Search

The high mass μ + μ − pairs produced by 280 GeV μ + on a carbon target are studied in a search for the Y production. The high mass continuum in the region 2–18 GeV is interpreted in terms of QED pair production and of μ pairs originating from the decay of hidden and open charm particles as well as of hadrons ( π , K) from deep inelastic interactions. The upper limit for the upsilon production by muons is found to be, at the 90% confidence level, σ γ ·(γ→μ + μ − ) −39 cm 2 /nucleon.

The method is described of measuring the polarization observables Σ , P and T for the reaction γ p → n π + in a double polarization experiment (polarized target + polarized beam). The measured angular distribution of these observables are presented for the photon energy range 280–420 MeV at c.m. pion emission angles between 30° and 150°. The obtained experimental data are included in the energy-independent multipole analysis of the reactions γ p → N π .

A multipole analysis of the γ p → n π + process using new data on the angular distributions of the polarized photon asymmetry has been made. At present the difference between the phase of the resonance amplitude M 1+ 3 2 and the corresponding πN scattering phase shift is found to be −2.5° ± 1.1°. The problem of the ambiguous solutions of a system of equations with respect to the multipole amplitude has been discussed.

Results are given of a calculation of the main characteristics of Cerenkov's shower gamma spectrometers with lead glass radiators having different transparencies and thickness for gamma-quantum energies of 50 to 1000 MeV.

The results of measurement of differential cross sections for the process γp → nπ+ are presented for γ-ray energies 260, 290, 320 MeV and pion angles 90°–180°.

A method of applying the results of the theory of branching processes to the calculation of the main characteristics of shower γ-spectrometers is presented. Expressions for the energy resolution and instrumental line shape are obtained.

The results of an energy-independent multipole analysis of pion photoproduction on protons are presented for the region of the P33 resonance. The analysis includes the phenomenological fitting of the experimental data by the linear model. We have obtained the channel amplitudes of the γp→nπ+ process without using the Watson theorem and the isospin amplitudes of the γp→nπ+ and γp→pπ0 processes using the πN phase shifts. All the results are discussed and compared with the theoretical predictions. From the channel amplitudes obtained an attempt has been made to evaluate the phases of M1+(3).

The results of the phenomenological analysis of the positive photopion angular distributions are presented for the photon energies 230, 260, 290, 320 and 350 MeV. Along with the Moravcsik fit a new form of fitting is used.

In deep inelastic interactions of 200 GeV muons with a carbon target, we have found 17 events of the type μ ± N→ μ ± μ ∓ μ ∓ X (“wrong-sign” dimuons). We derive upper limits of 1.2% (90% CL) on D 0 - D 0 transitions (mixing) or, alternatively, of 9 pb (90% CL) cross section for B B pair production as possible sources of such events.

The investigation of reactions of the type’ + p → π+ + n due to bremsstrahlung from electron accelerators necessitates determination of the energy of the γ ray responsible for the event of interest. Since there is a kinematic relationship between the γ-quantum energy and the energy and angle of emission of the π meson formed, this problem can be solved by an apparatus which detects only π+ mesons emitted at a given angle with a particular energy. The use of scintillation counters with a small entrance aperture as a π+-meson detector ensures sufficiently accurate angular discrimination.