orthopositronium


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orthopositronium

[¦ȯr·thō‚päz·ə′trō·nē·əm]
(particle physics)
The state of positronium in which the positron and electron have parallel spins.
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The triplet state (orthopositronium, o-Ps) is limited to decay into an odd number of photons and lives in vacuum over three orders of magnitude longer than the singlet state ([[tau].sub.o-Ps] = 142 ns) [35-37].
The most precise measurements studied the angular correlation operators in the decay of orthopositronium states into three photons and determined mean values of final state operators odd under the CP and CPT conjugations, finding no violation signal at the sensitivity level of [10.sup.-3] [39,40].
With this in mind, let us denote the orthopositronium formed in the gas by the [[beta].sup.+]-decay positron as [[beta].sup.+]-orthopositronium: [sup.3] [([e.sup.+.sub.[beta]][e.sup.-]).sub.1].
This has set a precedent of complete degeneration of para- and orthopositronium while maintaining superantipodal symmetry in the final state of [[beta].sup.+]-decay [sup.22]Na and others.
The magnitude of this lifetime (1.8-2.1 ns) is typical of the "pick-off" annihilation of orthopositronium atoms formed at the interfacial regions of the grains [12].
Glashow of Harvard University suggested that orthopositronium could provide a sensitive way to search for the mirror universe.
By the new QED effect and the reformulated BS equation, another new QED effect, a term in the orthopositronium decay rate that is missing in the conventional QED is discovered.
There is the possibility that conversions of this sort occur in processes involving light diatomic molecules (in particular, [D.sub.2]) as they interact with positrons in the process of production of orthopositronium [o-Ps, [sup.T]Ps [equivalent to] [sup.3]([e.sup.+][e.sup.-]).sub.1]].
It is now the 20th anniversary of the observation of anomalies of orthopositronium annihilation (both discovered in 1987) in experiments conducted by two groups of researchers: one group in the USA, headed by the late Prof.
Expansion of the Standard Model (SM) for the quantitative description of the orthopositronium lifetime anomalies allows formulation of additional experimental tests of supersymmetry in the final state of the positron beta-decay of nuclei such as [sup.22]Na, [sup.68]Ga, and resolution of the results of the last Michigan experiment (2003).
The yield of positronium ([I.sub.2]) and the parameters of its annihilation at the passage through organic liquids were measured by two techniques: either angular (parapositronium) or temporal (orthopositronium) correlations of annihilation quanta were registered.
A proposed experiment is connected to othopositronium annihilation anomalies, which, being related to one of known unmatter entity, orthopositronium (built on electron and positron), opens a way to expand the Standard Model.