Compare conversion and chi^2 methods for extracting yields
Updated on Fri, 2008-04-11 14:51. Originally created by jwebb on 2008-04-11 14:24.
![](/STAR/files/userfiles/87/image/04-11-2008-yield-comparison/chi2-distribution-will.png)
Abstract: We compare yields extracted using the EEmc Gammas via conversion method, systematics II with estimates based on a chi^2/ndf analysis of the SMD response.
1.0 Event Sample and Cuts
Use the Gamma tree production in the silver run list.
Cuts:
1) gamma candidate pT > 8 GeV in the EEmc
2) gamma is 90% isolated (90% of ET summed w/in R<0.3 is in the gamma candidate).
3) charged particle veto (Epre1 shows no energy summed over R<0.3).
Figure 1 -- Yields extracted using the conversion method, plotted vs D. Blue data points indicate extracted gamma yield. Dashed blue line represents EM background. Red line hadronic background.
![](/STAR/files/userfiles/87/image/04-11-2008-yield-comparison/highpt.png)
2.0 Shower Shape for chi2 Comparison
Pibero worked up a shower shape for events w/ pT > 8.0 GeV... but this produced chi2 values which were far too large. So I'm falling back to an older shower shape,
Figure 2 -- chi2/ndf distribution for the above events. The chi2 is calculated by taking a shower shape, derived by summing single gammas identified as part of an eta --> 2 gamma decay. At left are "Will's" photons, at right are "Pibero's". Summing the events below the blue line yields 501 events for Will's shape, 436 for Pibero's.
![](/STAR/files/userfiles/87/image/04-11-2008-yield-comparison/chi2-distribution-will.png)
![](/STAR/files/userfiles/87/image/04-11-2008-yield-comparison/chi2-distribution-pibero.png)
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