Tagger Momentum resolution
The tagger calibration runs have been taken with the beam passing though the four chambers.
For each run the reconstucted electron momentum (4 cluster algorithm) has been fitted with a gaussian function after requiring no energy in the CU: the fit gives the offset in momentum reconstruction and the resolution.
For the same runs the clusters position in the vertical (non bent) plane have been used to calculate the angle difference between the incoming and outcoming direction of the beam and therefore the multiple scattering
The picture below showes an example of this analysis with the 1.5 GeV beam.
All the result from the calibration runs have been summarized in the following picture.
The The tagger energy linearity plot has a slop of 1.004 +- 0.005
The The multiple scattering plot fit gives: x/x0 = 2.94 +- 0.03
The The (rescaled) momentum resolution fit gives a constant value: c = (1.395 +- 0.007)%
Notice that some of the runs have a different magnet current (this is necessary if we don't change the geometry), but, after rescaling the resolution to the same bending power we observe
The momentum resolution, at different bending power, can be evalueted with:
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dp/p(%) = c*BL_max/BL = 1.395*0.7089/BL |
Calibration of the bending magnet
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B*L (T*m) = 0.0012271*I(A) - 7.60132e-08*I^2(A^2) |
Angular reconstruction
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