Precision determination of electroweak coupling from atomic parity violation and implications for particle physics

Area of Science:

• Atomic Physics
• Particle Physics
• Quantum Electrodynamics

Background:

• Parity violation in atoms is a sensitive probe of the electroweak interaction.
• Previous calculations had significant theoretical uncertainties.
• Cesium-133 is a suitable atom for high-precision parity violation measurements.

Purpose of the Study:

• To perform a high-precision calculation of parity violation in cesium.
• To reduce theoretical uncertainty by a factor of two.
• To extract the weak charge of the 133Cs nucleus and test the Standard Model.

Main Methods:

• High-precision atomic structure calculations.
• Combining theoretical calculations with experimental measurements.
• Analysis of parity-violating neutral current interactions.

Main Results:

• Reduced theoretical uncertainty in parity violation calculations by a factor of two.
• Extracted the weak charge of the 133Cs nucleus: QW = -73.16(29)expt(20)theor.
• Achieved the most accurate test to date of the Standard Model's low-energy electroweak sector.

Conclusions:

• The extracted weak charge agrees with the Standard Model predictions.
• Confirmed the energy dependence (running) of the electroweak force over four orders of magnitude.
• Constrained new physics scenarios, increasing the lower limit on masses of extra Z bosons.