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In the following table are the parameters for beam divergence as function of the nominal energy momentum of the electron beam.
Divergence |
|
|
|
|
|
Momentum | 0.5 | 1 | 1.5 | 2.5 | (GeV) |
Horizontal | 10.03 | 7.17 | 4.82 | 3.17 | (mrad) |
Vertical | 7.19 | 4.45 | 3.38 | 2.33 | (mrad) |
The beam momentum dispersion has been derived from the Tagger Calibration.
Description of the analysis
We used the following variables : TAG_XYZ, TAG_NUM_CLUSTERS_LAYER
Work and work only on "4 points" events, i.e. one cluster per tagger layer.
Use the highest cluster to draw interesting distributions : +
- spot : Horizontal, Vertical position and correlation
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- divergence : Horizontal, Vertical angles and correlation
Beam spot is truncated by the scintillators, so we need to get the min/max of
both horizontal and vertical distributions. Boundaries are defined as :
+ Number of Hits > Maximum hits / 10.
Each distribution is then fitted within these boundaries with a Gaussian
function, in order to retrieve the first two moments.
Horizontal and vertical angle distributions are fitted equally with a Gaussian
function within +/- 1.5*RMS of the distribution in order to fit the peak and
exclude tails.
This analysis is done on all good tagged photons runs and global parameters are
derived for each beam momentum as shown on the following plot :+
- beam spot : Truncated Gaussian function parameters (Min, Max, Mean, RMS)
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- + Horizontal/Vertical position (mm) : Min (blue triangle), Mean (Black circle), Max (red triangle)
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- + Horizontal/Vertical dispersion (mm): RMS (Black circle)
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- beam divergence : Horizontal/Vertical angles in mrad, clearly depend upon beam
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- momentum.
Click on the thumbnail to open the Beam statistics plot for Tagged photons runs :
Please find in attachment all the beam spot plots in the Tagger and in the CU for all the runs