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Direct Observation of the Hyperfine Transition of the Ground State Positronium
We report the first direct measurement of the hyperfine transition of the
ground state positronium. The hyperfine structure between ortho-positronium and
para-positronium is about 203 GHz. We develop a new optical system to
accumulate about 10 kW power using a gyrotron, a mode converter, and a
Fabry-P\'{e}rot cavity. The hyperfine transition has been observed with a
significance of 5.4 standard deviations. The transition probability is measured
to be s for the first time, which
is in good agreement with the theoretical value of
s
Measurement of Positronium hyperfine splitting with quantum oscillation
Interference between different energy eigenstates in a quantum system results
in an oscillation with a frequency which is proportional to the difference in
energy between the states. Such an oscillation is observable in polarized
positronium when it is placed in a magnetic field. In order to measure the
hyperfine splitting of positronium, we perform the precise measurement of this
oscillation using a high quality superconducting magnet and fast
photon-detectors. A result of ~GHz is obtained which is consistent with both theoretical
calculations and previous precise measurements.Comment: 4 figures accepted by Phys. Lett.
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