c For Collider Flux, Phase Space
c  #if LEGS_IN == 1
c	flux = 2*sqrtS
c#else
c	flux = 4/hbar_c2*sqrtS*momspec(SPEC_K,1)
c#endif
c	fac = fac/((2*pi)**(3*LEGS_OUT - 4)*2*spin_df*sqrtS*flux)

c Comments for DM DM annihilation ---> sigma v
#if LEGS_IN == 1
         flux = 2*sqrtS
#else
         flux = 4/hbar_c2*sqrtS*momspec(SPEC_K,1)
         flux = flux/momspec(SPEC_K,1)
#endif
         fac = fac/((2*pi)**(3*LEGS_OUT - 4)*2*spin_df*sqrtS*flux)
         fac = fac*4D0*sqrtS**3D0/
     &        (sqrtS**4-(momspec(SPEC_M,1)**2-momspec(SPEC_M,2)**2)**2)
         fac = fac*2.99792D-26