Searching for a Heavy Higgs boson in a Higgs-portal B-L Model

TL;DR

This paper investigates the potential to discover a heavy Higgs boson from a $U(1)_{B-L}$ extension of the Standard Model at the HL-LHC, focusing on decay modes and background reduction techniques.

Contribution

It provides a detailed analysis of heavy Higgs discovery prospects in a $U(1)_{B-L}$ model, including novel background reduction methods for challenging channels.

Findings

Heavy Higgs below 500 GeV can be discovered via $ZZ$ decay modes.

Clean $4\ell$ and $2\ell 2j$ final states are promising for detection.

Background reduction techniques are crucial for the $WW$ channel.

Abstract

We study the discovery prospects of a heavy neutral scalar arising from a $U(1)_{B-L}$ extension of the Standard Model (SM) during the Large Hadron Collider's high luminosity runs (HL-LHC). This heavy neutral scalar mixes with the SM Higgs boson through a Higgs portal and interacts with the SM particles with an interaction strength proportional to the sine of the mixing angle. The mixing between the two Higgs bosons is constrained by direct and indirect measurements. We choose an experimentally viable mixing angle and explore in detail the $ZZ$ and $WW$ decay modes of the heavy Higgs boson. For the $ZZ$ case, we focus on the cleanest $4\ell$ and $2\ell 2j$ final states and find that a heavy Higgs boson of mass smaller than 500 GeV can be discovered at the HL-LHC. For the $WW$ decay mode, we analyze the $\ell jj \slashed{E}_T$ signature. We implement novel background reduction techniques in order to tackle the huge background by performing both cut-based and multivariate analyses. However, large backgrounds render this channel challenging. We briefly discuss the discovery prospects of the heavy $Z'$-boson arising in this model.