Improved evidence for direct CP violation in B0 ->pi(+)pi(-) decays and model-independent constraints on phi(2)

We present a new measurement of the time-dependent CP-violating parameters in B-0 ->pi(+)pi(-) decays with 275x10(6) B (B) over 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 B-0 ->pi(+)pi(-) events and measure the CP-violating parameters: S-pi pi=-0.67 +/- 0.16(stat)+/- 0.06(syst) and A(pi pi)=+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-pi pi value. Using isospin relations, we obtain 95.4% confidence intervals for the Cabibbo-Kobayashi-Maskawa quark-mixing matrix angle phi(2) of 0 degrees

Keywords:

• Quantum electrodynamics
• Standard deviation
• KEKB
• Pi
• Physics
• CP violation
• Isospin
• Collider
• Electron–positron annihilation
• Resonance
• Particle physics
• Nuclear physics

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