Improved Evidence for Direct CP Violation in B0 --> pi+ pi- Decays and Model-Independent Constraints on phi_2

Abstract

We present a new measurement of the time-dependent CP-violating parameters in B0 --> pi+ pi- decays with 275 x 10^6 BB-bar pairs collected with the Belle detector at the KEKB asymmetric-energy e+e- collider operating at the Upsilon(4S) resonance. We find 666 +/- 43 B0 --> pi+ pi- events and measure the CP-violating parameters: S_pipi = -0.67 +/- 0.16(stat) +/- 0.06(syst) and A_pipi = +0.56 +/- 0.12(stat) +/- 0.06(syst). We find evidence for large direct CP-violation with a significance greater than 4 standard deviations for any S_pipi value. Using isospin relations, we obtain 95.4% confidence intervals for the CKM angle phi_2 of 0 deg. < phi_2 < 19 deg. and 71 deg. < phi_2 < 180 deg.

arXiv comment10 pages, 4 figures, the title and abstract have been changed on May 13th, submitted to Phys. Rev. Lett., replaced on Apr. 30th to a paper draft that is submitted to PRL. Original comments: 13 pages, 6 figures, contributed to the 2005 Aspen Winter Conference on The Higest Energy Physics, Feb. 13-19, 2005, Aspen, Colorado, U.S.A

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Cited by in corpus (13)

• Two body B decays with isosinglet final states in SCET
• Observation of Direct CP-Violation in B0 --> pi+pi- Decays and Model-Independent Constraints on phi2
• Exploring B_{d,s}-> KK decays through flavour symmetries and QCD-factorisation
• Measurement of CP-Violating Asymmetries in B0-->(rhopi)0 Using a Time-Dependent Dalitz Plot Analysis
• Direct CP violation in $B^{\pm }\to p\bar{p}{K}^{(\ast )\pm }$
• Mixing-induced CP asymmetry in B-> K* gamma decays with perturbative QCD approach
• Radiative corrections to hard spectator scattering in $B\to \pi \pi$ decays
• Measurements of CP-Violating Asymmetries in B0 to a1(1260)^{+-} pi^{-+} Decays
• Supersymmetric Contributions to Bs->K+K-
• Measurements of B Decays to Two Kaons
• Looking for Delta I = 5/2 amplitude components in B -> pi pi and B -> rho rho experiments
• Measurement of the CKM angle alpha with the B-factories
• Measurement of Branching Fraction and Direct CP Asymmetry in B0-->rho0 pi0 Decays