Measurement with emulsion

Grain density and range in emulsions :

In principle, one of the simplest methods of determining the mass of a charged particle is to compare the grain density in its track with that of a proton. The range of two particles of the same charge and velocity are proportional to their mass. The range is proportional to the kinetic energy of the particle, and the kinetic energy depend on the mass of particle and its velocity). 

Observations of tracks-density and range made on tracks recorded in a stack of stripped emulsions