Measurement of open beauty production at HERA

Abstract The first observation of open b production in ep collisions is reported. An event sample containing muons and jets has been selected which is enriched in semileptonic b quark decays. The visible cross section σ(ep → b b X → μ X′) for Q 2 GeV 2 , 0.1 y 0.176 ± 0.016 ( stat.) +0.026 −0.017 (syst.) nb for the muons to be detected in the range 35° θ μ p ⊥ μ >2.0 GeV in the laboratory frame. The expected visible cross section based on a NLO QCD calculation is 0.104 ± 0.017 nb . The cross sections for electroproduction with Q 2 GeV 2 and photoproduction are derived from the data and found to be σ(ep→eb b X)=7.1±0.6 ( stat.) +1.5 −1.3 (syst.) nb and σ(γp→b b X)=111 ± 10 ( stat.) +23 −20 (syst.) nb at an average 〈W γp 〉∼180 GeV , respectively.