I have been informed be Elke that a 3.58 mrad change in the horizontal BeamLine angle was expected going from Run 15 pp200 to Run 15 pAu200 operation. These plots demonstrate that we see something close to this. Shown errors are statistical only and don't reflect possible systematics issues like pile-up contamination (though I gave some modest effort to exclude pile-up) and TPC distortion mis-correction (we know that the TPC SpaceCharge & GridLeak correction is really bad for the pAu200, and we know that the Minuit Vertex Finder has biases that grow with worse calibration).

pp200:

pAu200:

Looking at the difference for pAu200 with respect to the pp200 BeamLines...

Difference in x slope:
(-4.14344e-03 ± 3.32543e-05) - (-4.02421e-04 ± 6.93300e-05) = (-3.741 ± 0.075) mrad (stat. error only)

Difference in y slope:
(4.13220e-04 ± 3.21901e-05) - (4.49672e-04 ± 7.12753e-05) = (-0.036 ± 0.078) mrad (stat. error only)

-Gene