The urge and the interest to find those ultimate elements in terms of which everything else is made of are almost as old as the human civilization. However, as our knowledge increases what were thought to be elementary may turn out to be composites. Consequently, the class of these supposedly fundamental elements changes with time. Such was, for example, the periodic table of atoms in the last century. Today we know that all different molecules, atoms, and nuclei are complexes resulting from the existence and the interactions of some thirty particles which are called “elementary particles”.
REFERENCES
1.
An interesting and personal account of this discovery was given by Thomson in his book Recollections and Reflections (G. Bell and Sons, Ltd., 1936).
2.
3.
4.
5.
H. Weyl, Gruppentheorie und Quantenmechanik (1931), 2nd ed., p. 234.
6.
7.
Compare also Blackett and Occhialini,
Proc. Roy. Soc.
A139
, 699
(1933
).8.
9.
The antiproton was first observed by
Chamberlain
, Segrè
, Wiegand
, and Ypsilantis
, Phys. Rev.
100
, 947
(1955
).The antineutron was first observed by
Cork
, Lambertson
, Piccioni
, and Wenzel
, Phys. Rev.
104
, 1193
(1956
).10.
Proceedings of Solvay Congress, Brussels (1933). While the possible existence of a neutral particle in beta decay was first suggested by Pauli at the American Physical Society Meeting in Pasadena in 1931, serious discussions of its existence and its properties did not appear in any literature until 1933.
11.
12.
For a detailed discussion of these experiments see, e.g., C. S. Wu, The Neutrino, Memorial Volume to Wolfgang Pauli (Pergamon Press, 1960)
and J. S. Allen, The Neutrino (Princeton University Press, 1958).
13.
Cowan
, Reines
, Harrison
, Kruse
, and McGuire
, Science
124
, 103
(1956
).14.
15.
16.
17.
Convincing evidence of this was given by the experiment done by
Conversi
, Pancini
, and Piccioni
, Phys. Rev.
71
, 209
(1947
);and by the theoretical analysis made by
Fermi
, Teller
, and Weisskopf
, Phys. Rev.
71
, 314
(1947
)18.
19.
Such possibilities have been discussed theoretically, prior to the discovery of π meson, by
Sakata
and Ionue
, Progr. Theoret. Physics (Kyoto)
1
, 143
(1946
)20.
21.
22.
Brown
, Camerini
, Fowler
, Muirhead
, Powell
, and Ritson
, Nature
163
, 47
(1949
).23.
For a detailed list of references of these discoveries see e.g.,
Franzinetti
and Morpurgo
, Nuovo cimento Supplement
6
, No. 2
, 469
(1957
).24.
25.
26.
27.
28.
Alvarez
, Eberhard
, Good
, Grazino
, Ticko
, and Wojcicki
, Phys. Rev. Letters
2
, 215
(1959
).29.
The λ̄ particle was first observed by
Prowse
and Baldo Ceolin
, Nuovo cimento
10
, 635
(1958
).30.
In Fig. 3 (and also in Table 2) it is shown that, unlike the neutral π meson, the particle is different from its antiparticle This was first predicted by
Gell‐Mann
and Pais
, Phys. Rev.
97
, 1387
(1955
).Furthermore, it can be shown that these two neutral particles, and possess some extremely interesting properties. For example, a particle once produced may later change automatically into its antiparticle Such unusual conversions have recently been observed by
Muller
, Birge
, Fowler
, Good
, Hirsch
, Matsen
, Oswald
, Powell
, White
, and Piccioni
, Phys. Rev. Letters
4
, 418
(1960
).31.
32.
33.
Wu
, Ambler
, Hayward
, Hoppes
, and Hudson
, Phys. Rev.
105
, 1413
(1957
).34.
35.
36.
The possibility of a two‐component relativistic theory of a spin particle was first discussed by
H.
Weyl
, Z. Physik
56
, 330
(1929
).However, in such a theory parity is not manifestly conserved; therefore it was always rejected before the discovery of right‐left asymmetry. (Cf. W. Pauli, Handbuch der Physik, Verlag Julius Springer, Berlin, 1933, Vol. 24, pp. 226–7.)
The possible use of this two‐component theory for expressing the nonconservation property of parity in neutrino processes was independently considered by
Lee
and Yang
, Phys. Rev.
105
, 1671
(1957
);37.
The first conclusive proof that neutrino behayes like a left‐hand screw (and not like a right‐hand screw) was given by
Goldhaber
, Grodzins
, and Sunyar
, Phys. Rev.
109
, 1015
(1958
).38.
39.
C. N.
Yang
, International Congress on Theoretical Physics, Seattle, 1956, Revs. Modern Phys.
29
, 231
(1957
);This possibility was also considered by
L.
Landau
, Nuclear Phys.
3
, 127
(1957
),See also footnote (9) of an earlier paper by
Wick
, Wightman
, and Wigner
, Phys. Rev.
88
, 101
(1952
).40.
See also the discussions by Serber and Oppenheimer in the Proceedings of Solvay Congress, Brussels (1948).
41.
More recent analysis on Universal Fermi Interactions were made by
Feynman
and Gell‐Mann
, Phys. Rev.
109
, 193
(1958
);42.
43.
Laotse, Tao Té Chin, p. 1 (about 550 B. C.).
This content is only available via PDF.
© 1960 American Institute of Physics.
1960
American Institute of Physics
You do not currently have access to this content.