FCAL Reconstruction 04/08/2012

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 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

FCAL energy corrections

What's the deal with FCAL energy correction? current code by Mihajlo (DocDB 1093) what does this adjust 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,$\epsilon$.

In reconstruction, get E_corrected from E_clust by solving this equation iteratively.

Energy resolution

Using current calibration coefficients:

Fit to black curve says sigma(E) = 6.1%/sqrt(E) ⊕ 1.9%

Using same calibration scheme, but readjust coefficients for single block clusters

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Fit to red curve says sigma(E) = 6.4%/sqrt(E) ⊕ 1.9%