Measurement of the b(b)over-bar production cross section in 920 GeV fixed-target proton-nucleus collisions

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