Journal article
Improved evidence for direct CP violation in B0→π π- decays and model-independent constraints on 2
K Abe, I Adachi, H Aihara, K Arinstein, Y Asano, T Aushev, AM Bakich, Y Ban, E Barberio, M Barbero, A Bay, U Bitenc, I Bizjak, S Blyth, A Bondar, A Bozek, M Bračko, J Brodzicka, TE Browder, P Chang Show all
Physical Review Letters | AMER PHYSICAL SOC | Published : 2005
Abstract
We present a new measurement of the time-dependent CP-violating parameters in B0→π+π- decays with 275×106 BB̄ pairs collected with the Belle detector at the KEKB asymmetric-energy e+e- collider operating at the Υ(4S) resonance. We find 666±43 B0→π+π- events and measure the CP-violating parameters: Sππ=-0.67±0.16(stat)±0. 06(syst) and Aππ=+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 Sππ value. Using isospin relations, we obtain 95.4% confidence intervals for the Cabibbo-Kobayashi-Maskawa quark-mixing matrix angle 2 of 0°<2<19° and 71°<2<180°. © 2005 The American Physical Society.