Leading-jet Angular Distributions
Within the framework of leading-order perturbative QCD we expect
events with large total transverse energies to arise from 2 -> 2
scattering, and hence to contain two jets in the final state.
Higher order corrections to the leading-order process can give rise
to additional jets. In the parton shower
Monte Carlo picture, initial and final state gluon radiation can give
rise to multijet events. In this picture we would not expect
the leading-jet angular distribution to be very different from the
2 -> 2 scattering prediction even when there are many jets in the
final state. In the figure below we see that indeed this is the case.
The angular distributions for two-jet, three-jet, four-jet, five-jet, and
six-jet events are all similar to the Rutherford scattering form, and
are all well described by both the parton-shower Monte carlo predictions
and by the complete 2 -> N matrix element predictions.
Leading-jet Angular Distributions Figure
Figure caption: Leading-jet angular distributions for events
containing two, three, four, five, and six jets with transverse
energy > 20 GeV. The CDF data
(solid points) are compared with HERWIG predictions (open points)
and NJETS predictions (histograms) for events with total-transverse-energy
exceeding 420 GeV and multijet mass exceeding 600 GeV/c^2.
The curves show the Rutherford scattering form (1 - cos theta)^-2.
More information can be found in
prl 75, 608 (1995)