CXXIII. Observations on the multiple scattering of ionizing particles in photographic emulsions.— Part V . Scattering measurements on tracks of slow protons

Abstract

The scattering constant has been determined by measurements of the multiple scattering along proton tracks ending in the emulsion. A value of 27·8±0·5 has been obtained (for β ²∼0·03 and an average cell-size of 72 µ). A simple method involving the combined measurements of multiple scattering and residual range has been used to identify the particles. A parameter was determined for each track (R being the range in microns and the mean angle of multiple scattering—per 100 μ—measured along the faster half of the trajectory); P is a linear function of the logarithm of the mass of the particle. A scale of values of P has been calibrated experimentally using tracks of protons from artificial sources and those of σ-mesons. Using this method tracks of 83 protons have been identified amongst a group of 136 particles of charge |e| ejected from cosmic ray stars. The mean value of P for the 83 protons was found to be 4·275±0.013. The resolution between τ-mesons, protons, deuterons and tritons was found to be satisfactory. An appendix gives the coupling matrix calculated for the sagitta method, taking into account the loss of energy.