Search for Physics beyond the Standard Model in four- and three-top quark production

TL;DR

This CMS study analyzes multi-top quark final states using the full Run 2 dataset at 13 TeV to search for beyond-Standard-Model effects in three frameworks: SMEFT, top-philic heavy resonances, and the top-Yukawa coupling structure. It combines exclusive signal and control regions with multivariate discrimination and high-$H_T$ tails, constraining EFT Wilson coefficients, heavy-boson couplings, and Yukawa modifiers through LO simulations with MG5_aMC@NLO and SMEFTsim or Demartin parametrizations. No significant deviation from the SM is observed, but the results set competitive limits on four-fermion operators, top-Higgs interactions, and resonance couplings, highlighting the sensitivity of $t\bar{t}t\bar{t}$ and related multi-top processes to BSM physics. These constraints improve our understanding of top-quark interactions at high energy and guide future high-luminosity searches.

Abstract

A reinterpretation of four-top quark ($t\bar{t}t\bar{t}$) production is presented using the full Run 2 dataset recorded by the CMS experiment, corresponding to an integrated luminosity of 138 fb$^{-1}$. The analysis targets BSM scenarios using the existing $t\bar{t}t\bar{t}$ production measurement, including constraints on effective field theory (EFT) operators, top-philic heavy resonances, and the top-Yukawa coupling. The results provide competitive limits on several new physics models and demonstrate the sensitivity of multi-top final states to a wide range of BSM effects.

Figures (4)

• Figure 1: Postfit BDT score $\text{t} \bar{\text{t}} \text{t} \bar{\text{t}}$ (left) and $H_{\mathrm{T}}$ (right) distributions in the dilepton SR, with the ratio panels for SM and BSM hypotheses CMS-PAS-TOP-24-008.
• Figure 2: Negative log-likelihood difference from the best fit value for the one-dimensional scan of $c_{tt}$ (left), and the two-dimensional scan of the $c_{tH}^{Re}$ and $c_{tH}^{Im}$ (right) showing the structure of the Yukawa coupling CMS-PAS-TOP-24-008.
• Figure 3: Upper limits found for coupling of a pseudoscalar singlet (left) and a vector octet (right) boson as a function of their mass CMS-PAS-TOP-24-008. The blue line shows the limit where the partial decay width of the boson would be higher than 10 GeV and our simulation is no longer valid.
• Figure 4: One-dimensional likelihood scans of the even (left) and odd (right) Yukawa coupling modifiers CMS-PAS-TOP-24-008.