Here, we follow closely the discussion of the resolution and uncertainty along the padrow given in the previous Section.
The first term in Equation 15 is independent of
crossing angle. This is the component of the resolution that the
cluster/hitfinder estimates in TPHIT.DZ. Figure 27
shows the average residual and estimated uncertainty as a function of
for non-overlapping hits in a Au+Au event. The residual approaches
the estimated uncertainty for small 
, but crossing angle effects
dominate the resolution otherwise.
Figure 27: Average value of the residual (solid crosses) and estimated
uncertainty calculated by the hifinder (dashed lines) as a function
of crossing angle for isolated hits in a Au+Au event. For large
, crossing angle effects dominate the effects of noise.
In Figure 28, it is seen that those hits with large
energy loss show the fastest increase with crossing angle, similar to
the large-
effect discussed above.
Figure 28: Average value of the residual as a function
of crossing angle for isolated hits of varying amplitude
in a Au+Au event. Large-amplitude hits show increased
degradation in resolution with crossing angle.
For the tracker to update the uncertainty in the time direction according
to Equation 15, the constants 
and 
must be determined.
As in the case with the resolution along the padrow, the coefficient
corresponding the magnitude of finite electron statistics distortions,
, vanishes with the current slow simulator.
Fits of the width of the residual distribution for non-overlapping
hits from Au+Au collisions, for various cuts on 
and 
,
show best fit for 
for the outer sector and
for the inner.
Again, the values of these numbers may change as the
configuration paramters of the simulator
and hitfinder change.
As an example, the z-resolution of hits from a Au+Au event, integrating
over dE/dx and crossing angles, is RMS=2.4 mm, 
=1.5 mm, while
selecting hits with crossing angles 
gives 
=219 
m.