Parity-violating polarization in np → dγ with a pionless effective field theory

We consider the two-nucleon weak interaction with a pionless effective field theory. Dibaryon fields are introduced to ensure fast convergence of the perturbative expansion. Weak interactions are accounted for with the parity-violating dibaryon-nucleon-nucleon vertices, which contain unknown weak coupling constants. We apply the model to the calculation of a parity-violating observable in the radiative neutron capture on a proton at threshold. Result is obtained up to the linear order of the weak dibaryon-nucleon-nucleon coupling constants. We compare our result to the ones obtained from other approaches, and discuss investigation of the weak interaction in few-body systems.