Observation of Diffractively Produced W Bosons in pp Collisions in the CMS Experiment

TL;DR

This paper reports the observation of diffractively produced W bosons in proton-proton collisions at 7 TeV using CMS data, indicating a diffractive component in W production supported by large rapidity gaps.

Contribution

First evidence of diffractive W boson production in proton-proton collisions at the LHC using CMS data and forward energy flow analysis.

Findings

Approximately 300 events with large rapidity gaps observed

Charged leptons predominantly found opposite to the gaps

Supports the existence of a diffractive component in W production

Abstract

A study of forward energy flow in leptonically decaying W bosons using data of an integrated luminosity corresponding to 36 pb-1 of pp collisions at a center-of-mass energy of 7 TeV is presented. This data was recorded with the CMS detector during the 2010 running of the LHC. In this sample of W events, about 300 events with no significant energy deposits in one of the forward calorimeters are observed. This corresponds to a large pseudorapidity gap of at least 1.9 units. The majority of the charged leptons from these W decays are found in the hemisphere opposite to the gap. This gives a strong indication of a diffractive component in the W production, which can be explained in terms of diffractive parton distribution functions (PDF) which have, on average, a smaller x than the conventional parton PDFs.