Speaker
Jenifer Nebreda
(Universidad Complutense de Madrid)
Description
We report on our recent results [1] in the study of the chiral extrapolation of the phase-shifts in elastic pion-pion scattering, using both standard and unitarized ChPT to one and two loops. In the standard ChPT approach, limited to low momenta, we study the S, P and D waves. For the vector phase shift we find a behavior that would seemingly contradict the results of lattice and other effective theories, but that can be explained with a very simple model. In fact, the calculations using the IAM to unitarize the amplitudes reconcile these "strange" behavior at low energy with what is expected intuitively for this channel. The unitarization extends the analysis to energies of around 1 GeV, being compatible with standard ChPT at low energies for the S and P waves. The D waves cannot be generated to this order with this method. When comparing with lattice results in the I=2 channel phase shifts, we find an agreement of standard ChPT below 200 MeV up to pion masses of 400-450 MeV, and a nice improvement beyond 200 MeV when using the IAM. We have also performed a Montecarlo analysis to provide an estimation of the uncertainties.
We also report on the results [2] on the strange and light quark mass dependence of the light resonances reproduced within the IAM approach in SU(3) to one loop. The scalar resonances, sigma and kappa, are shown to behave very differently than the vector resonances, rho and K*, which has to be taken into account in the lattice studies.
[1] J. Nebreda, J. R. Pelaez, G. Rios, arXiv:1101.2171. To appear in Phys. Rev. D (May 2011).
[2] J. Nebreda and J. R. Pela´ez, Phys. Rev. D 81, 054035 (2010).
Primary author
Jenifer Nebreda
(Universidad Complutense de Madrid)
