  We have studied the impact of charged track resolution on Higgs mass and
production cross section measurement in the process $e^+e^- \to Z^0 H, Z^0 \to
\ell^+\ell^-, H \to X$ for Higgs masses between 120 and 160 GeV, and on smuon
mass measurement using smuon pair production for three different mass pairs,
assuming the International Linear Collider(ILC) is operated at 500 GeV center
of mass energies (CME) with integrated luminosities of 500 $fb^{-1}$. The
effect of initial state radiation (ISR), beamstrahlung and beam energy spread
on Higgs and smuon mass measurement are also estimated. Using fast Monte Carlo
simulations of the 2001 North American baseline detector designs (LD and SD),
we find that the ISR and beamstrahlung have significant impact on Higgs and
smuon mass measurement; Charged track momentum resolution affect Higgs mass
significantly with better track performance yielding better Higgs mass
resolution and precision for the track momentum resolution improvement up to a
factor of about 5; Track momentum resolution has little effect on the
measurement precision of the Higgsstrahlung cross section, the branching ratio
of $H \to C\bar{C}$, the smuon and neutralino masses; Beam energy spread better
than about 0.2% has little effect on Higgs, smuon and neutralino masses; The SD
detector provides a more accurate measurement than the LD of the Higgs mass.
