Photonic events with missing energy in $e^{+}e^{-}$ collisions at $\sqrt{s}=189 GeV$

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 w...

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Detalles Bibliográficos
Autores principales: 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.
Lenguaje:eng
Publicado: 2000
Materias:
Particle Physics - Experiment
Acceso en línea:https://dx.doi.org/10.1007/s100520000522
http://cds.cern.ch/record/436490
Descripción
Sumario: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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