Yu. G. Sobolev

Origin of the low-mass electron pair excess in light nucleus-nucleus collisions

Abstract We report measurements of electron pair production in elementary p + p and d + p reactions at 1.25 GeV / u with the HADES spectrometer. For the first time, the electron pairs were reconstructed for n + p reactions by detecting the proton spectator from the deuteron breakup. We find that the yield of electron pairs with invariant mass M e + e − > 0.15 GeV / c 2 is about an order of magnitude larger in n + p reactions as compared to p + p . A comparison to model calculations demonstrates that the production mechanism is not sufficiently described yet. The electron pair spectra measured in C + C reactions are compatible with a superposition of elementary n + p and p + p collisions, leaving little room for additional electron pair sources in such light collision systems.

Partial wave analysis of the reaction p(3.5 GeV)+p → pK+Λ to search for the “ppK−” bound state

Employing the Bonn-Gatchina partial wave analysis framework (PWA), we have analyzed HADES data of the reaction p(3.5GeV ) + p !pK + �. This reaction might contain information about the kaonic cluster ”ppK − ” via its decay into p�. Due to interference effects in our coherent description of the data, a hypothetical KNN (or, specifically ”ppK − ”) cluster signal must not necessarily show up as a pronounced feature (e.g. a peak) in an invariant mass spectra like p�. Our PWA analysis includes a variety of resonant and non-resonant intermediate states and delivers a good description of our data (various angular distributions and two-hadron invariant mass spectra) without a contribution of a KNN cluster. At a confidence level of CLs=95% such a cluster can not contribute more than 2-12% to the total cross section with a pK + � final state, which translates into a production cross-section between 0.7 µb and 4.2 µb, respectively. The

Experimental investigations of changes in the rate of beta decay of radioactive elements

Changes in the rate of the beta decay of radioactive elements whose periods are about 24 h and 27 d are detected on the basis of long-term investigations performed with the aid of scintillation and germanium-lithium gamma detectors. The use of the scintillation procedure yields results whose level of significance is much higher than 5%, while the procedure based on germanium—lithium detectors gives a more than 1% deviation from the average value of fluxes of gamma rays accompanying, for example, 60Co beta decay. With allowance for the rotation of the laboratory frame together with the Earth, deviations of the change in the rate of beta decay of radioactive elements single out three directions in the physical space.

EXPERIMENTAL INVESTIGATIONS OF CHANGES IN β-DECAY RATE OF 60Co AND 137Cs

Results of simultaneous measurements of beta-decay rate with the aid of Ge(Li)-detectors performed at two laboratories 140km apart (INR RAS, Troitsk, Co-60, and JINR, Dubna, Cs-137) during a period from 15.03.2000 till 10.04.2000, are presented. Regular deviations of the count rate of gamma-quanta following the beta-decay of

pK + Λ final state: Towards the extraction of the ppK − contribution

\sim

Complete and incomplete fusion of 6Li ions with Bi and Pt

0.7% (INR RAS, Co-60) and

Study of exclusive one-pion and one-eta production using hadron and dielectron channels in pp reactions at kinetic beam energies of 1.25 GeV and 2.2 GeV with HADES

\sim

Search for N N decoupled dibaryons using the process p p ---> gamma gamma X below the pion production threshold

0.2% (JINR, Cs-137) from the statistical average, are observed. The analysis of extremum deviations of gamma-quanta count rate shows that the set of directions of tangents to the Earths parallels of latitude at the extremum points of trajectories of motion in the space of each laboratory clearly forms three separate compact subsets of directions which agree, for two laboratories, to an accuracy of

Inclusive dielectron production in proton-proton collisions at 2.2 GeV beam energy

\pm10^\circ

g-factor measurements of μs isomeric states in neutron-rich nuclei around 68Ni produced in projectile-fragmentation reactions

. This phenomenon is shown not to be explained on the basis of traditional notion. A possible explanation is suggested basing on the hypothesis that there exists a new anisotropic interaction caused by the cosmological vectorial potential \textbf{A}