I. Some remarks on the V-particles. Offprint from: Physical Review, Vol. 86, 1 June 1952. [With:] II. (With R. JOST). Selection rules imposed by charge conjugation and charge symmetry. Offprint from: Physical Review, Vol. 87, 1 September 1952. [With:] III. Isotopic spin and mass quantization. Offprint from: Physica, Vol. 19, 1953. THE 'PERIODIC TABLE' FOR ELEMENTARY PARTICLES

PAIS, Abraham

A propos de cet article

First edition, very rare offprints, of the classification of elementary particles, analogous to the periodic table for the classification of elements. "After the war, physicists began to discover new types of particles in cosmic-ray showers . . . These unstable particles had decay lifetimes much longer than would be expected from their high production rates. They were initially dubbed 'V' or 'strange' particles: 'V' because of the forked tracks they made in cloud chambers, 'strange' because they were easily produced but took longer than expected to decay . . . Pais's attention was riveted by a paper published in 1950 that described 34 cloud-chamber photographs of strange particles, confirming earlier observations that 'new unstable neutral and charged particles exist.' Startled by the news, Pais was thrilled to behold another, improved chance to put into practice his intuition that particles could be grouped into families . . . The conventional approach to organizing particles was to look for selection rules, or limitations on a particle's behavior imposed by the need to conserve a certain quantity. The conserved quantity was then usually referred to as a quantum number. Instead of seeking selection rules that were always satisfied, Pais decided to look for rules that applied only in certain cases or for certain forces. 'Thus I looked for selection rules which would hold for strong and electromagnetic but not for weak processes'. He wrote, 'the search for ordering principles at this moment may ultimately have to be likened to a chemist's attempt to build up the periodic system if he were only given a dozen odd elements' [I.]. This insight, which expanded and transformed the notion of a selection rule, 'marks the birth of theoretical particle physics'. In 1951 Pais found such a principle: that 'the new particles interact strongly only when pairs of them are involved, but weakly when interacting alone'. An implication was that strange particles came in pairs, a phenomenon known as 'associated production.' The experimental case was weak, and several colleagues told him he was simply wrong. Still, Pais described his idea at the Institute and at the Second Rochester Conference in 1952 . . . Pais presciently observed that physicists may be witnessing 'the unfolding of an ordering in which one talks of families of elementary particles rather than of elementary particles themselves'. Pais's paper containing this insight appeared in 1952 [I.]. The idea of associated production was confirmed by the end of the next year with experiments at the cosmotron (a high-energy accelerator at Brookhaven National Laboratory that was the first machine able to recreate the energies of cosmic rays in huge quantities and in the confines of the laboratory). After the Second Rochester Conference, Pais collaborated with Jost in exploring the link between selection rules, symmetries, and group theory, or the mathematical encoding of invariances and symmetries [II.]. 'Now the possibility dawned on me to try to give that new rule a group theoretical foundation'. One group, known as 'isospin,' was already known in nuclear physics as applied to protons and neutrons. Pais decided to try to expand that group to look for a bigger one - to look for a 'higher symmetry' - that would involve a new quantum number; it would have to hold for strong and electromagnetic interactions but be violated in the weak interaction [III.]. This was the first introduction of the concept of a higher symmetry in physics, an expansion of physicists' quest for invariances into a new domain. In the same paper Pais also proposed that 'the element of space-time is not a point but it is a manifold,' which brought into physics an idea that (unknown to Pais) mathematicians already knew under the name 'fibre bundles'" (Crease, Abraham Pais 1918-2000, National Academy of Sciences, 2011). 3 offprints, 8vo, pp. 663-672; 871-875; 869-887. Original printed wrappers (I) and self-wrappers (II, III).

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Détails bibliographiques

• Titre: I. Some remarks on the V-particles. Offprint from: Physical Review, Vol. 86, 1 June 1952. [With:] II. (With R. JOST). Selection rules imposed by charge conjugation and charge symmetry. Offprint from: Physical Review, Vol. 87, 1 September 1952. [With:] III. Isotopic spin and mass quantization. Offprint from: Physica, Vol. 19, 1953. THE 'PERIODIC TABLE' FOR ELEMENTARY PARTICLES
• Reliure: Soft cover
• Édition: 1st Edition
• État de l'article: Near Fine