ESTIMATE OF THE PRIMARY COSMIC-RAY COMPOSITION FROM A MULTI-PARAMETRIC FIT OF MACRO MULTIMUON EVENTS

Multimuon data from the MACRO experiment at Gran Sasso have been analy sed using a new method which allows one to estimate the primary cosmic ray fluxes. The estimated all-particle spectrum is higher and flatter than the one obtained from direct measurements but is consistent with EAS measurements. The average mass number shows a weak dependence on the primary energy below 10(6) GeV. Even within large uncertainties ou r data support a possible increase of the average mass number at highe r energies.