[Sane-analysis] Reminder of Sane Meeting at 3:30pmToday Wed Oct 8th in f226

[Whitney R. Armstrong]

Hi Oscar,

I have added comments below. 

On Thu, Oct 09, 2014 at 12:15:50AM -0400, O. A. Rondon wrote:
>Hi,
>
>Here are the items we discussed at the meeting that I said I would look up:
>
>- question of trend of d2 with E' or x.
>
>I see a similar trend as Whit but for the SLAC data vs lower x limit
>in the d2 integral, not for SANE. See plots on page 5 here (plots on P.
>4 are the same, except they have a typo (fixed for those on p. 5,
>changes things a bit)
>https://userweb.jlab.org/~rondon/analysis/asym/world/A180_Aperp-q2-x_d2-xmin.pdf

To be clear, when you say "not for SANE", you mean "not for Hovannes's SANE 
analysis".

>The low x and min E' limits are related, but not identical.

It is *very* interesting that I am getting almost exactly the same x dependence 
as E155x shown on page 5. (for my results see 
http://quarks.temple.edu/~whit/SANE/analysis_main/results/d2p_vs_cut_2.png)  
The x-axis shows increasing E' cut starting at 800 MeV in steps of 100MeV.
Mapping the E' lower limit to x, roughly corresponds to 0.2 to 0.4.

The agreement between my analysis and E155x highlights the need for the 
cherenkov window cut to remove tracker pairs.

>
>For SANE d2 vs min E', I see the same trend we saw at the meeting, shown
>above on p. 7, and with different g1 inputs on the top plot of page 5 (or 4)

I believe this to be a consequence of Hovannes's analysis not correctly 
treating the background.

>
>- question of CLAS e+/e- fit
>
>This is discussed in great detail in my wiki page
>https://hallcweb.jlab.org/experiments/sane/wiki/index.php/Scaling_fits_to_Hall_C_positron_data
>
>Summaries of e+/e- models that I've looked into (saves actually reading
>the wiki page ;-) ), including the direct fits to Hall C pairs data for
>5.9 GeV (top left), Hovhannes Wiser pi0 simulation (top right), and CLAS
>(Vipuli) fit (bottom left), are here
>https://userweb.jlab.org/~rondon/analysis/asym/pairs_models.pdf
>
>The plain CLAS fit is the blue curve (pairs for just CLAS target). The
>red curve is my expectation of what BigCal would see (includes tracker).
>
>The Hall C fits for 4.7 GeV data are here
>https://userweb.jlab.org/~rondon/analysis/asym/pairs_models_5_9-4_7.pdf
>
>Finally, the fit by Vipuli in all detail is here
>("Report on pair Background")
>https://userweb.jlab.org/~rondon/sane/mtg7/index.html
>
>and the code I used to get the SANE e+/- background from the CLAS fit (a
>nontrivial job) is in this spreadsheet
>https://userweb.jlab.org/~rondon/sane/analysis/pairs/pair_run_plan_short.ods
>
>with this code I get f(E'=900 MeV)= 0.25 for CLAS only, and  f=0.62 for
>SANE, without the tracker, 0.71 with the tracker.  I estimated the
>tracker X0 using 9 mm of plastic.

This is an underestimate for the tracker thickness. The tracker is at least 
12mm of plastic (one layer was a double layer) plus some additional thickness 
for the WLS fibers and glue. 

I am using the fits from the thesis of Robert Fersch.  
http://www.jlab.org/Hall-B/general/thesis/Fersch_thesis.pdf
It appears to be doing a good job based on my agreement with SLAC d2. It could 
certainly do better for cuts less than 1200MeV.

I am currently implementing your pion cross section fits into my simulation.  
This should help understand lower E' background better. 

Cheers,
Whit

>
>Cheers,
>
>Oscar
>
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