Search

We study a possibility of generation of the neutrino masses by a quark condensate resulting from a spontaneous break-down of the chiral symmetry. The existence of exotic scalar interactions between Majorana neutrinos and quarks in vacuum as well as in nuclear medium gives rise to a Majorana mass matrix. We construct the Majorana mass matrix and set limits on coupling constants of the exotic scalar interactions based on experiments searching for the neutrinoless double-beta decay.We study a possibility of generation of the neutrino masses by a quark condensate resulting from a spontaneous break-down of the chiral symmetry. The existence of exotic scalar interactions between Majorana neutrinos and quarks in vacuum as well as in nuclear medium gives rise to a Majorana mass matrix. We construct the Majorana mass matrix and set limits on coupling constants of the exotic scalar interactions based on experiments searching for the neutrinoless double-beta decay.

Within left-right symmetric model a generalization of the Majorana neutrino mass for the case of light and and heavy neutrinos is introduced and analyzed. Further, current status of calculation of the neutrinoless double beta decay matrix elements is shortly reviewed. An important connection between them and matrix element of double Gamow-Teller operator is established. A new way of fixing quenching of axial-vector coupling constant gA is presented.

The fundamental importance of searching for neutrinoless double-beta decay (0νββ-decay) is widely recognized. Observation of the decay would tell us that the total lepton number is not conserved and that, consequently, neutrinos are massive Majorana fermions. A brief history of the double-beta decay is presented. The 0νββ-decay is discussed in context of neutrino oscillation data. The perspectives of the experimental 0νββ-decay searches are analyzed. The importance of reliable determination of the 0νββ-decay nuclear matrix elements is pointed out. The problem of distinguishing of the light-neutrino exchange, heavy-neutrino exchange and the trilinear R-parity breaking supersymmetric (\(\not R_p \) SUSY) mechanisms of the 0νββ-decay is addressed. Further, the process of resonant neutrinoless double-electron capture (0νɛɛ) is revisited. Arguments are presented that an experimental search for the 0νɛɛ might be feasible.

The role of the nucleon weak magnetism and pseudoscalar coupling interactions in the calculation of the 2β0v-decay of48Ca mediated by heavy Majorana neutrinos has been examined. The effect of a finite nucleon size has been taken into account by employing the phenomenological form factors and form factors calculated in the framework of the quark confinement model. By using the PCAC predictions it has been found that by taking into account these interactions the absolute values of the 2β0v-decay matrix elements of48Ca reduces considerably, which provides us with less stringent limits on the parameter of the non-conservation of the lepton charge.

Already long time ago the shape of the electron spectrum in β‐decays of 3H and 187Re has been recognized as an important tool for understanding of neutrino masses. The sensitivity of KATRIN (in preparation, tritium β‐decay) and the MARE (under consideration, 187Re β‐decay) experiments to neutrino mass will reach the sub eV domain. In view of this experimental progress there is a request for a highly accurate theoretical description of the electron endpoint spectra. By taking the advantage of the elementary particle treatment of 3H and 3He the relativistic form for β‐decay endpoint spectrum of tritium is obtained by taking into account also the effect of nuclear recoil. Further, the currently unknown shape of the electron spectrum for the β‐decay of 187Re is presented. It is found that the first forbidden 187Re(5/2+)→187Os(1/2−)β‐decay transition is accompanied with emission of mostly p3/2‐state electrons.

Alternative approaches to the calculation of two-neutrino double beta decay amplitudes are suggested which include neither the evaluation of the intermediate nucleus spectrum nor the closure approximation.