Measurement of the Time-Dependent CP Asymmetry of Partially Reconstructed B0->D*+D*- Decays

TL;DR

This paper reports a new measurement of the time-dependent CP asymmetry in B0->D*+D*- decays, using partial reconstruction and a large data sample, providing results consistent with the Standard Model.

Contribution

It introduces a partial reconstruction technique to measure CP asymmetry parameters in B0 decays with high precision.

Findings

Measured CP asymmetry parameters S and C with statistical and systematic uncertainties.

Extracted CP-even components S+ and C+ consistent with Standard Model expectations.

Results support the small penguin contribution hypothesis in B0 decays.

Abstract

We present a new measurement of the time-dependent CP asymmetry of B0->D*+D*- decays using (471+-5) million BBbar pairs collected with the BaBar detector at the PEP-II B Factory at the SLAC National Accelerator Laboratory. Using the technique of partial reconstruction, we measure the time-dependent CP asymmetry parameters S=-0.34+-0.12+-0.05$ and C=+0.15+-0.09+-0.04. Using the value for the CP-odd fraction R_perp=0.158+-0.028+-0.006, previously measured by BaBar with fully reconstructed B0->D*+D*- events, we extract the CP-even components S+=-0.49+-0.18+-0.07+-0.04 and C+=+0.15+-0.09+-0.04. In each case, the first uncertainty is statistical and the second is systematic; the third uncertainty on S+ is the contribution from the uncertainty on R_perp. The measured value of the CP-even component S+ is consistent with the value of sin(2Beta) measured in b->(ccbar)s transitions, and with the Standard Model expectation of small penguin contributions.