The STAR experiment

AuAu@19.6GeV: Data selection

Updated on Tue, 2007-11-20 23:45. Originally created by chajecki on 2007-11-20 23:18.

1. Event selection

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AuAu@19.6GeV: SH moments - why some bins are not shown on plots?

Updated on Tue, 2007-11-20 07:33. Originally created by chajecki on 2007-11-20 07:31.

Some bins are not shown on the plot like for example 1st and 4th bin in A10 on left figure below because they are above the scale.

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AuAu@19.6GeV:Dependence of fitted HBT radii on Coulomb radius

Updated on Tue, 2007-11-20 07:39. Originally created by chajecki on 2007-11-20 06:44.

Dependence of fitted hbt radii on Coulomb radius :
Figure shows results for the most central AuAu@19.6GeV for fit range Q: [0,0.16] GeV/c

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AuAu@19.6GeV:Dependence of fitted HBT radii on fit range

Updated on Tue, 2007-11-20 07:37. Originally created by chajecki on 2007-11-20 05:58.

Dependence of fitted HBT radii on fit range for two analyses (w/ and w/o electron cut)

the most central AuAu@19.6 GeV collisions (bin1)

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AuAu@19.6GeV: Fit Study

Updated on Mon, 2007-11-26 01:57. Originally created by chajecki on 2007-11-20 02:37.

The goal of this study is to understand the discrepancy in fit results from analyses w/ and w/o electron cut. Here I will mostly focus on the first kT bin (0.15-0.25 GeV/c) since the l

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Single-particle plots made using the new pixel fast simulator

Updated on Mon, 2007-11-19 15:23. Originally created by wleight on 2007-11-19 15:23.

Attached are pdf files giving efficiencies for all three inner silicon detectors vs.

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Cross Talk in the BSMD

Updated on Tue, 2007-11-27 11:27. Originally created by betan on 2007-11-19 15:04.

With the StEmcSimulatorMaker recently cleaned up and streamlined (thanks again, Adam), it wasn't a difficult task to simulate the effect of cross talk between the fibers in the BSMD readout. Nom

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L2 Testbed

Updated on Mon, 2007-11-19 19:51. Originally created by jwebb on 2007-11-17 17:43.

L2 Testbed

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A Brief Overview of the New Pixel Fast Simulator

Updated on Thu, 2007-11-15 13:32. Originally created by wleight on 2007-11-15 13:24.

The new StPixelFastSimMaker imposes the pixel structure on the PXL detector and the strip structure on the IST detector. For each event the simulator loops over StMcPixelHits, determines which p

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g-g suppression in Pythia

Updated on Sun, 2008-07-27 23:46. Originally created by kocolosk on 2007-11-15 11:18.

I'm concerned about an apparent deficit of g-g scattering events in our CDF Tune A Pythia samples. I first noticed this deficit when I was looking at MC asymmetries for pi-minus production, where the difference between asymmetries from g-g and q-g events is extreme. For reference, here is Vogelsang's prediction for the subprocess mixture for inclusive pi0 production:

Compare that to the following plot from Pythia for pi-plus production after combining partonic samples starting at 3_4:

If I add 2_3 GeV the gg contribution at low pT gets a boost, but I'm still seeing ~zero pions from g-g scattering at 8 GeV, where Vogelsang predicts 20% g-g.

Renee suggested skipping the observables and just plotting the event partonic pT. The turnover from gg to qg occurs at 3 GeV ... seems too low to me. On the other hand, the mixture is ~20% g-g at 16 GeV, which seems about right.

One other tidbit for any Pythia tuners out there. When I was running standalone Pythia to get the various partonic xsections for weighting purposes I saw a number of advisory warnings like

Advisory warning: maximum violated by  1.120D+00 in event     625
XSEC(28,1) increased to  5.982D-01

in this case, I was running the 5_7 sample. The initial max value for the q-g xsec was 5.3392D-01, and the final measured xsec was 1.515D-01. Not sure if it's significant.

Update 11-19-2007

I looked into the relationship between charged pion p_{T} and event partonic p_{T} in more detail. Here are plot of charged pion multiplicity and mean pion p_{T} versus event p_{T}:

so g-g events actually produce more charged pions per event, but these pions are all at low p_{T}. The second conclusion is reinforced by the PDF I've linked at the bottom of the page, which shows pion p_{T} spectra split by subprocess for a range of partonic p_{T} bins. The g-g events have a much steeper slope. Those plots are not normalized by the # of events per subprocess, so the conclusion about the number of pions per event is not immediately evident.

Update 11-27-2007

I tried manually rescaling the g-g scattering contribution to the PYTHIA asymmetries; it looks like increasing the g-g by a factor of 5 does a decent job of reproducing the NLO theoretical predictions:

no rescaling