相关论文: Orthopositronium: Annihilation of positron in gase…
The resolve of the 'orthopositronium-lifetime puzzle' needs study of the "isotope anomaly" in gaseous neon and also of the contribution ~ 0.002 of nonperturbative mode into orthopositronium annihilation. The Michigan results (2003) are…
Whether in the Standard Model or beyond it, neutrinos contribute to the invisible decay mode of orthopositronium but practically not at all to that of parapositronium. Although this remark does not resolve the orthopositronium decay puzzle,…
The intrinsic decay rate of orthopositronium formed in ${\rm SiO_2}$ powder is measured using the direct $2\gamma$ correction method such that the time dependence of the pick-off annihilation rate is precisely determined. The decay rate of…
We briefly review the theoretical and experimental results concerning decays of positronium. Possible solutions of the "orthopositronium lifetime puzzle" are discussed. Positronium annihilation into neutrinos is examined and disagreement is…
Positronium annihilation amplitudes that are computed by assuming a factorization approximation with on-shell intermediate leptons do not exhibit good analytical behaviour. Using dispersion techniques, we find new contributions that…
The electron-positron annihilation spectrum observed by SPI/INTEGRAL during deep Galactic Center region exposure is reported. The line energy (510.954$\pm$0.075 keV) is consistent with the unshifted annihilation line. The width of the…
I consider the problem of the evaluation of the orthopositronium decay rate, including second order radiative corrections. I present a brief theoretical discussion of this problem and a review of the results available in literature, and,…
The analytical method to determine geometry and size of nano-scale defects in oil and gas species and materials is proposed. The modeling is carried out with the parameters of the positron spectra in the angular distribution method of…
We point out that some models with infinite additional dimension(s) of Randall-Sundrum type predict the disappearance of orthopositronium (o-Ps) into additional dimension(s). The experimental signature of this effect is the o-Ps ->…
The possibility that the Galactic dark matter is composed of neutralinos that are just above half the $Z^o$ mass is examined, in the context of the Galactic positron excess. In particular, we check if the anomalous bump in the cosmic ray…
More than 10^43 positrons annihilate every second in the centre of our Galaxy yet, despite four decades of observations, their origin is still unknown. Many candidates have been proposed, such as supernovae and low mass X-ray binaries.…
Rates of the two-, three-, four- and five-photon annihilations of the electron-positron pairs are determined numerically for the three-body positronium ion Ps$^-$ ($e^- e^+ e^-$) and four-body bi-positronium `molecule' Ps$_2$ ($e^- e^+ e^-…
Positron scattering and annihilation on noble gas atoms below the positronium formation threshold is studied ab initio using many-body theory methods. The many-body theory provides a near-complete understanding of the…
The intrinsic decay rate of orthopositronium formed in ${\rm SiO_2}$ powder is measured using the direct $2\gamma$ correction method such that the time dependence of the pick-off annihilation rate is precisely determined using high…
We present a spectral analysis of the e+e- annihilation emission from the Galactic Centre region based on the first year of measurements made with the spectrometer SPI of the INTEGRAL mission. We have found that the annihilation spectrum…
Bound state properties of the negatively charged Ps$^{-}$ ion (or $e^{-} e^{+} e^{-}$) are discussed. The expectation values of operators which correspond to these properties have been determined with the use of the highly accurate wave…
One of the features of the triplet state of positronium (ortho-Positronium)atoms is its relatively longer lifetime when compared to the singlet states ofpositronium (para-Positronium) atoms. The most probable decay of ortho-Positronium is…
Observations of soft gamma rays emanating from the Milky Way from SPI/\textit{INTEGRAL} reveal the annihilation of $\sim2\times10^{43}$ positrons every second in the Galactic bulge. The origin of these positrons, which annihilate to produce…
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…
High energy (~GeV) positrons are seen within cosmic rays and observation of a narrow line at 511 keV shows that positrons are annihilating in the galaxy after slowing down to ~keV energies or less. Our state of knowledge of the origin of…