Static TPC distortion/alignment (update)

 We have decided to revisit TPC alignment (August 2014,  with new Space Charge and Gread Leak corrections obtained with the August alignment using the same 2014 AuAu200 low luminosity data sample as before.
One additional step in this new alignment with respect to old one was removing overall shift and overall rotation each half of TPC seen as west - east step function on result plots.

An other iteration has been made by HFT group (Mustafa, Hao, Alex) in order to use HFT to align TPC super sectors (
using cosmics data.

The results of the TPC super sector alignments (old, new and with HFT) are presented on the result plots below.

The legend : shifts (x in row direction, y in pad direction, z) and rotations (alpha, beta, gamma) versus sector.
Black markers :  TPC only, August 2014 (20140101.001112) version obtained with old SC & GL
Red markers:     TPC only, January 2015 (20140101.001454) version obtained with new SC & GL.
Green markers:  TPC + HFT, January 2015 (20140105.000100) version obtained from janauary TPC only by HFT group. 


  • There is some dependence of alignment parameters on SC&GL parameterization.
  • TPC only alignment does not have  enough significance to fix Super sector rotation around Z (gamma).
  • Using HFT it is possible to measure rotation around Z.
  • TPC only alignment with correction from HFT is in DB since January 2015.