Lepton pair production in ultra-peripheral collisions

Abstract

The lepton pair production in ultra-peripheral collisions (UPC) is studied in the classical field approximation. We derive a general form of the cross section in terms of photon distributions which depend on the transverse momentum and coordinate based on the wave packet form of nuclear wave functions. Such a general form of the cross section in the classical field approximation contains the results of the generalized equivalent photon approximation (EPA) as well as the corrections beyond EPA in the Born approximation. By rewriting the general form of the cross section in light-cone coordinates, we find a good connection with the transverse momentum dependent distribution (TMD) factorization formalism in the Born approximation. Our numerical results are consistent with current experimental data.

Exploring gluon tomography with polarization dependent diffractive J/$ψ$ production

“…The squared F(x, k ⊥ ) is simply the standard photon TMD distribution f (x, k ⊥ ). Note that the incoming photon carries different transverse momenta in the amplitude and the conjugate amplitude since we fixed b⊥ [81][82][83][84][85][86][87].…”