Pionic Hydrogen

Physics interest:

• Precise determination of the pion-nucleon scattering lengths.
• Extraction of the pion-nucleon coupling constant
  and the pion-nucleon σ-term.
• The pionic deuterium level shift reveals isospin breaking effects by constraining the scattering lengths as obtained from pionic hydrogen.
• The pionic deuterium ground state width is dominated by true absorption and directly related to pion production strength α at threshold.

Challenge:

• To measure the strong interaction width Γ and shift ε of the ground state of pionic hydrogen with high precision better than 1% for the shift and about 2% for the width.

Approach:

• Use the PSI cyclotron trap to produce pionic atoms in a controlled environment.
• Use crystal spectrometers and CCD detectors to measure precisely the X-ray energies and line shapes.
• Perform measurements at different hydrogen densities.
• Perform measurements for different transitions.
• Perform measurements of muonic hydrogen to quantify the Doppler broadening of X-ray lines from Coulomb explosion.
• Correlate cascade theory to the Doppler broadening corrections.