Speaker
Description
Measurement of cosmic-ray component spectra with KM2A can be explored through template fitting as a practical route to studying the mass evolution of Galactic cosmic rays around the knee. In this work, the relative contributions of different mass groups are inferred by fitting the distribution of the muon-to-electromagnetic shower ratio in reconstructed-energy bins with a Markov Chain Monte Carlo method. Previous studies indicate that, in Monte Carlo (MC) tests, this approach can recover the input composition to a reasonable level and shows only weak sensitivity to the assumed composition model used to generate the templates. Building on that basis, the present study examines several methodological extensions under limited MC data statistics. In particular, the fit is restricted to the peak region of the distribution, and template-shape optimization is explored to reduce the influence of statistical fluctuations in the MC data. Smoothed and parameterized templates are further investigated as practical options for suppressing fluctuations in MC data and improving fit stability. Tests on MC data suggest that the updated procedure retains acceptable closure and does not show strong sensitivity to the composition model adopted in template construction. When applied to real KM2A data, the all-particle behavior remains relatively stable under different template treatments, while composition-sensitive observables still exhibit noticeable dependence on the details of the template description and fit configuration. At the present stage, the reconstructed results tend to favor a lighter composition, with enhanced proton and light-component fractions and reduced heavy components, whereas the total flux remains broadly compatible with reference expectations. These results support the feasibility of template-based composition reconstruction with KM2A and motivate further refinement of template modeling and fitting strategy toward a more robust composition measurement around the knee.
