Precision Spectroscopy of the Pionic Helium-4.

Area of Science:

• Atomic Physics
• Quantum Electrodynamics
• Nuclear Physics

Background:

• Pionic atoms provide a sensitive probe of fundamental physics.
• Precise calculations of transition frequencies are crucial for determining fundamental constants.

Purpose of the Study:

• To calculate the (n,ℓ)=(17,16)→(16,15) transition frequency in pionic helium-4 with high accuracy.
• To improve upon existing theoretical predictions and provide a benchmark for experimental measurements.
• To estimate the impact of collisional effects on transition frequencies.

Main Methods:

• Relativistic and quantum electrodynamic corrections were included up to O(R_{∞}α^{5}).
• Theoretical calculations were performed to a precision of 4 parts per billion (ppb).
• Collisional effects between pionic helium and target helium were theoretically estimated.

Main Results:

• The transition frequency was calculated with unprecedented accuracy (4 ppb).
• The results significantly improve upon previous theoretical values.
• Collisional effects were found to influence transition frequencies.

Conclusions:

• The precise calculation provides a new benchmark for pionic helium-4 spectroscopy.
• Future experiments reaching ppb accuracy will enable a 2-3 order of magnitude improvement in the pion mass determination.