Angular resolution of LHAASO-KM2A with improved shower front profile and time structure

The angular resolution of an extensive air shower (EAS) array plays a critical role in determining the sensitivity of the source. The profile of the shower front is known to be curved. The existing reconstruction method is to fit the shower front into a cone. Here a better description the function of the shower front is presented. According to the probability density function of the temporal distribution of secondary particles at different distances from the shower axis, an improved functional form of the shower front is obtained, which enhances the accuracy of cosmic ray direction reconstruction.