The flavor ratio of the atmospheric neutrino flux and its zenith angle dependence have been studied in the multi-GeV energy range using an exposure of 25.5 kiloton-years of the Super-Kamiokande detector. By comparing the data to a detailed Monte Carlo simulation, the ratio (μ/e)DATA/(μ/e)MC was measured to be 0.66 ± 0.06(stat.) ± 0.08(sys.). In addition, a strong distortion in the shape of the μ-like event zenith angle distribution was observed. The ratio of the number of upward to downward μ-like events was found to be 0.52+0.070.06(stat.) ± 0.01(sys.), with an expected value of 0.98 ± 0.03(stat.) ± 0.02(sys.), while the same ratio for the e-like events was consistent with unity.
|Original language||English (US)|
|Number of pages||9|
|Journal||Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics|
|State||Published - Sep 17 1998|
Bibliographical noteFunding Information:
We gratefully acknowledge the cooperation of the Kamioka Mining and Smelting Company. The Super-Kamiokande experiment has been built and operated from funding by the Japanese Ministry of Education, Science, Sports and Culture, and the United States Department of Energy.