Chronology of Milestone Events in Particle Physics - PANOFSKY 1951
Chronology of Milestone Events in Particle Physics


Panofsky, W.K.H.; Aamodt, R.L.; Hadley, J.;
The Gamma-Ray Spectrum Resulting from Capture of Negative Mesons in Hydrogen and Deuterium
Phys. Rev. 81 (1951) 565;

Reprinted in
The Physical Review - the First Hundred Years, AIP Press (1995) 824.

mesons produced in an internal wolfram target bombarded by 330 MeV protons in the l84-inch cyclotron are absorbed in a high pressure hydrogen target. The resulting gamma-ray spectrum is analyzed outside the shielding of the cyclotron by means of a 30-channel electron-positron pair spectrometer. The principal results are as follows.
(1) The gamma-rays result from two competing reactions: p n and p n o; o 2.
(2) The ratio between the 0 yield to the single gamma-ray yield is =0.944 0.20.
(3) The mass difference between the meson and the o meson is given by 10.6 2.0 electron masses.
(4) The mass is 275.2 2.5 electron masses.
The large mass difference between and o precludes the conclusion that the unexpectedly small o to ratio is due to the small amount of momentum space available for o emission. It rather indicates that o emission is slowed down by the nature of the coupling of the o field to the nucleons. The experiment has been repeated by substituting D2 for H2 in the vessel. The result is that the reaction deuteron 2n and deuteron 2n compete in the ratio 2 : 1. The reaction deuteron 2n o is absent.

Accelerator LBL-CYC-184IN Detectors SPEC

Related references
More (earlier) information appears in
W. K. H. Panofsky, R. L. Aamodt, and H. F. York, Phys. Rev. 78 (1950) 825;
J. Steinberger, W. K. H. Panofsky, and J. Steller, Phys. Rev. 78 (1950) 802;
See also
F. Adelman and S. B. Jones, Science 111 (1950) 226;
W. Cheston and L. Goldfarb, Phys. Rev. 78 (1950) 320A;
W. K. H. Panofsky, Post Deadline Paper, New York Meeting A.P.S. (1950);
W. B. Fretter, Phys. Rev. 73 (1948) 41;
W. B. Fretter, Phys. Rev. 76 (1949) 216;
C. Y. Chao, Phys. Rev. 75 (1949) 581;
B. P. Gregory, B. Rossi, and J. Tinlot, Phys. Rev. 77 (1950) 299;
M. F. Kaplon, B. Peters, and H. L. Brandt, Phys. Rev. 76 (1949) 1735;
A. G. Carlson, J. E. Hooper, and D. T. King, Phil. Mag. 41 (1950) 701;
Manon, H. Muirhead, and Rachat, Phil. Mag. 41 (1950) 583;
M. Conversi, E. Pancini, and O. Piccioni, Phys. Rev. 68 (1945) 232;
R. Bjorklund et al., Phys. Rev. 77 (1950) 213;

  p n p, mass, cs
  p n 2 p, mass, cs
  deuteron 2n p
  deuteron 2n p
  deuteron 2n o p
  o 2

Particles studied
  o ex, mass

Record comments
Confirmation of the o and o decay. Direct determination of the parity.
  New Comments List of Comments NY