No abstract

No abstract

The phenomenon of double beta decay is discussed rather fully both from the experimental and from the theoretical point of view, the relation between double beta decay and the possible kinds of inverse beta decay being also briefly treated. A summary of the available experimental data is given, all methods of detection of the various double beta decay processes being considered. The theory of double beta decay, both in the no-neutrino and in the two-neutrino cases, is worked out, ab initio, on the basis of a nucleon-lepton interaction without conservation of parity. It is particularly emphasized that, with a ' twocomponent neutrino ' type nucleon-lepton interaction without conservation of parity, absence of no-neutrino /3p decay does not by itself uniquely imply that neutrino and anti-neutrino are distinguishable and that the total lepton charge is conserved.Comparison of the experimental limits on the double beta decay half-lives with the corresponding theoretical values indicates that two neutrinos are emitted together w-ith two electrons in each double beta decay process-this conclusion is, however, not yet certain and must be confirmed by further experimental work. A treatment is given of the implications of the actual occurrence of two-neutrino rather than no-neutrino double beta decay for the problems of neutrino-anti-neutrino identity and conservation of total lepton charge.It is concluded, on the basis of (i) the available double beta decay, inverse beta decay and muon decay experimental data and (ii) the provisional assumption of the universal applicability of ' two-component neutrino ' type coupling, that a verdict may be tentatively reached in favour of a ' Dirac ' neutrino, operationally distinguishable from a ' Dirac ' anti-neutrino, and with conservation of total lepton charge valid in all neutrino interactions. 9 1 , I N T R O D U C T I O N N the process of double beta decay, the (very long-lived) nucleus ( A , Z ) disintegrates spontaneously to the isobaric nucleus ( A , Z i: 2) with the simultaneous I emission of two electrons-negatrons or positrons-accompanied by either ( U ) two anti-neutrinos or neutrinos, or ( b ) no anti-neutrinos or neutrinos. Alternative to the emission of two positrons, emission of one positron and absorption of one orbital negatron, or absorption of two orbital negatrons, is always possible energetically. T h e existence of double beta decay is expected on general theoretical

No abstract

When particles interact with each other through the intervening mechanism of a field, the description of their dynamical behavior by means of action-at-a-distance potentials is only of an approximate nature. Two-body, three-body, • • •, ra-body potentials may be regarded as successive stages of this approximation; their relative magnitudes are examined systematically for several types of classical and quantized fields, e.g., electromagnetic, mesotron, etc. It is found that the description of electrons in atomic systems by the customary two-body potentials is an excellent approximation; in nuclei, independent of the details of the field, one finds: three-body potentials ~^{Vn/c) X (two-body potentials) • • •, m-body potentials ==(*>» A) m~2 X (two-body potentials), where v n is the average velocity of the heavy particles in the nucleus. The usual description of nuclei in terms of two-body potentials cannot therefore be considered satisfactory, except in the case of the deuteron.