Speaker
Description
The nucleon self-energy is calculated in SU(2) covariant chiral perturbation theory (ChPT) to analyze the pion mass dependence of the nucleon mass up to chiral order $\mathcal{O}(q^6)$, i.e., including two-loop diagrams. In a first step, all diagrams are expressed by a small set of (scalar) master integrals. The extended on-mass-shell (EOMS) renormalization scheme is applied, where (next to the divergent pieces) certain infrared regular parts of the integrals are systematically subtracted, gaining renormalized expressions consistent with the power counting. The master integrals are dimensionally regularized and calculated in two ways: Firstly, a $1/m_0$ expansion (with $m_0$ being the nucleon mass in the chiral limit) is performed, using the strategy of regions to differentiate between the infrared singular and regular part. The corresponding result is in agreement with the results from heavy-baryon ChPT and infrared renormalization. Secondly, the master integrals are solved numerically (using the sector decomposition method) to obtain a fully covariant result that is to be compared to the lattice data.
