On the Forward-Backward Asymmetry of Leptonic Decays of $t\bar{t}$ at the Fermilab Tevatron

Abstract

We report on a study of the measurement techniques used to determine the leptonic forward-backward asymmetry of top anti-top quark pairs in Tevatron experiments with a proton anti-proton initial state. Recently it was shown that a fit of the differential asymmetry as a function of $q_l{\eta }_l$ (where $q_l$ is the charge of the lepton from the cascade decay of the top quarks and ${\eta }_l$ is the final pseudorapidity of the lepton in the detector frame) to a hyperbolic tangent function can be used to extrapolate to the full leptonic asymmetry. We find this empirical method to well reproduce the results from current experiments, and present arguments as to why this is the case. We also introduce two more models, based on Gaussian functions, that better model the $q_l{\eta }_l$ distribution. With our better understanding, we find that the asymmetry is mainly determined by the shift of the mean of the $q_l{\eta }_l$ distribution, the main contribution to the inclusive asymmetry comes from the region around $|q_l{\eta }_l|=1$, and the extrapolation from the detector-covered region to the inclusive asymmetry is stable via a multiplicative scale factor, giving us confidence in the previously reported experimental results.

26 pages, 12 figures

References in corpus (12)

• PYTHIA 6.4 Physics and Manual
• Matching NLO QCD computations with Parton Shower simulations: the POWHEG method
• Top Quarks, Axigluons and Charge Asymmetries at Hadron Colliders
• Constraining heavy colored resonances from top-antitop quark events
• Massive color-octet bosons and the charge asymmetries of top quarks at hadron colliders
• Axigluons cannot explain the observed top quark forward-backward asymmetry
• Top-Quark Forward-Backward Asymmetry in Randall-Sundrum Models Beyond the Leading Order
• Forward-backward asymmetry of top quark in unparticle physics
• Forward-backward asymmetry and differential cross section of top quark in flavor violating $Z^{\prime }$ model at $\mathcal{O}({\alpha }_s^2{\alpha }_X)$
• Measurement of the inclusive leptonic asymmetry in top-quark pairs that decay to two charged leptons at CDF
• One-side Forward-backward Asymmetry in Top Quark Pair Production at CERN Large Hadron Collider
• Data driving the top quark forward--backward asymmetry with a lepton-based handle

Cited by in corpus (3)

• Asymmetries in top quark pair production at hadron colliders
• Measurement of the inclusive leptonic asymmetry in top-quark pairs that decay to two charged leptons at CDF
• Combined Forward-Backward Asymmetry Measurements in Top-Antitop Quark Production at the Tevatron