# Perturbative unitarity bounds for effective composite models

## TL;DR

This paper derives unitarity bounds for effective operators in composite models, providing crucial constraints on parameter space that complement existing experimental limits at the LHC.

## Contribution

It introduces the unitarity bounds for dimension-5 and dimension-6 operators in composite models and compares these theoretical limits with experimental exclusion curves.

## Key findings

- Unitarity bounds significantly restrict the parameter space of composite models.
- Many regions of the (M, Λ) parameter space are excluded by the unitarity bounds.
- The bounds are important for interpreting LHC search results.

## Abstract

In this paper we present the partial wave unitarity bound in the parameter space of dimension-5 and dimension-6 effective operators that arise in a compositeness scenario. These are routinely used in experimental searches at the LHC to constraint contact and gauge interactions between ordinary Standard Model fermions and excited (composite) states of mass $M$. After deducing the unitarity bound for the production process of a composite neutrino, we implement such bound and compare it with the recent experimental exclusion curves for Run 2, the High-Luminosity and High-Energy configurations of the LHC. Our results also applies to the searches where a generic single excited state is produced via contact interactions. We find that the unitarity bound, so far overlooked, is quite complelling and significant portions of the parameter space ($M,\Lambda$) become excluded in addition to the standard request $M \le \Lambda$.