Mulit-Photon Events with Large Missing energy in e+e- collisions at sqrt(s)=192-209 GeV

Abstract

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 expectation from the Standard Model process e+e- -> nu nu gamma gamma(gamma). No evidence for new physics contributions to this final state is observed. Upper limits on sigma (e+e- -> XX) BR^2(X -> Ygamma) 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 fb to 60 fb, while for the special case of massless Y the range is 20 fb to 40 fb. The limits apply to pair production of excited neutrions (X=nu^*,Y=nu), to neutralino production (X=~chi^0_2, Y=~chi^0_1) and to supersymmetric models in which X=~chi^0_1 and Y=~G is a light gravitino.

18 pages, 4 figures, Submitted to Phys. Letts B

References in corpus (2)

• Single- and Multi-Photon Events with Missing Energy in e+e- Collisions at LEP
• Search for Associated Production of Massive States Decaying into Two Photonsin e+e- Annihilations at sqrt(s) = 88-209 GeV

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• Search for diphoton events with large missing transverse energy in 6.3 fb-1 of ppbar collisions at sqrt(s)=1.96 TeV