Eur. Phys. J. C (2023) 83: 1112
https://doi.org/10.1140/epjc/s10052-023-12277-1

Regular Article - Theoretical Physics

Prospects for extra Higgs boson search via $pp\to H,A\to \tau \mu ,\tau \tau$ at the high luminosity Large Hadron Collider

¹ Department of Physics, National Taiwan University, 10617, Taipei, Taiwan
² Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 73019, Norman, OK, USA

^a wshou@phys.ntu.edu.tw

Received: 11 July 2023
Accepted: 21 November 2023
Published online: 7 December 2023

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 and final states, where $j_{\tau }=\pi ,\rho ,a_1$ and 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 ${\rho }_{\mathit{tt}}$ 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.