Diffractive gauge bosons production beyond QCD factorization

Abstract

We discuss single diffractive gauge boson ð Ã ; W AE ; ZÞ production in proton-proton collisions at different (Large Hadron Collider and Relativistic Heavy Ion Collider) energies within the color dipole approach. The calculations are performed for gauge bosons produced at forward rapidities. The diffractive cross section is predicted as a function of the fractional momentum and invariant mass of the lepton pair. We found a dramatic breakdown of the diffractive QCD factorization caused by an interplay of hard and soft interactions. Data from the CDF experiment on diffractive production of W and Z are well explained in a parameter-free way.

Breakdown of QCD factorization in hard diffraction

“…Abelian diffractive radiation of any particle is described by the same Feynman graphs, only couplings and spin structure are different [15]. In Fig.…”

Hard hadronic diffraction is not hard

“…Recently, in Refs. [11,16,33] it was explicitly shown that factorisation in diffractive Abelian radiation is therefore even more broken due to presence of spectator partons in the colliding hadrons. Besides, the saturated shape of the dipole cross section (3), therefore, leads to several unusual features of diffractive DY cross section.…”

“…In general, diffractive radiation of any Abelian particle is given by the same graphs as the diffractive DY process, with an appropriate use of couplings and spin structure [33]. In Fig.…”

“…In the diffractive channel, the DY and electroweak gauge boson production has been studied within the dipole formalism in Ref. [33].…”

Single-diffractive Drell–Yan pair production at the LHC

“…In such a process, the invariant mass of the lepton pair can easily be reconstructed and, depending on experimental capabilities, pushed to rather low values, allowing a detailed characterisation of the hard-scale dependence of the suppression factor. Although estimates of the latter are present in the literature for the specific process at hand [27][28][29], we take a conservative approach and avoid to introduce any suppression factor. We further assume factorisation to hold and adopt factorised expressions for the relevant cross sections.…”