## Tensor Forces and the Ground-State Structure of Nuclei

Two-nucleon momentum distributions are calculated for the ground states of nuclei with mass number A {le} 8, using accurate variational Monte Carlo wave functions derived from a realistic Hamiltonian with two- and three-nucleon potentials. The momentum distribution of 'np' pairs is found to be much larger than that of 'pp' pairs for values of the relative momentum in the range (300--600) MeV/c and vanishing total momentum. This large difference, more than an order of magnitude, is seen in all nuclei considered, and has a universal character originating from the tensor components present in any realistic nucleon-nucleon potential. The correlations inducedmore »