Statistical analysis of low-level material screening measurements via gamma-spectroscopy.

Area of Science:

• Nuclear Physics
• Particle Physics
• Experimental Physics

Background:

• Accurate background estimations are crucial for neutrinoless double beta decay (0nubetabeta) experiments.
• Low-level material screening using gamma spectrometry requires reliable statistical limits.
• Existing methods may not fully incorporate physical constraints or multiple data sources.

Purpose of the Study:

• To present a custom Bayesian statistical method for background estimations in 0nubetabeta experiments.
• To establish reliable statistical limits for low-level material screening measurements.
• To improve the incorporation of physical knowledge and multiple data streams into limit calculations.

Main Methods:

• Development of a Bayesian statistical analysis framework.
• Integration of sample and background spectra data.
• Incorporation of the physical constraint of non-negative counting rates.
• Adherence to the international standard ISO 11929-7.
• Extension to incorporate multiple gamma lines from various radionuclides.

Main Results:

• The method provides continuous confidence intervals transitioning from two-sided intervals to single-sided upper limits.
• Demonstrated reliability in setting statistical limits for material screening.
• Successfully combined data from sample and background spectra.
• Physically realistic constraints (non-negative rates) were incorporated.

Conclusions:

• The presented Bayesian method offers a robust approach for background estimations in sensitive rare event searches.
• This method enhances the reliability of material screening for experiments like 0nubetabeta.
• The approach aligns with international standards and improves data analysis by incorporating physical knowledge.