A new contribution to the conventional atmospheric neutrino flux

Atmospheric neutrinos are an important background to astrophysical neutrino searches, and are also of considerable interest in their own right. This paper points out that the contribution to conventional atmospheric νeνe of the rare semileptonic decay of KSKS becomes significant at high energy. Although the KS→πeνKS→πeν branching ratio is very small, the short KSKS lifetime leads to a high critical energy, so that, for vertical showers, the inclusion of KSKS semileptonic decay increases the conventional νeνe flux by ≈≈30%30% at energies above 100 TeV. In this paper, we present calculations of the flux of νeνe from KSKS. At energies above their critical energies, the νeνe fluxes from kaon decay may be simply related to the kaon semileptonic widths; this leads to a near-equality between the flux of νeνe from K+,KLK+,KL and KSKS.