[Halld-cal] MC Michel Spectra selection cuts

[Elton Smith]

Hi Andrei,

Following our discussion at the reconstruction meeting yesterday, it 
would be nice to be able for Will to compare his electron spectra with 
the Michel generated MC.

Thresholds: The flash threshold is 5 counts above threshold. This 
corresponds to an attenuated energy of Th0=2.3 MeV using the following 
constants:
Th0 = 5 peak counts * 15 int cts/peak * 0.03 MeV/int count
Due to attenuation lambda, the threshold is in fact higher depending on 
the position of the hit, i.e.
Energy Thresh (z) > Th0 x exp [(L/2 + z)/lambda]; upstream
Energy Thresh (z) > Th0 x exp [(L/2 - z)/lambda]; downstream
where z is measured relative to the center of the module and increases 
downstream. For the attenuation length you can check what is currently 
in ccdb. See for example
https://logbooks.jlab.org/files/2015/09/3352084/ccdb_get_attenuation_parameters_col0.pdf
You can either use an average or a range based on the measured distribution.

It would be nice to see the spectra by varying the threshold Th between 
0.5xTh0 and 2xTh0.

You also mentioned that we might consider including selection cuts, 
which Will is using in his analysis. He uses the following selection cuts:
1. late time hit cut
2. requirement that energy is deposited in at least 2 channels
3. the electron energy is deposited in less than 4 modules
4. at least one point object is in the distribution.

Cuts 1 and 3 should all be satisfied by bona fide events, so no need to 
add to MC.
Cut 2 will likely be relaxed as the analysis evolves, so no need to add 
at this time.

The only cut, which should be included, is #4. This requires that at at 
least one cell have a hit on both ends, i.e. the threshold requirement 
(above) be satisfied for at least one cell for both upstream and 
downstream hits.


Send questions or clarifications to me or Will.


Thanks, Elton.


Elton Smith
Jefferson Lab MS 12H3
12000 Jefferson Ave STE 4
Newport News, VA 23606
(757)269-7625
(757)269-6331 fax