  We report on a search for direct scalar bottom quark (sbottom) pair
production in $p \bar{p}$ collisions at $\sqrt{s}=1.96$~TeV, in events with
large missing transverse energy and two jets of hadrons in the final state,
where at least one of the jets is required to be identified as originating from
a $b$ quark. The study uses a CDF Run~II data sample corresponding to
2.65~fb${}^{-1}$ of integrated luminosity. The data are in agreement with the
standard model. In an R-parity conserving minimal supersymmetric scenario, and
assuming that the sbottom decays exclusively into a bottom quark and a
neutralino, 95$\%$ confidence-level upper limits on the sbottom pair production
cross section of 0.1~pb are obtained. For neutralino masses below 70~GeV/$c^2$,
sbottom masses up to 230~GeV/$c^2$ are excluded at 95$\%$ confidence level.
