geant pbar absorbtion

 The default way of running geant utilized GHESIA for cross sections, in particular absorption.
BRAHMS looked at this for the 2002 p-bar/p letter and found it was inadaquate. ALICE in their papers from
~2013 also investigated this in the pp paper dealing with the p-bar/p vs energy paper.

Her I put some of this information.

  1. This is an ensemble of e-mails and some plots by Pawel Stazsel from 2001 
  2. Physics Letter from ALICE detailing p-bar efficiencies  pdf
  3. The key figues from 2 is here showing the difference between the geant and fluka efficinecy. This is not the final correction difference which depends on the material budgets which is shown in the second plot.
  5. For STAR at mid-rapidity and the runs w/o HFT there is very little material at mid-rapidity, thus expect the effects to be order 1% at most For run run 14-16 it is certainly different and should be quantified.,

Efeect of p and pbar for ALICE

Summary request to S&C is the attached pdf