Search for resonant t t-bar production in proton-proton collisions at sqrt(s) = 8 TeV

TL;DR

This paper searches for heavy resonances decaying into top-antitop pairs in proton-proton collisions at 8 TeV, using advanced jet substructure techniques, and sets the most stringent limits to date on such particles.

Contribution

It introduces optimized methods for detecting high-mass top-antitop resonances using jet substructure in CMS data at 8 TeV.

Findings

No significant excess observed over standard model predictions.

Excluded a leptophobic Z' resonance below 2.4 TeV at 95% CL.

Set new upper limits on broad Z' and Kaluza-Klein gluon production.

Abstract

A search is performed for the production of heavy resonances decaying into top-antitop quark pairs in proton-proton collisions at sqrt(s) = 8 TeV. Data used for the analyses were collected with the CMS detector and correspond to an integrated luminosity of 19.7 inverse femtobarns. The search is performed using events with three different final states, defined by the number of leptons (electrons and muons) from the t t-bar to W b W b decay. The analyses are optimized for reconstruction of top quarks with high Lorentz boosts, where jet substructure techniques are used to enhance the sensitivity. Results are presented for all channels and a combination is performed. No significant excess of events relative to the expected yield from standard model processes is observed. Upper limits on the production cross section of heavy resonances decaying to t t-bar are calculated. A narrow leptophobic topcolor Z' resonance with a mass below 2.4 TeV is excluded at 95% confidence level. Limits are also derived for a broad Z' resonance with a 10% width relative to the resonance mass, and a Kaluza-Klein excitation of the gluon in the Randall-Sundrum model. These are the most stringent limits to date on heavy resonances decaying into top-antitop quark pairs.