Searching for extra Higgs bosons via $pp\to H,A\to \tau\mu, \tau\tau $ at the Large Hadron Collider

Abstract

We extend heavy Higgs searches at the Large Hadron Collider for $H \to \tau \mu$ by CMS, and $H \to \tau\tau$ by ATLAS and CMS, to study discovery prospects of extra Higgs states in $pp \to H,A \to \tau \mu, \tau\tau$ with $e\mu + E_T$ and $j_{\tau} \mu + E_T$ final states, where $j_{\tau} = \pi \, , \rho\, , a_1$ and $E_T$ is missing transverse energy. In a general two Higgs doublet model without $Z_2$ symmetry, extra Yukawa couplings $\rho_{\tau\tau}$ and $\rho_{\tau\mu}$ can drive $H,A \to \tau\tau$ and $\tau\mu$ channels at hadron colliders, following gluon-gluon fusion production with extra $\rho_{tt}$ couplings. The light Higgs boson $h(125)$ is found to resemble closely the Standard Model Higgs boson; in the alignment limit of $\cos\gamma \to 0$ for $h$--$H$ mixing, flavor changing neutral Higgs couplings such as $h \to \tau\mu$ are naturally suppressed, but the couplings of the heavier $H$ is optimized by $\sin \gamma \to 1$. We define various signal regions for $H,A \to \tau\mu$ and $\tau \tau$ and evaluate physics backgrounds from dominant processes with realistic acceptance cuts and tagging efficiencies. Two different studies are presented. We first perform a parton level study without any hadronization and with minimal detector smearing. We then include hadronization using PYTHIA 8.2 and fast detector simulation using DELPHES to give event level simulation. Results for $\sqrt{s}= 13$ TeV appear promising, which we extend further to $\sqrt{s} = 14$ TeV for the High Luminosity LHC.