ar X iv : 0 71 0 . 30 50 v 1 [ he p - ph ] 1 6 O ct 2 00 7 Theoretical progress on ππ scattering lengths and phases
نویسنده
چکیده
ππ scattering at low energy is sensitive to the structure of the QCD vacuum. I review the calculations of the ππ scattering lengths and phases, and group them in three cathegories: 1. those based on very general theoretical constraints (like dispersion relations and crossing symmetry) and phenomenology, 2. those which in addition make explicit use of chiral symmetry, 3. the firstprinciple ones, done with lattice QCD. I then compare these to the experimental results. Thanks to recent progress in all these and in the experimental determination of the scattering lengths we are improving substantially our knowledge of the QCD vacuum.
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