  We study the nonperturbative renormalization of the nucleon-nucleon (NN)
interaction at next-to-leading order (NLO) and next-to-next-to-leading order
(NNLO) of chiral effective field theory. A systematic variation of the cutoff
parameter is performed for values below the chiral symmetry breaking scale of
about 1 GeV. The accuracy of the predictions is determined by calculating the
$\chi^2$ for the reproduction of the NN data for energy intervals below
pion-production threshold. At NLO, the NN data are described well up to about
100 MeV laboratory energy and, at NNLO, up to about 200 MeV---with,
essentially, cutoff independence for cutoffs between about 450 and 850 MeV.

Nuclear Theory;Nuclear Experiment