Yesterday, I calculated the tracking resolution as a function of monte-carlo pT.  The fit values seemed a little low, however: I was anticipating a constant width of ~5% (varsigma_0) and a linear width of ~1% (varsigma_1).  My calculation gave a constant width of ~3% and a linear width of ~0.1%... I checked the resolution as a function of total momentum (magnitude of the 3-vector) rather than pT, and the results can be seen below.  It does not make a substantial difference.