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25 April 2024 |
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An Improved Limit on Invisible Decays of Positronium | | A. Badertscher
; P. Crivelli
; W. Fetscher
; U. Gendotti
; S. Gninenko
; V. Postoev
; A. Rubbia
; V. Samoylenko
; D. Sillou
; | | Date: |
29 Sep 2006 | | Abstract: | 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 evid ence 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 $(6.31pm0.28) imes 10^6$ orthopositronium decay s, no evidence for invisible decays in an energy window [0,80] keV was found and an upper limit on the branching ratio of orthopositronium invdecay could be set: $invdecay<4.2 imes 10^{-7}$ (90% C.L.)
Our results provide a limit on the photon mirror-photon mixing strength $epsilon leq 1.55 imes 10^{-7}$ (90% C.L.) and rule out particles lighter than the electron mass with a fraction $Q_x leq 8 imes 10^{-7}$ of the electron charge. Furthermore, upper limits on the branching ratios for the decay of parapositronium $Br(p-Ps o invisible)leq 4.3 imes 10^{-7}$ (90% C.L.) and the direct annihilation $Br(e^+e^- o invisible)leq 2.1 imes 10^{-8}$ (90% C.L.) could be set. | | Source: | arXiv, hep-ex/0609059 | | Services: | Forum | Review | PDF | Favorites | |
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