Difference between revisions of "FCAL Reconstruction 04/08/2012"
(→FCAL energy corrections) |
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| + | ==Efficiency== | ||
There is a tunable parameter in the FCAL code with default: | There is a tunable parameter in the FCAL code with default: | ||
| Line 13: | Line 14: | ||
In b1pi events: | In b1pi events: | ||
| − | * Overall efficiency increases by ~6%: 78% -> 84% | + | * Overall FCAL efficiency increases by ~6%: 78% -> 84% |
| − | * 15% in total photon count (after timing cut) (1.18->1.36) | + | * 15% in total "photon" count (after timing cut) (1.18->1.36) |
1-block "clusters" will collect less energy than multi-block clusters of same photon energy-->will affect energy calibration, energy resolution | 1-block "clusters" will collect less energy than multi-block clusters of same photon energy-->will affect energy calibration, energy resolution | ||
| + | |||
| + | ==Energy resolution== | ||
| + | |||
| + | [[File:SinglePhotonFCAL.sigma_E_err.minBlock1%2BminBlock2.svn8951.png]] | ||
| + | |||
| + | * red: <code style="color:red">MIN_CLUSTER_BLOCK_COUNT = 1</code> | ||
| + | * black: <code>MIN_CLUSTER_BLOCK_COUNT = 2</code> | ||
| + | |||
| + | Fit to black curve says sigma(E) = 6.1%/sqrt(E) ⊕ 1.9% | ||
| + | |||
| + | [[File:SinglePhotonFCAL.mean E err.minBlock1+minBlock2.svn8951.png]] | ||
| + | |||
| + | Need to recalibrate energy corrections at low E. | ||
==FCAL energy corrections== | ==FCAL energy corrections== | ||
| − | What's the deal with FCAL energy correction? current code by Mihajlo ([ | + | What's the deal with FCAL energy correction? |
| + | * current code by Mihajlo ([https://halldweb.jlab.org/doc-private/DocDB/ShowDocument?docid=1093 DocDB 1093]) | ||
| + | * non-linear correction corrects for attenuation, lack of full containment? | ||
| + | |||
| + | Assume form | ||
| + | |||
| + | [[File:Nonlin energy corr eq.png]], | ||
| + | |||
| + | where E_c is the energy of clustered blocks and E_gamma is the energy of thrown photon. | ||
| + | |||
| + | Fit MC data for A,B,C,<math>\epsilon</math>. | ||
| + | |||
| + | In reconstruction, get E_corrected from E_clust by solving this equation iteratively. | ||
| + | |||
| + | The simplest option for recalibrating would be to use the current scheme but re-fit for A,B,C,<math>\epsilon</math> using sample with 1 block clusters. But is there a better way? | ||
| + | |||
| + | ===E_raw/E_thrown plots=== | ||
| + | |||
| + | Check for theta dependence (currently not accounted for): | ||
| + | |||
| + | [[File:SinglePhotonFCAL.ratio 2D theta.svn8951.png]] | ||
| + | |||
| + | Only apparent at low angles near hole in FCAL. | ||
| + | |||
| + | Dependence on number of blocks in cluster | ||
| − | + | [[File:SinglePhotonFCAL.ratio 2D n_blocks.svn8951.png]] | |
Latest revision as of 17:11, 24 February 2017
Efficiency
There is a tunable parameter in the FCAL code with default:
MIN_CLUSTER_BLOCK_COUNT = 2;
At lower energies (<~500 MeV), this causes photon reconstruction efficiency to be lower because often only one block has energy deposited in it (above the 20 MeV threshold in mcsmear).
In single photon sample:
- red:
MIN_CLUSTER_BLOCK_COUNT = 1 - black:
MIN_CLUSTER_BLOCK_COUNT = 2
In b1pi events:
- Overall FCAL efficiency increases by ~6%: 78% -> 84%
- 15% in total "photon" count (after timing cut) (1.18->1.36)
1-block "clusters" will collect less energy than multi-block clusters of same photon energy-->will affect energy calibration, energy resolution
Energy resolution
- red:
MIN_CLUSTER_BLOCK_COUNT = 1 - black:
MIN_CLUSTER_BLOCK_COUNT = 2
Fit to black curve says sigma(E) = 6.1%/sqrt(E) ⊕ 1.9%
Need to recalibrate energy corrections at low E.
FCAL energy corrections
What's the deal with FCAL energy correction?
- current code by Mihajlo (DocDB 1093)
- non-linear correction corrects for attenuation, lack of full containment?
Assume form
,
where E_c is the energy of clustered blocks and E_gamma is the energy of thrown photon.
Fit MC data for A,B,C,
.
In reconstruction, get E_corrected from E_clust by solving this equation iteratively.
The simplest option for recalibrating would be to use the current scheme but re-fit for A,B,C, using sample with 1 block clusters. But is there a better way?
E_raw/E_thrown plots
Check for theta dependence (currently not accounted for):
Only apparent at low angles near hole in FCAL.
Dependence on number of blocks in cluster
