Speaker
Dr
Dmitry Ryabchikov
(Institute for High Energy Physics)
Description
Diffractive production of $\pi^+\pi^-\pi^-$ and $\pi^-\pi^0\pi^0$ final states
are subjects of comprehensive studies performed recently by VES and COMPASS experiments.
The $3\pi$ states are produced at VES by 29 GeV/c $\pi^-$ beam on Be target
( $87x10^6$ $\pi^+\pi^-\pi^-$ events and $32x10^6$ $\pi^-\pi^0\pi^0$ events analyzed at 0 < t' < 1 GeV/c$^2$).
At COMPASS $3\pi$ states are produced by 160 GeV/c $\pi^-$ beam impinging on liquid hydrogen target ( 50x10$^6$ $\pi^+\pi^-\pi^-$ events and $3.5x10^6$ $\pi^-\pi^0\pi^0$ events analyzed at 0.1 < t' < 1 GeV/c$^2$).
The COMPASS collaboration pioneered the application of novel methods of partial-wave analysis:
mass-independent PWA in multiple (m,t')-cells, mass-dependent analysis performed at-once for density matrices
measured in all t' regions, the analysis with free shapes of $\pi^+\pi^-$ isobars. The COMPASS observed new narrow state: a_1(1420).
The VES has leading world statistics of $\pi^+\pi^-\pi^-$ and $\pi^-\pi^0\pi^0$ events, compatible in two final
states. This makes perspective the comparison of isospin relations between two states, using both: PWA with established shapes of isobars
and PWA with freed $\pi\pi$ isobars.
Primary author
Dr
Dmitry Ryabchikov
(Institute for High Energy Physics)
