Z.Phys.C

In the diffraction dissociation of π− into μ+μ−π− on a Cu nucleus at 50 GeV/c, the cross section\(\sigma _{\mu ^ +\mu ^ -\pi ^ -} \) for the 1+S(ρ0π) wave was measured. The branching ratio of ρ0→μ+μ− could be calculated from the ratio of this and the corresponding cross sections in the diffraction dissociation of π− into π+π−π−. The obtained value\(BR_{\rho ^0\to \mu ^ +\mu ^ -}= (4.6 \pm 0.2_{stat^ \pm}\pm 0.2_{syst} )10^{ - 5} \) is in good agreement with the branching ratio\(BR_{\rho ^0\to e^ +e^ -} \), as expected ifeμ universality holds.

Nucl.Phys.A

Antiproton- 3 He annihilation events at rest have been detected using a self-shunted streamer chamber. The ratio of the cross section for annihilation on neutrons and on protons has been measured (0.467 ± 0.035). It is compared with other results from annihilation on free nucleons, deuterium, 3 He and 4 He. The low value of the ratio seems to indicate a strong isospin dependence of the antinucleon-nucleon P-wave amplitude.

Nucl. Instrum. Meth. A

This article presents the results obtained in a test of the Cherenkov method for simultaneous measurement of the mean energy and direction of a collimated 650 MeV proton beam from the phasotron of the Laboratory of Nuclear Problems. To make requirements to the proton beam intensity less strict, the Vavilov-Cherenkov radiation (VChR) was registered in a wide range of wavelengths, and the LiF radiator dispersion effect was eliminated by an achromatic LK-4 glass prism. Equations and formulae are given to calculate parameters of a system like this. The test results have shown that the mean energy of protons can be determined with an accuracy of ΔE = ±0.2 MeV; at the same time the beam oblique angle is measured with an accuracy of Δα = ±25″.

Phys. Lett. B

Inelastic p - 3 He events at 192.8 MeV/ c are detected with a self-shunted streamer chamber. The measured reaction cross section is 392±23.8mb. This result is briefly discussed and compared with other reaction cross sections for low-energy p with light nuclei.

Nucl. Instrum. Meth. A

The design and the mass production of the proportional wire chambers for the barrel part of the uranium-gas sampling hadron calorimeter of the L3 detector at the CERN Large Electron-Positron storage ring (LEP) are described. The chambers meet the specific requirements arising from the limited space available to the calorimeter, the radioactivity of uranium, and the physics criteria of good energy and position resolution for incident hadrons. The mass production techniques employed ensured that all of the 371664 chamber cells have uniform response (with 5% accuracy) to ionizing particles. Over 8000 chambers of the same design, in 53 different sizes, were manufactured and tested at the ITEP (Moscow), at the University of Michigan (Ann Arbor) and at the IHEP (Beijing).

Nucl.Phys.A

The analysis is based upon p̄Ne annihilation events at rest and at 607 MeV/c detected with a self-shunted streamer chamber exposed to the LEAR beams. The main measured quantities are the following: charged-prong multiplicity, negative pion multiplicity; momentum, angular and rapidity distributions. General distributions are given as well as distributions as functions of charged prong multiplicity. A correlation is found between high multiplicity and depth of the annihilation point. The data are compared with recent theoretical analyses.

Phys.Lett.B

The contribution of an extra Z′-boson to the elastic ( ν̄ ) p-scattering, π 0 neutrino-production on nuclei and some diffractive reactions is calculated in the frame of the superstring inspired E 6 -model. We give quantitative estimations of this contribution and its dependence on model parameters.

Phys.Lett.B

A pion or a kaon may behave as a leading particle in low-energy antiproton-nucleus reactions, in qualitative agreement with a quark model picture describing beam fragmentation.

Instrum. Exp. Tech.

A new method for recurrent calculations of spectral coefficients is used in the analyzer. A spectrum analyzer developed in accordance with up-to-date digital processing conceptions is based on very-large-scale-integration components, such as a high-speed field programmable gate array (FPGA) and a specialized signal microprocessor. The analyzer is based on a personal computer PCI card and operates on the Windows platform.

