Study of longitudinal development of cosmic-ray induced air showers with LHAASO-WFCTA

Abstract

The Wide Field-of-view Cerenkov Telescope Array (WFCTA) is an important component of Large High Altitude Air Shower Observatory (LHAASO), which aims to measure the individual energy spectra of cosmic rays from ~30 TeV to a couple of EeV. The longitudinal development is one of the main tools to distinguish nuclei from each other. WFCTA is composed of 18 imaging air Cerenkov telescopes, each telescope has 32 × 32 pixels, covers a field of view 16o × 16o (each pixel corresponding to 0.5o × 0.5o). The first telescope started in operation since February 2019, up to now, there are 18 telescopes in operation. Cerenkov photon detected by different pixels were generated at different height (or different traversed material). The distribution of dN/dθ (θ is the angle between the direction of Cerenkov photon and the direction of primary particle) is reconstructed from the image of WFCTA to study the longitudinal development of the shower (similar to dN/dX). In this paper, the dN/dθ reconstructing method and the preliminary result on the particle identification power based on this method will be shown.