Simulation on gamma ray astronomy research with LHAASO-KM2A

LHAASO (Large High Altitude Air Shower Observatory) is a large project to research on high energy gamma ray astronomy and cosmic ray physics. KM2A (one KM2 Array), one main part of the LHAASO project, using a 1 km2 array composed of electron detectors (ED) and muon detectors (MD), focuses on gamma ray astronomy above 30 TeV and cosmic ray physics in the “knee” region. Accurate measurement of gamma ray energy spectra above 30 TeV is crucial to identify the sources as the galactic cosmic ray accelerators. Monte Carlo simulation indicates that cosmic gamma rays can be distinguished from cosmic nuclei background by using muon content in extensive air showers (EAS). With the sensitivity of about 1% of the integral flux of Crab Nebula, the high duty cycle of at least 90 % and the full sky survey, the KM2A array would be very useful in discovering the galactic gamma ray sources and identifying the cosmic ray sources with gamma-ray emission. A detailed simulation is carried out for studying performance and expectation of the KM2A array in gamma ray astronomy above 30 TeV.