AcerMC Generator of SM backgrounds to the Higgs searches at LHC

by Borut Paul KERSEVAN (Jozef Stefan Inst., Ljubljana, Slovenia)

Friday 1 Mar 2002, 14:00 → 15:00 Europe/Zurich

TH Auditorium (CERN)

The physics programme of the general purpose LHC experiments focuses on the searches for the New Physics with distinctive signatures indicating production of the Higgs boson, SUSY particles etc. Recent measurements at LEP favour a light Higgs boson, which suggests an emphasis on the channels characterised by the presence of the heavy flavour jets and/or multiple isolated leptons. The expected environment will in most cases be very difficult, with the signal to background ratio on the level of a few percent. The AcerMC Monte Carlo generator gives a possibility to generate some of the Standard Model background processes which were recognised as very dangerous for the searches at LHC, and generation of which was either unavailable or not straightforward so far. The program itself provides a library of the massive matrix elements (coded by MADGRAPH) and native phase space modules for generation of a set of selected processes. The hard process event can be completed by the initial and final state radiation, hadronisation and decays through the existing interface with either PYTHIA 6.2 or HERWIG 6.3 event generators. A distinctive feature of AcerMC is the efficient phase space sampling, achieved by a combination of multi-channel self-optimising approach and a modified ac-VEGAS routine. The achieved typical efficiency for generation of unweighted events is on the order of 20%-30%, which is considered to be an achievement, given the complicated topology of the implemented processes. The structure of the program and some interesting phenomenological results will be presented.