CERN Accelerating science

Article
Report number hep-ex/0005002 ; CERN-EP-2000-050 ; CERN-EP-2000-050
Title Photonic events with missing energy in $e^{+}e^{-}$ collisions at $\sqrt{s}=189 GeV$
Author(s)

Abbiendi, G. ; Ackerstaff, K. ; Ainsley, C. ; Akesson, P.F. ; Alexander, G. ; Allison, John ; Anderson, K.J. ; Arcelli, S. ; Asai, S. ; Ashby, S.F. ; Axen, D. ; Azuelos, G. ; Bailey, I. ; Ball, A.H. ; Barberio, E. ; Barlow, Roger J. ; Batley, J.R. ; Baumann, S. ; Behnke, T. ; Bell, Kenneth Watson ; Bella, G. ; Bellerive, A. ; Bentvelsen, S. ; Bethke, S. ; Biebel, O. ; Bloodworth, I.J. ; Bock, P. ; Bohme, J. ; Boeriu, O. ; Bonacorsi, D. ; Boutemeur, M. ; Braibant, S. ; Bright-Thomas, P. ; Brigliadori, L. ; Brown, Robert M. ; Burckhart, H.J. ; Cammin, J. ; Capiluppi, P. ; Carnegie, R.K. ; Carter, A.A. ; Carter, J.R. ; Chang, C.Y. ; Charlton, David G. ; Ciocca, C. ; Clarke, P.E.L. ; Clay, E. ; Cohen, I. ; Cooke, O.C. ; Couchman, J. ; Couyoumtzelis, C. ; Coxe, R.L. ; Cuffiani, M. ; Dado, S. ; Dallavalle, G.Marco ; Dallison, S. ; Davis, R. ; Roeck, A.de ; Dervan, P. ; Desch, K. ; Dienes, B. ; Dixit, M.S. ; Donkers, M. ; Dubbert, J. ; Duchovni, E. ; Duckeck, G. ; Duerdoth, I.P. ; Estabrooks, P.G. ; Etzion, E. ; Fabbri, F. ; Fanti, M. ; Faust, A.A. ; Feld, L. ; Ferrari, P. ; Fiedler, F. ; Fleck, I. ; Ford, M. ; Frey, A. ; Furtjes, A. ; Futyan, D.I. ; Gagnon, P. ; Gary, J.W. ; Gaycken, G. ; Geich-Gimbel, C. ; Giacomelli, G. ; Giacomelli, P. ; Gingrich, D.M. ; Glenzinski, D. ; Goldberg, J. ; Grandi, C. ; Graham, K. ; Gross, E. ; Grunhaus, J. ; Gruwe, M. ; Gunther, P.O. ; Hadju, C.C. ; Hanson, G.G. ; Hansroul, M. ; Hapke, M. ; Harder, K. ; Harel, A. ; Hargrove, C.K. ; Harin-Dirac, M. ; Hauke, A. ; Hauschild, M. ; Hawkes, C.M. ; Hawkings, R. ; Hemingway, R.J. ; Hensel, C. ; Herten, G. ; Heuer, R.D. ; Hildreth, M.D. ; Hill, J.C. ; Hobson, P.R. ; Hocker, James Andrew ; Hoffman, Kara Dion ; Homer, R.J. ; Honma, A.K. ; Horvath, D. ; Hossain, K.R. ; Howard, R. ; Huntemeyer, P. ; Igo-Kemenes, P. ; Imrie, D.C. ; Ishii, K. ; Jacob, F.R. ; Jawahery, A. ; Jeremie, H. ; Jones, C.R. ; Jovanovic, P. ; Junk, T.R. ; Kanaya, N. ; Kanzaki, J. ; Karapetian, G. ; Karlen, D. ; Kartvelishvili, V. ; Kawagoe, K. ; Kawamoto, T. ; Kayal, P.I. ; Keeler, R.K. ; Kellogg, R.G. ; Kennedy, B.W. ; Kim, D.H. ; Klein, K. ; Klier, A. ; Kobayashi, T. ; Kobel, M. ; Kokott, T.P. ; Komamiya, S. ; Kowalewski, Robert V. ; Kress, T. ; Krieger, P. ; von Krogh, J. ; Kuhl, T. ; Kupper, M. ; Kyberd, P. ; Lafferty, G.D. ; Landsman, H. ; Lanske, D. ; Lawson, I. ; Layter, J.G. ; Leins, A. ; Lellouch, D. ; Letts, J. ; Levinson, L. ; Liebisch, R. ; Lillich, J. ; List, B. ; Littlewood, C. ; Lloyd, A.W. ; Lloyd, S.L. ; Loebinger, F.K. ; Long, G.D. ; Losty, M.J. ; Lu, J. ; Ludwig, J. ; Macchiolo, A. ; Macpherson, A. ; Mader, W. ; Mannelli, M. ; Marcellini, S. ; Marchant, T.E. ; Martin, A.J. ; Martin, J.P. ; Martinez, G. ; Mashimo, T. ; Mattig, Peter ; McDonald, W.John ; McKenna, J. ; McMahon, T.J. ; McPherson, R.A. ; Meijers, F. ; Mendez-Lorenzo, P. ; Merritt, F.S. ; Mes, H. ; Michelini, A. ; Mihara, S. ; Mikenberg, G. ; Miller, D.J. ; Mohr, W. ; Montanari, A. ; Mori, T. ; Nagai, K. ; Nakamura, I. ; Neal, H.A. ; Nisius, R. ; O'Neale, S.W. ; Oakham, F.G. ; Odorici, F. ; Ogren, H.O. ; Oh, A. ; Okpara, A. ; Oreglia, M.J. ; Orito, S. ; Pasztor, G. ; Pater, J.R. ; Patrick, G.N. ; Patt, J. ; Pfeifenschneider, P. ; Pilcher, J.E. ; Pinfold, J. ; Plane, David E. ; Poli, B. ; Polok, J. ; Pooth, O. ; Przybycien, M. ; Quadt, A. ; Rembser, C. ; Rick, H. ; Robins, S.A. ; Rodning, N. ; Roney, J.M. ; Rosati, S. ; Roscoe, K. ; Rossi, A.M. ; Rozen, Y. ; Runge, K. ; Runolfsson, O. ; Rust, D.R. ; Sachs, K. ; Saeki, T. ; Sahr, O. ; Sang, W.M. ; Sarkisian, E.K.G. ; Sbarra, C. ; Schaile, A.D. ; Schaile, O. ; Scharff-Hansen, P. ; Schmitt, S. ; Schroder, Matthias ; Schumacher, M. ; Schwick, C. ; Scott, W.G. ; Seuster, R. ; Shears, T.G. ; Shen, B.C. ; Shepherd-Themistocleous, C.H. ; Sherwood, P. ; Siroli, G.P. ; Skuja, A. ; Smith, A.M. ; Snow, G.A. ; Sobie, R. ; Soldner-Rembold, S. ; Spagnolo, S. ; Sproston, M. ; Stahl, A. ; Stephens, K. ; Stoll, K. ; Strom, David M. ; Strohmer, R. ; Surrow, B. ; Talbot, S.D. ; Tarem, S. ; Taylor, R.J. ; Teuscher, R. ; Thiergen, M. ; Thomas, J. ; Thomson, M.A. ; Torrence, E. ; Towers, S. ; Trefzger, T. ; Trigger, I. ; Trocsanyi, Z. ; Tsur, E. ; Turner-Watson, M.F. ; Ueda, I. ; Vannerem, P. ; Verzocchi, M. ; Voss, H. ; Vossebeld, J. ; Waller, D. ; Ward, C.P. ; Ward, D.R. ; Watkins, P.M. ; Watson, A.T. ; Watson, N.K. ; Wells, P.S. ; Wengler, T. ; Wermes, N. ; Wetterling, D. ; White, J.S. ; Wilson, G.W. ; Wilson, J.A. ; Wyatt, T.R. ; Yamashita, S. ; Zacek, V. ; Zer-Zion, D.

