Proc. Neutrino Astrophysics - MPP Theory Group

Data
Monte Carlo
total νe CC νµ CC NC
single ring 1453 1551.5 539.7 927.8.0 84.0
e-like 718 593.8 537.2 8.9 47.7
µ-like 735 957.7 2.5 918.9 36.3
multi ring 533 596.6 148.4 241.3 206.9
total 1986 2148.1 605.6 1076.5 290.9
Table 1: Summary of the Sub-GeV sample compared with Monte Carlo estimation, for 20.1
kton-years of Super-Kamiokande.
Data Monte Carlo
single ring 288 304.8
e-like 149 120.5
µ-like 139 184.3
2 rings 207 221.0
3 rings 110 133.0
total 605 658.8
Table 2: Summary of the Multi-GeV sample compared with Monte Carlo estimation, for 20.1
kton-years of Super-Kamiokande.
Finally the preliminary analysis of partially contained events, i.e. interactions with particles
exiting the inner detector, provided 156 data and 210.6 MC events. According to the
simulations charged current νµ and ¯νµ interactions constitute 97% of this sample.
Conclusions
The deficit of muon neutrinos reported from earlier experiments have been confirmed during
the first year of data collection in Super-Kamiokande. The double rato values of R = 0.63 ±
0.03(stat) ± 0.05(sys) for the Sub-GeV sample and R = 0.60 ± 0.06(stat) ± 0.07(sys) for the
Multi-GeV sample are consistent with results from Kamiokande, IMB and Soudan.
The angular asymmetry observed with much smaller statistical weight in Ref. [6] is observed
in the present sample for both Sub-GeV and Multi-GeV cuts. Those results strongly
suggest the neutrino oscillation interpretation. However, more data are needed to exclude
any possibility of detector related biases.
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