E05-102 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:

1.)

2.)

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.

3.)

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:

4.)

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).

6.)

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.

Last modified: 12/07/11