Electron angular correlation in neutrinoless double beta decay and new   physics
  The angular correlation of the electrons in the neutrinoless double beta decay ($0\nu2\beta$) is calculated taking into account the nucleon recoil, the $S$ and $P$-waves for the electrons and the electron mass using a general Lorentz invariant effective Lagrangian. We show that the angular coefficient is essentially independent of the nuclear matrix element models. We work out the angular coefficient in several scenarios for new physics, in particular, in the left-right symmetric models. 
A. Ali (DESY, Hamburg), A.V. Borisov and D.V. Zhuridov (MSU, Mosow)