Pseudoscalar pair production via off-shell Higgs in composite Higgs models

TL;DR

This paper introduces a novel search strategy for a narrow pseudoscalar particle produced via off-shell Higgs decay in composite Higgs models, focusing on the $Z\,\gamma$ decay channel to set bounds on the model's parameters.

Contribution

It proposes a new experimental approach to detect pseudoscalar pairs through off-shell Higgs in composite models, emphasizing the $Z\gamma$ decay mode and estimating bounds on the Higgs-$\eta$ coupling.

Findings

Potential to exclude large values of the compositeness scale $f$.

Analysis strategy for observing the $Z\gamma Z\gamma$ channel.

Sensitivity depends on photon identification and multiplicity prediction.

Abstract

We propose a new type of search for a pseudoscalar particle $\eta$ pair produced via an off-shell Higgs, $pp\to h^*\to \eta\eta$. The search is motivated by a composite Higgs model in which the $\eta$ is extremely narrow and decays almost exclusively into $Z\gamma$ in the mass range $65$ GeV$\lesssim m_\eta \lesssim 160$ GeV. We devise an analysis strategy to observe the novel $Z\gamma Z\gamma$ channel and estimate potential bounds on the Higgs-$\eta$ coupling. The experimental sensitivity to the signatures depends on the power to identify fake photons and on the ability to predict large photon multiplicities. This search allows us to exclude large values of the compositeness scale $f$, being thus complementary to other typical processes.