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Published May 1, 1949 | public
Journal Article Open

The energy spectrum of the decay particles and the mass and spin of the mesotron


Energy values determined from curvature measurements of 75 cloud-chamber tracks of decay particles of cosmic-ray mesotrons at sea level, in a magnetic field of 7250 gauss, are here reported. The observed spectrum extends from 9 Mev to 55 Mev with an apparently continuous distribution of intermediate energy values and a mean energy of 34 Mev. The shape of the spectrum and the value of its upper limit are strong evidence that the mesotron disintegrates into an electron and two neutrinos. It is concluded that the mesotron has half-integral spin. The value of the observed upper limit of the energy spectrum corresponds to a mass value of the mesotron equal to 217±4 electron masses.

Additional Information

©1949 The American Physical Society. Received 11 March 1949. We wish to acknowledge the assistance of Dr. E.W. Cowan who provided the counter circuits, and of Mr. Robert C. Hsiao who shared in the operation of the equipment and in the measurements.


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