Measurement of the $t\bar{t}$ production cross section in the all-hadronic channel in ATLAS with $\sqrt s =7$ TeV data

A measurement of the $t\bar{t}$ production cross section in the all-hadronic channel is presented. The analysis is performed using 4.70/fb of pp collisions produced at the LHC with a centre-of-mass energy of $\sqrt{s}$= 7 TeV and recorded with the ATLAS detector. After selecting events passing a multi-jet trigger and kinematic requirements, events are required to have two reconstructed jets tagged as $b$-jets to identify $t\bar{t}$-event candidates. A kinematical fit which exploits the event topology of the all-hadronic $t\bar{t}$ final state is used to compute the top mass in the selected events. This variable is finally used to measure the total $t\bar{t}$ cross section using an unbinned likelihood fit, giving as a result $\sigma_{t\bar{t}}$ = 168 +/- 12 (stat.) +60 -57 (syst.) +/- 7 (lumi.) pb, consistent with the Standard Model prediction.