  A d-wave superconducting ground state for a doped Mott insulator is obtained.
It is distinguished from a Gutzwiller-projected BCS superconductor by an
explicit separation of Cooper pairing and resonating valence bond (RVB)
pairing. Such a state satisfies the precise sign structure of the t-J model,
just like that a BCS state satisfies the Fermi-Dirac statistics. This new class
of wavefunctions can be intrinsically characterized and effectively manipulated
by electron fractionalization with neutral spinons and backflow spinons forming
a two-component RVB structure. While the former spinon is bosonic, originated
from the superexchange correlation, the latter spinon is found to be fermionic,
accompanying the hopping of bosonic holons. The low-lying emergent gauge fields
associated with such a specific fractionalization are of mutual Chern-Simons
type. Corresponding to this superconducting ground state, three types of
elementary excitations are identified. Among them a Bogoliubov nodal
quasiparticle is conventional, while the other two are neutral excitations of
non-BCS type that play crucial roles in higher energy/temperaure regimes. Their
unique experimental implications for the cuprates are briefly discussed.
