xi Particle Physics.
(saɪ, zaɪ, ksaɪ, gzaɪ)
[Gr. ξεῖ, ξῖ, name of the fourteenth letter (ξ, ξ) of the Greek alphabet.]
Either of a pair of hyperons (and their antiparticles) having a mass of approximately 1320 MeV, spin of ½, hypercharge -1, isospin ½, and even parity, which on decaying usually produce a lambda particle and a pion. Freq. represented by ξ. Usu. attrib.
| 1954 Gell-Mann & Pais in Proc. Glasgow Conf. Nucl. & Meson Physics (1955) 344 It is interesting to consider the ‘cascade particle’, which we shall call ξ- and which has the decay scheme ξ- →λ0 + π- + (∼ 65 MeV). 1964 New Scientist 20 Feb. 460/3 According to the conservation of baryons and hypercharge, the omega-minus should be produced in collisions between K-minus mesons and protons and should decay (weakly, with a change of hypercharge) to a xi-particle and pion, or to a lambda-particle and K-minus. 1974 Nature 13 Dec. 524/1 The elementary particles nearly obey a number of simple and elegant symmetry rules. Many useful approximate calculations can be made assuming that the symmetries are perfect—for instance..by assuming that the proton and neutron have the same interactions as the lambda, sigma and xi hyperons. 1980 J. S. Trefil From Atoms to Quarks vii. 109 There are two xi particles, one neutral and one with a negative charge. |