Chiral 2π-exchange NN potentials: Relativistic 1/M² corrections

We calculate in baryon chiral perturbation theory the relativistic 1/M² corrections to the leading order two-pion exchange diagrams. We give explicit expressions for the corresponding one-loop NN amplitudes in momentum space. The resulting isovector central and isoscalar spin-spin and tensor NN amplitudes involve nonstatic terms proportional to the squared nucleon center-of-mass momentum p². From the two-pion exchange box diagrams we obtain an isoscalar quadratic spin-orbit NN amplitude. We give also analytical expressions for the corresponding NN potentials in coordinate space. The diagrammatic results presented here make the chiral NN potential complete at next-to-next-to-next-to-leading order.