The dynamics and time scales of higher-order correlations
are studied
in supercooled colloidal systems. A combination of X-ray photon correlation
spectroscopy (XPCS) and X-ray cross-correlation analysis (XCCA) shows
the typical slowing of the dynamics of a hard sphere system when approaching
the glass transition. The time scales of higher-order correlations
are probed using a novel time correlation functiongC, tracking the time evolution of cross-correlation
functionC. With an increasing volume fraction, the
ratio of relaxation times ofgCto the standard individual particle relaxation time obtained
by XPCS increases from ∼0.4 to ∼0.9. While a value of
∼0.5 is expected for free diffusion, the increasing values
suggest that the local orders within the sample are becoming more
long-lived for larger volume fractions. Furthermore, the dynamics
of local order is more heterogeneous than the individual particle
dynamics. These results indicate that not only the presence but also
the lifetime of locally favored structures increases close to the
glass transition.