Difference between revisions of "Photon Reconstruction in b1pi events 02/10/2012"
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After correcting these two issues: | After correcting these two issues: | ||
| − | [[.. | + | [[Image:PhotonEvsTheta recon FCAL Feb12.aggressiveTrackMatching.png]] |
| − | We can make a timing cut (t_shower-t_flight) < | + | We can make a timing cut (t_shower-t_flight) < 1 ns: |
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| + | [[..]] | ||
===Timing=== | ===Timing=== | ||
Revision as of 12:21, 22 February 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 this has some issues.
- Only one matching FCAL cluster per track is allowed with the current code. Frequently hadronic showers are grouped into multiple clusters.
- The match radius is hardcoded as 5 cm, but in the calib/PID/photon_track_matching this parameter is set to 15 cm.
After correcting these two issues:
We can make a timing cut (t_shower-t_flight) < 1 ns:
[[..]]
Timing
t_shower-t_flight:
Not centered on 0???
Try to cut on timing info (tproj-2.3 < 1.4):
Too few.
Distribution doesn't match thrown.
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.
