Simulation study of air shower particles near the core region

The ARGO-YBJ experiment has two kinds of signals in the shower working mode which allows coverage of the energy region from TeV to PeV region. One is the digital strip pattern, another is so-called ‘big pad’ mode, which is the analog signal counting the pulse height on half of an RPC, proportional to the number of hitting particles. In this paper by using the Monte Carlo simulation method the ARGO-YBJ sensitivity to the cosmic ray composition is discussed, by using the ‘big pad’ signal for measuring the number of particles detected close to the shower core.