Illustration of correlations in the azimuthal angle relative to the direction
of the leading "calorimeter jet" (JetClu, R = 0.7) in the event, jet1.
The "transverse" region is defined by
60o <|| <120o
and |eta| < 1.
The "transverse" region is perpendicular to the plane of the hard 2-to-2 scattering and is very sensitive to
the "underlying event" component of the QCD Monte-Carlo models.
For studies of the "transverse" region we allow the leading jet to be in the region |eta(jet1)| < 2,
but when studying charged particles withing the leading jet we require that |eta(jet1)| < 0.7.