LNGS Wiki Pages

We plan to publish a paper about the precise measurement for the half-life of the 215Po α-decay using LaBr3 scintillation detector. For this purpose, we need to analyze the systematic uncertainty in detail. This page lists the possible factors we need to consider. The systematic uncertainty will include two parts, one is from the instrument uncertainty, and the other is contributed by the analysis.

• Time resolution of the digitizer, that is around 32 ns.
• Analyze subsets of the data to check the measurement stability related to the temperature fluctuation, for example.
• Check the delay distribution of events

• Show a residue plot, that can be obtained from the subtraction of the fit and the data
• Use different energy windows
• Check the uncertainty from different fitting methods. For this, we need to produce fake data that should contain the time information. Then we use the fitting function (and parameters) applied in the measured dataset to fit the fake data.
• For the background, we can change the background by one sigma (as used in the paper), and refit the exponential curve. Alternatively, we can use the background extracted from the range that is not in our region of interest.
• Fit the measured data and the fake data using different methods, like ROOT software and BAT (BAT can give the likelihood)

For cross-check, we should do independent analysis. There are a few more points that can help us confirm the analysis,

• Varying the fit range. This factor includes both the statistical and systematic uncertainties, so we probably won't include this part into the uncertainty.
• Integrate one or two hours signal events and see whether it is Poisson distribution.
• We constrain the integral range strictly, so that the data is as clean as possible. We analyze the golden dataset and the obtained result can be used as a reference.