Chiral expansion of nucleon PDF at $x\sim m_{\pi }/M_N$

Abstract

Based on the chiral perturbation theory, we investigate the low-energy dynamics of nucleon parton distributions. We show that in different regions of the momentum fraction $x$ the chiral expansion is significantly different. For nucleon parton distributions these regions are characterized by $x\sim 1$, $x\sim m_{\pi }/M_N$ and $x\sim (m_{\pi }/M_N{)}^2$. We derive extended counting rules for each region and obtain model-independent results for the nucleon parton distributions down to $x\gtrsim m_{\pi }^2/M_N^2\approx 10^{-2}$.

Comments: 9 pages, 4 figures. Invited contribution presented at the Lightcone 2013+ Conference, Skiathos, Greece, 20-24 May, 2013. To be published in Few Body Systems