Atmospheric neutrino physics with the MACRO detector

Abstract

We present the measurement of the flux and angular distribution of atmospheric v μ using the MACRO detector. Three different event topologies are detected in two different energy ranges. High energy neutrinos ( E v ∼ 80 GeV ) via the identification of upward throughgoing muons. Lower energy neutrinos ( E v ∼ 4 GeV ) via the upgoing stopping and partially contained downgoing muons (ID+UGS), or via the partially contained upgoing muons (IU). The measured flux is reduced with respect to the predictions. For the high energy sample, globally the flux reduction is 0.74 ± 0.054 stat+sys ± 0.12 th ; the reduction varies with the zenith angle. The ratio of measured to expected events is almost constant with the zenith angle for the low energy events, and is 0.57 ± 0.08 stat+sys ± 0.14 theor for the IU sample, and 0.71 ± 0.09 stat+sys ± 0.17 theor for the (ID+UGS). All the data sets are consistent within a scenario of neutrino oscillations, with maximum mixing and Δm 2 ∼ 10 −3 ÷ 10 −2 eV 2.