  For comparison of inclusive jet cross sections measured at hadron-hadron
colliders to next-to-leading order (NLO) parton-level calculations, the energy
deposited in the jet cone by spectator parton interactions must first be
subtracted. The assumption made at the Tevatron is that the spectator parton
interaction energy is similar to the ambient level measured in minimum bias
events. In this paper, we test this assumption by measuring the ambient charged
track momentum in events containing large transverse energy jets at
$\sqrt{s}=1800$ GeV and $\sqrt{s}=630$ GeV and comparing this ambient momentum
with that observed both in minimum bias events and with that predicted by two
Monte Carlo models. Two cones in $\eta$--$\phi$ space are defined, at the same
pseudo-rapidity, $\eta$, as the jet with the highest transverse energy
($E_T^{(1)}$), and at $\pm 90^o$ in the azimuthal direction, $\phi$. The total
charged track momentum inside each of the two cones is measured. The minimum
momentum in the two cones is almost independent of $E_T^{(1)}$ and is similar
to the momentum observed in minimum bias events, whereas the maximum momentum
increases roughly linearly with the jet $E_T^{(1)}$ over most of the measured
range. This study will help improve the precision of comparisons of jet cross
section data and NLO perturbative QCD predictions. %this is new The
distribution of the sum of the track momenta in the two cones is also examined
for five different $E_T^{(1)}$ bins. The HERWIG and PYTHIA Monte Carlos are
reasonably successful in describing the data, but neither can describe
completely all of the event properties.
