Limits on the Production of Narrow t-tbar Resonances in p-pbar Collisions at sqrt(s)=1.96 TeV

TL;DR

This study searches for narrow resonances in top quark pair production in proton-antiproton collisions at 1.96 TeV, setting upper limits on Z' boson production and excluding certain mass ranges for specific models.

Contribution

It provides the first limits on narrow Z' resonances decaying to top quark pairs at the Tevatron energy.

Findings

Excluded Z' bosons below 720 GeV/c2 for topcolor models.

Set upper cross section limits of 0.64 pb for Z'-like states above 700 GeV/c2.

No evidence found for narrow t-tbar resonances within the studied mass range.

Abstract

We search for evidence of resonant top quark pair production in 955 pb-1 of p-pbar collisions at sqrt(s)=1.96 TeV recorded with the CDF II detector at the Fermilab Tevatron. For fully reconstructed candidate t-tbar events triggered on leptons with large transverse momentum and containing at least one identified b-quark jet, we compare the invariant mass spectrum of t-tbar pairs to the expected superposition of standard model t-tbar, non-t-tbar backgrounds, and a simple resonance model based on a sequential Z' boson. We establish upper limits for sigma(p-pbar to Z') times Br(Z' to t-tbar) in the Z' mass interval from 450 GeV/c2 to 900 GeV/c2. A topcolor leptophobic Z' is ruled out below 720 GeV/c2, and the cross section of any narrow Z'-like state decaying to t-tbar is found to be less than 0.64 pb at 95% C.L. for M(Z') above 700 GeV/c2.