B0 -> pi+ pi- pi0 time-dependent Dalitz analysis from Belle

TL;DR

This paper reports a time-dependent Dalitz plot analysis of B0 decays to three pions, measuring CP violation parameters and constraining the CKM angle phi_2 using data from the Belle detector.

Contribution

It provides the first detailed measurement of CP violation parameters in B0 -> pi+ pi- pi0 decays and constrains the CKM angle phi_2 with a comprehensive Dalitz and isospin analysis.

Findings

Measured CP violation parameters for B0 -> rho+-pi-+ and B0 -> rho0pi0 decays.

Constrained the CKM angle phi_2 to (83^{+12}_{-23}) degrees.

Identified a large disfavored region for phi_2 at 68.3% confidence level.

Abstract

We present the results of a time-dependent Dalitz plot analysis of B0 -> pi+ pi- pi0 decays based on a 414fb^-1 data sample that contains 449MBB pairs collected on the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric energy e+e- collider. The direct CP violating parameters of B0 -> rho+-pi-+ decay mode are measured to be A_rhopi^+- = +0.22 +- 0.08(stat.) +- 0.05(syst.) and A_rhopi^-+ = +0.08 +- 0.17(stat.) +- 0.12(syst.). We also measure the CP violating parameters of the decay mode B0 -> rho0pi0 as A_rho0pi0 = -0.45 +- 0.35(stat.) +- 0.32(syst.) and S_rho0pi0 = +0.15 +- 0.57(stat.) +- 0.43(syst.). Combining our analysis with information on charged B decay modes, we perform a full Dalitz and isospin analysis and obtain a constraint on the CKM angle phi_2, phi_2 = (83^+12_-23)^\circ. A large CKM-disfavored region (phi_2<8^\circ and 129^\circ <phi_2) also remains at 68.3% confidence level.