Constraints on rB and gamma in B+- -> D(*)0K+- decays by a Dalitz analysis of D0 -> Ks pi+ pi-

TL;DR

This study uses Dalitz analysis of D0 decays to measure CP violation parameters in B+- decays, constraining amplitude ratios and phases, and estimating the CKM angle gamma with associated uncertainties.

Contribution

It provides the first constraints on rB and precise measurements of strong phases and gamma in B+- -> D(*)0 K+- decays using a large BaBar dataset.

Findings

rB < 0.19 at 90% CL

gamma = 70 +/- 26 degrees

Measured strong phases deltaB and deltaB*

Abstract

We report on a study of direct CP violation in the decay B- -> D(*)0 K- with a Dalitz analysis of the D0 -> Ks pi- pi+ decay using a sample of 227 million BBbar pairs collected by the BaBar detector. Reference to the charge-conjugate state is implied here. We constrain the amplitude ratio rB=|A(B- -> D0bar K-)|/|A(B- -> D0 K-)| to be <0.19 at the 90% confidence level and rB*=|A(B- -> D*0bar K-)|/|A(B- -> D*0 K-)| = 0.155 +0.070-0.077 +/- 0.040 +/- 0.020 and we measure the relative strong phase deltaB=(114 +/- 41 +/- 8 +/- 10) deg and deltaB*=(303 +/- 34 +/- 14 +/- 10) deg between the amplitudes A(B- -> D(*)0bar K-) and A(B- -> D(*)0 K-). From these samples we measure gamma =(70 +/- 26 +/- 10 +/- 10) deg. The first error is statistical, the second error accounts for experimental uncertainties and the third error reflects the Dalitz model uncertainty. For this preliminary result we have quoted confidence intervals obtained with a Bayesian technique assuming a uniform prior in rB, gamma and deltaB.