An approach to identify the mass and energy of the primary cosmic rays around the knee region using arrival time distribution of secondary charged particles in extensive air showers

Abstract

In this study a method will be presented to discriminate the mass and energy of the primary cosmic rays. This method uses the time distribution of secondaries in air showers originated from different primaries generated by CORSIKA Monte Carlo code at the Tehran 1200 m level (35°43′N, 51°20′E, 1200 m a.s.l).Simulations were performed for four primary energies (0.3, 1, 3 and 10 PeV) around the knee of cosmic ray spectrum. Three parameters of time distribution rise time, fall time and time of maximum were defined as mass and energy discriminator. By calculating Merit Factor(MF) ability of these parameters to discriminate mass and energy was evaluated. Heavy and light primary particles slightly separated in vertical 10 PeV showers by comparing time distribution’s fall time of secondary particles with MF = 1.68 ± 0.08 in 10 m from the shower core but for inclined showers this method does not work. In the same way, energy of primary particles also can be discriminated with one order of magnitude accuracy with MF = 2.17 ± 0.19 for showers with energy 0.3 and 3 PeV and MF = 2.09 ± 0.13 for showers with energy 1 and 10 PeV in 25 m 25 m from the shower core. In case of inclined showers, unlike mass discrimination their energies can be separated well. Effect of timing uncertainty of detectors on the ability of this method on energy discrimination is also studied. The results of this study can be applied in parallel with the common shower reconstruction techniques and other data analysis methods to improve estimation of high and ultra-high energy primary particle’s energy.