2,001 research outputs found
Search for CP-violation in Positronium Decay
CP-violation in the quark sector has been well established over the last
decade, but has not been observed in the lepton sector. We search for
CP-violating decay processes in positronium, using the angular correlation of
(\vec{S}\cdot\vec{k_{1}})(\vec{S}\cdot\vec{k_{1}}\times\vec{k_{2}}), where
\vec{S} is the the positronium spin and \vec{k_{1}}, \vec{k_{2}} are the
directions of the positronium decay photons. To a sensitivity of
2.2\times10^{-3}, no CP-violation has been found, which is at the level of the
CP-violation amplitude in the K meson. A 90% confidence interval of the
CP-violation parameter (C_{CP}) was determined to be -0.0023 < C_{CP} < 0.0049.
This result is a factor 7 more strict than that of the previous experiment
Results of a Search for Paraphotons with Intense X-ray Beams at SPring-8
A search for paraphotons, or hidden U(1) gauge bosons, is performed using an
intense X-ray beamline at SPring--8. "Light Shining through a Wall" technique
is used in this search. No excess of events above background is observed. A
stringent constraint is obtained on the photon--paraphoton mixing angle, for .Comment: 10 pages, 4 figure
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
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