FCCee-Polarimeter

MC simulations for the project of FCC-ee Compton beam polarimeter.

The method is discussed in the publication https://arxiv.org/abs/1803.09595.

Tested with python 3.85 [GCC 9.3.0] and ROOT 6.22/03 on Linux Mint kernel 5.4.0-58-generic

1. Simulation parameters may be altered in the hardware.py.
2. Use mc-compton.py for Monte-Carlo generation of photon and electron distributions.
3. The result will be saved to a root file with a name, similar to Sun Dec 13 10:49:17 2020.root.
4. For fitting, alter the filename in eFit.py (somewhere around 140 line) and run the script.
5. Bear in mind that the fitting procedure is quite long at this stage.
   On my Intel(R) Core(TM) i3-6100U CPU @ 2.30GHz laptop the fit (with default parameter set) converges after 197 iterations, which takes

Real Time = 4115.06 seconds Cpu Time = 4122.41 seconds.

If this method is ever used, the fitting procedure should definitely be improved.

The fit result with default settings is:

 FCN=6447.49 FROM MIGRAD    STATUS=CONVERGED     208 CALLS         209 TOTAL
                     EDM=2.08144e-09    STRATEGY= 1  ERROR MATRIX UNCERTAINTY   0.8 per cent
  EXT PARAMETER                  PARABOLIC         MINOS ERRORS
  NO.   NAME      VALUE            ERROR      NEGATIVE      POSITIVE
   1  X_{0}        1.15679e-02   1.00231e-02
   2  X_{1}        3.47635e+02   3.26152e-03
   3  Y_{0}       -1.06824e+00   4.15379e-05
   4  Y_{1}        1.06820e+00   4.07565e-05
   5  #kappa       1.62800e+00     fixed
   6  P_{#parallel}   0.00000e+00     fixed
   7  P_{#perp}    1.02652e-01   1.65003e-03
   8  #sigma_{x}   1.96462e-01   4.54456e-03
   9  #sigma_{y}   2.36739e-02   2.45517e-05
  10  norm         5.22868e+07   1.41892e+04
Chi2: 6447.487180
NDF: 6119
Probability: 0.001729
A = 347.6238 +/- 0.0105 (0.00003)
1.627839909428406 0.00012432482133096817
E = 45.59708 +/- 0.00348