Measurement of CP-Violating Asymmetries in B0->(rho pi)0 Using a Time-Dependent Dalitz Plot Analysis

TL;DR

This paper reports a measurement of CP-violating asymmetries in B0 meson decays to rho pi using a time-dependent Dalitz plot analysis, providing insights into the CP violation parameters and the Unitarity Triangle angle alpha.

Contribution

It extends previous analyses by incorporating interference effects between rho resonances and measures multiple CP-violation parameters from a large data sample.

Findings

Measured direct CP-violation parameters Acp and C.

Estimated the mixing-induced CP-violation parameter S.

Provided a value for the Unitarity Triangle angle alpha.

Abstract

We present the preliminary measurement of CP-violating asymmetries in B0->(rhopi)0->pi+pi-pi0 decays using a time-dependent Dalitz plot analysis. The results are obtained from a data sample of 213 million Y(4S)->BB-bar decays, collected by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. This analysis extends the narrow-rho quasi-two-body approximation used in the previous analysis, by taking into account the interference between the rho resonances of the three charges. We measure 16 coefficients of the bilinear form factor terms occurring in the time-dependent decay rate of the B0 meson with the use of a maximum-likelihood fit. We derive the physically relevant quantities from these coefficients. We measure the direct CP-violation parameters Acp = -0.088 +- 0.049 +- 0.013 and C = 0.34 +- 0.11 +- 0.05, where the first errors are statistical and the second systematic. For the mixing-induced CP-violation parameter we find S = -0.10 +- 0.14 +- 0.04, and for the dilution and strong phase shift parameters respectively, we obtain dC = 0.15 +- 0.11 +- 0.03 and dS = 0.22 +- 0.15 +- 0.03. For the angle alpha of the Unitarity Triangle we measure (113 +27 -17 +-6) deg, while only a weak constraint is achieved at the significance level of more than two standard deviations. Finally, for the relative strong phase delta+- between the B0->rho-pi+ and B0->rho+pi- transitions we find (-67 +28 -31 +- 7) deg, with a similarly weak constraint at two standard deviations and beyond.