Speaker
Summary
The NA48/2 experiment has collected an unprecedented
sample of 3-pion decays of charged kaons. The high statistics and the
good resolution of the detectors allow a unique investigation of the
detailed phase space distributions of these decays. The effects of final
state pion rescattering observed in the Dalitz plot distribution of the
$K^\pm\to\pi^\pm\pi^0\pi^0$ decays turned out to be a powerful tool for
extraction of the S-wave pion-pion scattering lengths. The recent results
obtained using a number of different theoretical approaches will be
discussed.
The NA48/2 experiment at the CERN SPS has also collected about 10**6
K± decays into pi+ pi- e± ν (Ke4) in 2003 and 2004.
The analysis of a partial sample of ~500000 such events allows a
precise measurement of the decay parameters. The form factors of the
reaction and their dependence with dipion and dilepton masses have been
measured. Thanks to a sizeable acceptance at large Mpipi, a high sensitivity
to the pi-pi scattering lengths a00 and a02 is achieved. These almost model
independent measurements can be confronted with the predictions from
different calculations, in particular within the framework of
Chiral Perturbation Theory.
