A search for resonant production of $t\bar{t}$ pairs in $4.8\ \rm{fb}^{-1}$ of integrated luminosity of $p\bar{p}$ collisions at $\sqrt{s}=1.96\ \rm{TeV}$

TL;DR

This study searches for a hypothetical resonance producing top-antitop pairs in proton-antiproton collisions at 1.96 TeV, using a matrix element technique, but finds no evidence and sets exclusion limits on certain models.

Contribution

Introduces a matrix element reconstruction method to search for ttbar resonances in collider data, providing new exclusion limits.

Findings

No evidence of resonant ttbar production was observed.

Leptophobic Z' bosons with mass below 900 GeV are excluded at 95% confidence level.

The technique improves sensitivity in resonance searches.

Abstract

We search for resonant production of tt pairs in 4.8 fb^{-1} integrated luminosity of ppbar collision data at sqrt{s}=1.96 TeV in the lepton+jets decay channel, where one top quark decays leptonically and the other hadronically. A matrix element reconstruction technique is used; for each event a probability density function (pdf) of the ttbar candidate invariant mass is sampled. These pdfs are used to construct a likelihood function, whereby the cross section for resonant ttbar production is estimated, given a hypothetical resonance mass and width. The data indicate no evidence of resonant production of ttbar pairs. A benchmark model of leptophobic Z \rightarrow ttbar is excluded with m_{Z'} < 900 GeV at 95% confidence level.