STAR Muon Telescope Detector development

["Ma, Rongrong" <marr AT bnl.gov>]

Hello Dandan, Gaohan, Wei, Kaifeng

Since you are doing or have done the momentum smearing procedure for 
extracting the Jpsi lineshape from embedding, I think it would be good to 
agree upon the procedure such that consistent results can be obtained. In the 
end, we should only use one common smearing factor for one dataset (Isobar or 
27 GeV).

The main metrics to determine the smearing factor is to match either the Jpsi 
invariant mass distribution or Jpsi width vs. pt between embedding and data. 
Since the Jpsi width depends on pt, it is important to make sure that the 
Jpsi spectrum shapes in data and embedding are similar. 

Here is the procedure I am suggesting: 
1) Determine input Jpsi spectrum shape for toyMC
- For 27 GeV analysis for which we do not have corrected Jpsi spectra yet, I 
suggest to extract the raw Jpsi yield vs. pt from data, parameterize the 
distribution and use it as input to ToyMC. In order to have an accurate 
parameterization, we should try to have as many pt bins as possible in the 
distribution of raw Jpsi yield vs. pt. I know this is challenging, but let's 
do our best. 
- For Isobar analysis, we have two approaches: i) parameterize the raw Jpsi 
yield vs. pt from data as done for 27 GeV (the more pt bins, the better); ii) 
use the preliminary Jpsi spectra as input and apply detector efficiency. Both 
approaches should give similar shapes

2) Run toyMC to obtain either the Jpsi invariant mass or Jpsi width vs. pt, 
depending on which method you want to use, by scanning the smearing factor. 
Actually it will be nice to try both methods, since currently we see very 
different results from the two methods, which is puzzling. We should try to 
understand this. 

3) Calculate chi2 between data and toyMC, and determine the best smearing 
factor that matches toyMC to data

4) As a sanity check, we should make the following plot: 
- Compare Jpsi yield vs. pt between data and toyMC with best smearing factor 
to make sure their shapes are similar
- Compare Jpsi width vs. pt between data and toyMC with best smearing factor
- Compare Jpsi invariant mass for both pt integrated and in different pt bins 
between data and toyMC with best smearing factor

Hopefully, we can arrive at consistent results from different analyzers and 
using different methods. 

Please let me know if you have any comments. Thanks. 

Best
Rongrong