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-----Original Message-----
From: McCormick, Jeremy I. 
Sent: Tuesday, November 25, 2014 3:03 PM
To: 'Nathan Baltzell'
Cc: Andrea Celentano; 'Holly Vance'; Uemura, Sho
Subject: HPS Java energy conversion code

Hi,

Here's the information about what is in LCSim right now for ADC to energy conversion.

(All file locations are relative to the HPS Java trunk directory.)

The main Driver is here.

ecal-recon/src/main/java/org/hps/recon/ecal/EcalRawConverterDriver.java

This actually uses the following class to perform the conversion to energy.

ecal-recon/src/main/java/org/hps/recon/ecal/EcalRawConverter.java

There are several different algorithms there for doing the conversion, but the one being used I think is the following.

gain * adcSum * gainFactor * ecalReadoutPeriod;

where

adcSum = pedestal subtracted ADC sum

gain = individual channel gain factor

The gainFactor and ecalReadoutPeriod are defined in 

ecal-recon/src/main/java/org/hps/recon/ecal/ECalUtils.java

where

gainFactor = 2.0 / (Math.pow(2, nBit) - 12) / 15.0545;  

ecalReadoutPeriod = 4.0

When this is applied to the current cosmic data, I get some pretty wild crystal energy estimates ranging between -1.0 and 1.0 GeV, but as I understand it these should be more like Gaussian distributions around 0.

Right now, Nathan says the gains are too high by a factor of 4.  Getting calibrated channel gains in the conditions system should correct this problem.

I'll send along in another email a steering file you can use to test this conversion algorithm.  I also have some plots too which I'll generate and send out as a .root file.

--Jeremy

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