Photon Reconstruction in b1pi events 02/10/2012
Contents
BCAL
Thrown photons
Look at the distribution of decay photons from the pi0.
For comparison with reconstructed data, useful to look at z rather than theta. This is the z that the photon would reach the inner radius of the BCAL, given its momentum and vertex.
Reconstructed photons
Spectrum of reconstructed "photons": exclude clusters that can be matched to a charged track.
Where does each of these peaks come from?
- Peaks at upstream and downstream ends of detector from noise that cause garbage timing info?
- Other three sharp peaks? Look like FDC structure, but spacing is not right?
Cuts
- A timing cut fabs(t_shower-t_flight) < 1 ns can be applied to remove many of the extra "photons". (Red curve below)
- I don't think low energy showers are well understood at the moment, so remove clusters with E<60 MeV. (Green)
- Also, cut out a problem area at forward angles and lower energies (E<120 MeV && z>325 cm) (Blue)
More work needed to optimize cuts.
With all cuts:
Number of "photons" decreases from 44,000 to 13,000.
FCAL
Thrown photons
Reconstructed photons
Way too many reconstructed. Clusters matched to charged tracks are vetoed, but maybe this is not optimized properly.
Timing
t_shower-t_flight:
Not centered on 0???
Try to cut on timing info ():
Two gamma invariant Mass
Look at pairs of 2 BCAL photons, subject to cuts described above. Using truth vertex information.
Later should add FCAL photons.
Compare KLOE algorithm to GlueX algorithm.
GlueX is in red, KLOE in black.
