Combined SM Higgs Limits at the Tevatron
We combine results from CDF and DO on direct searches for a standard model (SM) Higgs boson (H) in pbar-p collisions at the Fermilab Tevatron at sqrt{s}=1.96 TeV. Compared to the previous Higgs Tevatron combination, more data and new channels (WH to tau nu b bbar, VH to tau tau b bbar/jj tau tau, VH to jj b bbar, t tbar H to t tbar b bbar) have been added. Most previously used channels have been reanalyzed to gain sensitivity. We use the latest parton distribution functions and gg to H theoretical cross sections when comparing our limits to the SM predictions. With 2.0-3.6fb^-1 of data analyzed at CDF, and 0.9-4.2fb^-1 at DO, the 95% C.L. upper limits on Higgs boson production are a factor of 2.5 (0.86) times the SM cross section for a Higgs boson mass of mH=115 (165) GeV/c^2. Based on simulation, the corresponding median expected upper limits are 2.4 (1.1). The mass range excluded at 95% C.L. for a SM Higgs has been extended to 160<mH<170 GeV/c^2.