All hadronic decay of tt_bar pairs at LHC

An investigation has been made of the potential of the ATLAS detector at the LHC to study the ``all hadronic'' decay of tt_bar pairs in which both W bosons decay to jets, leading to a multi-jet final state. Various kinematic variables for signal and background events have been analyzed. It is demonstrated that performing a kinematic fit of the selected events to the tt_bar hypothesis allows extraction of the signal above background, and subsequent study of the kinematic properties of the individual top quarks and of the tt_bar pairs. It is also shown that an effective way to further suppress the large QCD multijet background in this decay mode is to select a subsample of high p_T top events after the kinematic fit.