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Register a new userFirst test of $O(alpha ^{2})$ correction of the orthopositronium decay rate
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Positronium is an ideal system for the research of the bound state QED. New precise measurement of orthopositronium decay rate has been performed with an accuracy of 150 ppm. This result is consistent with the last three results and also the 2nd order correction. The result combined with the last three is 7.0401$pm0.0007mu mathrm{sec}^{-1}$ (100 ppm), which is consistent with the 2nd order correction and differs from the 1st order calculation by 2.6$sigma$ It is the first test to validate the 2nd order correction.
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The intrinsic decay rate of orthopositronium formed in ${rm SiO_2}$ powder is measured using the direct $2gamma$ correction method such that the time dependence of the pick-off annihilation rate is precisely determined. The decay rate of orthopositronium is found to be $7.0396pm0.0012 (stat.)pm0.0011 (sys.)mu s^{-1}$, which is consistent with our previous measurements with about twice the accuracy. Results agree well with the $O(alpha^2)$ QED prediction, and also with a result reported very recently using nanoporous film.
The order - alpha radiative corrections to the differential decay rate of polarized orthopositronium are obtained. Their influences on the three photons coincidence rate as a function of positronium polarization is considered.
Recently, much work has been devoted to the calculation of order $alpha$ corrections to the decay rate of pionium, the $pi^+ pi^-$ bound state. In previous calculations, nonrelativistic QED corrections were neglected since they start at order $alpha^2$ in hydrogen and positronium. In this note, we point out that there is one correction which is actually of order $alpha$ times a function of the ratio $mu_r alpha / m_e$, where $mu_r$ is the reduced mass of the system. When $mu_r alpha ll m_e$, this function can be Taylor expanded and leads to higher order corrections. When $mu_r alpha approx m_e$, as is the case in pionium, the function is of order one and the correction is of order $alpha$. We use an effective field theory approach to calculate this correction and find it equal to $0.4298 alpha Gamma_0$. We also calculate the corresponding correction to the dimuonium ($mu^+ mu^-$ bound state) decay rate and obtained a result in agreement with Jentschura et al.
The intrinsic decay rate of orthopositronium (o-Ps) formed in SiO_2 powder was measured using a modified method which determined the time dependence of the pick-off annihilation rate using high-energy-resolution germanium detectors. That is, the main systematic error due to thermalization was accounted for and integrated into the time spectrum fitting procedure. The averaged value was found to be lambda_(o-Ps)=7.0399+0.0020-0.0021(stat.) +-0.0015(sys.) mu s^{-1}, which agrees well with the O(alpha^2) QED prediction; varying 2.8-4.2 experimental standard deviations from other measurements.
Positronium is an ideal system for the research of the bound state QED. New precise measurement of orthopositronium decay rate has been performed with an accuracy of 150 ppm, and the result combined with the last three is 7.0401 +- 0.0007 mu s^-1. It is the first result to validate the 2nd order correction. The Hyper Fine Splitting of positronium is sensitive to the higher order corrections of the QED prediction and also to the new physics beyond Standard Model via the quantum oscillation into virtual photon. The discrepancy of 3.5 sigma is found recently between the measured values and the QED prediction (O(alpha^3)). It might be due to the contribution of the new physics or the systematic problems in the previous measurements: (non-thermalized Ps and non-uniformity of the magnetic field). We propose new methods to measure HFS precisely without the these uncertainties.
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