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ISSN - 00319007, EISSN - 10797114, Physical Review Letters, 2005, vol. 95, p. -

Improved evidence for direct CP violation in B0→π+π- decays and model-independent constraints on 2

Abe K., Adachi I., Aihara H., Arinstein K., Asano Y., Aushev T., Bakich A. M., Ban Y., Barberio E., Barbero M., Bay A., Bitenc U., Bizjak I., Blyth S., Bondar A., Bozek A., Bračko M., Brodzicka J., Browder T. E., Chang P., Chao Y., Chen A., Chen K. F., Chen W. T., Cheon B. G., Chistov R., Choi S. K., Choi Y., Choi Y. K., Chuvikov A., Cole S., Dalseno J., Dash M., Dong L. Y., Drutskoy A., Eidelman S., Enari Y., Fang F., Fratina S., Gabyshev N., Garmash A., Gershon T., Gokhroo G., Golob B., Gorišek A., Haba J., Hara K., Hara T., Hastings N. C., Hayashii H., Hazumi M., Hinz L., Hokuue T., Hoshi Y., Hou S., Hou W. S., Hsiung Y. B., Iijima T., Imoto A., Inami K., Ishikawa A., Ishino H., Itoh R., Iwasaki M., Iwasaki Y., Kakuno H., Kang J. H., Kang J. S., Kapusta P., Katayama N., Kawai H., Kawasaki T., Khan H. R., Kibayashi A., Kichimi H., Kim S. M., Kinoshita K., Korpar S., Križan P., Krokovny P., Kumar S., Kuo C. C., Kusaka A., Kuzmin A., Kwon Y. J., Leder G., Lee S. E., Lesiak T., Li J., Lin S. W., MacNaughton J., Majumder G., Mandl F., Marlow D., Matyja A.

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.