A. Ekimov

Study of π−N→ηπ−N and π−N→η′π−N reactions at 37 GeV/c

Abstract A partial-wave analysis of the ηπ− and η′π− systems produced in the reactions π−N→η(η′)π−N on a berylium target at a beam momentum of pπ− = 37 GeV/c is performed. It is shown that (1) all the waves with negative exchange naturality are negligibly small for both systems; (2) the matrix element squared of the P+ wave with JPC = 1−+ for the η′π− system significantly exceeds that for the ηπ− system, which could testify to the dominance of systems with a valence gluon (q q g) in the JPC = 1−+ wave formation; (3) the ratio R = Br(a2−→η′π−)/BR(a−2→ηπ−) = (4.7±1.0(stat.) ±0.4(syst.)) × 10−2 has been obtained.

Search for the f1(1285) → π+π-π0 decay with the VES detector

The isospin violating decay f1(1285) → π ππ has been studied at VES facility. This study is based at the statistics acquired in πBe interactions at 27, 36.6 and 41 GeV/c in diffractive reaction πN → (f1π )N . The f1(1285) → πππ decay is observed. The ratio of decay probabilities BR(f1(1285) → πππ) to BR(f1(1285) → ηπ π) ·BR(η → γγ) is ∼ 1.4%.

Natural parity resonances in ηπ+π−

Abstract Results of a partial wave analysis of the ηπ+π− final state are presented using 4.2×104 events with |t|

Evidence for a scalar meson resonance in the {pi}{sup -}p{yields}n{omega}{phi} reaction

The charge‐exchange reaction π−p→nω(780)φ(1020) is studied with the VES setup. The (ωφ) system is observed at relatively low background. Its invariant mass distribution peaks near threshold. The two‐particles partial wave analyses shows that the Jpc = 0++ state dominates. This wave is compared with 0++ component in the (ωω) system at the comparable mass, which was measured earlier.

RECENT RESULTS FROM VES EXPERIMENT

The charge-exchange reaction π-p → ω(780)ɸ(1020)n is studied with the VES setup. The (ωΦ) system is observed at relatively low background. Its invariant mass distribution peaks near threshold. The two-particles partial wave analyses shows that the JPC = 0++ state dominates. Comparison with scalar wave in ωω system at the comparable mass gives evidence for violation of the OZI rule. Another subject is a search for possible transition f0(980) → a0(980), which violates the isospin symmetry.

Analysis of the reaction π−Be → π−π0π0Be at VES

We present the results of the analysis of diffractive reaction π−Be → π−π0π0Be measured with upgraded VES detector with the statistics of about 16 · 106 events. The mass-independent partial-wave analysis is performed using set of 70 partial waves corresponding to natural-parity exchange mechanism and restricting the rank of spin-density matrix Nr = 1. The data is divided into 40 MeV m(3π) bins and in 10 intervals of momentum transfer squared t′. The sub-density-matrix of mass independent PWA is subject to further mass dependent fits using Breit-Wigner resonant terms and coherent non-resonant backgrounds.

Analysis of the reaction π{sup −}Be → π{sup −}π{sup 0}π{sup 0}Be at VES

We present the results of the analysis of diffractive reaction π−Be → π−π0π0Be measured with upgraded VES detector with the statistics of about 16 · 106 events. The mass-independent partial-wave analysis is performed using set of 70 partial waves corresponding to natural-parity exchange mechanism and restricting the rank of spin-density matrix Nr = 1. The data is divided into 40 MeV m(3π) bins and in 10 intervals of momentum transfer squared t′. The sub-density-matrix of mass independent PWA is subject to further mass dependent fits using Breit-Wigner resonant terms and coherent non-resonant backgrounds.

Analysis of the reaction

We present the results of the analysis of diffractive reaction π−Be → π−π0π0Be measured with upgraded VES detector with the statistics of about 16 · 106 events. The mass-independent partial-wave analysis is performed using set of 70 partial waves corresponding to natural-parity exchange mechanism and restricting the rank of spin-density matrix Nr = 1. The data is divided into 40 MeV m(3π) bins and in 10 intervals of momentum transfer squared t′. The sub-density-matrix of mass independent PWA is subject to further mass dependent fits using Breit-Wigner resonant terms and coherent non-resonant backgrounds.

\pi^{−}Be \to \pi^{-}\pi^{0}\pi^{0}Be

Partial wave analysis of the π–A π+π–π– system produced by 29 GeV/cπ– beam on a beryllium target is presented. About 30 × 106 |events in the wide t′|range 0–0.8 GeV2/c2 are collected with upgraded VES setup. The size of the data sample is 2.5 times larger than one previously analyzed by VES. Data are analyzed using formalism of the density matrix with unlimited rank. We discuss status of the a1(1420) a2(1700) a3(1875) states and a structure of exotic ρ(770)π P-wave with JPC = 1-+. Parameters of a3(1875) are estimated as M = 1985 ± 20 MeV/c2, Γ = 200 ± 50 MeV/c2 (preliminary).

at VES

Preliminary results obtained by studying K−π−, K−π−π0, and K−π−η systems in the VES experiment are presented. No statistically significant signals from possible resonances were observed in two- and three-particle mass spectra of doubly charged (sub)systems.