The STAR experiment

Motivation:
Estimates of trigger bias systematic error are derived from simulation. This page compares yields obtained from data and simulation to test the validity of the PYTHIA event generator and our detector geometry model.

Conditions:

• Simulation DB timestamp: dbMk->SetDateTime(20050506,214129). I pick this table up from the DB, rather than from Dave's private directory. Dave changed the timestamps on the files in his directory, so the two files do not match. It turns out that in this case they only differ by one tower (4580), and this tower's status is != 1 in both tables, so there is effectively no difference.
• Data runlist: I use a version of the jet golden run list containing 690 runs. I have heard there is an updated version floating around, but I have yet to get my hands on it
• Simulation files obtained from production P05ih, including larger event samples from Lidia's recent email (http://www.star.bnl.gov/HyperNews-star/protected/get/starsoft/6437.html) but excluding the 2_3, 45_55, and 55_65 GeV samples.
• This is strictly a charged hadron comparison, there is no dE/dx PID cut. The dE/dx dsitributions in simulation are way off.
• Cuts: nFitPoints>25 && |dca|<1. && |eta|<1. && |vz|<60. && pt>2. Also for data I require good spin info and relative luminosity information (these conditions are mostly subsumed by the runlist requirement).

Procedure
Combine PYTHIA partonic pt samples by filling histograms with weight = sample_weight/nevents, using sample_weights

• 3_4 = 1.287;
• 4_5 = 3.117e-1;
• 5_7 = 1.360e-1;
• 7_9 = 2.305e-2;
• 9_11 = 5.494e-3;
• 11_15 = 2.228e-3;
• 15_25 = 3.895e-4;
• 25_35 = 1.016e-5;
• above_35 = 5.299e-7;

Normalized simulation histograms to data, plot yields for MB, HT1, HT2, JP1, and JP2 triggers vs. pt, eta, phi, and z-vertex. Use StEmcTriggerMaker to emulate trigger response in simulation. Also plot eta, phi, and z-vertex yields in slices of pt.

Results:
At the moment I've just linked the raw PDFs at the bottom of the page. The index in the title indicates the charge of the particle being studied. The plots are perhaps a bit hard to follow without labels (next on the list), so here's a guide. Page 1 has pt distributions for the triggers in the order listed above. Pages 2-6 are eta distributions, with each page devoted to a single trigger, again in the order given above. The first plot on each page is integrated over all pt, and then the remaining plots separate the distribution into 1 GeV pt slices. Pages 7-11 repeat this structure for phi, and 12-16 do the same for the z-vertex distributions.

Conclusions:
The agreement between data and simulation appears to be me to be quite good across the board. The jet-patch triggers are particularly well-modeled. A few notes:

• The HT2 pt distributions (page 1, third plot on top row) look funny in simulation. What's with the spike at 6 GeV in the h- plot?
• HT2 eta distribution on the east side for h+ (page 4) has spikes.
• Phi looks good to me
• Vertex distributions for calo triggers in simulation are awfully choppy, but overall the agreement seems OK.

In order to better understand possible anisotropies in the azimuthal distribution of SpaceCharge (see, for example, zerobias data from day 47 of 2004), I have examined the signed DCA (sDCA) aziumthal distributions from several productions. I have separated these distributions into a static component and a dynamic component by determining <sDCA> in each phi bin for each dataset examined, and then looking at the differences from this mean. The mean does not truly equal the static component, but it is very helpful to subtract this component in order to see the the time-evolving component as both components are of similar magnitudes.

In the plots below, the first row shows the <sDCA> value for each phi bin (the bins are aligned along TPC sectors going from 2 o'clock, 1 o'clock, 12 o'clock, .... , 3o'clock with increasing phi). In the subsequent rows, I plot sDCA-<sDCA> versus day (with each phi bin offset) to see what's happening on sub-day time scales, versus day in a colored 2D graph to see what's happening on larger time scales, and versus SpaceCharge to see what's happening versus luminosity.

Additional comments below the plots.

2004

2004 AuAu200	early RFF data	FF data	late RFF data
<sDCA>
sDCA - <sDCA> vs. day
sDCA - <sDCA> vs. day
sDCA - <sDCA> vs. SpaceCharge

The <sDCA> values appear to have fluctuation on the +/-200 micron scale in azimuth. The FF and late RFF data show a feature at phi~3 that is probably due to backgrounds from the collider entering the TPC and causing SpaceCharge distortions in only one region in phi. All of the fluctuations seem to subside to well below 100 microns at the lowest luminosities, implying that <sDCA> perhaps does represent well the static misalignments/distortions.

For the early RFF data, there are some unusual structures. The above SpaceCharge plot for this data was set so that the range of sDCA at higher luminosities could be viewed. Here is a plot of the same data with the range modified to see more clearly the low luminosity data, for which the fluctuations are again well below 100 microns.

 

2005

For the 2005 data, I wanted to compare the P06ic production (which includes SVT and SSD in tracking) with the P06ib production (TPC-only tracking). However, only a small number of tracks actually included SVT or SSD hits in the P06ic data sample.

 

2005 CuCu	P06ib 200GeV RFF data	P06ic 200GeV RFF data	P06ic 62GeV RFF data
<sDCA>
sDCA - <sDCA> vs. day
sDCA - <sDCA> vs. day
sDCA - <sDCA> vs. SpaceCharge

Here, we again see <sDCA> distortions on the order of +/-200 microns, which are there independently of the SVT and SSD usage. This time, the feature at phi~3 is much more prominent, subsiding as the days progressed. It should be considered that the dip in this particular distortion is still atop the ~400 micron peak in the <sDCA> distribution at the same phi, so it is not reversing, but just decreasing relative to the average. A compensating feature appears at phi~4.5, which should exist if the E-by-E SpaceCharge code is working properly since it tries to pull the mean of all sDCAs to zero. It is difficult to say exactly what this means in terms of how the backgrounds causing this look.

There appears to be an "event" of some sort for only the first few runs on day 40, as seen by the offset sDCA-<sDCA> plots.

The 62 GeV CuCu data appears to have smaller static and dynamic distortions.

 

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Gene Van Buren

In light of the current issues with azimuthal discrepancies in alignment calibration of the SVT for CuCu200 data and effects seen in the P06ic test production, please see my contribution on this topic using global track SpaceCharge azimuthal anisotropy from my SpaceCharge studies.

Time	Talk	Presenter
15:00	STAR Inner Silicon tracking detector committee report ( 00:20 ) 1 file	(All)

Time	Talk	Presenter
11:00	SVT Software and hardware maintainability ( 00:20 ) 1 file	Rene Bellwied (WSU)
11:20	SSD Software and hardware maintainability and plans ( 00:20 ) 4 files	Howard Matis (LBNL)