A Study of Single Top at CMS

This note describes a study of the detection of single electroweak t-quark production using the CMS detector at the LHC. We conclude that CMS will be able to isolate a sample of single top events with a signal to background of order 3.5:1 and a clear peak visible in the Wb invariant mass distribution. We expect about 6600 signal events after cuts in 10 fb-1. The dominant background is W+jets with the biggest contribution coming from W+charm with the charm jet mistagged as a b-jet. It might therefore be worthwhile to develop a b-tagging algorithm having greater rejection against such mistags, even at the cost of some signal efficiency. We find that a forward jet tag is very effective in enhancing the signal to background ratio. This means that jets need to be found with good efficiency up to large rapidities, at least |eta|~4 in the HF calorimeter. Our understanding of the signal will depend on how well we can believe the Monte Carlo for W+jets production. The correct modelling of jet flavors in the W+jets events and the correct jet rapidities are important. The Monte Carlo will have to be be benchmarkedat the LHC using Z+jets events.