Constraining $qqtt$ operators from four-top production: a case for enhanced EFT sensitivity

TL;DR

Four-top production at the LHC provides unexpectedly strong constraints on $qqtt$ operators, surpassing top-pair measurements in sensitivity due to multiple operator insertions and high energy thresholds, thus enhancing EFT-based top physics studies.

Contribution

This work demonstrates that four-top production offers competitive and robust constraints on $qqtt$ operators, highlighting its importance for probing new physics in the top-quark sector.

Findings

Four-top production constrains $qqtt$ operators as effectively as top-pair measurements.

Sensitivity is enhanced by multiple operator insertions and high energy thresholds.

Future higher luminosity will further improve constraints and top physics insights.

Abstract

Recently, experimental collaborations have reported $\mathcal{O}(10)$ upper limits on the signal strength of four-top production at the LHC. Surprisingly, we find that the constraining power of four-top production on the $qqtt$ type of operators is already competitive with the measurements of top-pair production, even though the precision level of the latter is more than two orders of magnitude better. This is explained by the enhanced sensitivity of the four-top cross section to $qqtt$ operators, due to multiple insertion of operators in the squared amplitude, and to the large threshold energy of four-top production. We point out that even though the dominant contribution beyond the standard model comes from the $\mathcal{O}(C^4/\Lambda^8)$ terms, the effective field theory expansion remains valid for a wide range of underlying theories. Considering the possible improvements of this measurement with higher integrated luminosity, we believe that this process will become even more crucial for probing and testing the standard model deviations in the top-quark sector, and will eventually provide valuable information about the top-quark properties, leading to significant improvements in precision top physics.