SEZIONE PAVIA Chiral Perturbation Theory (ChPT) is an effective field theory for the strong force used to describe meson interactions. Such theory has been very successful so far in describing low energetic processes. However it is not clear how much it can be trusted for very precise determinations of hadronic observables. Indeed many unknown parameters enter into the theory and limit its predictive power. In the first part of the seminar I will investigate this aspect and attempt a first answer.
The second part focuses instead on a new extension of ChPT out of its usual energy range. This is called harp ion ChPT and it is expected to be particularly useful for the analysis of lattice data. I will provide arguments that support the use of such extension. As an application I will show the results of this procedure applied to semileptonic decays of B and D mesons