A search for cosmogenic production of ${\hat{I}}^2$-neutron emitting radionuclides in water

Abstract

Here we present the first results of WATCHBOY, a water Cherenkov detector designed to measure the yield of ${\hat{I}}^2$-neutron emitting radionuclides produced by cosmic ray muons in water. In addition to the ${\hat{I}}^2$-neutron measurement, we also provide a first look at isolating single-${\hat{I}}^2$ producing radionuclides following muon-induced hadronic showers as a check of the detection capabilities of WATCHBOY. The data taken over $207$ live days indicates a ${}^9$Li production yield upper limit of $1.9\times 10^{-7}\hat{I}{¼}^{-1}{g}^{-1}{\mathrm{cm}}^2$ at $\sim 400$ meters water equivalent (m.w.e.) overburden at the $90\%$ confidence level. In this work the ${}^9$Li signal in WATCHBOY was used as a proxy for the combined search for ${}^9$Li and ${}^8$He production. This result will provide a constraint on estimates of antineutrino-like backgrounds in future water-based antineutrino detectors.

11 pages, 12 figures