The longitudinal response function of the deuteron in chiral effective field theory

We use chiral effective field theory (χEFT) to make predictions for the longitudinal electromagnetic response function of the deuteron, f _L , which is measured in d(e, e′N) reactions. In this case the impulse approximation gives the full χEFT result up to $\mathcal{O}(P^4 )$ relative to leading order. By varying the cutoff in the χEFT calculation between 0.6 and 1 GeV we conclude that the calculation is accurate to better than 10% for values of q ² within 4 fm^?2 of the quasi-free peak, up to final-state energies E _np = 60 MeV. In these regions χEFT is in reasonable agreement with predictions for f _L obtained using the Bonn potential. We also find good agreement with existing experimental data on f _L , albeit in a more restricted kinematic domain.