[Sane-analysis] Bigcal Re-Calibration Progresss

[O. A. Rondon]

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,