A Study of ttbar + Higgs at CMS

This note describes a study of the detection of a light Higgs boson produced in association with ttbar, using the CMS detector at the LHC. We conclude that CMS will be able to isolate a sample of Higgs events with a signal to background of order 1:1 and a clear peak visible in the bbar invariant mass distribution. We expect about 400 signal events after cuts for an integrated luminosity of 100 fb**-1. We find that the dominant background is ttbar + bbar, coming from a massive virtual gluons splitting into two b-quarks. We conclude that it would be very worthwhile to develop a b-quark tagging algorithm with high efficiency and good rejection against mistags specifically for this signal. We also find that there is a definite angular correlation between one of the t-quarks and the bbar coming from the Higgs decay. This angular correlation is not present for ttbb background physics processes.