DiffractiveW±production at hadron colliders as a test of color singlet exchange mechanisms

Abstract

We revisit diffractive and exclusive W ± X production at hadron colliders in different models for soft colour exchanges. The process pp → p[W ± X]p, and in particular a W ± charge asymmetry, has been suggested as a way to discriminate diffractive processes as being due to pomeron exchange in Regge phenomenology or QCD-based colour reconnection models. Our detailed analysis of the latter models at LHC energies shows, however, that they give similar results as pomeron models for very leading protons and central W ± X production, including a vanishing W ± charge asymmetry. We demonstrate that soft colour exchange models provide a continuous transition from diffractive to inelastic processes and thereby include the intrinsic asymmetry of inelastic interactions while being at the same time sensitive to the underlying hadronisation models. Such sensitivity also concerns the differential distributions in proton momentum and W ± transverse momentum which opens possibilities to discriminate between different colour reconnection models. * Gunnar.Ingelman@physics.uu.se † Roman.Pasechnik@thep.lu.se ‡ Johan.Rathsman@thep.lu.se § Dominik.Werder@physics.uu.se

Testing Pomeron flavour symmetry with diffractive W charge asymmetry

“…Other approaches to hard diffraction are also possible. Most interestingly, theories based on soft exchanges involving a change in the colour flow [21][22][23] can exhibit diffractive signatures, including the diffractive production of electroweak boson, without drawing on the concept of Pomeron [24]. Acceptance Table 2.…”

Diffractive W production in SCI models

“…One important difference between soft color exchange and pomeron based models is that a sample based on a cut on the forward beam particle momentum fraction z can contain events where the t-channel exchange between the hard subprocess and the beam is not effectively color-singlet because final state beam particles of sizeable momentum fraction can also be obtained from regular diquark fragmentation. Recently diffractive gauge boson production was considered as a sensitive way to investigate the production mechanism [4] based on a measurement of A = (W + −W − )/(W + +W − ), explored in the context of soft color exchange models in [5].…”

Probing the Pomeron structure using dijets andγ+jetevents at the LHC

“…The distribution shows the increase in cross section for very small momentum losses of the beam protons, typical for diffractive scattering. In order to compare [19] with models which describe diffractive scattering in terms of a Pomeron without additional Reggeons, it is therefore important to constrain the analysis to the region of phase space where the momentum loss of the leading final state protons is very small, so that the background due "non-diffractive" events can be neglected. Treating diffractive and non-diffractive events on the same footing is a drawback for the computational performance of the SCI implementation, since the monte carlo integration is computationally very intensive.…”