Projection for ZZZ Production Cross Section Measurements at the HL-LHC

TL;DR

This paper develops a method to select and reconstruct ZZZ events at the HL-LHC, estimating expected yields and backgrounds to aid in studying quartic gauge couplings beyond the Standard Model.

Contribution

It introduces a new code for ZZZ event reconstruction and analyzes its potential for signal detection in HL-LHC conditions.

Findings

Expected ZZZ signal of 1.42 events with low background in the fully leptonic channel.

Potential for signal extraction in mixed leptonic-hadronic ZZZ final states.

Optimized variables for separating ZZZ signal from backgrounds.

Abstract

Triple gauge boson (tri-boson) production is one of the ways to study the Quartic Gauge Couplings (QGC) and the anomalous QGC beyond the Standard Model of particle physics. In particular, we investigated the signal selection criteria for ZZZ production in the High Luminosity Large Hadron Collider (HL-LHC) scenario. We wrote code which selects and reconstructs 3 desired Z bosons from the produced electrons, muons and jets. We ran the code on selected Monte Carlo Simulation samples, including the ZZZ signal samples and other background (e.g. top pair production TT) samples. We made plots of event variables and looked for variables that can potentially separate the signal from the backgrounds. Then we put constraints on these variables to optimize the signal to background ratio for various types of final states of ZZZ and obtained the expected yields of the decays at the HL-LHC. We expect to see 1.42 +/- 0.25 ZZZ event with 0.82 +/- 0.60 background event in the rare fully leptonic channel. Furthermore, signal extraction in the 2 leptonic Z and 1 hadronic Z channel shows potential and is worth further investigation.