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arXiv · 1705.10431

$P-$state Positronium for Precision Physics: an Ultrafine Splitting at $α^6$

Henry Lamm
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Abstract

An "ultrafine" splitting in positronium between the $L=1$ spin-singlet state and the spin-average of the spin-triplet states is shown to arise only at order $α^6$. The QED prediction for $n=2$ states is $Δ_{2,P}=(683/172800)mα^6=73.7(1.2)$ kHz. This represents the smallest leading-order QED splitting known. Current experimental efforts could observe this splitting, and its observation can constrain new ultralight interactions, such as axions or $Z'$.

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Henry Lamm. 2017-05-30. $P-$state Positronium for Precision Physics: an Ultrafine Splitting at $α^6$. https://doi.org/10.1103/physreva.96.022515

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