A. Tsvetkov

Data implying formation of a moving source in collisions of carbon-12 nuclei with various target nuclei at 3.6 GeV/nucleon

Abstract Inclusive spectra of protons emitted in the interaction of 12C-projectiles at an energy of 3.6 GeV/nucleon and C, Cu, Sn and Pb target nuclei were measured. The analysis of the experimental data suggests that in all these interactions the main contribution to proton cross sections in the investigated kinematic region is due to emission from a moving source with a rapidity which differs greatly from the target nucleus rapidity, yt, as well as from that of the effective fireball. The properties of this source such as the excitation energy depend only slightly on the combination of the colliding nuclei.

A new VME-based high voltage power supply for large photomultiplier systems

Abstract We describe a new high voltage power supply, developed for the leadglass calorimeter of the WA98 experiment at CERN. The high voltage is produced for each of the 10 080 photomultiplier tubes of the detector individually, by the same number of active bases with on-board Greinacher voltage multipliers. The full VME-based HV controller system, which addresses each base via bus cables once per second, is miniaturized and fits into a single VME crate. The main advantages of this approach are the low heat dissipation, the considerably reduced amount of cabling and cost, as well as the high stability and low noise of the system.

Development of the technology for large-scale production of lead tungstate single crystals for physical experiments

The scientific principles underlying the technology for growing crystals of lead tungstate PbWO4 (PWO) with controlled properties are discussed. The developed technology is implemented at the North Crystals Company in mass production of PWO crystals with 100% reproducibility of operating parameters. This made it possible to solve the problem associated with the preparation of PWO crystals for the ALICE experiment at CERN and to produce the pilot batch of large-sized PWO crystals (diameter, 46 mm; length, 250 mm) with required characteristics for the CMS experiment at CERN. More than 10000 PWO scintillators of high optical quality for the ALICE experiment were fabricated over a short time according to the proposed technique.

Universal proton rapidity distributions in high energy nucleus-nucleus collisions

Abstract Inclusive spectra of protons emitted in the interaction of 3 He ions with an energy of 4.9 GeV/nucleon with nuclei of C, Cu and Pb were measured. The analysis of these data as well as of those available on nucleus-nucleus interactions at other energies (0.8, 2.1 and 3.6 GeV/nucleon) and for other combinations of colliding nuclei (from 3 He + C to Ar + Pb) has shown that in the target nucleus fragmentation domain the invariant cross section is described by a certain universal function if we go over into the appropriate moving frame. It is natural to interpret the latter as a real physical object, i.e. a moving source. This source turns out to be highly heated (the average energy being ⪆ 90 MeV/nucleon), at the same time its inner properties (the excitation energy and distribution form) do not depend either on the collision energy or on the projectile-target combination. On the other hand, the source velocity and the number of nucleons involved in it are systematically dependent on the collision conditions.

Large-angle two-particle correlations in nucleus-nucleus collisions at 3.6 GEV/nucl.

Abstract For nucleus-nucleus collisions at 3.6 GeV/nucl., we have measured correlations between a charged particle emitted in the range from 10° to 18° and identified a charged fragment (proton, deutron or pion) emitted at a certain angle in the range of 45°–130°. The following projectile-target combinations were studied: C+Al (45°, 60°, 80°, 130°); C+Cu (45°, 60°, 80°); C+Pb (45°, 60°, 80°, 130°); He+Al (45°, 80°, 130°); He+Pb (45°, 80°, 130°). In all the studied reactions, correlated particle emission has been observed.