  Assuming a phenomenological self-energy $Im \Sigma(\omega) \sim
|\omega|^{\beta\}, (\beta=1 $), which becomes gapped below $T_c$, we derived a
new gap equation. The new gap equation contains the effect of the kinetic
energy gain upon developing a superconducting order parameter. However, this
new kinetic energy gain mechanism works only for a repulsive pairing potential
leading to a s-wave state. In this case, compared to the usual potential energy
gain in the superconducting state as in the BCS gap equation, the kinetic
energy gain is more effective to easily achieve a high critical temperature
$T_c$, since it is naturally Fermi energy scale. In view of the experimental
evidences of the d-wave pairing state in the hole-doped copper-oxide high-$T_c$
superconductors, we discuss the implications of our results.
