Some time ago we showed that the charge-symmetry-breaking interaction, as obtained from the mass four hypernuclei ({sub [Lambda]}4H, {sub [Lambda]}4He), was spin-independent; a result which cannot be understood with the conventional meson-exchange models. The calculations of ({sub [Lambda]}4H, {sub [Lambda]}4He) are currently being extended to include noncentral nuclear and hypernuclear forces which could modify this result. At a more fundamental level we intend to study quark-structure contributions to the charge-symmetry-breaking interaction.

We study the interplay between charge symmetry breaking and renormalization in the NN system for S-waves. We find a set of universality relations which disentangle explicitly the known long distance dynamics from low energy parameters and extend them to the Coulomb case. We analyze within such an approach the One-Boson-Exchange potential and the theoretical conditions which allow to relate the proton-neutron, proton-proton and neutron-neutron scattering observables without the introduction of extra new parameters and providing good phenomenological success.

This thesis discusses two key topics: strangeness and charge symmetry violation (CSV) in the nucleon. It also provides a pedagogical introduction to chiral effective field theory tailored to the high-precision era of lattice quantum chromodynamics (QCD). Because the nucleon has zero net strangeness, strange observables give tremendous insight into the nature of the vacuum; they can only arise through quantum fluctuations in which strange–antistrange quark pairs are generated. As a result, the precise values of these quantities within QCD are important in physics arenas as diverse as precision tests of QCD, searches for physics beyond the Standard Model, and the interpretation of dark matter direct-detection experiments. Similarly, the precise knowledge of CSV observables has, with increasing experimental precision, become essential to the interpretation of many searches for physics beyond the Standard Model. In this thesis, the numerical lattice gauge theory approach to QCD is combined with the chiral perturbation theory formalism to determine strange and CSV quantities in a diverse range of observables including the octet baryon masses, sigma terms, electromagnetic form factors, and parton distribution functions. This thesis builds a comprehensive and coherent picture of the current status of understanding of strangeness and charge symmetry violation in the nucleon.

Variational calculations indicate that a reasonable description of .lambda.p scattering and of .lambda. separation energies can be obtained in terms of .lambda. N plus dispersive and TPE .lambda. NN forces. Results for the .lambda lambda. interaction and for 6/sub .lambda./He obtained from an analysis of 1°/sub .lambda lambda./Be are discussed. Coulomb and .lambda. N charge symmetry breaking effects in the A = 4 hypernuclei are discussed.