Low energy neutrinos from stopped muons in the Earth

Wan-Lei Guo

doi:10.1103/physrevd.99.073007

Abstract

We explore the low energy neutrinos from stopped cosmic ray muons in the Earth. Based on the muon intensity at the sea level and the muon energy loss rate, the depth distributions of stopped muons in the rock and sea water can be derived. Then we estimate the $\mu^-$ decay and nuclear capture probabilities in the rock. Finally, we calculate the low energy neutrino fluxes and find that they depend heavily on the detector depth $d$. For $d = 1000$ m, the $\nu_e$, $\bar{\nu}_e$, $\nu_\mu$ and $\bar{\nu}_\mu$ fluxes in the range of 13 MeV $ \leq E_\nu \leq$ 53 MeV are averagely $10.8 \%$, $6.3\%$, $3.7 \%$ and $6.2 \%$ of the corresponding atmospheric neutrino fluxes, respectively. The above results will be increased by a factor of 1.4 if the detector depth $d < 30$ m. In addition, we find that most neutrinos come from the region within 200 km and the near horizontal direction, and the $\bar{\nu}_e$ flux depends on the local rock and water distributions.

Highlights

Atmospheric neutrinos are a very important neutrino source to study the neutrino oscillation physics
Combining the atomic capture percentages and the corresponding Dμ− in Table I, one can find that the averaged decay probability Dμ− 1⁄4 60.65% and nuclear capture probability Cμ− 1⁄4 39.35% for negative muons stopped in the rock
The νe flux depends on the local rock and water distributions for a given detector

Summary

INTRODUCTION

Atmospheric neutrinos are a very important neutrino source to study the neutrino oscillation physics. A large amount of muons are produced and some of them can penetrate the rock and sea water of Earth’s surface to significant depths These penetrating muons are the important background source for some underground experiments [3]. It is well known that these muons will stop in the Earth and produce the low energy neutrinos through decay or nuclear capture [4]. These neutrinos are not included in the previous literatures [5,6,7].

DISTRIBUTIONS OF STOPPED MUONS

NEUTRINO ENERGY SPECTRA FROM A STOPPED MUON

NEUTRINO FLUXES FROM STOPPED MUONS

Findings

CONCLUSIONS