The pionic hydrogen experiment at PSI
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A new high-precision determination of the strong-interaction shift (∈1s) and broadening (Γ1s) of the ground state in pionic hydrogen (πH) has been started at PSI. This constitutes a direct measurement of the πN scattering lengths and is an important test of the methods of chiral perturbation theory.
The experiment will be conducted in two steps. In the first step we aim for a precision of 0.2% for ∈1s and 3% for Γ1s. A new method of energy calibration is used: by measuring πH simultaneously with pionic oxygen (πO), systematic errors are suppressed. The goal for the second step is an accuracy of 1% for Γ1s.
Key wordsexotic atoms pion-nucleon interaction x-ray spectroscopy
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