Heavy Physics Contributions to Neutrinoless Double Beta Decay from QCD

Area of Science:

• Nuclear Physics
• Particle Physics
• Quantum Chromodynamics

Background:

• Neutrinoless double beta decay is a key process for understanding neutrino mass nature.
• Experimental efforts worldwide seek to observe this lepton number violating decay.
• Connecting decay rates to beyond the standard model (BSM) physics requires nonperturbative quantum chromodynamics (QCD) insights.

Purpose of the Study:

• To compute matrix elements of short-range operators contributing to neutrinoless double beta decay.
• To provide essential inputs for model-independent calculations of this decay process.
• To clarify the role of short-range operator contributions versus long-range neutrino exchange.

Main Methods:

• Lattice quantum chromodynamics (QCD) was employed to calculate matrix elements.
• Effective field theory methods were utilized in conjunction with lattice QCD results.
• Focus was on leading order π⁻→π⁺ exchange diagrams involving short-range operators.

Main Results:

• The necessary matrix elements of short-range operators were computed using lattice QCD.
• These results are crucial for understanding contributions from heavy beyond the standard model (BSM) mediators.
• Calculations indicate short-range operator contributions may rival or exceed those from long-range neutrino exchange.

Conclusions:

• The computed lattice QCD matrix elements enable model-independent calculations of two-nucleon decay.
• These findings serve as vital input for nuclear many-body calculations of experimental decays.
• Short-range operator contributions are potentially as significant as long-range neutrino exchange in neutrinoless double beta decay.