A Novel Experimental Search Channel for Very Light Higgses in the 2HDM Type I

Abstract: We present a reinterpretation study of existing results from the CMS Collaboration, specifically, searches for light Beyond the Standard Model (BSM) Higgs pairs produced in the chain decay $pp\to H_{\rm SM}\to hh(aa)$ into a variety of final states, in the context of the CP-conserving 2-Higgs Doublet Model (2HDM) Type-I. Through this, we test the Large Hadron Collider (LHC) sensitivity to a possible new signature, $pp\to H_{\rm SM}\to ZA\to ZZ h$, with $ZZ\to jj \mu^+\mu^-$ and $h\to b\bar b$. We perform a systematic scan over the 2HDM Type-I parameter space, by taking into account all available theoretical and experimental constraints, in order to find a region with a potentially visible signal. We investigate the significance of it through a full Monte Carlo simulation down to the parametrised detector level. We show that such a signal is an alternative promising channel to standard four-body searches for light BSM Higgses at the LHC already with an integrated luminosity of ${\cal L} = 300~{\rm fb}^{-1}$. For a tenfold increase of the latter, discovery should be possible over most of the allowed parameter space.