Run 15 pAu200

Preliminary calibration (no tilt, from HFT):

Xin Dong determined the position of the beam spot at z=0 in global coordinates (see the last result on this page: VPDMB purity check and vertex position check for pAu 200 GeV)

Run 15 pAu200 preliminary 2

Final calibration?

Run 15 pAu200 preliminary 2

The first preliminary calibration, using HFT only, found (x₀,y₀) = (0.096 ± 0.009, -0.272 ± 0.009), using a production of data from run 16125048. The HFT cannot, however, determine a beam tilt. Using the same data, with TPC-found primary vertices, I find similar (x₀,y₀) = (0.105 ± 0.007, -0.278 ± 0.007), which essentially agrees within errors.

The agreement gave me some confidence in the cuts I was using to remove pile-up:

multiplicity > 20
BEMC matches > 1
TOF matches > 0
rank > -5

To get better statistics, I decided also to include some MuDsts from other runs produced by FastOffline in the same fill (19028): runs 16125050-16125063. Doing so gave much smaller errors, but also moved the (x₀,y₀) to a slightly different position, by ~1/3^rd of a mm in x: (0.066 ± 0.002, -0.264 ± 0.001):

Given the higher confidence in HFT results due to the absence of systematics from the TPC (e.g. pile-up, distortions), I will enter in the database the (x0,y0) from the HFT-based calibration, but the slopes from the TPC-based calibration: dx/dz = -0.00414 ± 0.00003, dy/dz = 0.00041 ± 0.00003.

-Gene