Search for pair production of heavy particles decaying to a top quark and a gluon in the lepton+jets final state in proton-proton collisions at $\sqrt{s}$ = 13 TeV

TL;DR

This paper reports a search for heavy particles decaying into a top quark and a gluon in proton-proton collisions at 13 TeV, using CMS data, setting new limits on their production and mass.

Contribution

It introduces a novel deep neural network analysis to search for pair-produced heavy resonances decaying to top quarks and gluons, providing the most stringent limits to date.

Findings

No significant deviation from the standard model observed.

Upper limits on production cross sections range from 0.8 to 120 fb.

Mass exclusion limits reach up to 1700 GeV for certain particles.

Abstract

A search is presented for the pair production of new heavy resonances, each decaying into a top quark (t) or antiquark and a gluon (g). The analysis uses data recorded with the CMS detector from proton-proton collisions at a center-of-mass energy of 13 TeV at the LHC, corresponding to an integrated luminosity of 138 fb$^{-1}$. Events with one muon or electron, multiple jets, and missing transverse momentum are selected. After using a deep neural network to enrich the data sample with signal-like events, distributions in the scalar sum of the transverse momenta of all reconstructed objects are analyzed in the search for a signal. No significant deviations from the standard model prediction are found. Upper limits at 95% confidence level are set on the product of cross section and branching fraction squared for the pair production of excited top quarks in the $\mathrm{t^*}$ $\to$ tg decay channel. The upper limits range from 120 to 0.8 fb for a $\mathrm{t^*}$ with spin-1/2 and from 15 to 1.0 fb for a $\mathrm{t^*}$ with spin-3/2. These correspond to mass exclusion limits up to 1050 and 1700 GeV for spin-1/2 and spin-3/2 $\mathrm{t^*}$ particles, respectively. These are the most stringent limits to date on the existence of $\mathrm{t^*}$ $\to$ tg resonances.