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Search for electron neutrino appearance in a 250 km long-baseline experiment |
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| Authors: | Ahn M H Aoki S Ashie Y Bhang H Boyd S Casper D Choi J H Fukuda S Fukuda Y Gran R Hara T Hasegawa M Hasegawa T Hayashi K Hayato Y Hill J Ichikawa A K Ikeda A Inagaki T Ishida T Ishii T Ishitsuka M Itow Y Iwashita T Jang H I Jang J S Jeon E J Joo K K Jung C K Kajita T Kameda J Kaneyuki K Kato I Kearns E Kibayashi A Kielczewska D Kim B J Kim C O Kim J Y Kim S B Kobayashi K Kobayashi T Koshio Y Kropp W R Learned J G Lim S H Lim I T Maesaka H Maruyama T Matsuno S Mauger C Mcgrew C Minamino A Mine S Miura M Miyano K Morita T Moriyama S Nakahata M Nakamura K Nakano I Nakata F Nakaya T Nakayama S |
| Institution: | Department of Physics, Seoul National University, Seoul 151-742, Korea. |
| Abstract: | We present a search for electron neutrino appearance from accelerator-produced muon neutrinos in the K2K long-baseline neutrino experiment. One candidate event is found in the data corresponding to an exposure of 4.8 x 10(19) protons on target. The expected background in the absence of neutrino oscillations is estimated to be 2.4+/-0.6 events and is dominated by misidentification of events from neutral current pi(0) production. We exclude the nu(micro) to nu(e) oscillations at 90% C.L. for the effective mixing angle in the 2-flavor approximation of sin((2)2theta(microe)( approximately 1/2sin((2)2theta(13))>0.15 at Deltam(2)(microe)=2.8 x 10(-3) eV(2), the best-fit value of the nu(micro) disappearance analysis in K2K. The most stringent limit of sin((2)2theta(microe)<0.09 is obtained at Deltam(2)(microe)=6 x 10(-3) eV(2). |
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