Muon-Induced Production of $^{16}$N

The Sudbury Neutrino Observatory (SNO) is a 1000-tonne heavy-water Cherenkov neutrino detector located in Sudbury, Ontario, Canada. Cosmic-ray muons pass through SNO at a rate of approximately 2.6 per hour, and they are easily vetoed. However, muon-induced spallation products with long lifetimes represent a background that must be considered. In particular, $^{16}$N can be produced by (n,p) and ($\mu^-$,$\nu_{\mu}$) reactions on $^{16}$O. The $\beta^-$ decay of any $^{16}$N ($T_{1/2}=7.13$~s, $Q = 10.44$~MeV) in the heavy water would represent an important background in SNO's neutrino measurements. We have investigated the production of $^{16}$N by muons in the salt phase of the SNO experiment and found an initial $^{16}$N activity in the 391-day salt-phase dataset consistent with zero: $-0.97\pm1.3$~kton$^{-1}$. The result will be compared with theoretical expectations.