Recent progress in low energy hadronic physics

by Gilberto Colangelo (University of Bern)

Thursday 18 Sept 2008, 14:00 → 15:00 Europe/Zurich

TH Theory Conference Room (CERN)

The very high statistics measurement of $K_{e4}$ decays recently performed by NA48 provides a highly sensitive test of the theory prediction of the pi pi scattering lengths. At the precision reached it is essential to properly account for all isospin breaking effects. I will discuss the latter and show that, once corrected, these data (and also older ones by the Geneva-Saclay and E865) beautifully confirm the theory prediction. Other tests are provided also by the cusp measurement in $K \to 3 \pi$ decays (also done at NA48) and of the lifetime of pionic atoms done by DIRAC. All these measurements provide an experimental determination of some combinations of low energy constants. Recent progress in lattice calculations allows a comparably precise first principle calculations of the latter. The present status of these will be reviewed.