Speaker
Description
The VES experiment has collected high statistics for exclusive reactions with three pion final states:
$ \pi^-\pi^-\pi^+ $ (about $30\cdot10^6$ events) and $\pi^-\pi^0\pi^0 $ (about $16\cdot10^6$ events).
The $ 3\pi $ systems are produced by $\pi^-$ beam ( $ E_{beam} = 28.9 $ GeV ) impinging on the beryllium target.
The dominant production mechanism is the pomeron exchange between incoming beam pion and the target.
At low momentum transfer squared $t' < 0.05 GeV^2 $ the data clearly shows coherent diffractive production
on the whole nucleus which is replaced by incoherent process on the individual nucleons at higher $ 0.05 < t' < 1 $ GeV$^2$.
The mass-independent partial wave analysis is performed dividing data into
the bins of $ m(3\pi) $ and $t'$.
The comparison of results with two models of PWA: using formalism of full rank density matrix
and, oppositely, using rank=1 is presented.
The predicted isospin relations (assuming $ I =1 $ of $ 3\pi$ systems) and observed ones for intensities and relative phases in $ \pi^-\pi^-\pi^+ $ and $\pi^-\pi^0\pi^0 $ are shown.
