Archive of historical materials
Note: On the Heavy Quantum Hypothesis and Observed Cosmic Ray
OU1937-A2 (6 pages) Date: None
In this note, Yukawa attempted to determine whether his hypothesis of heavy quanta was correct based on the experimental data. What was then called a “heavy quantum” was later called a meson. It is a particle with the mass that is about halfway between the mass of an electron and that of a proton. In 1936, Neddermeyer and Anderson discovered “new particles” when observing cosmic rays using a cloud chamber. Immediately after that, Street and Stevenson captured the tracks of the new particles. In this note, Yukawa analyzes the paper announced by Street and Stevenson before starting his in-depth examination. The new particle was later found to be a muon (mu particle), but it could not be distinguished from Yukawa’s heavy quantum at that time.
Yukawa determined the mass of the particle discovered in the cosmic ray observation was 200 times the mass of an electron, and calculated the energy loss and the degree of bend caused by the magnetic field. As you can see from pages 2, 3 and 4, the calculations are written on exam answer sheets used by the School of Science, Osaka Imperial University. In those years when desktop calculators nor computers had not been developed yet, Yukawa performed the calculations by hand and organized the relationship between track radius and energy into a table. Pages 3 and 4 are filled only with the hand-performed calculations to obtain the necessary data. (Written by Yutaka Hosotani)
