Search for β+\beta^+EC and ECEC processes in 112^{112}Sn

Limits on $\beta^+$EC (here EC denotes electron capture) and ECEC processes in $^{112}$Sn have been obtained using a 380 cm$^3$ HPGe detector and an external source consisting of 53.355 g enriched tin (94.32% of $^{112}$Sn). A limit with 90% C.L. on the $^{112}$Sn half-life of $4.7\times 10^{20}$ y for the ECEC(0$\nu$) transition to the $0^+_3$ excited state in $^{112}$Cd (1871.0 keV) has been established. This transition is discussed in the context of a possible enhancement of the decay rate by several orders of magnitude given that the ECEC$(0\nu)$ process is nearly degenerate with an excited state in the daughter nuclide. Prospects for investigating such a process in future experiments are discussed. The limits on other $\beta^+$EC and ECEC processes in $^{112}$Sn were obtained on the level of $(0.6-8.7)\times 10^{20}$ y at the 90% C.L.Comment: 14 pages, 4 figure

Probing particle and nuclear physics models of neutrinoless double beta decay with different nuclei

Half-life estimates for neutrinoless double beta decay depend on particle physics models for lepton flavor violation, as well as on nuclear physics models for the structure and transitions of candidate nuclei. Different models considered in the literature can be contrasted - via prospective data - with a "standard" scenario characterized by light Majorana neutrino exchange and by the quasiparticle random phase approximation, for which the theoretical covariance matrix has been recently estimated. We show that, assuming future half-life data in four promising nuclei (Ge-76, Se-82, Te-130, and Xe-136), the standard scenario can be distinguished from a few nonstandard physics models, while being compatible with alternative state-of-the-art nuclear calculations (at 95% C.L.). Future signals in different nuclei may thus help to discriminate at least some decay mechanisms, without being spoiled by current nuclear uncertainties. Prospects for possible improvements are also discussed.Comment: Minor corrections in the text, references added. Matches published version in Phys. Rev. D 80, 015024 (2009

Double electron capture in 156Dy, 162Er and 168Yb

The double electron capture half-lives of 156Dy, 162Er and 168Yb are evaluated using the pseudo SU(3) model, which describes ground and excited bands as well as their B(E2) and B(M1) transition strengths in remarkable agreement with experiment. The best candidate for experimental detection is the decay 156Dy -> 156Gd, with tau{1/2} (0+{gs} --> 0+{gs}) = 2.74 E22 yrs and tau{1/2} (0+{gs} --> 0+{1}) = 8.31 E24 yrs.Comment: 7 pages, 1 figure. Physics Letters B, in pres

Signatures of superconducting gap inhomogeneities in optical properties

Scanning tunneling spectroscopy applied to the high-$T_{c}$ cuprates has revealed significant spatial inhomogeneity on the nanoscale. Regions on the order of a coherence length in size show variations of the magnitude of the superconducting gap of order $\pm20$ or more. An important unresolved question is whether or not these variations are also present in the bulk, and how they influence superconducting properties. As many theories and data analyses for high-$T_{c}$ superconductivity assume spatial homogeneity of the gap magnitude, this is a pressing question. We consider the far-infrared optical conductivity and evaluate, within an effective medium approximation, what signatures of spatial variations in gap magnitude are present in various optical quantities. In addition to the case of d-wave superconductivity, relevant to the high-$T_c$ cuprates, we have also considered s-wave gap symmetry in order to provide expected signatures of inhomogeneities for superconductors in general. While signatures of gap inhomogeneities can be strongly manifested in s-wave superconductors, we find that the far-infrared optical conductivity in d-wave is robust against such inhomogeneity.Comment: 8 pages, 7 figure

Effect of deformation on two-neutrino double beta decay matrix elements

We study the effect of deformation on the two-neutrino double beta decay for ground state to ground state transitions in all the nuclei whose half-lives have been measured. Our theoretical framework is a deformed QRPA based in Woods-Saxon or Hartree-Fock mean fields. We are able to reproduce at the same time the main characteristics of the two single beta branches, as well as the double beta matrix elements. We find a suppression of the double beta matrix element with respect to the spherical case when the parent and daughter nuclei have different deformations

Ефективні епоксидні зв`язуючі і склопластики для відновлення та посилення будівельних конструкцій

A study of the effectiveness of surfactants and organosilicon substances use to improve the technological properties of epoxy binder, adhesion and strength properties and reduce the residual stresses of cured epoxy polymers in order to create an epoxy binder for the manufacture of the fiberglass. The optimal composition has been developed, which allowed to obtain glass-reinforced materials with high deformation and strength properties.Проведено дослідження ефективності застосування поверхнево-активних та кремнійорганічних речовин для покращення технологічних властивостей епоксидного зв’язуючого, адгезійно-міцнісних властивостей та зниження залишкових напружень отверджених епоксиполімерів з метою створення епоксидного зв’язуючого для виготовлення склопластиків. Розроблений оптимальний склад, що дозволив отримати склоармовані матеріали з підвищеними деформаційно-міцнісними властивостями

Double Beta Decay: Historical Review of 75 Years of Research

Main achievements during 75 years of research on double beta decay have been reviewed. The existing experimental data have been presented and the capabilities of the next-generation detectors have been demonstrated.Comment: 25 pages, typos adde

Double beta decay: present status

The present status of double beta decay experiments (including the search for $2\beta^{+}$, EC$\beta^{+}$ and ECEC processes) are reviewed. The results of the most sensitive experiments are discussed. Average and recommended half-life values for two-neutrino double beta decay are presented. Conservative upper limits on effective Majorana neutrino mass and the coupling constant of the Majoron to the neutrino are established as $< 0.75$ eV and $<g_{ee} > < 1.9 \cdot 10^{-4}$, respectively. Proposals for future double beta decay experiments with a sensitivity for the $$ at the level of (0.01-0.1) eV are considered.Comment: 33 pages included 7 figures and 14 tables; an extended version of the invited talk at 13th Lomonosov Conference of Elementary Particle Physics, 23-29 August, 2007, Moscow, Russi