Are the LHC experiments such as ATLAS or CMS equally effective at detecting antimuons as they are at detecting muons? Or is there an asymmetry?
If you had 50 muons and 50 antimuons, would the numbers detected be in the same ratio?
One can search for "muon spectrometers LHC" and find a number of entries that describe the spectrometers. Look at this dimuon event at CMS
Both charges are identified, and the series of detectors used is illustrated behind the event tracks.
Identification involves identifying a track in the accurate track detector in the center, with track detectors outside , where only weakly interacting particles arrive to be measured, because of the huge mass density of the magnet before them.
There is no difference between positive or negative muons as far as tracks identified in the detector go, the charge identified by the curvature of the charged track in the tracking detector.