CERN-PS-212()
LIFETIME MEASUREMENT OF PI+ PI- ATOMS TO TEST LOW-ENERGY QCD PREDICTIONS
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- Approved: Feb 8, 1996,
- Completed: 9999
DIRAC Collaboration
The goal of the DIRAC experiment is to measure the [pi+pi-] atom lifetime of order 1 fs (ground-state) with 10% precision. The experimental setup consists of a precise magnetic double arm spectrometer, installed in the high energy and high intensity proton beam of the CERN Proton Synchrotron. This measurement will provide - in a model independent way - the S-wave pion scattering length difference |a_0 - a_2| with 5% precision. Low energy QCD in the framework of chiral perturbation theory (ChPT) predicts nowadays scattering lengths with very high accuracy of less than 2%. Therefore, such a measurement will check sensitively the understanding of chiral symmetry breaking in QCD by giving an indication about the size of the quark condensate, an order parameter of QCD.
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