[en] A collection of stories is presented on discoveries of 2β decay (including neutrinoless one) which were refuted in the subsequent investigations.

[en] The demands of the future high sensitivity 2β decay experiments (aiming to observe the neutrinoless 2β decay or to advance restrictions on the neutrino mass to m_ν ≤ 0.01 eV) are considered and requirements for their sensitivity and discovery potential are formulated. The most realistic 2β projects are reviewed. Only those with high energy resolution would completely satisfy these severe requirements. At the same time, most of the recent projects (CAMEO, CUORE, DCBA, EXO, etc.) could certainly advance the limit on the neutrino mass to m_ν ≤ 0.05 eV

[en] The double beta decay experiment NEMO-3 has taken data from February 2003 to January 2011. The two-neutrino decay half lives were measured for seven different isotopes (¹⁰⁰Mo, ⁸²Se, ¹¹⁶Cd, ¹⁵⁰Nd, ⁹⁶Zr, ⁴⁸Ca and ¹³⁰Te). No evidence for neutrinoless double beta decay is observed. The 0νββ half-life limits are found to be T_1/2^0ν(¹⁰⁰Mo)>1.0×10²⁴yr(90%C.L.) and T_1/2^0ν(⁸²Se)>3.2×10²³yr(90%C.L.)

[en] The double beta decay experiment NEMO-3 has compleated data taking in January 2011. The aim of the experiment is to search for the neutrinoless double beta decay and investigate the two-neutrino double beta decay in seven different isotopes (¹⁰⁰Mo, ⁸²Se, ¹¹⁶Cd, ¹⁵⁰Nd, ⁹⁶Zr, ⁴⁸Ca and ¹³⁰Te). After analysis of the most part of available data corresponding to 4.5 yr no evidence for 0νββ decay in ¹⁰⁰Mo and ⁸²Se is found. The half-life limits at 90% C.L. are 1.0x10²⁴ yr and 3.2x10²³ yr respectively. The two-neutrino decay half live values were precisely measured for all investigated isotopes.

[en] A programme which uses Monte-Carlo method for simulation of neutron and gamma-ray movement in the shielding for NEMO-3 experiment is described. As shielding materials Fe and Pb with different thickness were used. It was found that suppression coefficient for thermal neutrons can be about 10⁶ and for gamma-quanta it reaches 10³

[en] Very few exactly solvable models of the two-particle systems with relativistically invariant interaction are know at present. They include the circular motion solutions for interactions described by the Fokker-type action integrals, and the one-dimensional motions

[en] The authors propose an application of the elastic neural net for ring recognition in RICH detectors. The method has been developed to find rings distorted due to misalignment of detectors and contaminated by noise. The algorithm was tested on simulated data of COMPASS RICH-1 detector. Reconstruction efficiency is 99.95% for triple LEPTO events taking 5 ms per event

[en] The NEMO-2 tracking detector located in the Frejus Underground Laboratory was designed as a prototype of the detector NEMO-3 to study 0ν and 2ν double-beta decay (β β) physics. A β β 2ν half-life of T_1/2 = (3.75 ± 0.35 (stat) ± 0.21 (syst)) centre dot 10¹⁹ y was measured with an enriched cadmium source (0.92 mol y of ¹¹⁶Cd). Limits on half-lives of 6.2 centre dot 10²¹ y for β β 0ν and 1.2 centre dot 10²¹ y for β β 0ν χ⁰ decays of ¹¹⁶Cd were obtained (CL=90%)

[en] A relativistic two-particle system with an arbitrary linear combination of scalar and vector time-asymmetric Fokker-type interactions in a two-dimensional spacetime is considered within the framework of the front form of dynamics. It is shown that the corresponding mass-shell equation takes the form of a linear relation between the generators of the Lie algebra so(2,1). An algebraic quantization of the system is proposed and a closed form for the mass spectrum is obtained. The relativistic wave equation obtained by Barut and Rasmussen for the H atom is generalized to the case of an arbitrary linear combination of scalar and vector interactions. An extension of the results to the system in four-dimensional spacetime is suggested. (author)

[en] NEMO 3 is a currently running experiment to search for the neutrinoless double beta decay (0vββ) and to study the two-neutrino double beta decay (2vββ) with 10 kg of enriched isotopes. No evidence for the 0vββ-decay is found after 1409 effective days of data collection with 7 kg of ¹⁰⁰Mo, T_1/2^0v>1.1·10²⁴ yr at 90% CL, and with 1 kg of ⁸²Se, T_1/2^0v>3.6·10²³ yr at 90% CL. The corresponding limits on the effective Majorana neutrino mass are v><0.45-0.93 eV for ¹⁰⁰Mo and v><0.89-2.43 eV for ⁸²Se depending on the nuclear matrix element calculations.