Improved limit on invisible decays of positronium
- ETH Zuerich, Zurich (Switzerland)
- Inst. Nucl. Research, INR Moscow (Russian Federation)
- Laboratoire Physique des Particules Annecy, LAPP (France)
The results of a new search for positronium decays into invisible final states are reported. Convincing detection of this decay mode would be 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. Mirror matter could be a relevant dark matter candidate. In this paper the setup and the results of a new experiment are presented. In a collected sample of about (6.31{+-}0.28)x10{sup 6} orthopositronium decays, no evidence for invisible decays in an energy [0,80] keV was found and an upper limit on the branching ratio of orthopositronium o-Ps{yields}invisible could be set: Br(o-Ps{yields}invisible)<4.2x10{sup -7}(90%C.L.) Our results provide a limit on the photon mirror-photon mixing strength {epsilon}{<=}1.55x10{sup -7}(90%C.L.) and rule out particles lighter than the electron mass with a fraction Q{sub x}{<=}3.4x10{sup -5} of the electron charge. Furthermore, upper limits on the branching ratios for the decay of parapositronium Br(p-Ps{yields}invisible){<=}4.3x10{sup -7}(90%C.L.) and the direct annihilation Br(e{sup +}e{sup -}{yields}invisible){<=}2.1x10{sup -8}(90%C.L.) could be set.
- OSTI ID:
- 21010968
- Journal Information:
- Physical Review. D, Particles Fields, Vol. 75, Issue 3; Other Information: DOI: 10.1103/PhysRevD.75.032004; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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