Double beta decay

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

Nuclear matrix elements for double-βdecay

“…The theory of 0νββ decay was first formulated by Furry [18] and further developed by Primakoff and Rosen [19], Molina and Pascual [20], Doi et al [1], Haxton and Stephenson [21], and, more recently, by Tomoda [2] and Šimkovic et al [3]. All these formulations often differ by factors of 2, by the number of terms retained in the nonrelativistic expansion of the current and by their contribution.…”

“…The theory of 2νββ decay was developed by Primakoff and Rosen [19], Konopinski [76], Doi et al [1] and Haxton et al [21]. The calculation of 2νββ turns out to be more complex than that of 0νββ.…”

CUORE: a cryogenic underground observatory for rare events

“…(2), could be in the range 0.01 eV to the present bounds [8,10]. Considering this range, could a next generation 0νββ -decay experiment detect it?…”

“…This would violate lepton number conservation (∆L = 2) [1], and would require neutrinos to be Majorana particles. There are many reviews on the subject [2,3,4,5] The decay rate for the process involving the exchange of a Majorana neutrino can be expressed as follows:…”

Double Beta Decay: Theory, Experiment and Implications

“…Double beta decay has been and continues to be a popular topic since first discussed by Maria Goeppert-Meyer in nineteen thirties. There have been numerous earlier reviews, beginning with the "classics" by Primakoff and Rosen [1], Haxton and Stephenson [2] and Doi, Kotani and Takasugi [3], to the more recent ones, often devoted to particular aspects of the ββ decay [4,5,6,7,8,9,10]. Many details are also described in the monograph [11].…”