Anti-proton production from proton beam (Mu2e request)

The Mu2e experiment observes a discrepancy in anti-proton production for proton beam at 10 GeV on several targets, see page 18 of:

https://indico.fnal.gov/getFile.py/access?contribId=123&sessionId=40&resId=0&materialId=slides&confId=9717

and also visible on the validation plots:

http://g4validation.fnal.gov:8080/G4WebAppNG/DisplayTest_1.xhtml?selectedTestDescription=47

This production process is an issue to Mu2e as being the third dominant source of background to the experiment.