Meson spectroscopy at VES and COMPASS

Diffractive production of π- π- π+ and π- π0 π0 final states is the subject of comprehensive studies performed recently by the VES and the COM-PASS experiments. COMPASS pioneered the application of novel methods of partial-wave analysis: mass-independent PWA inmultiple (m3π, t’)-cells, mass-dependent analysis of spin-density matrices performed simultaneously in all measured t’ bins, the analysis with freed shapes of π+ π- isobars. In addition, COMPASS observed a new narrow state: a1(1420). VES has world-leading data samples on π- π- π+ and π- π0 π0, that yield compatible results and show the potential for a detailed comparison of isospin relations between different decay channels, using the PWA methods with fixed and freed shapes of ππ isobars.

High spin resonances produced in π+π−π− and π−π0π0 systems at VES setup

A study of high spin resonances produced in π+π−π− and π−π0π0 systems with 29 GeV/c π− beam on Be target is presented. About 87 million events for the first one and 32 million events for the second one are collected with VES setup in a wide range of transfer momentum squared 0 < |t′| < 1 GeV2/c2. For both reactions this is the largest statistics in the world. The data are analysed using the PWA formalism of full rank density matrix and rank 1 density matrix. The a3(1875) and a4(2040) meson parameters are given and their production mechanism is discussed.