V. A. Viktorov

Study of the electromagnetic transition form-factor in ω→π0μ+μ− decay

Abstract Sixty events of the rare eletromagnetic decay ω → π 0 μ + μ − have been detected. The branching ratio for this decay been obtained to be BR( ω → π 0 μ + μ − ) = (9.6 ± 2.3) × 10 −5 . The effective mass spectrum for muon pairs has been measured and the electromagnetic transition form-factor for the vertex ωπ 0 , F ω ( m μμ 2 ; m π 2 0) = (1 − m μμ 2 / Λ 2 ) −1 , has been determined, Λ = (0.65 ± 0.03) GeV/ c 2 . The results are compared with the vector-meson dominance model.

Investigation of the electromagnetic structure of the η meson in the decay η → μ+μ−γ

Abstract 600 events of the rare electromagnetic decay η → μ + μ − γ have been detected. The branching ratio has been measured as BR( η → μ + μ − γ ) = (3.1 ± 0.4) × 10 −4 . The electromagnetic form factor of the η meson, F ( m μμ 2 ;0 ) = (1 − m μμ 2 / Λ 2 ) −1 , has been determined. Λ = (0.72 ± 0.09) GeV/ c 2 is in good agreement with the vector meson dominance model.

Study of the radiative decayη′→π+π−γ

The radiative decayη′→π+π−γ has been studied with the statistics of ≃2000 events. Different ways of describingmππ distribution are considered. It is shown that if the dominating contribution to this process is made by the decay channel η′→ργ, then the generally accepted ways of describing the ρ peak do not agree with experimental data.

Observation of D(1285)→φγ radiative decay

Abstract The D(1285) radiative decay has been observed, 19±5 events of this type have been detected. The branching ratio Br[D(1285)→ φγ ] = (0.9±0.2±0.4) × 10 −3 and the partial width γ [D(1285)→ φγ ] = 23 ±5±10) keV have been determined. The conclusion has been made that, most probably, the E(1420) meson does not belong to the axial nonet.

Study of η→μ+μ− decay

Abstract The muon pair mass spectrum in the reactionπ − p→μ + μ − n has been investigated at 25 and 33 GeV/ c . A peak corresponding to the rareη→μ + μ − decay is observed. The measured branching ratio for this decay is (6.5 ± 2.1) × 10 −6 in agreement with theoretical estimates.

Investigation of the diffractive reaction p + N → [∑+ K 0] + N at the proton energy of E p =70 GeV and observation of the decay process X(2000) → ∑+ K 0

The diffractive reaction p + N → [∑+K0] + N induced by 70-GeV protons is investigated at the SPHINX facility. The measured mass spectrum of the ∑+K0 system originating from this reaction shows a resonance structure with a mass of M=1995±18 MeV and a width of Γ=90±32 MeV. The cross section for the formation of this structure is found to be σ=182±38 nb per target nucleon. These data comply well with the results that we obtained previously in studying the reaction p + N → [∑0K+] + N, where we observed the formation of the X(2000) → ∑0K+ state, a candidate for an exotic baryon with hidden strangeness. The measured ratio R of the two branching fractions, R = Br[X(2000) → ∑+K0]/Br[X(2000) → ∑0K+] = 1.91 ± 0.38, is consistent with the value of R=2 expected for an isospin-1/2 baryon.

Study of the Reaction K- p --> anti-K0 n at Momenta of 25-GeV/c and 40-GeV/c

ALPHA EFFECTIVE FOUND TO BE (0.39 +- 0.02) + (0.84 +- 0.07)*T. THIS PAPER IS THE SAME AS W. D. APEL ET AL., NP B129, 275 (1977).