feynlag.pheno.loop.A_one_zgamma

feynlag.pheno.loop.A_one_zgamma(x, y, sw2)

$W$ form factor for $Zgamma$: $A_1^{Zgamma}=4(3-t_W^2)I_2+[(1+2/x)t_W^2-(5+2/x)]I_1$, with $t_W^2=s_W^2/c_W^2$.