Kappa[i] = 0.5/(Nd - Mass[i]);
Kappa[i] = 0.5/(Nd + Mass[i]);
multi1d<Real> massToKappa(const multi1d<Real>& Mass){  multi1d<Real> Kappa(Mass.size());  for(int i=0; i < Kappa.size(); ++i)    Kappa[i] = 0.5/(Nd - Mass[i]);  return Kappa;}