Neutrino-induced upward stopping muons in Super-Kamiokande

Abstract

A total of 137 upward stopping muons of minimum energy 1.6 GeV are observed by Super-Kamiokande during 516 detector live days. The measured muon flux is 0.39+/-0.04(stat.)+/-0.02(syst.)x10^{-13}cm^{-2}s^{-1}sr^{-1} compared to an expected flux of 0.73+/-0.16(theo.)x10^{-13}cm^{-2}s^{-1}sr^{-1}. Using our previously-published measurement of the upward through-going muon flux, we calculate the stopping/through-going flux ratio R}, which has less theoretical uncertainty. The measured value of R=0.22+/-0.02(stat.)+/-0.01(syst.) is significantly smaller than the value 0.37^{+0.05}_{-0.04}(theo.) expected using the best theoretical information (the probability that the measured R is a statistical fluctuation below the expected value is 0.39%). A simultaneous fitting to zenith angle distributions of upward stopping and through-going muons gives a result which is consistent with the hypothesis of neutrino oscillations with the parameters sin^2 2\theta >0.7 and 1.5x10^{-3} < \Delta m^2 < 1.5x10^{-2} eV^2 at 90% confidence level, providing a confirmation of the observation of neutrino oscillations by Super-Kamiokande using the contained atmospheric neutrino events.Comment: 15 pages, including 7 figures. Submitted to Physics Letters Revision fixes typo in author fiel

Atmospheric Neutrino Fluxes

“…[6,7] A consistent pattern of energy and pathlength dependence emerges that clearly points to neutrino oscillations as the explanation. Because atmospheric ν e behave normally to the precision measured so far, the main effect must lie in the ν µ ↔ ν τ sector (or involve sterile neutrinos, which are now disfavored).…”

Neutrino mixing and leptonic CP phase in neutrino oscillations

“…Rapidly growing interest in neutrino physics has recently been stimulated by new data from facilities at Kamiokande [1], Super-Kamiokande [2], LSND [3], CHOOZ [4], and some others [5,6]. These data are indicative, directly or indirectly, of the Pontecorvo (vacuum) oscillations [7] of neutrinos of three types, ν e , ν µ , and ν τ .…”

“…These data are indicative, directly or indirectly, of the Pontecorvo (vacuum) oscillations [7] of neutrinos of three types, ν e , ν µ , and ν τ . The frequency of these oscillations, i.e., of the ν i ν k transitions in oscillations, is proportional to sin 2 , where p ν is the ultrarelativistic neutrino momentum and t = L / c is the time it takes for a neutrino to run from source to detector (the distance L is called the "base length"). In what follows, we set c = 1 for convenience.…”

“…Like , the matrix is unitary; i.e., = 1. Previous analysis of experimental data [1][2][3][4][5][6] gave the following mixing angles [8,9,11] (4) …”

“…1 Below, we will consider the possibility of determining the leptonic CP phase δ l from the data obtained in the today and immediate-future experiments of the type [1][2][3][4][5][6], where oscillations were not observed directly but only the oscillation-averaged probabilities P(ν α ν β ) of ν α ν β transitions were measured.…”