Contact interactions involving right-handed neutrinos and SN 1987A

Nonstandard lepton-quark contact interactions may arise at low energies as a consequence of a common quark and lepton substructure or of heavy boson exchanges, when integrated out. There has recently been renewed interest @1# in contact interactions due to the fact that they are one of the potential explanations of the excess of events reported by H1 @2# and ZEUS @3#, the DESY ep collider at HERA, when measuring deep-inelastic ep scattering at high-Q and comparing with standard model predictions. The four-fermion operators that could contribute to the HERA excess involve the electron and the u and d quarks. The corresponding Lagrangian is written as an effective electron-quark interaction