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

[Whitney R. Armstrong]

Hi Oscar,

On Thu, Oct 09, 2014 at 04:07:48PM -0400, O. A. Rondon wrote:
>By the way, the method I use to get the pair dilution for SANE starting
>from the CLAS (Vipuli) dilution is explained in detail on slides 5 and 6
>here
>http://hallcweb.jlab.org/experiments/sane/rondon/snbkgd3-sdd.pdf

I cannot understand from these slides how you are calculating the background.  
How are things defined? It seems like there is a mix up between a ratio, which 
I call, defined as R=n(e+)/( n(DIS) + n(e+) ). This seems to be what you are 
calling f_CLAS on the bottom of slide 6. But on the next slide's table the 
ratio reaches a value of 1.23? 

I understand that the CLAS target is about 1/3 the length of the SANE target, 
but why would that make a huge difference? On slide 7 you calculate R_{H/C} but 
why wouldn't there be a compensating factor for the DIS cross section. The rate 
of DIS electrons increases with target length as well. 

Anyway, here are my very preliminary results from simulation.  
http://quarks.temple.edu/~whit/SANE/analysis_main/results/detectors/cherenkov/simulated_cherenkov3_952.png
Obviously I will have much higher statistics...

I also wanted to point out that the background coming from the tracker *does 
not* have the factor of 2 infront of it, unlike the the pairs coming from the 
target. But this is of course removed by the window cut.

Cheers,
Whit



On Thu, Oct 09, 2014 at 04:07:48PM -0400, O. A. Rondon wrote:
>Hi Whit,
>
>Some comments follow.
>
>Cheers,
>
>Oscar
>
>Whitney R. Armstrong wrote:
>> 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".
>>
>
>Yes, those are the data we have been showing.
>
>>> 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.
>>
>
>That is one thing I thought about, too. Namely, d2(low x) >0 corresponds
>to a region dominated by g1.
>
>On p. 6 of my d2 report, top plot, I show that it makes a difference
>whether one uses E155 g1 calculated at constant Q^2= 5 GeV^2 vs
>calculated at the Q^2 of each x bin. But there is little Q^2 dependence
>if g1 is calculated from PDF's.
>
>And the bottom plot shows that at middle x, x^2 g2bar is very sensitive
>to what model of g1 is used.
>
>> 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.
>>
>
>I'm not sure, because at E' = 1.5 GeV, where there is little background
>left, d2(Hovhannes) ~-.004 is many sigmas away from your Nachtmann d2(95
>or 96), which is zero within errors. Both d2's should be converging to
>the same value at this E'.
>
>Also, I like your small error bars, but they are about four times
>smaller than the ones I show. They are total errors, but the stat errors
>are 90% of the bars. I don't think the statistics are that different
>between your analysis and Hovhannes. Since he no ADC cut he actually
>should have more events.
>
>>>
>>> - 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.
>
>OK. That is easy to adjust in my code, but actually it would make the
>dilution even worse.
>
>By the way, the method I use to get the pair dilution for SANE starting
>from the CLAS (Vipuli) dilution is explained in detail on slides 5 and 6
>here
>http://hallcweb.jlab.org/experiments/sane/rondon/snbkgd3-sdd.pdf
>
>> 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'd be very cautious using Fersch's model, because for 5.7 GeV, his data
>go only up to 30 deg. and his fit doesn't agree well with the data even
>at this angle, see his Fig. 6.2.
>
>On the other hand, Vipuli's fit is for 5.7 GeV data for angles between
>36 and 44 deg. She sees little angular dependence, so her fit has only
>two parameters. I suggest using her fit rather than Fersch's, because
>hers is based on data closer to our kinematics.
>
>> I am currently implementing your pion cross section fits into my
>> simulation.  This should help understand lower E' background better.
>
>Great. Here are the new parameters for the pi0(PT) cross section:
>
>sigma_pi0(PT) = a*exp(C*PT), a = 10219+/-361, C = -8.675+/-0.065
>
>(the old parameters were similar a = 11150, c= -8.67, but had no errors)
>
>
>
>
>
>> Cheers,
>> Whit
>>
>>>
>>> Cheers,
>>>
>>> Oscar
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>
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>>> Sane-analysis mailing list
>>> Sane-analysis at jlab.org
>>> https://mailman.jlab.org/mailman/listinfo/sane-analysis
>>
>
>
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