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Update to fitting procedure

Updated on Fri, 2013-02-01 13:56. Originally created by sgliske on 2013-02-01 13:56.

Some changes in the fitting routine are suggested and the results are compared.

Changes in Fitting

The three fitting options are labeled "oldest" "noLM" and "LM", where LM stands for low mass.  "noLM" is an update of "oldest" and "LM" is an update of "noLM."
  • noLM vs "Oldest":
    • Signal fraction functional form now includes third Gaussion (with no skewing and common mean) instead of just two skewed Guassions
    • Other background functional form is now a skewed Gaussion, in order to model the turn on region at low mass
  • noLM vs LM
    • "noLM" does the usual two step fit:
    1. Fit the MC data to template functional forms
    2. Fit the data with the template functional forms to determine 3 weights and the data/MC energy scale
    • "LM" adds some extra steps
    1. Fit the MC data to template functional forms
    2. Fit the data with the template functional forms
    3. By hand, fit the residuals to skewed Gaussion to determine the mean
    4. Fit the data with the template functional forms and an additional skewed Gaussion (with mean fixed at value from 3), to determine 4 weights, the data/MC energy scale, and the sigma and skewness of the additional Gaussion
    • Note: 0.5 +/- 0.35 of the normalized weight for the additional function added to the signal fraction
      • 0.35 is so 1.5 sigma covers the full range, and this uncertainty is added to the systematic uncertainty

Results

Each of the attached PDF files is organized as follows:
  • pages 1-7 are the data/template plots for each pT bin, starting with pT bin 5-6 GeV.
  • page 8 is the pi0 peak position plot
  • page 9 is the cross section
The results for the three different options are attached at the bottom.

Conclusions

The cross section doesn't change all that much.  The LM seems preferable, as it best accounts for the low mass peak.
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