Search for the Standard Model Higgs boson in e+e− collisions at –209 GeV

A search for the Standard Model Higgs bosonhas been performed with the OPAL detector at LEP based on the full data sample collected at –209 GeV in 1999 and 2000, corresponding to an integrated luminosity of approximately 426 pb−1. The data are examined for their consistency with the background-only hypothesis and various Higgs bosonmass hypotheses. A lower bound of 109.7 GeV is obtained on the Higgs bosonmass at the 95% confidence level. At higher masses, the data are consistent with both the backgroundand the signal-plus- backgroundhypotheses.