Nucl. Instrum. Meth. A

The performances of the TOF scintillation counters used in the SIGMA-AIAKS spectrometer are presented. The counters, made of NE110, are 150, 65 and 10 cm long, 10 cm wide and 1.5 cm thick. The time resolutions for minimum ionizing particles have been measured to be σ t = 0.18 ns, 0.14 ns and 0.11 ns respectively. The main contribution to the resolution is given by the photoe collection statistics determined by the decay time of the scintillator and the difference of the optical paths in the counter. The scintillation counters, assembled into hodoscopes of 1.5 × 3.2 m 2 and 0.65 × 0.8 m 2 are used for identification of particles through the TOF. The algorithms of off-line data processing are also presented.

Phys. Rev. D

A nonperturbative method is used to find the solution of neutron-antineutron transitions in an external magnetic field. The convergency of the method is very high, and allows one to obtain a practically exact solution of the problem for all physical values of the parameters of applied magnetic field. In the resonant region of frequencies the eigenstate and initial-value problems are solved exactly, with the shift and the width of the resonance calculated to second order in the ratio of coupling and applied frequencies. The obtained results go over smoothly into the first-order perturbation results for frequencies far out of resonance.

Few Body Syst.

It is shown that the inclusion of the exchange interaction between nuclei of a mesic molecule removes the degeneracy of the Coulomb levels and doubles the levels. For the ground state of thepdμ-molecular ion the splitting is estimated to amount to ΔE∼10−2 eV. Possible experiments for detection of this effect are discussed.

AIP Conf. Proc.

First measurement of the spin rotation parameters R and A in π‐p elastic scattering in the region of pion‐nucleon resonances has been performed at the Leningrad Nuclear Physics Institute. The experiment was carried out on a pion channel of the LNPI synchrocyclotron using a polarized target with LNPI synchrocyclotron using a polarized target with horizontally oriented polarization vector and a multi‐plate carbon polarimeter consisting of optical spark chambers with television read‐out. Results at the energies 450 and 560 MeV are given in comparison with the predictions of phase‐shift analyses.

AIP Conf. Proc.

A 40%‐asymmetry has been revealed in the hard scattering region at 40 GeV. Systematic errors in the experiment are noticeable. The observed effect requires detailed discussion of the production mechanisms.

AIP Conf. Proc.

Spin asymmetry of the protons emitted in the (85–95)°L.S. angular region in the π+d↑→p+x reaction was measured using a deuteron frozen‐spin target and a 40 GeV/c pion beam. The experimental results for (0.3–0.7) GeV/c momenta of the protons asre discussed and compared with the predictions of some models of cumulative particle production.

Z. Phys. C

The π−p interactions with at least one charged secondary produced at polar angle ∼90° in c.m.s. and having the transverse momentum above 1 GeV/c were investigated. The data were obtained using streamer chamber magnetic spectrometer RISK at 38 GeV/c π beam from Serpukhov accelerator. The analyzis of associated production in reconstructed events suggests, that if the transverse momentum of a pair of oppositely charged secondaries compensates the trigger particlep⊥ practically completely, this pair is the product of the ρ0 decay in marked fraction of such events. We observed a large spin-alignment for the ρ0-mesons selected as described above: the probability of zero spin projection onto the normal to the ρ0 production plane is equal to ρ00T=0.86±0.23. The enhancement of the number of events, in which the ρ0 picks up practically full momentum transfer carrying by the exchange, and also the enlarged tensor polarization for the ρ0-mesons in these events could be qualitatively explained as manifestation of direct ρ0-production via the QCD higher twist processes in the highp⊥π−p collisions. At the same time, the observed effects are markedly larger than the values predicted with QCD model in which the higher twist corrections were included.

Nucl. Phys. B Proc. Suppl.

The analysis of p 3 He annihilation events at rest (from the PS 179 experiment at LEAR) gives the value 0.467 ± 0.035 for the ration between the annihilation cross sections on n and on p. This low value indicates a strong isospin dependence of the N N amplitude in P wave.