CH ROOT Nonuniform Binning

Rebinning via Energy Calibration

Regarding use of 4096 channel peak sensing ADC

• Create an array 4097 entries long to be used for bin edges.

double bins[4097];

• Open a for loop for bin creation.

for(int i=0; i<=4096; i++){

• Fill the array with values for bin edges using the energy calibration fit for HPGe detector. I used i*i here instead of i²(i**2) because the ROOT interpreter doesn't seem to enjoy proper math formulation.

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, or alternatively, the length of the array is Total ADC Channels + 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.

PAA->Project("Gd_In","-36.2928+0.449519*(PADC.PADC785N[9])-0.000000861277*(PADC.PADC785N[9])*(PADC.PADC785N[9])");

• You can no longer use the Gd_In->Draw(); command, but instead have to use Gd_In.Draw(); This is due to the histogram not being a pointer.

Gd_In.Draw();

Debugging

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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PAS Experiment