First muon-neutrino disappearance study with an off-axis beam
Abe K., Abgrall N., Ajima Y., Aihara H., Albert JB., Andreopoulos C., Andrieu B., Anerella MD., Aoki S., Araoka O., Argyriades J., Ariga A., Ariga T., Assylbekov S., Autiero D., Badertscher A., Barbi M., Barker GJ., Barr G., Bass M., Batkiewicz M., Bay F., Bentham S., Berardi V., Berger BE., Bertram I., Besnier M., Beucher J., Beznosko D., Bhadra S., Blaszczyk FDMM., Blondel A., Bojechko C., Bouchez J., Boyd SB., Bravar A., Bronner C., Brook-Roberge DG., Buchanan N., Budd H., Calland RG., Calvet D., Caravaca Rodríguez J., Cartwright SL., Carver A., Castillo R., Catanesi MG., Cazes A., Cervera A., Chavez C., Choi S., Christodoulou G., Coleman J., Collazuol G., Coleman W., Connolly K., Curioni A., Dabrowska A., Danko I., Das R., Davies GS., Davis S., Day M., De Rosa G., De André JPAM., De Perio P., Dealtry T., Delbart A., Densham C., Di Lodovico F., Di Luise S., Dinh Tran P., Dobson J., Dore U., Drapier O., Duboyski T., Dufour F., Dumarchez J., Dytman S., Dziewiecki M., Dziomba M., Emery S., Ereditato A., Escallier JE., Escudero L., Esposito LS., Fechner M., Ferrero A., Finch AJ., Frank E., Fujii Y., Fukuda Y., Galymov V., Ganetis GL., Gannaway FC., Gaudin A., Gendotti A., George MA., Giffin S., Giganti C.
We report a measurement of muon-neutrino disappearance in the T2K experiment. The 295-km muon-neutrino beam from Tokai to Kamioka is the first implementation of the off-axis technique in a long-baseline neutrino oscillation experiment. With data corresponding to 1.43×1020 protons on target, we observe 31 fully-contained single μ-like ring events in Super-Kamiokande, compared with an expectation of 104±14(syst) events without neutrino oscillations. The best-fit point for two-flavor ν μ→ν τ oscillations is sin2(2θ 23)=0.98 and |Δm322|=2.65×10 -3eV2. The boundary of the 90% confidence region includes the points ( sin2(2θ 23), |Δm322|)=(1.0,3.1×10 -3eV2), (0.84, 2.65×10 -3eV2) and (1.0, 2.2×10 -3eV2). © 2012 American Physical Society.