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

TL;DR

This paper investigates the potential to discover extra Higgs bosons decaying into tau and muon or tau pairs at the LHC, using detailed simulations and considering a general two Higgs doublet model with flavor-changing couplings.

Contribution

It provides a comprehensive analysis of search strategies for heavy Higgs bosons in tau-muon and tau-tau channels, including realistic detector effects and different collider energies.

Findings

Promising sensitivity for heavy Higgs discovery at 13 and 14 TeV LHC.

Effective signal regions and background suppression techniques identified.

Simulation results support future experimental searches for flavor-changing Higgs decays.

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.