[Sane-analysis] Bigcal Re-Calibration Progresss

Fri Jun 13 13:06:03 EDT 2014

Hello Everyone,

I wanted to give a brief update regarding the Bigcal re-calibration and 
summarize the conclusions from our last meeting.

First, I showed on Wednesday that the new calibration *significantly* impacts 
the asymmetry results. The new calibrations improve the overall behavior bin to 
bin and are consistent with A_parallel measured by CLAS.

Secondly, when looking at the asymmetries for the RCS and Protino separately 
(http://quarks.temple.edu/~whit/SANE/analysis_main/results/combined-split_asym_para59_251.png)
it was noted that between x ~ 0.3 to 0.4 there is clear difference between the 
top and bottom. Possible explanations include the calibrations, noisy/bad 
blocks, or background contamination (through differing kinematics). The latter 
is nearly ruled out because it persists through the background subtraction (as 
seen here 
http://quarks.temple.edu/~whit/SANE/analysis_main/results/asymmetries/A1A2_59_noel_split_253.png).
However, it is possibly a combination of a noisy block causing bad causing the 
average kinematics to be skewed and thus calculating the wrong background 
correction. For reference here is the background corrections plot 
http://quarks.temple.edu/~whit/SANE/analysis_main/results/asymmetries/bg_corrections_para59_251.png.

Or it is the calibration... 

In order to provide a check, I have been looking at the eta mass peak (548 
MeV/c^2) in the two photon mass spectrum. After spending two days iterationg 
over just the two sections of bigcal to improve the calibrations, I produce the 
following fits.

The mass peak in the perpendicular calibration looks good (m_0 ~ 550):  
http://quarks.temple.edu/~whit/SANE/analysis_main/results/pi0calibration/FitEtaMass_perp_517.png

For the parallel calibration, the mass peak is shifted to lower values by about 
20-30 MeV (m_0 ~ 520).  
http://quarks.temple.edu/~whit/SANE/analysis_main/results/pi0calibration/FitEtaMass_para_517.png

Previously I had reported that the perpendicular calibration seemed to need 
more work. This was true when looking at the overall shift of the pi0 mass 
peak, but, when looking at the latest changes in the calibration coefficients 
for the parallel they are quite large (bottom right plot 
http://quarks.temple.edu/~whit/SANE/analysis_main/results/pi0calibration/pi0CalibrationCompare_para_517_c1_0.png).
Because the changes are large and fluctuate around zero a shift in the pi0mass 
peak is not observed (just a narrowing is), but these changes are just as 
important as the perpendicular.

I will continue to try to improve the calibrations by focusing on smaller 
sections (instead of all of RCS or Protvino at a time). My hope is that with 
improvement the parallel calibration's eta mass peak will move towards 550. It
appears to be doing so rather slowly. Look at these plots in order:
http://quarks.temple.edu/~whit/SANE/analysis_main/results/pi0calibration/FitEtaMass_para_514.png
http://quarks.temple.edu/~whit/SANE/analysis_main/results/pi0calibration/FitEtaMass_para_515.png
http://quarks.temple.edu/~whit/SANE/analysis_main/results/pi0calibration/FitEtaMass_para_516.png
http://quarks.temple.edu/~whit/SANE/analysis_main/results/pi0calibration/FitEtaMass_para_517.png

Thank you for your time, and as always, your comments and questions are 
appreciated.

Cheers,
Whit

On Wed, Jun 04, 2014 at 03:29:54PM -0400, O. A. Rondon wrote:
>Hi Whit,
>
>Neat results. I agree that for perp the eta might be there, but I would
>suggest plotting errors on the histos (both 80 and 180 data) to see if
>at 80 deg it's not just statistics, like the big jump near 300 (MeV)
>probably is.
>
>Could you also add an explanation of what is being plotted in each
>panel? The meaning of the mass plot is clear (at least of the blue
>histo), and I guess the mass vs xi, yi (i= 1, 2) probably are the mass
>distributions vs the x, y coordinates of clusters 1 and 2 used to
>reconstruct the eta, but I'm not sure about the red mass histo in the
>mass 3 panel; the E2 panel's red and black histos; what D is in the
>massVSD; and what the clustx vs y1, y2 are (the y1,y2 scales here don't
>agree with the scales of the mass vs y1, y2 plots).
>
>Before devoting too much effort in finding the eta in the perp data, I
>would suggest recalculating A180 with the new calibration, to see if it
>makes a difference in the asymmetry.
>
>Cheers,
>
>Oscar
>
>Whitney R. Armstrong wrote:
>> Hello Everyone,
>>
>> I wanted to share some results in my refinement of the BigCal calibration from
>> pi0s.
>>
>> Below you will find plots showing the mass spectrum (above the pi0 mass) from
>> two photons (top central plots) for parallel and perpendicular configurations.
>>
>> In the mass plot you can see a bump near the eta mass (547 MeV).
>>
>> Parallel:
>> http://quarks.temple.edu/~whit/SANE/analysis_main/results/pi0calibration/etamass2-2000_1.png
>>
>> Perp:
>> http://quarks.temple.edu/~whit/SANE/analysis_main/results/pi0calibration/etamass2-2000_5.png
>>
>> Please note the following:
>>
>> 1) Only after recalibrating did the eta mass peak start to show up. This is
>> because the mass reconstructino of the eta is most sensitive to the energy
>> resolution and less sensitive to the position (due to the larger opening angle
>> for the eta compared to the pi0).
>>
>> 2) The parallel calibration is better than the perpendicular. That is, the perp
>> calibration can certainly be improved compared to the parallel, thus the eta
>> mass is resolved better for the parallel.
>>
>> 3) The background is much higher than the pi0, therefore, it does not seem
>> feasible to directly calibrate (like pi0) using the eta mass peak.  However,
>> because the two eta clusters are separated bny large distances (>90 cm), it
>> provides a nice confirmation that the opposite sides (eg the top and bottom)
>> are calibrated properly against each other.
>>
>> 4) All previous results were contaminated by the insidious behaviour of the old
>> calibration. The top (RCS) energies were shifted higher while the bottom
>> (Protvino) was shifted lower (thus producing a nicely centered pi0mass when
>> summing over the whole detector). This likely exlains why Anusha consistently
>> saw energy differences in the elastics. It also explains (the problem seen long
>> ago) that the top appeared to have all the higher energy events compared to the
>> bottom.  It would be interesting to look at both of these problems again.
>>
>> Please let me know if you have any suggestions on how to clean up the eta mass
>> spectrum.
>>
>> As always, your comments and questions are greatly appreciated.
>>
>> Cheers,
>> Whit
>>
>>
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>
>
>
>Also,
>
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