LHAASO-KM2A simulation

Abstract

At Yangbajing, with altitude of 4300m a.s.l., the LHAASO site is an ideal location for energy spectrum and composition measurements for cosmic rays, including gamma rays, above 30TeV because developing maxima of air showers are 1-2km above the ground. One main part of LHAASO (The Large High Altitude Air Shower Observatory) project, KM2A, using a 1$km^2$ array composed of electron detectors(ED) and muon detectors(MD), focuses on gamma ray astronomy above 30TeV and cosmic ray physics in the ”knee” region. Fine measurement of gamma ray energy spectra above 30TeV is crucial to identify sources as galactic cosmic ray accelerators. Monte Carlo simulation shows that primary gamma showers can be identified event by event using muon content. The observation is background free above 50TeV. With a sensitivity of about 1% $I_{crab}$, high duty cycle of at least 90 % and full sky survey, the array would be very useful in discovering galactic gamma ray sources and identifying cosmic ray sources. A simulation is carried out for optimizing performance of the KM2A array, mainly in gamma ray astronomy above 30TeV . Moreover, compared with the report at the last ICRC, the present one considers more details of detector parameterizations and improves analys