Neutrino-less Double Electron Capture - a tool to research for Majorana neutrinos

The possibility to observe the neutrino-less double $\beta$ decay and thus to prove the Majorana nature of neutrino as well as provide a sensitive measure of its mass is a major challenge of to-day's neutrino physics. As an attractive alternative we propose to study the inverse process, the radiative neutrino-less double electron capture $0 \nu 2EC$. The associated monoenergetic photon provides a convenient experimental signature. Other advantages include the favourable ratio of the $0 \nu 2EC$ to the competing $2\nu 2EC$ capture rates and, very importantly, the existence of coincidence trigger to suppress the random background. These advantages partly offset the expected longer lifetimes. Rates for the $0\gamma 2EC$ process are calculated. High Z atoms are strongly favoured. A resonance enhancement of the capture rates is predicted at energy release comparable to the $2P-1S$ atomic level difference. The resonance conditions are likely to be met for decays to excited states in final nuclei. Candidates for such studies are considered. The experimental feasibility is estimated and found highly encouraging.Comment: New figure added, table updated, physical background discusse

Conditions for detecting CP violation via neutrinoless double beta decay

Neutrinoless double beta decay data together with information on the absolute neutrino masses obtained from the future KATRIN experiment and/or astrophysical measurements give a chance to find CP violation in the lepton sector with Majorana neutrinos. We derive and discuss necessary conditions which make discovery of such CP violation possible for the future neutrino oscillation and mass measurements data.Comment: 15 pages, 4 figures, RevTe

The Single State Dominance Hypothesis and the Two-Neutrino Double Beta Decay of Mo100

The hypothesis of the single state dominance (SSD) in the calculation of the two-neutrino double beta decay of Mo100 is tested by exact consideration of the energy denominators of the perturbation theory. Both transitions to the ground state as well as to the 0+ and 2+ excited states of the final nucleus Ru100 are considered. We demonstrate, that by experimental investigation of the single electron energy distribution and the angular correlation of the outgoing electrons, the SSD hypothesis can be confirmed or ruled out by a precise two-neutrino double beta decay measurement (e.g. by NEMO III collaboration).Comment: 13 pages, RevTex, 1 figur

Diagnosis of infections in newborns using a new particle-mediated immunoassay for serum C-reactive protein

C-reactive protein (CRP) levels were measured using a new particle-mediated immunoassay. Tests for precision and linearity of this method gave satisfactory results. The minimum sensitivity of the assay was 1 ng/ml. Interference by bilirubin (<220mg/l) and haemoglobin (<20g/l) was not observed. Using this method, CRP was assayed as a means of monitoring for infection in newborns up to 72 h after delivery. The pattern of time course elevation curves was similar for both groups (10 healthy subjects and 26 patients), but the serum CRP (ng/ml) of infected newborns rose significantly higher than in healthy subjects at 24 h after birth. The rate of increase of CRP (∆CRP; ng/ml/h) may be a more useful parameter to detect infection, since a significant change in ∆CRP was apparent only 12 h after birth. The reported method was reliable and the parameters obtained were considered clinically useful for early detection of infection

Shell Model Study of the Double Beta Decays of 76^{76}Ge, 82^{82}Se and 136^{136}Xe

The lifetimes for the double beta decays of $^{76}$Ge, $^{82}$Se and $^{136}$Xe are calculated using very large shell model spaces. The two neutrino matrix elements obtained are in good agreement with the present experimental data. For $<1$ eV we predict the following upper bounds to the half-lives for the neutrinoless mode: $T^{(0\nu)}_{1/2}(Ge) > 1.85\,10^{25} yr.$, $T^{(0\nu)}_{1/2}(Se) > 2.36\,10^{24} yr.$ and $T^{(0\nu)}_{1/2}(Xe) > 1.21\,10^{25} yr$. These results are the first from a new generation of Shell Model calculations reaching O(10$^{8}$) dimensions

Constraining Almost Degenerate Three-Flavor Neutrinos

We discuss constraints on a scenario of almost degenerate three-flavor neutrinos imposed by the solar and the atmospheric neutrino anomalies, hot dark matter, and neutrinoless double $\beta$ decays. It is found that in the Majorana version of the model the region with relatively large $\theta_{13}$ is favored and a constraint on the CP violating phases is obtained.Comment: 19 pages (uses revtex), including 6 figures (uses epsf

Neutrinoless Double Beta Decay within QRPA with Proton-Neutron Pairing

We have investigated the role of proton-neutron pairing in the context of the Quasiparticle Random Phase approximation formalism. This way the neutrinoless double beta decay matrix elements of the experimentally interesting A= 48, 76, 82, 96, 100, 116, 128, 130 and 136 systems have been calculated. We have found that the inclusion of proton-neutron pairing influences the neutrinoless double beta decay rates significantly, in all cases allowing for larger values of the expectation value of light neutrino masses. Using the best presently available experimental limits on the half life-time of neutrinoless double beta decay we have extracted the limits on lepton number violating parameters.Comment: 16 RevTex page

A New Class of Majoron-Emitting Double-Beta Decays

Motivated by the excess events that have recently been found near the endpoints of the double beta decay spectra of several elements, we re-examine models in which double beta decay can proceed through the neutrinoless emission of massless Nambu-Goldstone bosons (majorons). Noting that models proposed to date for this process must fine-tune either a scalar mass or a VEV to be less than 10 keV, we introduce a new kind of majoron which avoids this difficulty by carrying lepton number $L=-2$. We analyze in detail the requirements that models of both the conventional and our new type must satisfy if they are to account for the observed excess events. We find: (1) the electron sum-energy spectrum can be used to distinguish the two classes of models from one another; (2) the decay rate for the new models depends on different nuclear matrix elements than for ordinary majorons; and (3) all models require a (pseudo) Dirac neutrino, having a mass of a several hundred MeV, which mixes with $\nu_e$.Comment: 43 pages, 10 figures (included), [figure captions are now included