  A systematic analysis of the complex lineshape at $(\pi,0)$ of heavily
overdoped Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ is presented. We show that a
coherent component in the quasi-particle excitation is correlated with the
superfluid density throughout the entire doping range and suggest it is a
direct measure of the order parameter of high temperature superconductors.
