Procesy elektromagnetyczne w układach kilkunukleonowych w ramach chiralnej teorii zaburzeń

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The Chiral Effective Field Theory (ChEFT) is a modern framework to analyze properties of few-nucleon systems in the low-energy regime. It is based on the most general elfective Lagrangian for pions and nucleons consistent with the chiral symmetry of QCD. For energies below the pion-production threshold it is possible to eliminate the pionie degrees of freedom and derive nuclear potentials and nuclear current operators solely in terms of nucleonic degrees of freedom. This is very important because, despite many elforts in the past, the consistence between two-nucleon forces, many-nucleon forces and corresponding current operators has not been achieved yet. In this thesis, we consider recently derived long-range two-pion exchange (TPE) contributions to the nuclear current operator which appear at higher order chiral expansions. These operators do not contain any new free parameters. Based on ChEFT dynamical picture, we study their role in the electron and photon scattering reactions and compare chiral predictions with those obtained in the conventional framework and to the existing experimental data. The bound and scattering states are calculated with five different chiral nucleon-nucleon potentials leading to the so-called theoretical uncertainty bands for the predicted observables.