[Halld-cal] Discussion of Bcal readout segementation

[Elton Smith]

Dear collaborators,

Yesterday we had a small phone conference to go over initial
calculations of the resolution for various segmentations of the SiPM into
Bcal readout channels. Below are some reference notes. Work and further
discussion will continue in the new year.

Cheers, Elton.

-------------------------------------
Phone conference Dec 15, 2010 to discuss first look at Bcal readout
segmentation
Attending: Zisis, George, Andrei, Irina (UofR), Elton (JLab); Matt, Dan
(IU), Will (USM)

o We reviewed plots of fractional energy resolution that Dan produced with
the new reconstruction code for the Bcal. Dan Bennet generated plots of
energy resolution for photons generated between 0.04 and 2 GeV, uniformly
along the calorimeter and uniform in azimuthal angle. The resolution was
calculated for various groupings of inner and outer layers and divided
into three lengths along the calorimeter module.

o The readout of individual SiPMs always gave the best resolution.
However, coarser subdivision of the outer region (2.2) did not degrade the
resolution very much relative to a 4.4 readout.

o Nominal summing of inner SiPM grouping of 2.4 (2 radial, 4 azimuthal)
resulted in the fractional energy resolution degraded by about 10% at the
lowest energies.

o Further work:
- Check outer segmentation of 4.1 vs 2.2.
- Check inner radial segmentation of six layers into two readout
channels of of 3+3 (nominal) vs 2+4. [Note that Dan's notation does not
allow for unequal number of channels to be summed].
- Investigate the z position resolution for these different configurations
- (Leave the phi segmentation at 4 for the inner region).

o Dan will send Andrei and Irina general information about how the plots
were generated. This will include copies of root scripts, etc. Andrei and
Irina will try to reproduce the existing energy resolution plots as a step
for further investigations.

Let me know if I forgot something or misinterpreted anything. I will send
this out tomorrow morning to the listserver.

Thanks, Elton.





Elton Smith
Jefferson Lab MS 12H5
12000 Jefferson Ave
Suite # 16
Newport News, VA 23606
elton at jlab.org
(757) 269-7625
(757) 269-6331 fax