During my presentation to JetCorr on May 29th, 2018 (see link at the end of this post), some were curious about why it is that the PHENIX data on slide 9 are systematically higher and have smaller error bars than do the STAR pp-data.  For reference, here's the plot:

And the answer is that we're only approximately comparing apples to apples in the above plot.  The PHENIX data are explained in detail starting on page 18 of the gamma-hadron analysis note:

https://drupal.star.bnl.gov/STAR/system/files/AnalysisNote_v5_0.pdf

The upshot is that PHENIX measured the ratio of the direct-photon cross-section to the pi0 cross-section (see figures 20 and 21 in the analysis note above) while STAR measured what we call R = 1/(1 + gamma/pi0) (defined on slide 7 of the presentation below).  What's plotted above is STAR's measured value of R, and the approximate value of R as calculated from PHENIX's measurement of the direct-photon-pi0 ratio:

R(PHENIX) ~ 1/[1 + (1.03/1.02)(PHENIX data)]

where the prefactor on the PHENIX data is to compensate for our gamma and pi0 reconstruction efficiency.  So while we expect the STAR and PHENIX data to be consistent, we shouldn't expect them to be nearly identical.

https://drupal.star.bnl.gov/STAR/blog/dmawxc/jetcorr-update-may-29th-2018