The ALPHA algorithm to evaluate the exact, tree-level matrix elements is reviewed in the context of multi-parton processes in QCD. The algorithm is suited for the authomatic calculation of tree-level scattering amplitudes and allows for straightforward inclusion of mass effects. It's CPU cost grows like Kn (K constant, n number of external particles) as opposed to the factorial growth of Feynman graphs. I also discuss the summation over colour configurations which is designed to allow the construction of parton-level event generators suitable to interfacing with a parton-shower evolution including the effects of colour-coherence. Explicit results for the total rates and differential distributions of processes with 8 final-state partons are given.
A New approach to multijet calculations in hadron collisions.
MORETTI, Mauro
2000
Abstract
The ALPHA algorithm to evaluate the exact, tree-level matrix elements is reviewed in the context of multi-parton processes in QCD. The algorithm is suited for the authomatic calculation of tree-level scattering amplitudes and allows for straightforward inclusion of mass effects. It's CPU cost grows like Kn (K constant, n number of external particles) as opposed to the factorial growth of Feynman graphs. I also discuss the summation over colour configurations which is designed to allow the construction of parton-level event generators suitable to interfacing with a parton-shower evolution including the effects of colour-coherence. Explicit results for the total rates and differential distributions of processes with 8 final-state partons are given.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
