  The top quark pair production cross section in the fully hadronic final state
is characterized by a six jet topology, two of which could be identified as
originating from a b-quark using ATLAS b-tagging algorithms. Compared to other
decay channels, this final state presents an advantageous larger branching
ratio; on the other hand it suffers from a very large QCD multi-jet background,
generally difficult to estimate from Monte Carlo simulation and therefore
evaluated using data-driven techniques. The analysis is performed using 36pb-1
of pp collisions produced at the LHC with a center-of-mass energy of 7 TeV. The
observed upper limit is set at 261 pb at 95% confidence level, where the
expected Standard Model cross-section for the ttbar process is 165+11-16 pb. In
the future, when the LHC luminosity increases, it is essential, to efficiently
trigger on these fully hadronic ttbar events, to use dedicated triggers. An
overview of the analysis for ttbar production cross section measurement in the
fully hadronic final state and the state-of-the-art of the b-jet trigger
performance estimation are presented in this contribution.
