There is a dip in the phi distribution of particles generated in embedding studies.  Jan Kapitan has been studying this problem and finds an odd dependence on the geometry tag.  The Y2008 tag (which should not be considered a production quality geometry tag) shows reasonable behavior, but tags y2008a-e show a dip in sector 24.

 

 

φ distribution of muons with eta>0 (red) and eta<0 (blue). Muons were generated with the attached kumac and reconstructed with the attached ROOT macro... which uses the P09if chain "trs fss y2008a Idst IAna l0 tpcI fcf ftpc Tree logger ITTF Sti genvtx NoSsdIt NoSvtIt MakeEvent bbcSim tofsim tags emcY2 EEfs evout -dstout IdTruth geantout big fzin MiniMcMk clearmem".

 

Simulation and reconstruction performed in the DEV library on 04/29/2011.

 

No statistically significant dips are observed.