Two neutrino double beta decay within the ξ\xi-approximation

We examine the contributions of odd-parity nuclear operators to the two-neutrino double beta decay $0^+\rightarrow 0^+$ amplitude, which come from the $P$-wave Coulomb corrections to the electron wave functions and the recoil corrections to the nuclear currents. Although they are formally of higher order in $\alpha Z/2$ or $v/c$ of the nucleon than the usual Fermi and Gamow-Teller matrix elements, explicit calculations performed within the QRPA show that they are significant when confronted with the experimental data.Comment: 9 pages, latex, no figure

Double beta decay to excited states in Nd150

The pseudo SU(3) model is used to study the double beta decay of Nd150 to the ground and excited states of Sm150 . Low lying collective excitations of Sm150 and its BE(2) intensities are well reproduced. Expressions for the two neutrino double beta decay to excited states are developed and used to describe the decay of Nd150 . The existence of selection rules which strongly restrict the decay is discussed.Comment: 22 pages, LaTeX, 1 figure with Postscript file available under request at [email protected]

Neutrinoless Double Beta Decay in Heavy Deformed Nuclei

The zero neutrino mode of the double beta decay in heavy deformed nuclei is investigated in the framework of the pseudo SU(3) model, which has provided an accurate description of collective nuclear structure and predicted half-lives for the two neutrino mode in good agreement with experiments. In the case of $^{238}U$ the calculated zero neutrino half-life is at least three orders of magnitude greater than the two neutrino one, giving strong support of the identification of the radiochemically determined half-life as being the two neutrino double beta decay. For $^{150}Nd$ the zero neutrino matrix elements are of the order of magnitude of, but lesser than, those evaluated using the QRPA. This result confirms that different nuclear models produce similar zero neutrino matrix elements, contrary to the two neutrino case. Using these pseudo SU(3) results and the upper limit for the neutrino mass we estimate the $\beta\beta_{0\nu}$ half-lives for six nuclei. An upper limit for majoron coupling constant is extracted from the experimental data.Comment: 19 pages, LaTeX, 2 figures not included, availables as poscript files upon reques

Covariant Quantum Dynamical Semigroups: Unbounded generators

A survey of the probabilistic approaches to quantum dynamical semigroups with unbounded generators is given. An emphasis is made upon recent advances in the structural theory of covariant Markovian master equations. The relations with the classical Levy-Khinchin formula are elucidated. As an example, a complete characterizations of the Galilean covariant irreversible quantum Markovian evolutions is given in terms of the corresponding quantum master and Langevin equations. Important topics for future investigation are outlined.Comment: 14 pages,Latex, no figures, submitted to the Semigroup Volume, Group 21, Goslar 199

Synthesis of 5-methyl-1,2,4-triazolo[1,5- a] pyrimidin-7(4 H)-one - A semi-product of the synthesis of antiviral drug triazide® in the conditions of microwave excitation

5-Methyl-1,2,4-triazolo[1,5-a]pyrimidine-7(4H)-one was synthesized (the intermediate product for the syn-thesis of the antiviral drug Triazide®) under microwave radiation. Conversion of the starting reagents to the target product reached 95% due to experimentally selected conditions. © 2019 Author(s)