Bakamjian-Thomas mass operator for few-nucleon systems from chiral dynamics

We present an exploratory study consisting in the formulation of a relativistic quantum mechanics to describe few-nucleon systems at low energy, starting from the quantum field theoretical chiral Lagrangian involving pions and nucleons. To this aim we construct a Bakamjian-Thomas mass operator and perform a truncation of the Fock space that respects at each stage the relativistic covariance. Such a truncation is justified, at sufficiently low energy, in the framework of a systematic chiral expansion. As an illustration we discuss the bound-state observables and low-energy phase shifts of nucleon-nucleon and pion-nucleon scattering at the leading order of our scheme.