Search for the Higgs Boson in the Channel H->ZZ*->4l with the ATLAS Detector

The decay channel H->ZZ*->4l provides a clean signature for the Higgs boson in the mass range between ~120 GeV and 2MZ, above which the "gold-plated" channel with two real Z bosons in the final state opens up. The signal cross section is several orders of magnitude smaller than those for the backgrounds, therefore a thorough understanding of the multi-lepton processes is needed to obtain a high background rejection. Crucial for this channel is also a very good knowledge of the trigger and detector response for lepton identification and reconstruction. The observability of the signal on top of the reducible tt, Zbb and of the irreducible ZZz backgrounds with the ATLAS Detector is discussed in the following, with particular emphasis on lepton reconstruction. The ATLAS discovery potential for the H->4l, including the most realistic and up-to-date description of the detector performance, is presented.