COmBined muon reconstruction for Atlas

The Atlas detector, which is being built for the LHC collider experiment at CERN, near Geneva, has as primary objective the discovery or exclusion of the Higgs boson. This boson is an important ingredient of the Standard Model of elementary particles, but has not yet been experimentally established. Atlas contains two tracking subdetectors, separated by a calorimeter, capable of detecting muon trajectories. The best measurement of the parameters of those particles, mostly muons with a large enough energy, that traverse the calorimeter are obtained by a global fit that includes both tracking subdetectors. A software package, COBRA, which implements an abstraction that allows for the application of the same track fit to either subdetector, the global fit, or any arbitrary detector configuration has been developed. The COBRA method and studies of its performance, based on single-track Monte Carlo simulation, are presented. The COBRA package is then used to assess the effect of combined reconstruction on the discovery potential of the Atlas detector in the fully leptonic decay channels of the Higgs boson.