Cannot fill a zds-Hpge timing histogram

[cnatzke]

Hi all,

I am trying to fill a matrix with the energy and time difference between the ZDS and HPGe but I am getting zero counts in the histogram. Does anyone see something I'm doing wrong?

fH2["singles_gamma_beta_timing"] = new TH2D("singles_gamma_beta_timing", "#beta-#gamma time difference;Sum Energy per 1 keV; |#Delta_t| [timestamp]", gamma_bin_max / gamma_binning, gamma_bin_min, gamma_bin_max, 2000, 0, 2000);

for (auto i = 0; i < fGrif->GetMultiplicity(); ++i)
{
	TGriffinHit * griffin_hit1 = fGrif->GetGriffinHit(i);
	fH2["singles_energy_channel"]->Fill(griffin_hit1->GetDetector(), griffin_hit1->GetEnergy());

	for (auto k = 0; k < fZDS->GetMultiplicity(); ++k)
	{
		TZeroDegreeHit *zds_hit = fZDS->GetZeroDegreeHit(k);
		if (zds_hit->GetKValue() != 60)
		{
			continue;
		}

		long beta_time_diff = TMath::Abs(griffin_hit1->GetTimeStamp() - zds_hit->GetTimeStamp());
		fH2["singles_gamma_beta_timing"]->Fill(griffin_hit1->GetEnergy(), beta_time_diff);
	}
}

[VinzenzBildstein]

When you say "zero counts", does that mean zero entries in the histogram, or no entries in the visible range (i.e. everything in over- or underflow)?
My guesses would be that either the default k-value for the ZDS is not 60, but something smaller than that.
The other possibility is that the multiplicity of the ZDS is zero (this would be because there is no ZDS in the analysis tree).
Fastest way to check this would be to open the analysis file (if you proof multiple at once, take the first one), and use the command

AnalysisTree->Draw("TZeroDegree.fHits.fKValue>>k(100,-0.5,99.5)","","",100000)

If that doesn't give you any events, try a) increasing the number of entries from 100000, or b) use the command

AnalysisTree->Draw("TZeroDegree.@fHits.size()>>m(10,-0.5,9.5)","","",100000)

[cnatzke]

Zero counts means no entries in the histogram.

These are files from 2017 so I used the command AnalysisTree->Draw("TZeroDegree.fZeroDegreeHits.fKValue>>k(100,-0.5,99.5)","","",100000) and got the following:

Does this mean the k-value filter in my fill loop is causing the issue?

[cnatzke]

In a selector I used the fill loop

	for (auto i = 0; i < fGrif->GetMultiplicity(); ++i)
	{
		griffin_hit1 = fGrif->GetGriffinHit(i);
		fH2["singles_energy_channel"]->Fill(griffin_hit1->GetDetector(), griffin_hit1->GetEnergy());
		fH1["hpge_kvalue"]->Fill(griffin_hit1->GetKValue());

and got the following for an HPGe k-value spectrum:

This doesn't look correct to me. Could this be something in the analysis tree? The plot for ZDS k-value shares the same distribution as this one.

[VinzenzBildstein]

No, this probably means that your k-values are much larger. Try doing the analysis-tree plot (which I assume is quicker?) with a histogram that has 1000 bins from -0.5 to 999.5 (or no binning at all). Another options is to use Scan instead of Draw to get the number directly.

And yes, I think this is exactly your issue. You could try commenting out the k-value check and you will get entries in that histogram.

[cnatzke]

this probably means that your k-values are much larger.

This was exactly the issue. I increased the range to 1000 and got the following:

Thanks for the help.