ALPGEN, a generator for hard multiparton processes in hadronic collisions

This paper presents a new event generator, ALPGEN, dedicated to the study of multiparton hard processes in hadronic collisions. The code performs, at the leading order in QCD and EW interactions, the calculation of the exact matrix elements for a large set of parton-level processes of interest in the study of the Tevatron and LHC data. The current version of the code describes the following final states: (W --> f (f) over bar')Q (Q) over bar + N jets (Q being a heavy quark, and f = l, q), with N less than or equal to 4; (Z/gamma* --> f (f) over bar )Q (Q) over bar + N jets (f = l, nu), with N less than or equal to 4; (W --> f (f) over bar') + charm + N jets (f = l, q, N less than or equal to 5); (W --> f (f) over bar') + N jets (f = l, q) and (Z/gamma* --> f (f) over bar) + N jets (f = l, nu), with N less than or equal to 6; nW + mZ + lH + N jets, with n + m + l + N less than or equal to 8, N less than or equal to 3, including all 2-fermion decay modes of W and Z bosons, with spin correlations; Q (Q) over bar + N jets, with t --> bf (f) over bar' decays and relative spin correlations included where relevant, and N less than or equal to 6; Q (Q) over barQ'(Q) over bar' + N jets, with Q and Q' heavy quarks (possibly equal) and N less than or equal to 4; HQ (Q) over bar + N jets, with t --> bf (f) over bar' decays and relative spin correlations included where relevant and N less than or equal to 4; N jets, with N less than or equal to 6. Parton-level events are generated, providing full information on their colour and flavour structure, enabling the evolution of the partons into fully hadronised final states.