Multi-photon events with large missing energy in e e- collisions at √s = 192-209 GeV

G Abbiendi; C Ainsley; PF Akesson; G Alexander; J Allison; P Amaral; G Anagnostou; KJ Anderson; S Arcelli; S Asai; D Axen; G Azuelos; I Bailey; E Barberio; T Barillari; RJ Barlow; RJ Batley; P Bechtle; T Behnke; KW Bell; PJ Bell; G Bella; A Bellerive; G Benelli; S Bethke; O Biebel; O Boeriu; P Bock; M Boutemeur; S Braibant; L Brigliadori; RM Brown; K Buesser; HJ Burckhart; S Campana; RK Carnegie; AA Carter; JR Carter; CY Chang; DG Charlton; C Ciocca; A Csilling; M Cuffiani; S Dado; A de Roeck; EA de Wolf; K Desch; B Dienes; M Donkers; J Dubbert; E Duchovni; G Duckeck; IP Duerdoth; E Etzion; F Fabbri; L Feld; P Ferrari; F Fiedler; I Fleck; M Ford; A Frey; P Gagnon; JW Gary; G Gaycken; C Geich-Gimbel; G Giacomelli; P Giacomelli; M Giunta; J Goldberg; E Gross; J Grunhaus; M Gruwé; PO Günther; A Gupta; C Hajdu; M Hamann; GG Hanson; A Harel; M Hauschild; CM Hawkes; R Hawkings; RJ Hemingway; G Herten; RD Heuer; JC Hill; K Hoffman; D Horváth; P Igo-Kemenes; K Ishii; H Jeremie; P Jovanovic; TR Junk; N Kanaya; J Kanzaki; D Karlen; K Kawagoe; T Kawamoto; RK Keeler; RG Kellogg; BW Kennedy

Journal article

Multi-photon events with large missing energy in e e- collisions at √s = 192-209 GeV

G Abbiendi, C Ainsley, PF Akesson, G Alexander, J Allison, P Amaral, G Anagnostou, KJ Anderson, S Arcelli, S Asai, D Axen, G Azuelos, I Bailey, E Barberio, T Barillari, RJ Barlow, RJ Batley, P Bechtle, T Behnke, KW Bell Show all

Physics Letters Section B Nuclear Elementary Particle and High Energy Physics | ELSEVIER SCIENCE BV | Published : 2004

DOI: 10.1016/j.physletb.2004.09.059

Open access

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 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 th..

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