  A measurement of jet activity in the rapidity interval bounded by a dijet
system is performed using pp collisions at 7 TeV recorded by the ATLAS detector
in 2010. The data are compared to LO predictions from PYTHIA, HERWIG++ and
ALPGEN event generators. The data are also compared to NLO parton shower
prediction from POWHEG, when interfaced to PYTHIA or HERWIG parton shower, and
all order resummation prediction from HEJ. In most of the phase-space regions
presented, the experimental uncertainty is much smaller than the spread of LO
Monte Carlo event generator predictions. In general, POWHEG+PYTHIA gave the
best description of the data.
