  In both particle physics and muon applications, a high-resolution muon
momentum measurement capability plays a significant role not only in providing
valuable information on the properties of subatomic particles but also in
improving the utilizability of cosmic ray muons. Typically, muon momentum is
measured by reconstructing a curved muon path using a strong magnetic field and
muon trackers. Alternatively, a time-of-flight and Cherenkov ring imager are
less frequently applied, especially when there is a need to avoid a magnetic
field. However, measurement resolution is much less than that of magnetic
spectrometers, approximately 20% whereas it is nearly 4% or less when using
magnets and trackers. Here, we propose a different paradigm to estimate muon
momentum that utilizes multiple pressurized gas Cherenkov radiators. Using the
fact that the refractive index of gas medium varies depending on its pressure
and temperature, we can optimize the muon Cherenkov threshold momentum levels
for which a muon signal will be detected. In this work, we demonstrate that
muon momentum can be estimated with mean resolution of {sigma_p}/p < 20% and
mean classification rate of 90.08% in the momentum range of 0.1 to 10.0 GeV/c
by analyzing optical photon signals from each Cherenkov radiator. We anticipate
our new spectrometer will significantly improve quality of imaging and reduce
scanning time in cosmic ray muon applications by being incorporated with
existing instruments.
