Search

The radiative decay Λ ( 1520 ) → Λ γ was measured directly in the study of the exclusive diffractive-like reaction p + N → Λ ( 1520 ) K + + N , Λ ( 1520 ) → Λ γ with the SPHINX spectrometer. The values of the branching and partial width of this radiative decay were obtained: BR [ Λ ( 1520 ) → Λ γ ] = ( 1.02 ± 0.21 ( stat ) ± 0.15 ( syst ) ) × 10 −2 and Γ [ Λ ( 1520 ) → Λ γ ] = 159 ± 33 ( stat ) ± 26 ( syst ) keV .

Total and differential cross sections for production of the ρ, ω, φ, and J/ψ vector mesons were measured in the Feynman‐x region 0.1≤xF≤0.8 with a 530 GeV/cπ− beam incident on beryllium and copper targets. Using the cross‐section parametrization Aα, we find α=0.76±0.02, 0.81±0.04, 0.87±0.04, and 0.97±0.06 for the ρ/ω, φ, Jψ and Drell‐Yan continuum, respectively. No statistically significant dependence of α on either xF or transverse momentum pT is observed. We have also studied the relative production rates of vector mesons as a function of the event inelasticity, as measured by transverse energy, ET. ET is defined as the scalar sum of transverse momenta for centrally produced charged particles. The relative rate of J/ψ’s and continuum muon pairs does not change with event inelasticity, contrary to the findings of a heavy‐ion collision experiment. On the other hand, the production rate of φ mesons as compared to ρ/ω increases with ET. We argue that the observed increase reflects a simple momentum conserva...

We present the results of an experimental investigation of the production in the nuclear Coulomb field of low-invariant-mass pions pairs by the reaction ..pi../sup -/Z..--> pi../sup -/..pi../sup 0/Z at 40 GeV. We have obtained for the first time the experimental value of the ..gamma -->..3..pi.. coupling constant F/sup 3pi/(0) = 13.0 +- 0.9 +- 1.3 GeV/sup -3/, where the first (second) error is statistical (systematic). This result is in agreement with calculations based on the theory of chiral anomalies.

Invariant mass spectrum of μ + μ − pairs produced by 70 GeV/ c protons in Be target are presented. Distinct enhancements in the mass regions of ϱ, ω mesons, φ meson and J/ψ particle are observed. For J/ψ production x and p ⊥ 2 distributions are given. The total cross section for the reaction p + Be → ( J ψ → μ + μ − ) + … is equal to 9.5 ± 2.5 nb/nucleus .

The vertex ..gamma -->..3..pi.. has been investigated in the reaction of pion pair production by pions in the nuclear Coulomb field, ..pi../sup -/+(Z,A)..--> pi../sup -/+..pi../sup 0/+(Z,A), in the region of low-invariant-mass ..pi../sup -/..pi../sup 0/ pairs. The experiment has been carried out in the 40-GeV pion beam of the IHEP accelerator (Serpukhov) with the SIGMA spectrometer. We have measured for the first time the cross section of the reaction in the region of momentum transfer squared q/sup 2/ ..3..pi.. coupling constant F/sup 3//sup ..pi../ = 12.9 +- 0.9 +- 0.5 GeV/sup -3/, where the first (second) error is statistical (systematic). The obtained result agrees with the calculations based on the Wess-Zumino-Witten effective Lagrangian. The hypothesis of chiral anomalies and the color-SU(3) quark symmetry are confirmed.

The reaction π−p→Ks0Ks0n was studied at the incident momentum 40 GeV/c making use of the 6 m magnetic spark spectrometer MSS ITEP. Partial wave analysis was carried out using ∼ 6700 events of this reaction with t′

About 7 × 10 3 events of Compton effect on pion in the reaction π − A → A π − γ st 40 GeV/ c were detected and for the first time the charged pion polarizability was obtained α π = (6.8 ± 1.4) × 10 −43 cm 3 .

The reaction π−A→Aπ− γ at 40 GeV/c was studied on “Sigma” spectrometer on six different nuclear targets in the region of four-momentum transfer |t

π − p , K − p and p p total cross-sections are measured at momenta up to 65GeV/c with statistical accuracy 0.3 ÷ 0.6% and systematical (scale) error ≈ 0.4%.

Absorption cross sections for pi /sup plus or minus /, K/sup plus or minus mesons, protons andantiprotons on Li, Be, C, Al, Cu, Sn, Pb and V in the momentum range from 6.65 to 60 GeV/c are measured at the 70 GeV IHEP accelerator. The cross sections are compared with calculations using the Glauber multiple- scattering model. Nucleus radii are found to be described by a power dependence on atomic weight R = r/sub o/A/sup 1/3/, where r/sub o/= 1.05 plus or minus 0.02 fm. (auth)

The A -dependence of J/ψ inclusive production by 43 GeV/ c π − -mesons was measured to be σ = (18 ± 6) A (0.92±0.06) nb/nucleus for x > 0.

Results of the experimental study of inclusive φ meson production off berillium nuclei by 70 GeV/ c protons in the beam fragmentation region x > 0.41 are presented. Fitting of the measured differential cross sections to the forms d σ d x ∼ (1 − x) n x and d σ d p 2 t ∼ exp (−bp 2 t ) gives the parameters n = 6.0 ± 1.7 and b = (2.4 ± 0.7) (GeV/ c ) −2 . In the framework of a quark-parton model the measured φ meson x -distribution suggests that in the region of x > 0.41 nearly 90% of the φ mesons are produced via a strange sea quark fusion. The ratio of the OZI-forbidden and OZI-allowed transition coupling constants has been found to be ten times smaller than the same ratio calculated from the partial decay widths. The total inclusive cross section is estimated to be σ (pN → φ X) = (0.7 ± 0.2) × 10 −27 cm 2 .