Professor Daniela Bortoletto

Abstract:

We report the measurements of the tt̄ production cross section and of the top quark mass using 1.02fb-1 of pp̄ data collected with the CDF II detector at the Fermilab Tevatron. We select events with six or more jets on which a number of kinematical requirements are imposed by means of a neural network algorithm. At least one of these jets must be identified as initiated by a b-quark candidate by the reconstruction of a secondary vertex. The cross section is measured to be σtt̄=8.3±1.0(stat)-1.5+2.0(syst) ±0.5(lumi)pb, which is consistent with the standard model prediction. The top quark mass of 174.0±2.2(stat)±4.8(syst)GeV/c2 is derived from a likelihood fit incorporating reconstructed mass distributions representative of signal and background. © 2007 The American Physical Society.

Abstract:

We have performed a search for new particles which decay to two photons using 1.2fb-1 of integrated luminosity from pp̄ collisions at s=1.96TeV collected using the CDF II detector at the Fermilab Tevatron. We find the diphoton mass spectrum to be in agreement with the standard model expectation, and set limits on the cross section times branching ratio for the Randall-Sundrum graviton, as a function of diphoton mass. We subsequently derive lower limits for the graviton mass of 230GeV/c2 and 850GeV/c2, at the 95% confidence level, for coupling parameters (k/M̄Pl) of 0.01 and 0.1, respectively. © 2007 The American Physical Society.