Spectral theory for a mathematical model of the weak interaction: The   decay of the intermediate vector bosons W+/-, II
  We do the spectral analysis of the Hamiltonian for the weak leptonic decay of the gauge bosons W+/-. Using Mourre theory, it is shown that the spectrum between the unique ground state and the first threshold is purely absolutely continuous. Neither sharp neutrino high energy cutoff nor infrared regularization are assumed. 
Walter H. Aschbacher, Jean-Marie Barbaroux, J\'er\'emy Faupin, and   Jean-Claude Guillot
math-ph math.FA math.MP math.SP