was evinced. It was concluded that the half-life obtained was due to pileup of pulses with lower energy; such pileup should display a half-life of one-half the 7.7-min half-life.The lack of an observed internal conversion line indicates that the 0+, T=l level 2 probably lies above the 7=3, T-0 level. This would require a positron end point for the 0.95-sec activity in K 38 of energy > 4.84 Mev. In any case the above argument indicates that the energy of the transition is greater than 4.76 Mev.
CONCLUSIONSThe experimental results reported in this paper together with the half-life measurement of Kline andWe report a comprehensive series of measurements made on the masses of L-mesons produced by the 184-inch cyclotron. A general ratio principle of measurement is employed which largely eliminates systematic errors. The particular method that we have developed is described in detail. The theory of nonequilibrium particle orbits in the cyclotron field is worked out to provide formulas from which momenta may be calculated, and to obtain the momentum distribution functions determined by the target and detector dimensions. The energy-loss processes in nuclear track emulsion, which is used as a stopping material and detector, are studied and the range-momentum exponent q is found. Several small corrections to the mean range are made. A number of range straggling effects are evaluated. The theoretical distribution of the quantity Rp~q (R being the range and p the momentum) is studied, and the first three moments of the distribution are calculated explicitly. The distribution is found to be closely gaussian. From the theory of the distribution of Rp~g, the best estimate and the statistical uncertainty of the mass ratio (e.g., of meson to proton) are evaluated. A number of effects influencing the ratio are studied, but all the corrections found are very small. The * This work was done under the auspices of the U. S. Atomic Energy Commission. 1 Many of the earlier measurements are reviewed in: J. A. ); Koslov, Fitch, and Rainwater, Phys. Rev. 95, 625 (A) (1954); Camac, Piatt, and Schulte, Phys. Rev. 89, 905 (A) (1953); 88, 134 (1952); A. D. McGuire et al., Phys. Rev. 95, 625 (1954).
The contributions to the range variance in nuclear track emulsion have been studied and the magnitude of the various effects calculated. Bohr straggling is found to be the most important effect when the energyis high, but for slow particles, a number of others combine to dominate the straggling. Range errors caused by distortion are also studied. Measurements are reported on the straggling of eighteen particle groups consisting of protons, pions, and muons. With the particle mass and velocity as variable parameters, the theoretical estimates are tested and a detailed accounting of the contributions to the straggling is made.
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