  We study the ^{1}S_{0} proton pairing gap in neutron star matter putting
emphasis on influence of the Dirac effective mass and the proton fraction on
the gap within the relativistic Hartree-Bogoliubov model. The gap equation is
solved using the Bonn-B potential as a particle-particle channel interaction.
It is found that the maximal pairing gap \Delta_{max} is 1-2 MeV, which has a
strong correlation with the Dirac effective mass. Hence we suggest that it
serves as a guide to narrow down parameter sets of the relativistic effective
field theory. Furthermore, the more slowly protons increase with density in the
core region of neutron stars, the wider the superfluid range and the slightly
lower the peak of the gap become.
