  An estimate of environmental background hit rate on triple-GEM chambers is
performed using Monte Carlo (MC) simulation and compared to data taken by test
chambers installed in the CMS experiment (GE1/1) during Run-2 at the Large
Hadron Collider (LHC). The hit rate is measured using data collected with
proton-proton collisions at 13 TeV and a luminosity of 1.5$\times10^{34}$
cm$^{-2}$ s$^{-1}$. The simulation framework uses a combination of the FLUKA
and Geant4 packages to obtain the hit rate. FLUKA provides the radiation
environment around the GE1/1 chambers, which is comprised of the particle flux
with momentum direction and energy spectra ranging from $10^{-11}$ to $10^{4}$
MeV for neutrons, $10^{-3}$ to $10^{4}$ MeV for $\gamma$'s, $10^{-2}$ to
$10^{4}$ MeV for $e^{\pm}$, and $10^{-1}$ to $10^{4}$ MeV for charged hadrons.
Geant4 provides an estimate of detector response (sensitivity) based on an
accurate description of detector geometry, material composition and interaction
of particles with the various detector layers. The MC simulated hit rate is
estimated as a function of the perpendicular distance from the beam line and
agrees with data within the assigned uncertainties of 10-14.5%. This simulation
framework can be used to obtain a reliable estimate of background rates
expected at the High Luminosity LHC.
