Neutron-Antineutron Oscillations from Lattice QCD.

Area of Science:

• Particle Physics and Cosmology
• Quantum Chromodynamics (QCD)
• Beyond Standard Model (BSM) Physics

Background:

• The matter-antimatter asymmetry in the Universe is a key unsolved problem.
• Neutron-antineutron oscillations are a predicted signature of baryon number violation in many BSM theories.
• Accurate theoretical predictions are crucial for interpreting experimental searches for these oscillations.

Purpose of the Study:

• To perform first-principles calculations of neutron-antineutron matrix elements.
• To connect the neutron-antineutron oscillation rate to constraints on |ΔB|=2 baryon number violation in BSM theories.
• To compare expected experimental bounds with predictions from a postsphaleron baryogenesis model.

Main Methods:

• Utilized a state-of-the-art lattice gauge field ensemble with physical quark masses.
• Employed nonperturbative renormalization with perturbative matching to the modified minimal subtraction scheme.
• Accounted for excited state effects using two-state fits.

Main Results:

• Calculated crucial neutron-antineutron matrix elements with controlled systematic uncertainties.
• Quantum chromodynamics predicts at least an order of magnitude more events for neutron-antineutron oscillations compared to previous MIT bag model estimates.
• Provided phenomenological implications for proposed neutron-antineutron oscillation experiments.

Conclusions:

• The study provides a more accurate theoretical prediction for neutron-antineutron oscillation signals.
• This work strengthens the potential of low-energy experiments to probe BSM physics and baryogenesis mechanisms.
• The findings suggest enhanced sensitivity for future experiments searching for baryon number violation.