Before Christmas Analysis

Elastic Proton Asymmetries:

I have returned to the analysis of data at pmiss = 0, which should approx. correspond to the elastic scattering of electrons on the polarized proton target. The idea is to extract proton polarization inside 3He Nucleus. Here are my data:

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Test with the MIT-Bates Data:

To double check that my code for the elastic-proton asymmetry calculation works properly, we compared the calculated values with the measurements from MIT-Bates. Here is the comparison. It seems that measured values (Crawford et al, PRL98) agree well with my calculations.

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Analysis Results:

I have modified my fitting technique. Earlier I was using central parameter values for both kinematics settings. That enabled me to fit both fitting points (longitudinal and transverse point) for each setting directly to a fitting curve. See the following link. MeetingNo70.html

For the latest analysis I considered different approach. For longitudinal points, \phi* angle is a priori 0. However, for transverse points phi* is equally distributed over wide range of angles +/-40deg. I have decided to consider this in my analysis, by integrating the elastic-asymmetry formula over the whole range of angles. This has introduced a following change in the elastic-scattering formula:

cos(phi*==0) --> 0.25*(2sigma + sin(2*sigma))/(sin(sigma))

where sigma corresponds to the width of the phi* distribution. When applied to my data this modification brings 8% correction to one of the terms in the asymmetry formula (1--> 0.926).

Because of this modification in the analysis, I was not able to fit my data points directly to the curve, but had to used point to point comparison. I also decided to analyze all 4 points (2x2) together and find a common polarization parameter. Here are my results:

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Error-bars shown correspond to the statistical errors of each measured points. The 2nd and 4th point (transverse points) have larger error-bars due to smaller absolute value of the asymmetry.

My analysis was primarily done in root. However to double check, I also did it in Mathematica: ProtonElasticAsymmetryDecember.pdf

As before we got a fitting parameter approx. 0.2, which means, that in the given conditions means 20% proton polarization in the 3He. Now we are in a search of a toy model, that would explain this kind of behavior.

NIKHEF Comparison:

As additional test I used my approach on NIKHEF Deuterium data. Here the same approach applies. In the low missing-momentum region this asymmetry should directly correspond to the elastic proton asymmetry (100% polarization).

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Measured values are: Q**2 = -0.21(GeV/c)**2, thetaBB=40deg, theta* = 90deg. phi* = 0, Asymmetry ~ -0.27.

Calculated asymmetry = -0.32, which deviates approx. 14% from the measured value.

After Christmas Analysis

2bbu vs. 2bbu

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Discussion with Zilu:

I continued my elastic asymmetry analysis (please see my web-page from last week). When Simon and I were in Boston, Zilu suggested to apply missing-energy cuts to my data, to divide missing energy (ME) peak into three regions. Low ME should correspond to 2 body breakup, high ME should correspond to 3 body breakup. The middle region is of course the mixture of the two. With these cuts (if they work) I should see cleaner picture of the asymmetry and should get better agreement with the elastic proton results for low ME at pmiss=0. I have considered his idea and here are the results.

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Analysis results:

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Plots considered during analysis:

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Theoretical predictions:

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New Asymmetry Results

I have re-analyzed the majority of 12.5 and 14.5deg data. Here are the results (quick) for Proton and Deuteron Longitudinal asymmetry.

14deg, HWP-in, (- sign coorection needed)

(Left: Protron, Right: Deuteron)

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14deg, HWP-out, (- sign coorection needed)

(Left: Protron, Right: Deuteron)

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12deg, HWP-in, (- sign coorection needed)

(Left: Protron, Right: Deuteron)

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12deg, HWP-out, (- sign coorection needed)

(Left: Protron, Right: Deuteron)

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Scaler analysis:

I have also continued my analysis of the false asymmetries using BB scalers. I have corrected bugs (nothing essential ) in my code and now I am running analysis for all production data on FARM. So far I was able to analyze all the runs. Unfortunately I have not been able to analyze them yet. I will show you the results next week:

Last modified: 12/07/11