B0->D*+D*-Ks)=(4.4\pm0.4\pm0.7)\times 10^{-3} and find evidence for the decay B0->D*- D+_{s1}(2536) with a significance of $4.6\sigma$. A time-dependent CP asymmetry analysis is also performed to study the possible resonant contributions to B0->D*+D*-Ks and the sign of cos2beta . Our measurement indicates that there is a sizable resonant contribution to the decay B0->D*+D*-Ks from a unknown $D^+_{s1}$ state with large width, and that cos2beta is positive at the 94 % confidence level under certain theoretical assumptions.