  We investigate the neutron scattering spectrum in iron pnictides based on the
random-phase approximation in the five-orbital model with a realistic
superconducting (SC) gap, Delta=5meV. In the normal state, the neutron spectrum
is suppressed by large inelastic quasi-particle (QP) scattering rate gamma* ~
Delta. In the fully-gapped s-wave state without sign reversal (s++), a
hump-shaped enhancement appears in the neutron spectrum just above 2Delta,
since the inelastic QP scattering is prohibited by the SC gap. That is, the
hump structure is produced by the dissipationless QPs for Ek<3Delta. The
obtained result is more consistent with experimental spectra, compared to the
results of our previous paper with Delta=50meV. On the other hand, both height
and weight of the resonance peak in the fully-gapped s-wave states with sign
reversal (s+-) are much larger than those observed in experiments. We conclude
that experimentally observed broad spectral peak in iron pnictides is created
by the present "dissipationless mechanism" in the s++ -wave state.