Affiliation (CERN)
Publication 2000
Imprint 2 May 2000
Number of pages 42
In: Eur. Phys. J. C 18 (2000) 253-272
DOI 10.1007/s100520000522
Subject category Particle Physics - Experiment
Accelerator/Facility, Experiment CERN LEP ; OPAL
Abstract Photonic events with large missing energy have been observed in e+e- collisions at a centre-of-mass energy of 189GeV using the OPAL detector at LEP. Results are presented for event topologies consistent with a single photon or with an acoplanar photon pair. Cross-section measurements are performed within the kinematic acceptance of each selection, and the number of light neutrino species is measured. Cross-section results are compared with the expectations from the Standard Model process e+e- to nu nubar + photon(s). No evidence is observed for new physics contributions to these final states. Upper limits are derived on sigma(e+e- to XY).BR(X to Y gamma) and sigma(e+e- to XX).BR**2(X to Y gamma) for the case of stable and invisible Y. These limits apply to single and pair production of excited neutrinos (X=nu*, Y = nu), to neutralino production (X=neutralino_2, Y=neutralino_1) and to supersymmetric models in which X = neutralino_1 and Y = light gravitino. The case of macroscopic decay lengths of particle X is considered for e+e- to XX, X to Y gamma, when M_Y is of order zero. The single-photon results are also used to place upper limits on superlight gravitino pair production as well as graviton-photon production in the context of theories with additional space dimensions.
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