Forward Backward Asymmetry In Top Quark Production In Ppbar Collisions At Sqrt S

Forward-Backward Asymmetry in Top Quark Production in Ppbar Collisions at Sqrt{s}

Reconstructable final state kinematics and charge assignment in the reaction p{bar p} --> t{bar t} allows tests of discrete strong interaction symmetries at high energy. We define frame dependent forward-backward asymmetries for the outgoing top quark in both the p{bar p} and t{bar t} rest frames, correct for experimental distortions, and derive values at the parton-level. Using 1.9 fb−1 of p{bar p} collisions at (square root)s = 1.96 TeV recorded with the CDF II detector at the Fermilab Tevatron, we measure forward-backward top quark production asymmetries in the p{bar p} and t{bar t} rest frames of A{sub FB}{sup p{bar p}} = 0.17 ± 0.08 and A{sub FB}{sup t{bar t}} = 0.24 ± 0.14.

Measurement of the Forward-backward Asymmetry in Top Quark-antiquark Production in Ppbar Collisions Using the Lepton+jets Channel

Search for Same-sign Top-quark Pair Production at Sqrt(s)

An inclusive search for same-sign top-quark pair production in pp collisions at sqrt(s) = 7 TeV is performed using a data sample recorded with the CMS detector in 2010, corresponding to an integrated luminosity of 35 inverse picobarns. This analysis is motivated by recent studies of p p-bar to t t-bar reporting mass-dependent forward-backward asymmetries larger than expected from the standard model. These asymmetries could be due to Flavor Changing Neutral Currents (FCNC) in the top sector induced by t-channel exchange of a massive neutral vector boson (Z'). Models with such a Z' also predict enhancement of same-sign top-pair production in pp or p p-bar collisions. Limits are set as a function of the Z' mass and its couplings to u and t quarks. These limits disfavour the FCNC interpretation of the Tevatron results.