# Determination of the ππ scattering lenghts from K<sup>±</sup> -->π<sup>±</sup>π<sup>0</sup>π<sup>0</sup> decays

- Institution: CERN
- Department: CERN Colloquium
- Speaker: Nicola Cabibbo, Italo Mannelli (Univ. La Sapienza, Roma and Scuola Normale Superiore, Pisa),
- Year: 2005
- Language: English
- Source: [CERN](https://videos.cern.ch/record/3016168)
- Licence: [CERN](http://copyright.web.cern.ch)
- Who can watch: Teens profiles and older (sources give no ratings; placed by Invisible Network from the source's own words)

The NA48/2 experiment at the CERN SPS has collected more than 100 million fully reconstructed K±-->π±π0π0 decays.

The preliminary analysis of a third of the data shows a sudden change of slope of the π0π0 invariant mass distribution in the region around 2m, where m is the mass of the charged pion. This anomaly, which was never observed before, is interpreted as a cusp-like effect resulting mainly from the contribution of the K±-->π±π0π0 decay amplitude through π+π- -->π0π0 charge exchange.

The study of this phenomenon is a new and potentially more accurate method to measure a0-a2, the difference of the I = 0 and I = 2 S-wave scattering lengths.

The colloquium will consist of two parts: the experiment, given by Italo Mannelli, and the theory by Nicola Cabibbo.

Organiser(s): Luis Alvarez-Gaume / PH-TH

Note: * Tea & coffee will be served at 16.00 hrs..

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## Lectures

1. [Determination of the ππ scattering lenghts from K<sup>±</sup> -->π<sup>±</sup>π<sup>0</sup>π<sup>0</sup> decays](https://invisiblenetwork.ai/learn/cern/3016168/cb5c6293e604), 1 h 8 min (CERN's player)