Journal ArticleDOI
Conversion of ortho-positronium in low-density oxygen gas
M Kakimoto,T Hyodo,T B Chang +2 more
TLDR
In this paper, high-resolution 2 gamma angular correlation method was used for the conservation of ortho-positronium in oxygen, and the existence of an inelastic conversion process was confirmed.Abstract:
Conservation of ortho-positronium in oxygen has been investigated by the high-resolution 2 gamma angular correlation method. The oxygen pressure was low enough to suppress possible conversion of para-positronium to ortho-positronium. Silica aerogel was used to form a sufficient number of positronium atoms in a restricted region necessary for the high-resolution angular correlation measurements. The existence of an inelastic conversion process has been reconfirmed. The cross sections for the elastic and inelastic conversion processes have been estimated to be (1.0+or-0.3)*10-19 cm2 and some 10-17 cm2, respectively.read more
Citations
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Journal ArticleDOI
Improved limit on invisible decays of positronium
A. Badertscher,Paolo Crivelli,W. Fetscher,Ulisse Gendotti,Sergei Gninenko,V. Postoev,André Rubbia,V.D. Samoylenko,D. Sillou +8 more
TL;DR: The results of a new search for positronium decays into invisible final states are reported in this article, which is a strong evidence for new physics beyond the standard model (SM): for example, the existence of extra dimensions, of milli-charged particles, of new light gauge bosons or of mirror particles.
Journal ArticleDOI
Momentum-transfer cross section for slow positronium-He scattering
TL;DR: In this article, the momentum transfer cross section for positronium-He scattering has been determined by analyzing the thermalization process of orthopositronium in the gas using the one-dimensional angular correlation of the annihilation radiation method.
Journal ArticleDOI
Angular correlation studies of positron annihilation in the noble gases
TL;DR: Two-dimensional angular correlation distributions have been measured for the first time for positron and positronium annihilation in low-density helium, neon, argon, krypton and xenon, and in a range of helium-xenon mixtures.
Journal ArticleDOI
Experimental Evidence for Spin-Orbit Interactions in Positronium-Xe Collisions
Haruo Saito,Toshio Hyodo +1 more
TL;DR: The lifetime of the magnetically unperturbed ortho-Ps in Xe gas of 1 atm decreases significantly when a magnetic field of 1.0 T is applied, attributed to the Ps spin conversion caused by spin-orbit interaction during Ps-Xe collision.
Journal ArticleDOI
Performance of three-photon PET imaging: Monte Carlo simulations.
TL;DR: In this paper, the basic characteristics of the three-gamma imaging in PET are studied by means of Monte Carlo simulations and analytical computations, and two typical configurations of human and small animal scanners are considered.
References
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Journal ArticleDOI
Potential energy curves for N2, NO, O2 and corresponding ions
TL;DR: In this paper, potential energy curves for the observed electronic states of N2, N2+), NO, NO(+), O2 and O2+ were calculated from published spectroscopic data by a numerical modification of the Rydberg-Klein method.
Journal ArticleDOI
Gaseous Reactions involving Positronium
H. S. W. Massey,C B O Mohr +1 more
TL;DR: In this article, the problems involved in providing a detailed interpretation of the processes involved in the ultimate fate of positrons slowed down in a gas are examined by considering the idealized case of a gas of atomic hydrogen.
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Ortho-Parapositronium Quenching by Paramagnetic Molecules and Ions
Journal ArticleDOI
Effect of the energy-loss process on the annihilation of orthopositronium in silica aerogel
TL;DR: The Doppler broadening of the two-photon annihilation line arising the intermediate lifetime of positronium in a magnetic field has been measured using a time selecting λ-ray spectrometer as discussed by the authors.
Journal ArticleDOI
Observation of positronium specular reflection from LiF.
M. Weber,S. Tang,S. Berko,B.L. Brown,K. F. Canter,Kelvin G. Lynn,Allen P. Mills,L.O. Roellig,A. J. Viescas +8 more
TL;DR: A monoenergetic positronium (Ps) beam of 0-60-eV energy and an angular width of 5-5.5% is created by charge-exchange collisions of a slow positron beam passing through an Ar gas cell.