ALPGEN, a generator for hard multiparton processes in hadronic collisions

This paper presents a new event generator, ALPGEN, dedicated to the study ofmultiparton hard processes in hadronic collisions. The code performs, at theleading order in QCD and EW interactions, the calculation of the exact matrixelements for a large set of parton-level processes of interest in the study ofthe Tevatron and LHC data. The current version of the code describes thefollowing final states: (W -> ffbar') QQbar+ N jets (Q being a heavy quark, andf=l,q), with N<=4; (Z/gamma* -> f fbar)+QQbar+Njets (f=l,nu), with N<=4; (W ->ffbar') + charm + N jets (f=l,q), N<= 5; (W -> f fbar') + N jets (f=l,q) and(Z/gamma* -> f fbar)+ N jets (f=l,nu), with N<=6; nW+mZ+lH+N jets, withn+m+l+N<=8 and N<=3 including all 2-fermion decay modes of W and Z bosons, withspin correlations; Q Qbar+N jets (N<=6) with t -> b f fbar' decays and relativespin correlations included if Q=t; Q Qbar Q' Qbar'+N jets, with Q and Q' heavyquarks (possibly equal) and N<=4; H Q Qbar+N jets (N<=4) with t -> b f fbar'decays and relative spin correlations included if Q=t; N jets, with N<=6.Parton-level events are generated, providing full information on their colourand flavour structure, enabling the evolution of the partons into fullyhadronised final states.Comment: 1+38 pages, uses JHEP.cls. Documents code version 1.2: extended list of processes, updated documentation and bibliograph