The STAR experiment

Hi GPC and PAs,

Here are some first comments on the paper draft:

(i) physics intro, 1st para: I find the physics intro to be a bit confusing. I looked briefly at refs [6,7] (Brodsky et al and Collins). Within my distinctly limited understanding of them I don't think the last sentence of the first paragraph is accurate, and the main physics point of interest in this measurement is missed.

Sti has a nice utility for providing Pull and residual plots for all detectors. The chain option is "StiPulls". The resulting ntuple is written to the .tag.root file.

Among other things, the ntuple stores the (position of the hit - position of the track) in the variables ending in "Pull". It should be noted that the variable contains this difference (or residual), and NOT the difference scaled by the error. This is left for the user. There are several branches of the pulls tree; one for global tracks, one for primary tracks, and one filled only during the outside-in pass of tracking.

Distortions in TPC data (track residuals) are seen in 2004-2006 data which are hypothesized to come from a floating Gating Grid wire. Notes from a meeting of TPC experts regarding the topic held in October 2006 can be found