We present the measurement of two event samples induced by atmospheric v(mu) of average energy (E) over bar(v) similar to 4 GeV. In the first sample, a neutrino interacts inside the MACRO detector producing an upward-going muon leaving the apparatus. The ratio of the number of observed to expected events is 0.57 +/- 0.05(stat) +/- 0.06(syst) +/- 0.14(theor) with an angular distribution similar to that expected from the Bartol atmospheric neutrino flux. The second is a mixed sample of internally produced downward-going muons and externally produced upward-going muons stopping inside the detector. These two subsamples are selected by topological criteria; the lack of timing information makes it impossible to distinguish stopping from downgoing muons. The ratio of the number of observed to expected events is 0.71 +/- 0.05(stat) +/- 0.07(syst) +/- 0.18(theor). The observed deficits in each subsample is in agreement with neutrino oscillations, although the significance is reduced by the large theoretical errors. However, the ratio of the two samples causes a large cancellation of theoretical and of some systematic errors. With the ratio, we rule out the no-oscillation hypothesis at 95% c.l. Furthermore, the ratio tests the pathlength dependence of possible oscillations. The data of both samples and their ratio favor maximal mixing and Delta m(2) similar to 10(-3)-10(-2) eV(2). These parameters are in agreement with our results from upward throughgoing muons, induced by v(mu) of much higher energies. (C) 2000 Elsevier Science B.V. All rights reserved.
|Autori:||Ambrosio M; Antolini R; Auriemma G; Bakari D; Baldini A; Barbarino GC; Barish BC; Battistoni G; Bellotti R; Bemporad C; Bernardini P; Bilokon H; Bisi V; Bloise C; Bower C; Brigida M; Bussino S; Cafagna F; Calicchio M; Campana D; Carboni M; Cecchini S; Cei F; Chiarella V; Choudhary BC; Coutu S; De Cataldo G; Dekhissi H; De Marzo C; De Mitri I; Derkaoui J; De Vincenzi M; Di Credico A; Erriquez O; Favuzzi C; Forti C; Fusco P; Giacomelli G; Giannini G; Giglietto N; Giorgini M; Grassi M; Gray L; Grillo A; Guarino F; Gustavino C; Habig A; Hanson K; Heinz R; Iarocci E; Katsavounidis E; Katsavounidis I; Kearns E; Kim H; Kyriazopoulou S; Lamanna E; Lane C; Levin DS; Lipari P; Longley NP; Longo MJ; Loparco F; Maaroufi F; Mancarella G; Mandrioli G; Margiotta A; Marini A; Martello D; Marzari-Chiesa A; Mazziotta MN; Michael DG; Mikheyev S; Miller L; Monacelli P; Montaruli T; Monteno M; Mufson S; Musser J; Nicolo D; Nolty R; Orth C; Osteria G; Ouchrif M; Palamara O; Patera V; Patrizii L; Pazzi R; Peck CW; Perrone L; Petrera S; Pistilli P; Popa V; Raino A; Reynoldson J; Ronga F; Satriano C; Satta L; Scapparone E; Scholberg K; Sciubba A; Serra P; Sioli M; Sirri G; Sitta M; Spinelli P; Spinetti M; Spurio M; Steinberg R; Stone JL; Sulak LR; Surdo A; Tarle G; Togo V; Vakili M; Vilela E; Walter CW; Webb R|
|Titolo:||Low energy atmospheric muon neutrinos in MACRO|
|Anno del prodotto:||2000|
|Digital Object Identifier (DOI):||10.1016/S0370-2693(00)00267-7|
|Appare nelle tipologie:||1.1 Articolo in rivista|