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, Namba T, Nambu R, Nishikawa K, Nishiyama S, Noda S, Obayashi Y, Okada A, Oyama Y, Pac M Y, Park H, Saji C, Sakuda M, Sarrat A, Sasaki T, Sasao N, Scholberg K, Sekiguchi M, Sharkey E, Shiozawa M, Shiraishi K K, Smy M, Sobel H W, Stone J L, Suga Y, Sulak L R, Suzuki A, Suzuki Y, Takeuchi Y, Tamura N, Tanaka M, Totsuka Y, Ueda S, Vagins M R, Walter C W, Wang W, Wilkes R J, Yamada S, Yamamoto S, Yanagisawa C, Yokoyama H, Yoo J, Yoshida M, Zalipska J
Department of Physics, Seoul National University, Seoul 151-742, Korea.
Phys Rev Lett. 2004 Jul 30;93(5):051801. doi: 10.1103/PhysRevLett.93.051801. Epub 2004 Jul 27.
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).
我们在K2K长基线中微子实验中，对加速器产生的μ子中微子出现电子中微子的情况进行了搜索。在对应于4.8×10¹⁹个靶上质子曝光量的数据中发现了一个候选事件。在无中微子振荡情况下的预期本底估计为2.4±0.6个事件，且主要由中性流π⁰产生的事件误识别所主导。在90%置信水平下，对于双味近似中的有效混合角sin²2θμe（约为1/2sin²2θ₁₃），当Δm²μe = 2.8×10⁻³ eV²（K2K中μ子中微子消失分析的最佳拟合值）时，我们排除了μ子中微子到电子中微子的振荡。在Δm²μe = 6×10⁻³ eV²时，得到了sin²2θμe < 0.09的最严格限制。
