PeV Neutrino Events at IceCube from Single Top-Quark Production
  Deep inelastic scattering of very high-energy neutrinos can potentially be enhanced by the production of a single top quark or charm quark via the interaction of a virtual $W$-boson exchange with a $b$-quark or $s$-quark parton in the nucleon. The single top contribution shows a sharp rise at neutrino energies above 0.5 PeV and gives a cross-section contribution of order 5 percent at 10 PeV, while single charm has a low energy threshold and contributes about 25 percent. Semi-leptonic decays of top and charm give di-muon events whose kinematic characteristics are shown. The angular separation of the di-muons from heavy quark production in the IceCube detector can reach up to one degree. Top quark production has a unique, but rare, three muon signal. 
Vernon Barger, Edward Basso, Yu Gao, and Wai-Yee Keung
hep-ph astro-ph.HE