Effective Lagrangian for pseudo-scalar mesons and axion

by Prof. Di Vecchia Paolo (Niels Bohr Institute and Nordita)

Thursday 15 Dec 2016, 11:30 → 12:30 Europe/Rome

2N44 (M.S. Angelo)

We extend the effective Lagrangian for pseudo-scalar mesons that includes the effect of the axial anomaly, gives a satisfactory spectrum of pseudo-scalar mesons and allows one to compute the $\theta$ dependence of hadronic processes, to include the axion. We use it to show that the $\theta$ dependence disappears and we compute various properties of the axion. In particular, we show that the mass of the axion is given, in the chiral limit, by the Weinberg-Wilczek formula in terms of the quark masses with the addition of a term containing the topological susceptibility of Yang-Mills theory. This additional factor is irrelevant at zero temperature but could become important at finite temperature.

Slides napoli16.pdf