I.M. Ivanchenko

Steering of charged particle trajectories by a bent crystal

Abstract The first experimental evidence has been obtained for steering of charged particle trajectories by a bent silicon crystal. The investigation has been performed at the Laboratory of High Energies, JINR. In the process of planar channeling, an 8.4 GeV proton beam has been deflected up to 26 mrad relative to the incident beam direction. This corresponds to a bending radius of 38 cm. The effective transverse component of the electric field acting on the proton beam is equal to 240 MV/cm. This is equivalent to a magnetic field of 81 T.

A high luminosity spectrometer for deep inelastic muon scattering experiments

Abstract A 50 m long magnetized iron torus enclosing a 40 m long target provides the luminosity and acceptance necessary for the study of deep inelastic muon scattering at high Q 2 . The construction and performance of this spectrometer and the associated trigger are described. Details of the data acquisition system and data analysis are also given.

Transmission regeneration of neutral K-mesons on hydrogen in the momentum region of 14–42 GeV/c

Abstract The measurements of the transmission regeneration amplitude on hydrogen in the momentum region of 14–42 GeV/c indicate that in accordance with the Pomeranchuk theorem its magnitude |ƒ° − ƒ °|/k decreases as energy increases and its phase is approximately constant and equal to arg (ƒ° − ƒ °) = (−118 ± 13)° .

Radiation from 10 GeV positrons channeled in silicon crystals

Abstract Radiation from 10 GeV positrons channeled along (110) planes in a 90 μm silicon crystal shows a prominent photon peak at about 50 MeV in agreement with theoretical predictions. The intensity is also in reasonable agreement with expectation. For positrons aligned within ≈20 μ rad to the planar direction, a sharp spectral peak of 25 MeV is also observed, the origin of which is not yet clear. For particles incident at angles near the channeling critical angle of ≈65 μ rad there appears to be structure in the photon spectrum which may correspond to harmonic structure predicted by theory. This is the first observation of such structure for ultrarelativistic particles.

A study of the semileptonic decays of neutral kaons

Dalitz plots of 74 000 Ke30 and 150 000 Kμ30 decays have been investigated to measure the t-dependence of the form factors ƒ+(t) and ƒ(t) describing the vector contribution to the decay matrix element. The decays were registered by a wire spark chamber spectrometer in the neutral beam of the Serpukhov accelerator. An analysis using a linear expansion of the form factors gives the slopes: λe+=0.0306±0.0034 for the Ke30 decays and λμ+ = 0.0427±0.0044, λ0 = 0.0341± 0.0067 for the Kμ30 decays. The ratio of the form factors ƒ− to ƒ+ has been found to be ξ(0)=ƒ−(0)/ƒ+(0)=−0.10±0.09. These results are compared with the relevant theoretical models. Together with the data of other experiments in which the parameters of muon and electron interactions are measured, the observed difference between λ+μ and λ+e gives some indication of the violation of μ-e universality.

KL0-KS0 transmission regeneration on hydrogen

The energy dependence of the modulus and phase of the KL0-KS0 regeneration amplitude on hydrogen in the range of 14–50 GeV has been investigated at the Serpukhov 70 GeV accelerator. It has been established that the modulus of the modified regeneration amplitude decreases with increasing momentum as 2|ƒ210(p)|/k = (0.84 ± 0.42) · p−0.50±0.15 mb. The amplitude phase is energy-independent and its mean value is ϕ210 = −132° ± 5°. The results obtained are compared with other experiments and with predictions of different theoretical models.

Filmless spark chamber system for operation with on-line computer

Abstract A system of nine wire spark chambers having magnetostrictive readout, data acquisition electronics used on-line with the computer BESM-3M located at a 1 km distance from the experimental area has been designed and tested using a negative pion beam of the Dubna synchrophasotron.

Spin alignment of K(892) mesons produced in neutron-carbon interactions

Abstract A new precise measurements of spin density matrix element ρ 00 of K ∗ (892) ± mesons produced inclusively in neutron-carbon interactions at ∼60 GeV have been carried out in the EXCHARM experiment at the Serpukhov accelerator. The values of ρ 00 obtained in the transversity frame are 0.393±0.011(stat)±0.018(sys) for K ∗ (892) + . An upper limit ρ 00 CL =90% has been obtained for K ∗ (892) − . Significant P T dependence of ρ 00 has been observed in K ∗ (892) + production. The investigation has been carried out at the Laboratory of Particle Physics, JINR.A new precise measurements of spin density matrix element

Neutral kaon regeneration on carbon in a momentum region of 16–40 GeV/c

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A spectrometer to study spontaneous radiation due to the channeling of high energy electrons and positrons in single crystals

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