K2K nu/mu oscillation analysis FINAL results

Updated using HARP result for evaluation of Far/Near ratio in entire period.
Please also refer to K2K full-paper.

1. Expectations at Super-K

Expected number of events at Super-K without oscillation

NSKexp = 158.1 +9.2-8.6

Reconstructed neutrino energy spectrum at Super-K without oscillation

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Effect of systematic unceratinties on energy spectrum at SK

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2. Observations

Total number of observed event at SK: 112
K2K-I K2K-II Total
FCFV 55 57 112
1-ring mu-like 30 28 58
e-like 3 6 9
multi-ring 22 23 45

Timing distributions
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3. Results

90% C.L. limit

1.9 < Delta-m2 < 3.5 x 10-3 eV2 at sin2(2theta) = 1.0

Best fit values

(Delta-m2, sin2(2theta) ) = 2.8x 10-3 eV2, 1.0)

Enu rec distribution

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Blue: null oscillation, Red: at best fit point.
KS probability: 37% for best fit, 0.07% for null oscillation.

Null oscillation probability

Total K2K-I only K2K-II only
All 0.0015% (4.3sigma) 0.18% 0.56%
Nevt only 0.06% (3.4sigma) 0.6% 2.8%
Spectrum only 0.42% (2.9sigma) 7.7% 5.2%

Contour plots