Evidence for direct CP violation in the decay B->D(*)K, D->KsPi+Pi- and measurement of the CKM phase phi3

TL;DR

This paper measures the CKM phase phi3 using Dalitz plot analysis of D meson decays in B->D(*)K processes, providing evidence for direct CP violation with a significance of 3.5 sigma.

Contribution

It introduces a novel Dalitz plot analysis method to extract phi3 from B->D(*)K decays, improving the precision of CP violation measurements.

Findings

Measured phi3 as 78.4 degrees with uncertainties

Ruled out CP conservation at 3.5 sigma

Used a combined fit of three decay modes

Abstract

We present a new measurement of the unitarity triangle angle phi3 using a Dalitz plot analysis of the KsPi+Pi- decay of the neutral D meson produced in B->D(*)K decays. The method exploits the interference between D0 and D0bar to extract the angle phi3, strong phase delta and the ratio r of suppressed and allowed amplitudes. We apply this method to a 605 fb-1 data sample collected by the Belle experiment. The analysis uses three decays: B->DK, and B->D*K with D*->DPi0 and D*->Dgamma, as well as the corresponding charge-conjugate modes. From a combined maximum likelihood fit to the three modes, we obtain phi3 = 78.4^+10.8_-11.6 +- 3.6 (syst) +- 8.9 (model) degrees. CP conservation in this process is ruled out at the confidence level (1-CL)=5x10^-4, or 3.5 standard deviations.