Measurement of muonic and electromagnetic components in cosmic ray air showers using LHAASO-KM2A prototype array

A LHAASO-KM2A prototype array, which is about 1% of the full one, had been in stable operation for about 3 years from 2014 to 2016. This work presents a combined measurement of shower muons and electromagnetic particles using its data. Benefiting from the wide dynamic range of the muon detectors and the surrounding electromagnetic detector array, the muon content was studied in detail for showers with energies from tens of TeV to tens of PeV. The results are compatible with the prediction of Monte Carlo simulation and no obvious excess is observed when taking into account that the mass composition increases above 1 PeV. The results also support a transition from light to heavy elements for cosmic rays in the “knee” region.