For kicks and grins, I decided to try to fit the efficiency curve I calculated from the Run 9 dijet embedding:

https://drupal.star.bnl.gov/STAR/blog/dmawxc/update-04112018-run-9-pp-efficiency-different-binning-0

Extrapolating from our usual a(1-exp(-bx)), I was thinking along the lines of a polynomial in x*exp(-bx) or something.  Below is one that did pretty all right, but it doesn't quite get the dip for pT around 1.5 GeV/c...