CMS Results at the $\text{t}\bar{\text{t}}$ threshold

TL;DR

This paper reports CMS experimental results near the top-antitop quark pair production threshold, analyzing 138 fb^{-1} of data, revealing an excess at low invariant mass that suggests possible new pseudoscalar states.

Contribution

It presents the first CMS analysis combining spin-sensitive variables with invariant mass to search for heavy (pseudo)scalar states near the t-tbar threshold.

Findings

An excess at low m_{tar t} favors a pseudoscalar hypothesis.

Results are compatible with non-relativistic QCD bound state models.

Analysis constrains models of heavy scalar and pseudoscalar particles.

Abstract

Recent results of CMS at the top-antitop quark pair production threshold in the dileptonic and semileptonic decay channels are presented. The results were obtained analyzing $138~\mathrm{fb}^{-1}$ of $pp$ collision data taken at $\sqrt{s}=13~\mathrm{TeV}$ with the CMS detector. Spin-sensitive variables are combined with the $t\bar t$ invariant mass $m_{t\bar t}$ to achieve high sensitivity for intermediate heavy pseudoscalar or scalar states. An excess in the data is observed for low values of $m_{t\bar t}$, favoring a pseudoscalar over a scalar hypothesis. The results are given in the interpretation of a simplified $t\bar t$ bound state model $\eta_t$ and in a generic model for heavy (pseudo)scalar production. The observed excess is compatible with non-relativistic QCD (NRQCD) calculations for a $t\bar t$ bound state.