A particle is scattered by a spherically symmetric potential at sufficiently low energy that the phase shifts δl=0 for l>1 (that is, only δ0 and δ1 are nonzero). Show that the differential cross section has the form
dΩdσ=A+Bcosθ+Ccos2θ
and determine A, B, and C in terms of the phase shifts. Determine the total cross section σ in terms of A, B, and C.