Constraining R-axion models through dijet searches at the LHC

TL;DR

This paper explores how LHC dijet searches, especially those involving fat-jets and ISR, can constrain R-axion models arising from dynamical supersymmetry breaking, providing new limits on model parameters.

Contribution

It applies novel jet reconstruction techniques and statistical analysis to set the first experimental limits on R-axion parameters using LHC data.

Findings

95% C.L. exclusion limits on R-axion mass and decay constant

Constraints on the number of color messengers in the model

Application of the $q_\mu$ statistical method to R-axion searches

Abstract

The search at hadron colliders for new massive resonances of a few 100 GeVs that couple effectively to colored states is an extremely challenging issue, due principally to the presence of large QCD multijet backgrounds at this energy, rendering the searches at the LHC particularly difficult. Recently, it was realized that these large backgrounds could be overcome by demanding one high-$p_T$ jet from initial-state radiation (ISR) and by means of novel jet-reconstruction techniques through which the resulting hadronized products of the massive resonances are reconstructed as a fat-jet, a unique large-radius jet. The ATLAS and CMS Collaborations have recently reported searches for the experimental signature of a single fat-jet in association with an ISR jet. Models of dynamical supersymmetry breaking with an spontaneously broken R-symmetry give rise to the appearance of a pseudo-Nambu-Goldstone boson called the R-axion, which naturally tends to be light. In the parameter space regions where the anomalous R-axion coupling to gluons is boosted, these models can be tested against these new LHC dijet searches. Taking into account the CMS search, we apply the $q_\mu$ statistical method to the signal events against the background-only expectation and obtain the 95\% C.L. exclusion limits on the most relevant model parameters for a particular messenger sector, namely, the R-axion mass $m_a$, the decay constant $f_a$, and the number of color messengers $N$, being these limits suitable to be applied to more general models with axion-like particles.