Events with a final state consisting of two or more photons and large missing transverse energy have been observed in e+e- collisions at centre-of-mass energies in the range 192-209 GeV using the OPAL detector at LEP. Cross-section measurements are performed within the kinematic acceptance of the selection and compared with the expectations from the Standard Model process e+e- → νν̄γγ (γ). No evidence for new physics contributions to this final state is observed. Upper limits on σ(e+e- → XX)·BR2(X → Yγ) are derived for the case of stable and invisible Y. In the case of massive Y the combined limits obtained from all the data range from 10 to 60 fb, while for the special case of massless Y the range is 20 to 40 fb. The limits apply to pair production of excited neutrinos (X = ν*, Y = ν), to neutralino production (X = χ̃ 20, Y = χ̃10) and to supersymmetric models in which X=χ̃10 and Y=G̃ is a light gravitino.
|ジャーナル||Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics|
|出版ステータス||Published - 2004 11月 25|
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