Double-beta decay in gauge theories

Abstract

Abstract. Neutrinoless double beta decay is a very important process both from the particle and nuclear physics point of view. From the elementary particle point of view it pops up in almost every model. In addition to the traditional mechanisms, like the light neutrino mass, λ and η terms etc we can have direct R-parity violating supersymmetric (SUSY) contributions. In any case its observation will severely constrain the existing models and will signal that the neutrinos are massive Majorana particles. From the nuclear physics point of view it is challenging, because: 1) The relevant nuclei have complicated nuclear structure.2) The energetically allowed transitions are exhaust a small part of all the strength. 3) One must cope with the short distance behavior of the transition operators, especially when the intermediate particles are heavy (eg in SUSY models). Thus novel effects, like the double beta decay of pions in flight between nucleons, have to be considered. 4) The intermediate momenta involved are about 100 M eV /c. Thus one has to take into account possible momentum dependent terms in the nucleon current. We find that, for the mass mechanism, such modifications of the nucleon current for light neutrinos reduce the nuclear matrix elements by about 25%, almost regardless of the nuclear model. In the case of heavy neutrino the effect is much larger and model dependent. Taking the above effects into account, the availabe nuclear matrix elements for the experimentally interesting nuclei A = 76, 82, 96, 100, 116, 128, 130, 136 and 150 and the presently available experimental limits on the half-life of the 0νββ-decay we have extracted the following

The exotic double-charge exchange μ−→e+ conversion in nuclei

“…2) The process is mediated by pions in flight between the two interacting nucleons. Then one distinguishes two possibilities [3,39]:…”

“…The particular expression holds, if the nucleon is assumed to have a finite size adequately described [26] by a dipole shape form factor with characteristic mass m A taking the value m A = 0.85GeV /c 2 2) The process is mediated by pions in flight between the two interacting nucleons. Then one distinguishes two possibilities [3,39]:…”

DOUBLE BETA DECAY

“…There were numerous earlier reviews of ββ decay, including the classics by Primakoff & Rosen (19), Haxton & Stephenson (20), and Doi, Kotani & Takasugi (21). More recent reviews, besides (1), include those by Boehm & Vogel (22) (where the phase-space integrals are listed), Suhonen & Civitarese (23) (which deals mostly with the nuclear matrix elements), Faessler & Šimkovic (24), Vergados (25), and Klapdor-Kleingrothaus (26). A rather complete list of experimental data can be found in the papers by Tretyak and Zdesenko (27,28).…”

Warm Dark Matter Sterile Neutrinos in Electron Capture and Beta Decay Spectra

“…In the next section we shall also consider integrated rates over particular energy ranges, which can be calculated numerically from Eq. (15). A convenient compact analytical expression of the integrated rate can be obtained from Eq.…”

“…Neutrinos in the keV mass scale open the possibility to detect warm dark matter in nuclear electron capture and beta decay. Heavier sterile neutrinos cannot be produced in weak nuclear decays, and there are of course many other candidate particles for DM unconnected in principle to weak nuclear processes, such as the lightest supersymmetric particles [15].…”