Measurement of the $b \bar b$ Production Cross Section in 920 GeV Fixed-Target Proton-Nucleus Collisions

Abstract

Using the HERA-B detector, the b-bbar production cross section has been measured in 920 GeV proton collisions on carbon and titanium targets. The b-bbar production was tagged via inclusive bottom quark decays into J/psi, by exploiting the longitudinal separation of J/psi->ll decay vertices from the primary proton-nucleus interaction. Both $e^+e^-$ and $μ^+μ^-$ channels have been reconstructed and the combined analysis yields the cross section $σ(b \bar b) = 32 ^{+14}_{-12} (stat) ^{+6}_{-7} (sys) nb/nucleon$.