Here's a set of histograms exploring how the quality of events depends on the location of the z coordinate of the vertex location. The terms "away" and "near" are used to denote tracks that are heading away from z=0 and towards z=0 respectively. The terms "center" and "corner" denote tracks that are heading in the specified direction at all (split at η=0) and ones that  have |η|>η0 where η0 represents the η corresponding to a track that would pass through z=200, r=200 with the given vertex location. These terms were chosen because they have the same number of letters. Before some example figures are presented, a quick reference for the relationship between z and η0...

Table showing the relationship between z, θ, and η assuming that the corner of the TPC lies at z = 200, r = 200:

Z-Coordinate (cm)	θ to Corner of TPC	η to Corner of TPC
0	0.785	0.881
10	0.811	0.846
20	0.838	0.809
30	0.866	0.771
40	0.896	0.733
50	0.927	0.693
60	0.960	0.653
70	0.994	0.611
80	1.030	0.569
90	1.068	0.525
100	1.107	0.481

 

And a figure showing the same:

 

Now for a quick glance at some of the relationships explored in the histograms. You can only tell so much from them because of the underlying z distributions, but if you want to look more closely the root file is attached.

 

The attached root file contains all of these 2d histograms.

 

Update:

These figures were produced from projections of the theta vs. z histogram. They look at how acceptance as a function of θ varies for different vertex locations. The projections were scaled so that each histogram would have the same number of counts for |η| < .45, a region where the acceptance should be the same for each vertex location used.

I tried to place the η reference lines about where it seemed like the acceptance was limited by the proximity to the endcap.

 

Also, the attached root file was edited so no underscores appear in histogram names.