Transverse Energy and Minijets in High Energy Collisions

Minijet production and transverse energy are important not only to understand hadronic collisions, but also for the interpretation of nucleus collisions at RHIC and LHC, where it determines the ``initial conditions'' for the flow in a hadronic soup or a plasma. For high collision energies and small qT (minijets) we enter the BFKL region. This implies that we must take into account off-shell parton cross sections and non-integrated structure functions (kT-factorization). It is also essential to avoid double counting, as one emitted parton is a participant in two different subcollisions. The LDC model, developed in Lund to describe DIS, provides a very convenient formalism to handle these problems. The result is a dynamical suppression of minijets for small qT. The resulting transverse energy flow is similar to the result from a ''naive'' calculation based on integrated structure functions with a qT cut-off around 2 GeV.