A. P. Ostankov

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.

Observation of a resonance with mass M=1814 MeV, decaying into π−ηη

Abstract The reaction π−N→π−ηηN off a carbon nucleus at Pπ=36 GeV/c has been studied with the help of the wide aperture magnetic spectrometer VES. In the π−ηη system a resonance with M=1814±10 (stat.)±23 (syst.) MeV, Γ=205±18 (stat.)±32 (syst.) MeV has been observed. Its most probable quantum numbers are IG=1+ or 2−.

Study of resonance production in diffractive reaction π−A → π+π−π−A

Abstract The results of the partial wave analysis of the diffractive reaction π − A → π + π − π − A at the momentum 36 GeV/ c on the scintillator target are presented. A resonance at m = 1.8 GeV with J PC = 0 − + (π(1800)) is clearly seen in this reaction. The characteristics of π(1800) point to the possible exotic nature of this object.

Study of

Dalitz plot of the

\eta'\to\eta\pi^+\pi^-

eta to etapi^+pi^-

Dalitz plot

decay is studied using the data collected with the VES spectrometer in two different exclusive reactions. The coefficients for the matrix element squared decomposition are measured on the largest statistics of

Measurement of form factors for the decay η′ å ηπ−π+

eta

Study of the reaction π− A → K+K−π−A at 37 GeV/c

decays reported so far.

Study of the wave with JPC=1−+ in the partial‐wave analysis of ήπ−, ηπ−, f1π−, and ρ0π− systems produced in π−N interactions at pπ−=37 GeV/c.

Form factors measured for the decay η′ å ηπ−π+ in π−A å η′π−A* reactions at a beam momentum of pπ = 28 GeV are presented. The distribution in Dalitz variables for 7000 decay events is described well within a linear and a nonlinear parametrization of the relavant matrix element. The slope parameter in the variable y differs from zero significantly. It is Reα = −0.072±0.012 (stat.)±0.006 (syst.) in the linear and a = −0.120±0.027 (stat.)±0.015 (syst.) in the nonlinear parametrization. In this decay, the C-violation parameter is compatible with zero, c = 0.021±0.024.

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

Abstract The reaction π − A → K + K − π − A was studied at the momentum of 37 GeV/c on the beryllium target at the wide aperture VES spectrometer. The partial-wave analysis of the K + K − π − system produced at low | t ′| 2 was performed. It is shown that in the wave with J P = 0 − there exists an object withmass 1.79±0.014 GeV/c 2 and width 0.21±0.07 GeV/c 2 decaying into κK − and | 0 (975) π − .