Ab Initio Uncertainty Quantification of Neutrinoless Double-Beta Decay in ^{76}Ge

Area of Science:

• Nuclear Physics
• Particle Physics
• Astroparticle Physics

Background:

• Observation of neutrinoless double-beta (0νββ) decay proves lepton number violation and Majorana nature of neutrinos.
• 0νββ decay links decay rate to neutrino mass scale via nuclear matrix elements (NMEs).
• Accurate NMEs are vital for designing and interpreting 0νββ experiments.

Purpose of the Study:

• To perform the first comprehensive ab initio uncertainty quantification of the 0νββ-decay NME.
• To calculate the NME for the key nucleus ^{76}Ge.
• To establish an upper limit for the effective neutrino mass.

Main Methods:

• Employed nuclear strong and weak interactions derived within chiral effective field theory.
• Utilized recently developed many-body emulators for calculations.
• Performed a conservative treatment of uncertainty quantification.

Main Results:

• Calculated the NME for ^{76}Ge as 2.60_{-1.36}^{+1.28}.
• Set an upper limit for the effective neutrino mass at 187_{-62}^{+205} meV.
• Combined NME with existing half-life sensitivity and phase-space factor.

Conclusions:

• The calculated NME provides crucial data for 0νββ decay experiments.
• The results aid in designing next-generation germanium detectors.
• The findings are important for exploring the inverted hierarchy region of neutrino masses.