Search for $t\bar{t}$ resonances in the semileptonic final state using pp collisions at $\sqrt s$ = 8 TeV recorded with the CMS detector

TL;DR

This study conducted a model-independent search for heavy resonances decaying into top-antitop pairs in proton-proton collisions at 8 TeV using the CMS detector, employing specialized techniques for different mass ranges, but found no evidence of such signals.

Contribution

It introduces two dedicated analysis methods optimized for different invariant mass ranges to improve sensitivity in searching for $t\bar{t}$ resonances at the LHC.

Findings

No evidence of $t\bar{t}$ resonance signals was observed.

Limits were set excluding certain models up to 2.7 TeV.

Constraints on Kaluza-Klein gluons below 2.5 TeV were established.

Abstract

Many extensions to the Standard Model predict gauge interactions with enhanced couplings to third generation quarks, especially the extremely heavy top quark\cite{theoretical}. These phenomena can lead to resonances in the production of $t\bar{t}$ pairs. In this note, a model-independent search for the production of heavy resonances decaying into top-antitop quark pairs in the semileptonic final state using pp collisions at $\sqrt s$ = 8 TeV recorded with the CMS detector is presented. The analysis focuses on the semileptonic decay channels into electrons or muons and covers the range of 0.5-3 TeV in the invariant mass of the $t\bar{t}$ pairs where the events present specific and different topologies. Therefore two dedicated analyses have been performed to achieve the best sensitivity on the whole invariant mass range: the threshold analysis (0.5-2 TeV) which is optimized for $t\bar{t}$ production at the kinematic production threshold, using standard top quark reconstruction techniques, and the boosted analysis (1-3 TeV) optimized for $t\bar{t}$ produced with high Lorentz boosts, using dedicated techniques for boosted top quarks reconstruction. No evidence of signal has been found. Thus the following limits at 95% C.L. on the production of non-SM particles in specific models are set: topcolor Z$^{\prime}$ bosons with a width of 1.2 (10) % of its mass are excluded for masses below 2.1 TeV (up to 2.7 TeV). In addition, Kaluza-Klein excitations of a gluon with masses below 2.5 TeV in the Randall-Sundrum model are excluded.