The Catalysis of Nuclear Reactions by mu Mesons [electronic resource].
- Washington, D.C. : U.S. Atomic Energy Commission, 1956. and Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
- Additional Creators:
- U.S. Atomic Energy Commission and United States. Department of Energy. Office of Scientific and Technical Information
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- Free-to-read Unrestricted online access
- In the course of a recent experiment involving the stopping of negative K mesons in a 10-inch liquid hydrogen bubble chamber, an interesting new reaction was observed to take place. The chamber is traversed by many more negative μ mesons than K mesons, so that in the last 75,000 photographs, approximately 2500 μ⁻ decays at rest have been observed. In the same pictures, several hundred π⁻ mesons have been observed to disappear at rest, presumably by one of the ''Panofsky reactions''. For tracks longer than 10 cm, it is possible to distinguish a stopping μ meson from a stopping π meson by comparing its curved path (in a field of 11,000 gauss) with that of a calculated template. In addition to the normal π⁻ and μ⁻ stoppings, we have observed 15 cases in which what appears (from curvature measurement) to be a μ⁻ meson comes to rest in the hydrogen, and then gives rise to a secondary negative particle of 1.7 cm range, which in turn decays by emitting an electron. (A 4.1-Mev μ meson from π - μ decay has a range of 1.0 cm.) The energy spectrum of the electrons from these 15 secondary particles looks remarkably like that of the μ meson. There are four electrons in the energy range 50 to 55 Mev, and none higher; the other electrons have energies varying from 50 Mev to 13 Mev. The most convincing proof that the primary particle actually comes to rest, and does not--for example--have a large resonant cross section for scattering at a residual range of 1.7 cm, is the following: In five of the 15 special events, there is a large gap between the last bubble of the primary track and the first bubble of the secondary track. This gap is a real effect, and not merely a statistical fluctuation in the spacing of the bubbles, since in some cases the tracks form a letter X, and in another case the secondary track is parallel to the primary, but displaced transversely by about 1 mm at the end of the primary. These real gaps appear also (although perhaps less frequently) between some otherwise normal-looking μ⁻ endings and the subsequent decay electron; they are thought to be the distance traveled by the small neutral mesic atom.
- Published through SciTech Connect., 12/10/1956., "ucrl--3620", Alvarez, L.W.; Crawford, J.A.; Good, M.L.; Bradner, H.; Gow, J.D.; Stevenson, M.L.; Ticho, H.K.; Falk-Vairant, P.; Crawford Jr, F.S.; Hosenfeld, A.R.; Solmitz, F.; Tripp, H.D., and Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
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