Hidden and Open Beauty Production in 920 GeV Proton-Nucleus Interactions

HERA-B is a fixed-target multi-particle spectrometer operating at the 920 GeV HERA proton beam at DESY. Approximately 150 million events were recorded with a dilepton trigger during the 2002-2003 Hera run. The collected data sample includes 300,000 leptonic J/ψ decays. The cross sections for the production of open beauty and ϒ in 920 GeV proton nucleus collisions, measured from these data, are presented. The open beauty cross section measurement is based on the inclusive decay of b hadrons into J/ψ. The ϒ cross section is measured in the dimuon and dielectron decay channels.