Improved measurement of the bb̄ production cross section in 920 GeV fixed-target proton-nucleus collisions

Abstract

A new measurement of the bb̄ production cross section in 920 GeV proton-nucleus collisions is presented by the HERA-B Collaboration. The bb̄ production is tagged via inclusive bottom quark decays into J/ψ mesons by exploiting the longitudinal separation of J/ψ→l+l- decay vertices from the primary proton-nucleus interaction point. Both e+e- and μ+μ- channels are reconstructed for a total of 83±12 inclusive b→J/ψX events found. The combined analysis yields a bb̄ to prompt J/ψ cross section ratio of Δσ(bb̄)ΔσJ/ψ=0.032±0. 005stat±0.004sys measured in the xF acceptance (-0.35