Pionic Hydrogen collaboration © 2007
Webmaster: D.Gotta
Design: M.Nekipelov
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Pionic Hydrogen
Measurement of the strong interaction width and shift of the ground state
"QCD Lamb shift"
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.
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Atomic cascade in pionic hydrogen:
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Final results
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ε1s /meV |
Γ1s / meV |
α / μb |
πH |
+ 7086 ± 10 |
856 ± 27 |
--- |
2014/2021 |
πD |
- 2356 ± 31 |
1171 +23/-49 |
251 +5/-11 |
2010 |
Related experiments:
- Precise determination of the charged pion mass.
- Fluorescence X-rays.
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