Comment on "Determination of the chiral coupling constants c_3 and c_4 in new pp and np partial-wave analyses"

Abstract

In a recent study [M.C.M. Rentmeester et al., Phys. Rev. C 67, 044001 (2003)], the Nijmegen group reports on the determination of the chiral low-energy constants (LEC), c_3 and c_4, involved in the 2-pi-exchange part of the NN amplitude at next-to-next-to-leading order (NNLO) of chiral perturbation theory. This analysis does not apply the uniquely-determined and model-independent NN amplitudes at NNLO and uses, instead, amplitudes that are up 90% smaller. We point out that this flaw produces a large systematic error, rendering the Nijmegen method unsuitable for a reliable determination of the LEC.