The STAR experiment

GridLeak plot for pp400 data with calibrated corrections, high luminosities

GridLeak plot for pp400 data with standard pp200 corrections, high luminosities

GridLeak plot for pp400 data with no correction, low luminosities

GridLeak plot for pp400 data with no correction, high luminosities

Looking at the residuals (GridLeak plots), I can see that things are similar to pp200, witth what appears to be an offset in GridLeak distortion at all z (our current understanding of the distortion has it go to zero at the ground planes, |z| = 208 cm). I include here three plots of GridLeak distortion residuals from tracks for high luminosity pp400 data (runs 6154024-6154031, bbce+bbcw > 2e5):

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Upgrades meeting

For this presentation, please see the page pp400 (2005).

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Biannual STAR Analysis Meeting

http://www.star.bnl.gov/protected/hbt/petrchal/talk/proc/wpcf.pdf

http://www.star.bnl.gov/protected/hbt/chajecki/proceedings/WPCF2005/

GridLeak plot for pp400 data with No corrections, low-range luminosities

GridLeak plot for pp400 with No correction, mid-range luminosities.

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I tried increasing SC scaling by 30% from standard pp200 (1.0e-8 => 1.3e-8) while holding the GL steady. The result is some remaining undercorrection: DCAs of about -300 microns at bbcsum=1.5e5, and ~0 at bbcsum=4.0e5. Conclusion is that this is pretty good, but we can do a little better. It appears to me that the offset needs to be decreased (actually, a linear fit to the uncorrected plots suggested this too), and the scaling also by just a little bit.

When I plot dca vs. zdce+zdcw, pp400 looks identical to pp200! Plotting dca vs. bbce+bbcw (which is the scaler quantity used for correcting pp200 data), shows that there is a difference! I was nearly fooled.