Strangeness -1 Meson-Baryon scattering from UCHPT, NLO

por Jose Antonio Oller (Universidad de Murcia)

martes 28 jun. 2005 17:00 → 18:00 Europe/Madrid

Sala Seminarios IFIC (Edf. Institutos de Investigación)

We first introduce briefly the formalism known as Unitary Chiral Perturbation Theory. This approach is suited to treatstrongly interacting system as the meson-meson, meson-baryon or nucleon-nucleon ones from chiral effective field theories. Then, we focus on the strangeness $-1$ meson-baryon scattering including the ten interacting coupled channels $\pi^0\Lambda$, $\pi^0\Sigma^0$, $\pi^- \Sigma^+$, $\pi^+\Sigma^-$, $K^-p$, $\bar{K}^0n$, $\eta \Lambda$, $\eta\Sigma^0$, $K^0\Xi^0$, $K^+\Xi^-$. We consider unitary chiral perturbation theory up to next-to-leading order, which makes use of the ${\mathcal O}(p^2)$ baryon chiral perturbation amplitudes. We reproduce many experimental data: several cross sections with $K^-p$ as initial state, precisely measured ratios at the threshold of $K^-p$ to several other channels and the recent data on kaonic hydrogen from the DEAR experiment (2004), around a factor of two more precise than the previous one from KEK (1998). We present our results at order $p$ and $p^2$. We will pay special attention to the value of the $K^-p$ elastic S-wave at threshold (relevant for the strong shift in kaonic hydrogen), the two $\Lambda(1405)$ poles, and how they manifest in the $\pi\Sigma$ event distributions. We will also discuss many other strangeness -1 resonances that orginate dynamically in our approach and show the SU(3) representation to which they belong.