Determination of the S-wave ππ scattering lengths from a study of K±→π±π0π0 decays

Abstract We report the results from a study of the full sample of ∼6.031×$ 10^{7} $K±→π±π0π0 decays recorded by the NA48/2 experiment at the CERN SPS. As first observed in this experiment, the π0π0 invariant mass (M00) distribution shows a cusp-like anomaly in the region around M00=2m+, where m+ is...
Ausführliche Beschreibung

Abstract We report the results from a study of the full sample of ∼6.031×$ 10^{7} $K±→π±π0π0 decays recorded by the NA48/2 experiment at the CERN SPS. As first observed in this experiment, the π0π0 invariant mass (M00) distribution shows a cusp-like anomaly in the region around M00=2m+, where m+ is the charged pion mass. This anomaly has been interpreted as an effect due mainly to the final state charge exchange scattering process π+π−→π0π0 in K±→π±π+π− decay. Fits to the M00 distribution using two different theoretical formulations provide the presently most precise determination of a0−a2, the difference between the ππ S-wave scattering lengths in the isospin I=0 and I=2 states. Higher-order ππ rescattering terms, included in the two formulations, allow also an independent, though less precise, determination of a2. Ausführliche Beschreibung