Observation of Large CP Violation and Evidence for Direct CP Violation in B0-->pi+pi- Decays

Abstract

We report the first observation of CP-violating asymmetries in B0 --> pi+pi- decays based on a 140 fb-1 data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. We reconstruct one neutral B meson as a B0 --> pi+pi- CP eigenstate and identify the flavor of the accompanying B meson from its decay products. We apply an unbinned maximum likelihood fit to the distribution of the time intervals between the two B meson decay points. The fit yields the CP-violating asymmetry amplitudes Apipi = +0.58+/-0.15(stat)+/-0.07(syst) and Spipi = -1.00+/-0.21(stat)+/-0.07(syst). We rule out the CP-conserving case, Apipi=Spipi=0, at a level of 5.2 standard deviations. We also find evidence for direct CP violation with a significance at or greater than 3.2 standard deviations for any Spipi value.

9 pages, 3 figures

References in corpus (7)

• Improved Measurement of Mixing-induced CP Violation in the Neutral B Meson System
• Evidence for B0->pi0pi0
• Impact of tag-side interference on time-dependent CP asymmetry measurements using coherent B0 B0bar pairs
• Measurements of Branching Fractions and CP-violating Asymmetries in B0->pi+ pi-, K+ pi-, K+ K- Decays
• Strong and Weak Phases from Time-Dependent Measurements of $B\to \pi \pi$
• Evidence for CP-Violating Asymmetries in B0->pi+pi- Decays and Constraints on the CKM Angle phi2
• Looking from the East at an Elephant Trotting West: Direct CP Violation in $B^0$ Decays

Cited by in corpus (55)

• Final State Interactions in Hadronic B Decays
• Physics at Super B Factory
• The 2004 UTfit Collaboration Report on the Status of the Unitarity Triangle in the Standard Model
• Charmless $B\to PP$ decays using flavor SU(3) symmetry
• Direct CP Violating Asymmetry in B0 -> K+pi- Decays
• Evidence for Direct CP Violation in B0 -> K+- pi-+ Decays
• Neutral B Flavor Tagging for the Measurement of Mixing-induced CP Violation at Belle
• Search for direct CP violating charge asymmetries in $K^{\pm }\to {\pi }^{\pm }{\pi }^{+}{\pi }^{-}$ and $K^{\pm }\to {\pi }^{\pm }{\pi }^0{\pi }^0$ decays
• Large electroweak penguin contribution in B -> K pi and pi pi decay modes
• Isospin-breaking effects on alpha extracted in B --> pi pi, rho rho, rho pi
• Observation of B0->pi0pi0
• Branching Fractions and CP Asymmetries in B0 -> pi0pi0, B+ -> pi+pi0 and B+ -> K+pi0 Decays and Isospin Analysis of the B -> pipi System
• Radiative corrections to hard spectator scattering in $B\to \pi \pi$ decays
• Improved Measurements of CP-Violating Asymmetry Amplitudes in B0 -> pi+pi- Decays
• On measuring alpha in B(t)-> rho^\pm pi^\mp
• Constraints on R-parity violating supersymmetry from neutral meson mixing
• Reexamining $B\to \pi \pi ,\pi K$ Decays in QCD Factorization Approach
• Search for $CP$ violation in ${\Lambda }_b^0\to p{K}^{-}$ and ${\Lambda }_b^0\to p{\pi }^{-}$ decays
• Direct CP Violation in Hadronic B Decays
• Improved Evidence for Direct CP Violation in B0 --> pi+ pi- Decays and Model-Independent Constraints on phi_2
• The puzzles in $B\to \pi \pi$ and $\pi K$ decays: possible implications for R-parity violating supersymmetry
• A New Method for Determining gamma from B-> pi pi Decays
• Reducing the Error on alpha in B-> pi pi, rho rho, rho pi
• The Matrix of Unitarity Triangle Angles for Quarks
• Improved Measurements of Partial Rate Asymmetry in B -> h h Decays
• Charmless $B\to PP$ decays and the new physics effects in the minimal supergravity model
• Two Higgs Bi-doublet Left-Right Model With Spontaneous P and CP Violation
• Bd^0(t)->pi^+pi^- and Bs^0(t)-> K^+ K^- Decays: A Tool to Measure New-Physics Parameters
• Search for direct CP violation in the decays K\pm \to 3π\pm
• Implications of new data in charmless B decays
• Exclusive $B\to PV$ Decays and CP Violation in the General two-Higgs-doublet Model
• Effects of Final-State Interactions in Hadronic B Decays
• Can there be any new physics in b -> d penguins
• Systematic Error on Weak Phase $\gamma$ from $B\to {\pi }^{+}{\pi }^{-}$ and $B\to K\pi$
• A novel observable for $CP$ violation in multi-body decays and its application potential to charm and beauty meson decays
• Search for direct CP-violation in K+- --> pi+-pi0pi0 decays
• Large Strong Phases and CP Violation in the Annihilation Processes ${\bar{B}}^0\to K^{+}{K}^{-}$, $K^{\ast \pm }{K}^{\mp }$, $K^{\ast +}{K}^{\ast -}$
• Isospin constraints from/on B->pipi
• Evidence of B0 --> rho0 pi0
• Role of final state interactions in the B meson decay into two pions
• Obtaining CKM Phase Information from B Penguin Decays
• B_s\to K^{(*)-}K^{(*)+}, K^{(*)-}π^{+}, K^{(*)-}ρ^{+} decays in R-parity violating supersymmetry
• Summary of ICHEP 2004
• Novel two-loop SUSY effects on CP asymmetry in $B\to \varphi K_s$
• Studying of Bs --> K(*)-pi+, K(*)-rho+ decays within supersymmetry
• CP violation in B meson decays
• Phenomenology of B -> pi pi, pi K Decays at O(alpha^2 beta_0) in QCD Factorization
• Model-independent Constraints on the Weak Phase $\alpha$ (or ${\varphi }_2$) and QCD Penguin Pollution in $B\to \pi \pi$ Decays
• CP violation of the two-body charmless hadronic B decays in the minimal supergravity Model
• Extension of the Buchalla-Safir bound
• Constraints upon the CKM angle phi_2 (alpha) from Belle
• Constraints upon the CKM angle phi_2 (alpha) from Belle and BaBar
• Highlights from Five Years at the B Factories
• Effects of Final State Interactions on Hadronic Charmless B Decays
• Rare Hadronic B Decays