At the Friday's data meeting a question about different absolute MIP values in data and MC was raised. Although the shape and resolution of electron data are consistent the mean of the visible energy distribution in terms of mip are far from being in agreement.

Trying to understand this I firstly asked Chris to apply his fitting function to the MC. The result for the summed ("green" + "clear") histogram is shown in this plot.


 

This agrees with what I got from the landau fit within 1%.

Then I simulated pure energy losses of 2 GeV positron in our scintillator in the native for GEANT energy units -- MeV without any
conversions, attenuation length correction pmt simulations etc. Here's the plot.


 

So the mean of this distribution is 97.6 MeV. If calibrated with beam muons our mip value should be roughly 2MeV ± 15% and therefore we should expect the corresponding mip distribution with a mean of 50-60 for 2 GeV positrons/electrons.


 

So at the moment data seems to have too high mip values. Could it be that for the hits summed at both ends  an incorrect adc2mip convertion factor is used???
 
 
  proverka