Street, J.C.; Stevenson, E.G.; Penetrating Corpuscular Component of the Cosmic Radiation
Phys. Rev. 51 (1937) 1005;
The confirmation of the validity of the Heitler theory of radiation and pair formation both by energy loss measurements (Anderson and Neddermeyer, Phys. Rev. 50 (1936) 263) and by the nature of shower formation (Carlson and Oppenheimer, Phys. Rev. 51 (1937) 220) leaves no explanation for the penetrating corpuscular rays except to assume that they are protons. However, the evidence against protons is strong. (C. G. and D. D. Montgomery, Phys. Rev. 51 (1937) 220) To investigate
the penetrating rays a vertical column was set up as follows: a counter, 10 cm Pb, a second counter, a cloud chamber in a magnetic field, a third and fourth counter, 3 cm Pb, and finally a cloud chamber containing 3 separated lead plates 1 cm thick. The counter telescope selected particles directed toward the visible region of the lower chamber where their absorption and shower production was observed. The distribution of the particles with respect to range and H
values was as follows: tabularcccc & & Fraction & Fraction cr & % of & with range & with range cr H x 10-6 & total tracks & > 3 cm Pb & > 6 cm Pb cr > 5 & 49& 1 & 1 cr 2.5 to 5 & 19 & .9& .7 cr 1.5 to 2.5 & 23 & .9 & .7 cr 0.7 to 1.5 & 9 & .7 & .3 cr tabular Only a single shower has been observed in 500 traversals of 1 cm of lead. The ionization density of protons with H < 2.5 x 106
distinguishes them, and two were observed. From the data in the table it is evident that the penetrating particles cannot be described as electrons obeying the Heitler theory nor can an appreciable fraction be protons.
Related references See also C. D. Anderson and S. H. Neddermeyer, Phys. Rev. 50 (1936) 263;
C. G. Montgomery and D. D. Montgomery, Phys. Rev. 50 (1936) 975;
J. F. Carlson and J. R. Oppenheimer, Phys. Rev. 51 (1937) 220;
Confirmation of the muon existence.