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

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dc.creatorBelle Collaboration
dc.creatorAbe, K.
dc.date2005-02-18
dc.date2005-05-14
dc.date.accessioned2026-07-07T11:58:02Z
dc.date.available2026-07-07T11:58:02Z
dc.descriptionWe 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.
dc.description10 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
dc.identifierhttps://arxiv.org/abs/hep-ex/0502035
dc.identifierhttp://arxiv.org/abs/hep-ex/0502035
dc.identifierPhys.Rev.Lett.95:101801,2005
dc.identifierdoi:10.1103/PhysRevLett.95.101801
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/206094
dc.subjectHigh Energy Physics - Experiment
dc.titleImproved Evidence for Direct CP Violation in B0 --> pi+ pi- Decays and Model-Independent Constraints on phi_2
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