The Nucleon-Nucleon Interaction in a Chiral Effective Field Theory

4.5. Results for the NNLO-ß approach 151
already in the Bonn potential, namely that this particular partial wave is essential dominated by
correlated TPE [213]. We also note that the description of 3 D1 and 3 D2 is worse in NNLO-ß than
in NNLO. For the F -waves, the differences between the two approaches are very small, with the
exception of 3 F4, which is improved in the presence of the isobar. The most significant effect in
the higher partial waves shows up in 3G5 as shown in fig. 4.17. Clearly, two-pion correlations not
related to the ß play an important role to bring the prediction for this partial wave in agreement
with the data. The deuteron properties for an exponential regulator with A = 1.05 Ge V are listed
in table 4.7. Most observables come out in between the NLO and NNLO results for the NNLO-ß
approach. The sole exception is the quadrupole moment, which is improved.
An important conclusion following from comparison of the NNLO and NNLO-ß results is that
simply using resonance saturation to encode the physics of the isobar in the dimension two pionnucleon
LECs turns out to be a sufficient procedure in the two-nucleon sector. We also note that
explicit isobar degrees of freedom were considered in ref. [78]. A direct comparison with their
work is, however, not possible since no separate result for fits with and without delta are given.