The STAR experiment

Notes from collaboration meeting

The following are notes I took during the STAR collaboration meeting at MIT, specifically the spin pwg session on 7/13/06. It's not an exhaustive summary,
since I'm just "kicking the tires" on drupal.

Correction factors are derived from simulation by taking the ratio of the reconstructed primary tracks matched to MC pions divided by the MC pions. Specifically, the following cuts are applied:

Monte Carlo

• |event_vz| < 60.
• |eta| < 1.
• nhits > 25
• geantID == 8||9 (charged pions)

Matched Reco Tracks

• |event_vz|<60.
• |reco eta| < 1.
• |global DCA| < 1.
• reco fit points > 25
• geantID of matched track == 8||9

The track yields and their associated yields are obtained from the minimc files that are produced automatically with each simulation request. I run a separate chain containing StEmcTriggerMaker on the MuDst simulation files to determine if each event would have satisfied EMC and BBC trigger conditions.


There is currently a bug in StDetectorDbMaker that makes it difficult to retrieve accurate prescales using only a catalog query for the filelist. This affects the absolute scale of each cross section and data points for HT1 and JP1 relative to the other three triggers. It's probably a 10%-20% effect for HT1 and JP1. With that in mind, here's what I have so far:


This plot is generated from a fraction of the full dataset; I stopped my jobs when I discovered the prescales bug.

The cuts used to select good events from the data are:

• golden run list, version c
• |vz| < 60.
• Right now I am only using the first vertex from each event, but it's easy for me to change

The cuts used to select pion tracks are the same as the ones used for "Matched Reco Tracks", except for the PID cut of course. For PID I require that the dE/dx value of the track is between -1 and 2 sigma away from the mean for pions.

As always, comments are welcome.

Triggers are
| mb | ht1 |
| ht2 | jp1 |
| jp2 | all |

Summary:

The goal of this analysis is to estimate the contribution to A_LL from particles that aren't charged pions but nevertheless make it into my analysis sample.

I've included an Excel spreadsheet with currently assigned systematic errors as an attachment.

These plots were made from 100 hijing events using perfect hits in the old three-layer IST and the HFT, but no SSD. Currently, it is not possible to make plots containing both the IST and the HFT as the bfc upgrade tags for the upgrade are upgr01, which contains the HFT and SSD but not the IST, and upgr02, which contains the HFT and IST but not the SSD.

I re-examined the data - pythia comparison in my analysis after some good questions were raised during my preliminary result presentation at today's Spin PWG meeting. In particular, there was some concern over occasionally erratic error bars in the simulation histograms and also some questions about the shape of the z-vertex distributions.

Statistical errors from MB || JP1 || JP2 from 2005: