gener->SetThetaRange(thmin,thmax);
gener->SetOrigin(0, 0, 0); //vertex position
gener->SetSigma(0, 0, 0); //Sigma in (X,Y,Z) (cm) on IP position
gener->SetThetaRange(thmin,thmax);
gener->SetOrigin(0, 0, 0); //vertex position
gener->SetSigma(0, 0, 0); //Sigma in (X,Y,Z) (cm) on IP position