Two-nucleon scattering: merging chiral effective field theory with dispersion relations

Understand

We consider two-nucleon scattering close to threshold.

• Partial-wave amplitudes are obtained by an analytic extrapolation of subthreshold reaction amplitudes calculated in a relativistic formulation of chiral perturbation theory.
• The constraints set by unitarity are used in order to stabilize the extrapolation.
• Neutron-proton phase shifts are analyzed up to laboratory energies $T_{{\rm lab}}\simeq250$ MeV based on the next-to-next-to-next-to-leading order expression for the subthreshold amplitudes.