A measurement is presented of the tt‾ production cross section (σtt‾) in proton-proton collisions at a centre-of-mass energy of 7TeV, in the all-jet final state that contains at least six jets, two of which are tagged as originating from b quarks. The data correspond to an integrated luminosity of 3.54 fb-1, collected with the CMS detector at the LHC. The cross section is determined through an unbinned maximum likelihood fit of background and tt‾ signal to the reconstructed mass spectrum of tt‾ candidates in the data, in which events are subjected to a kinematic fit assuming a tt‾ → W+bW-b‾ → 6 jets hypothesis. The measurement yields σtt‾ = 139±10 (stat.)±26 (syst.)±3 (lum.) pb, a result consistent with those obtained in other tt‾ decay channels, as well as with predictions of the standard model.
- Hadron-Hadron Scattering