CH ROOT Nonuniform Binning

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Rebinning via Energy Calibration

Regarding use of 4096 channel peak sensing ADC

  • Creates an array 4097 entries long to be used for bin edges
double bins[4097];
  • Opens a for loop for bin creation
for(int i=0; i<=4096; i++){
  • Fills arrays with values for bin edges using the energy calibration fit for HPGe detector
bins[i] =  i*i*(-0.000000861277) + i*(0.449519)-36.2928;
  • Cout statement to print bin edges to the terminal window as for loop is processing
cout << bins[i] << endl;
  • Closes the for loop and begins evaluation

At this point you should have an array filled with values for bin edges. Note that channel zero is now mapped to ~ -36KeV

Creating a Histogram Using bins[i]

  • Initialize the histogram you want to use. The value 4096 is found by (length of array) - 1
TH1F Gd_In = TH1F("Gd_In","",4096,bins)
  • Project the stored data from the ROOT TTree into the histogram using the same calibration used for binning. The ROOT TTree was named PAA in my case and the name of my histogram is Gd_In. I also pulled the data from channel 9 of the ADC and used a quadratic energy calibration to map from channel number to KeV.


Error: Bins must be in increasing order

This error was thrown by having an integer at +1 the value it should have been at when making the histogram. The following should allow you to find bins that are at a lower value than the previous. This for loop will parse through the entire bins array and print the bins

for(int i=0; i<=4096; i++){
if(bins[i]>=bins[i+1]){cout << i  <<"    " << bins[i] <<"     " << bins[i+1] << endl;

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