  The properties of pairing correlations in symmetric nuclear matter are
studied in the relativistic mean field (RMF) theory with the effective
interaction PK1. Considering well-known problem that the pairing gap at Fermi
surface calculated with RMF effective interactions are three times larger than
that with Gogny force, an effective factor in the particle-particle channel is
introduced. For the RMF calculation with PK1, an effective factor 0.76 give a
maximum pairing gap 3.2 MeV at Fermi momentum 0.9 fm$^{-1}$, which are
consistent with the result with Gogny force.
