  A new measurement of the b-bbar production cross section in 920 GeV
proton-nucleus collisions is presented by the HERA-B collaboration. The b-bbar
production is tagged via inclusive bottom quark decays into J/psi mesons, by
exploiting the longitudinal separation of J/psi->ll decay vertices from the
primary proton-nucleus interaction point. Both e+e- and mu+mu- channels are
reconstructed, for a total of 83 +- 12 inclusive b->J/psi X events found. The
combined analysis yields a b-bbar to prompt J/psi cross section ratio of
${\frac{{\Delta\sigma(bbbar)}}{{\Delta\sigma_{\jpsi}}}} = 0.032\pm 0.005 \stat
\pm 0.004 \sys$ measured in the x_f acceptance (-0.35 <x_f <0.15), extrapolated
to $\sigma(bbbar) = 14.9 \pm 2.2 \stat \pm 2.4 \sys $ nb/nucleon in the total
phase space.
