Update 09.21.2018 -- Pythia: Fitting Pi0 and Gamma-Direct Spectra With Power Laws

As we move forward with the unfolding, we'd like to use a power law as a prior.  So here are 4 spectra from Pythia fitted with power laws (that way we have a reasonable estimate of what the default parameters should be in the prior).

Here are the parameters organized into a table:

  a b
pi0 (9, 11) 1.60 2.45
gamma (9, 11) 1.74 3.04
pi0 (11, 15) 1.59 2.23
gamma (11, 15) 1.58 2.58

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To get a better fit, here're the same spectra fit over a smaller range: the pi0 spectra are fit over 'pTjet = 2 - 20' GeV/c and the gamma-direct spectra are fit over 'pTjet = 2' GeV/c to the upper limit of the trigger eT.

And in a table:

  a b
pi0 (9, 11) 1.67 2.40
gamma (9, 11) 1.74 2.65
pi0 (11, 15) 1.48 2.11
gamma (11, 15) 1.70 2.42

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To get an even better fit, I restricted the fit range further.  Below I fit each spectrum with a power law over 'pTjet = 2' GeV/c to either the upper limit on the trigger 'pT' (for the pi0 case) or the lower limit on the trigger 'pT' (for the gamma-direct case).

And in a table:

  a b
pi0 (9, 11) 1.48 2.30
gamma (9, 11) 1.46 2.48
pi0 (11, 15) 1.39 2.07
gamma (11, 15) 1.24 2.14