Yu.A. Belikov

A Study of the production and lifetime of the lightest relativistic hypernuclei

Abstract All results on the production cross sections of the lightest hypernuclei and the lifetimes of the hydrogen hypernuclei obtained in Dubna streamer chamber experiments are presented.

HBT measurement of the expansion velocity of pion production volume

Abstract Using a new method of data processing in the investigation of interference correlations of identical particles, a direct proof of nonstationarity of the π − production volume in central MgMg collisions at a beam momentum of p Iab = 4.4 GeV/c per nucleon was obtained. The velocity of a source of correlated π − meson pairs is introduced as a free parameter in the Lorentz transformed approximation formula of the interference peak. This velocity increases with increasing the velocity of a subset of π − mesons which are chosen for the interference analysis. The source velocity is the new experimentally measurable physical variable of interference analysis, apart from space-time sizes of the source.

A hypernuclear program for the Nuclotron accelerator

Abstract Hypernuclei have been investigated (production and decays) in the Dubna synchrophasotron beams. However, the experiments were interrupted due to a low data collection rate. The beams of the new accelerator Nuclotron allow one to increase the available statistics by a factor of 100 or more. Therefore hypernuclear lifetimes can be measured within 2 % errors significantly exceeding the results of the previous experiments. The study of Λ3H properties is discussed. It is possible to make an attempt to investigate the Coulomb dissociation of the hypernucleus.

Studying of hypernuclei with nuclotron beams

A spectrometer is created to study relativistic hypernuclei produced with beams of accelerated nuclei from the Nuclotron facility (Dubna, JINR). Test runs have been carried out and the conclusion is drawn that the properties of the facility meet the requirements of the task of searching for unknown and studying poorly known neutron-rich hypernuclei.

Relativistic hypernuclei at Dubna

At the Laboratory of High Energies (JINR, Dubna) a unique approach was elaborated with hypernuclei produced by the excitation of the beam nuclei and their decays observed at a distance of tens of cm behind the production target. While the very first experiments were carried out in the Synchrophasotron beams, more extensive hypernuclei research programme is planned for the Nuclotron accelerator and the new spectrometer created by the authors. At the time of the conference the first test run in the Nuclotron beam was in progress. Investigation of hydrogen hypernuclei isotopes is in the first line of the experimental research plans. Namely, lifetimes and production cross sections of Λ 4 H and Λ 3 H will be measured. Search for Λ 6 H is also among the tasks.

Pion production in nuclear charge exchange reactions A(t, 3He)

Abstract The charge exchange reaction (t, 3 He) on carbon and magnesium targets is investigated in experiments using a streamer chamber. The experimental pion longitudinal momentum spectrum is compared with the calculated one for events with a single secondary pion. From this comparison it follows that the contribution from quasi-free Δ − excitation in the target nucleus in a single pion channel is only 60–70%. The momentum of the pions in the remaining fraction of events is significantly higher than that of the pions produced in delta de-excitation. The contribution from several possible processes is analyzed. The data indicate a significant role of coherent pion production via N(1440) or/and N(1520) in the target nucleus while part of the pion spectrum can be explained by projectile excitation.

Direction of the expansion of the volume of pion generation in MgMg collisions at 4.3 GeV/c per nucleon

The relative velocities of elements of the volume of pion generation in central MgMg interactions at 4.3 GeV/c per nucleon in various directions and spacetime sizes of these elements are investigated by the method employing the interference correlations of negatively charged pions. The results are in agreement with the version where generation-volume elements fly apart predominantly in the longitudinal direction.