%O © 2005 The American Physical Society %D 2005 %V 94 %N 11 %I AMERICAN PHYSICAL SOC %L discovery1308459 %X We report the observation of the radiative decay B+-> K-1(1270)(+)gamma using a data sample of 140 fb(-1) taken at the Upsilon(4S) resonance with the Belle detector at the KEKB e(+)e(-) collider. We find the branching fraction to be B(B+-> K-1(1270)(+)gamma)=(4.3 +/- 0.9(stat.)+/- 0.9(syst.))x10(-5) with a significance of 7.3 sigma. We find no significant signal for B+-> K-1(1400)(+)gamma and set an upper limit B(B+-> K-1(1400)(+)gamma)< 1.5x10(-5) at the 90% confidence level. We also measure inclusive branching fractions for B+-> K(+)pi(+)pi(-)gamma and B-0-> K(0)pi(+)pi(-)gamma in the mass range 1 GeV/c(2)< M(K)(+(0))pi(+)pi(-)< 2 GeV/c(2). %K B DECAYS %J PHYS REV LETT %A HY Yang %A M Nakao %A K Abe %A K Abe %A H Aihara %A Y Asano %A T Aushev %A S Bahinipati %A AM Bakich %A Y Ban %A I Bedny %A U Bitenc %A I Bizjak %A S Blyth %A A Bondar %A A Bozek %A M Bracko %A J Brodzicka %A TE Browder %A MC Chang %A P Chang %A Y Chao %A A Chen %A WT Chen %A BG Cheon %A R Chistov %A SK Choi %A Y Choi %A YK Choi %A A Chuvikov %A S Cole %A J Dalseno %A M Dash %A S Eidelman %A Y Enari %A F Fang %A N Gabyshev %A A Garmash %A T Gershon %A G Gokhroo %A B Golob %A J Haba %A K Hayasaka %A H Hayashii %A M Hazumi %A L Hinz %A T Hokuue %A Y Hoshi %A YB Hsiung %A T Iijima %A A Imoto %A K Inami %A Y Iwasaki %A JH Kang %A JS Kang %A SU Kataoka %A N Katayama %A H Kawai %A T Kawasaki %A HR Khan %A H Kichimi %A HJ Kim %A JH Kim %A SK Kim %A SM Kim %A TH Kim %A K Kinoshita %A S Korpar %A P Krokovny %A CC Kuo %A A Kuzmin %A YJ Kwon %A JS Lange %A G Leder %A SH Lee %A T Lesiak %A J Li %A SW Lin %A G Majumder %A T Matsumoto %A A Matyja %A W Mitaroff %A K Miyabayashi %A H Miyake %A H Miyata %A R Mizuk %A T Nagamine %A Y Nagasaka %A E Nakano %A Z Natkaniec %A S Nishida %A O Nitoh %A S Ogawa %A T Ohshima %A T Okabe %A S Okuno %A SL Olsen %A W Ostrowicz %A P Pakhlov %A H Palka %A CW Park %A N Parslow %A R Pestotnik %A LE Piilonen %A M Rozanska %A H Sagawa %A Y Sakai %A N Sato %A T Schietinger %A O Schneider %A J Schumann %A C Schwanda %A AJ Schwartz %A R Seuster %A H Shibuya %A A Somov %A N Soni %A R Stamen %A S Stanic %A M Staric %A K Sumisawa %A T Sumiyoshi %A S Suzuki %A SY Suzuki %A O Tajima %A F Takasaki %A N Tamura %A M Tanaka %A GN Taylor %A Y Teramoto %A XC Tian %A T Tsukamoto %A S Uehara %A T Uglov %A K Ueno %A S Uno %A Y Ushiroda %A G Varner %A KE Varvell %A S Villa %A CH Wang %A MZ Wang %A M Watanabe %A A Yamaguchi %A Y Yamashita %A M Yamauchi %A Y Yuan %A LM Zhang %A ZP Zhang %A V Zhilich %A D Zontar %A D Zurcher %T Observation of B+-> K-1(1270)(+)gamma