## Low energy analysis of $πN$ scattering and the pion-nucleon sigma term with covariant baryon chiral perturbation theory    [PDF]

J. M. Alarcón, J. Martin Camalich, J. A. Oller
The pion-nucleon sigma term ($\sigma_{\pi N}$) is an observable of fundamental importance because embodies information about the internal scalar structure of the nucleon. Nowadays this quantity has triggered renewed interest because it is a key input for a reliable estimation of the dark matter-nucleon spin independent elastic scattering cross section. In this proceeding we present how this quantity can be reliably extracted by employing only experimental information with the use covariant baryon chiral perturbation theory. We also contrast our extraction with updated phenomenology related to $\sigma_{\pi N}$ and show how this phenomenology favours a relatively large value of $\sigma_{\pi N}$. Finally, we extract a value of $\sigma_{\pi N}=59(7)$ MeV from modern partial wave analyses data.
View original: http://arxiv.org/abs/1301.3067