[Halld-cal] BCAL energy correction

[Will Levine]

Hi all,
Following up on our discussion at the meeting today. Currently the
following energy correction procedure is used in the BCAL
reconstruction code:

1) After the clustering stage we have the "raw energy" E_raw, which is
just the sum of the energies of the individual hits in the cluster. We
also have a z-position of the cluster. These are the two inputs used.

2) The corrected energy is calculated as:
E_corrected = (E_raw/A(z))^(1/(1+e(z))

3) The scale factor A(z) and the nonlinearity e(z) are functions of z
and are parameterized by fourth-order polynomials.

This correction is discussed briefly in
http://argus.phys.uregina.ca/cgi-bin/private/DocDB/ShowDocument?docid=989
. I've looked into this more recently and found that this procedure
has some issues for certain ranges of z and E. I will try to put
together some plots that show the problem.

Will