Current experiments to determine the chemical composition and energy spectra of primary-cosmic-ray nuclei around ${10}^{14}$ eV maximize collecting power by using thin calorimeters of large area that measure primarily the electromagnetic fraction of the energy released when the nucleus interacts. Estimates of this fraction are model-dependent and differ by nearly a factor of 2 for a range of reasonable models. We discuss the consequences of this for composition studies using emulsion chambers.

• Received 7 March 1983

DOI:https://doi.org/10.1103/PhysRevD.28.464