Solar neutrinos can interact with the source isotope in neutrinoless double beta decay experiments through charged current and neutral current interactions. The charged-current product nucleus will then beta decay with a Q-value larger than the doubl
e beta decay Q-value. As a result, this process can populate the region of interest and be a background to the double beta decay signal. In this paper we estimate the solar neutrino capture rates on three commonly used double beta decay isotopes, uc{76}{Ge}, uc{130}{Te}, and uc{136}{Xe}. We then use the decay scheme of each product nucleus to estimate the possible background rates in those materials. As half-life sensitivities in future experiments approach $10^{28}$ y, this background will have to be considered.
Neutrinoless double beta decay, which is a very old and yet elusive process, is reviewed. Its observation will signal that lepton number is not conserved and the neutrinos are Majorana particles. More importantly it is our best hope for determining t
he absolute neutrino mass scale at the level of a few tens of meV. To achieve the last goal certain hurdles have to be overcome involving particle, nuclear and experimental physics. Nuclear physics is important for extracting the useful information from the data. One must accurately evaluate the relevant nuclear matrix elements, a formidable task. To this end, we review the sophisticated nuclear structure approaches recently been developed, which give confidence that the needed nuclear matrix elements can be reliably calculated. From an experimental point of view it is challenging, since the life times are long and one has to fight against formidable backgrounds. If a signal is found, it will be a tremendous accomplishment. Then, of course, the real task is going to be the extraction of the neutrino mass from the observations. This is not trivial, since current particle models predict the presence of many mechanisms other than the neutrino mass, which may contribute or even dominate this process. We will, in particular, consider the following processes: (i)The neutrino induced, but neutrino mass independent contribution. (ii)Heavy left and/or right handed neutrino mass contributions. (iii)Intermediate scalars (doubly charged etc). (iv)Supersymmetric (SUSY) contributions. We will show that it is possible to disentangle the various mechanisms and unambiguously extract the important neutrino mass scale, if all the signatures of the reaction are searched in a sufficient number of nuclear isotopes.
