arXiv subjects

Y. Fukuda et al

Publications and source records attributed to Y. Fukuda et al.

4 recordsLinked to original sources

arXiv1998

Evidence for oscillation of atmospheric neutrinos

We present an analysis of atmospheric neutrino data from a 33.0 kiloton-year (535-day) exposure of the Super-Kamiokande detector. The data exhibit a zenith angle dependent deficit of muon neutrinos which is inconsistent with expectations based on calculations of the atmospheric neutrino flux. Experimental biases and uncertainties in the prediction of neutrino fluxes and cross sections are unable to explain our observation. The data are consistent, however, with two-flavor nu_mu <-> nu_tau oscillations with sin^2(2theta)>0.82 and 5x10^-4 < delta m^2 < 6x10^-3 eV^2 at 90% confidence level.

hep-ex↗

arXiv1998

Measurements of the Solar Neutrino Flux from Super-Kamiokande's First 300 Days

The first results of the solar neutrino flux measurement from Super-Kamiokande are presented. The results shown here are obtained from data taken between the 31st of May, 1996, and the 23rd of June, 1997. Using our measurement of recoil electrons with energies above 6.5 MeV, we infer the total flux of 8B solar neutrinos to be 2.42+-0.06(stat.)+0.10-0.07(syst.)*10^6/cm^2/s. This result is consistent with the Kamiokande measurement and is 36% of the flux predicted by the BP95 solar model. The flux is also measured in 1.5 month subsets and shown to be consistent with a constant rate.

hep-ex↗

arXiv1998

Study of the atmospheric neutrino flux in the multi-GeV energy range

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 $0.66\pm0.06(stat.)\pm0.08(sys.)$. 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$^{+0.07}_{-0.06}(stat.)\pm0.01(sys.)$, with an expected value of $0.98\pm0.03(stat.)\pm0.02(sys.)$, while the same ratio for the $e$-like events was consistent with unity.

hep-ex↗

arXiv1998

Measurement of a small atmospheric $ν_μ/ν_e$ ratio

From an exposure of 25.5~kiloton-years of the Super-Kamiokande detector, 900 muon-like and 983 electron-like single-ring atmospheric neutrino interactions were detected with momentum $p_e > 100$ MeV/$c$, $p_μ> 200$ MeV/$c$, and with visible energy less than 1.33 GeV. Using a detailed Monte Carlo simulation, the ratio $(μ/e)_{DATA}/(μ/e)_{MC}$ was measured to be $0.61 \pm 0.03(stat.) \pm 0.05(sys.)$, consistent with previous results from the Kamiokande, IMB and Soudan-2 experiments, and smaller than expected from theoretical models of atmospheric neutrino production.

hep-ex↗