Particle decays in the presence of a neutrino background

Several non-threshold reactions which may be used to detect the cosmic neutrino background are presented. The corresponding cross sections are calculated analytically within the Standard Model. These reactions are sensitive not only to the electron neutrinos but also to the muon and tau neutrinos. Some possibilities of experimental observation of the neutrino background are indicated.Comment: 14 pages, 5 figures. A more detailed discussion on the observability of neutrino capture by muons is adde

CP violation in neutrino-photon scattering

It is shown that effects of CP violation arise in neutrino-photon scattering. Several CP-violating $\nu\gamma$ reactions are considered within the Standard Model and predictions for some observables are made. It is emphasized that neutrino-photon scattering may provide an experimental tool for testing the scale dependence of CP violation.Comment: 10 pages, 3 figures. Version accepted for publication in J. Phys.