[Frost] Scale factors and dilution factors

[Michael Dugger]

Hi,

At today's meeting I was not able to describe why the trigger issue might 
be important with regards to scale factors and dilution factors. I think I 
can do a better job in this email.

One thing that we are probably all aware of is that the scale factors are 
dependent upon angle and momentum. One of the reasons for this phase 
space dependence is that charged particles will typically lose more energy 
swimming through the butanol target than for the carbon target. The 
difference in eloss between the targets can be fairly large. As a
test, I ran a few events looking at the momentum differences at fixed 
eloss corrected momentum and lab angle, and found that a 500 MeV/c proton 
at 27 degrees can lose from about 14 to 57 MeV/c in momentum when 
originating from butanol, whereas the same proton event originating from 
the carbon target will lose about 19 MeV. This means that the CLAS seen 
kinematics will be different dependent upon which target the event comes 
from. From the small number of test events, I found that the proton events 
(500 MeV/c protons at 27 degrees) coming from the carbon target hit TOF 
paddle 22, but the events originating from butanol ranged between TOF 
paddles 21 through 23. It then follows that the efficiency for a proton 
with fixed lab angle and eloss corrected momentum will depend upon the 
target of origination.

The important thing to keep in mind is that the scale factors do not 
represent the ratio of butanol bound nucleons to that of carbon. The scale 
factors also include the ratio of efficiencies. If the efficiency ratios 
were equal to one (no z-vertex dependence on particle efficiency) than we 
would not see any structure in the scale factor phase space and the scale 
factors would just represent the ratio of bound nucleons between 
the butanol and carbon targets.

Since the scale factors contain the ratio of efficiency between events 
that originate in the butanol to those coming from the carbon (not always 
= 1), then events that have TOF trigger problems may very well have a 
different efficiency ratio than for events without TOF trigger issues.
This means that if the scale factors are measured using the reactions with 
pi+ pi- p in the final state, then these scale factors may not be correct 
for the single proton or single pion events.

Thanks for your time.

I hope this makes sense. If I got something wrong, please let me know.

Take care,
Michael