  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.
