Intro:

The inconsistency of the h-/h+ ratio across eta (east vs west) has been a consistent problem ever since Run 7 in STAR. The ratio, defined as the number of negative tracks divided by the number of positive track, shows a clear separation in the West  (0.0 < eta < 1.0) and East (-1.0 < eta < 0.0) ends of the TPC. This split is unphysical and the ratio, whatever it may be, should be the same for both the West and East sides.  It was shown that the difference between East and West, using the Run 10 data, vanished when using the y2000 sector alignment parameters. This resulted in implementing the y2000 alignment parameters in the database from then on. Therefore, I have examined the h-/h+ for the pp 500 RFF data for Run 9 (calibrated alignment) and Run 11 (y2000 alignment) to ensure that in pp data (typically AuAu data has been used for the diagnostic), we also see the improvement in the h-/h+ ratio.

Event and Track Selection:

We look only at events in Run 9 that fire the JP1 (230410) or the JP2 (230411) triggers and for Run 11 events that fire the JP1(320601) or the JP2*L2JetHigh (320602) triggers.  Then for both Runs we require that we look at tracks associated with the highest positve rank vertex. Tracks with nHits >12, nHits/nHistPoss > 0.51 and track pT > 0.2GeV are selected.

Results:

First, examing the h-/h+ ratio for global tracks in respectively Run 9 and Run 11.

  We clearly see a seperation in Run 9 across all track pT and it persists even in Run 11 but to a lesser degree. The low pT distributions in both Runs is very interesting since it is not seen in the earlier diagnostics of AuAu which uses global tracks. However, we know that pp500 is highly contaminated with pile-up and so we proceed by looking into the primary tracks' h-/h+distributions. 

The h-/h+ distribution of the pp500GeV for primary tracks behaves very similiarly to what is seen in the AuAu calculations. We see a clear separation at high pT ( >4 GeV) in the Run 9 data using a calibrated alignment and the separation disappears in the Run 11 data using y2000 alignment parameters. This indiccates that using the y2000 alignment parameters works very well for pp and AuAu data.

Conclusions:

The h-/h+ ratio problem is clearly evident in Run 9 pp500 RFF data. In previous calculations, there appears to be a larger h-/h+ split in FF data. However, it seen in RFF and applying the y2000 alignment paraments significantly improves any divergence of the h-/h+ ratio between the West and East ends of the TPC.