Search for pair-produced neutralinos in events with photons and missing energy from e+e- collisions at GeV

• Published in: The European physical journal. C, Particles and fields Particles and fields, 1999-01, Vol.6 (3), p.371-384
• Main Authors: Adye, T, Andersson, P, Barao, F, Baroncelli, A, Battaglia, M, K -H Becks, Beilliere, P, Yu Belokopytov, Berat, C, Bourdarios, C, Bruckman, P, Bugge, L, Buschmann, P, Carroll, L, Checchia, P, Contri, R, Cossutti, F, Crawley, H B, Damgaard, G, Davenport, M, Deghorain, A, Demaria, N, Dolbeau, J, Ekelof, T, Falk, E, Fassouliotis, D, Ferrari, P, Ferrer, A, Ferrer-Ribas, E, Fokitis, E, Fontanelli, F, Franek, B, Galloni, A, Gamba, D, Garcia, J, Gavillet, Ph, Gorski, M, Yu Gouz, Grahl, J, Harris, F J, Hrubec, J, Huet, K, Jackson, J N, Klein, H, Koratzinos, M, Kurvinen, K, Langefeld, P, Lapin, V, Ledroit, F, Leinonen, L, Loerstad, B, Lyons, L, Maio, A, Malychev, V, Mazik, J, Mazzucato, M, Miagkov, A, Mirabito, L, Mitaroff, W A, Moa, T, Morton, G, Neumeister, N, Nicolaidou, R, Ouraou, A, Paganoni, M, Paiano, S, Papadopoulou, Th D, Pape, L, Pukhaeva, N, Ratoff, P N, Regler, M, Rohne, O, Roudeau, P, Seager, P, Segar, A M, Shellard, R C, Simard, L, Smadja, G, Spiriti, E, Squarcia, S, Stevenson, K, Strub, R, Tilquin, A, Timmermans, J, Tome, B, Tortora, L, Treille, D, Vallazza, E, Van Apeldoorn, G W, Vassilopoulos, N, Ventura, L, Venus, W, Verlato, M, Vertogradov, L S, Vrba, V, Wilkinson, G R, Zalewski, P, Zevgolatakos, E, Zimin, N I, Zucchelli, G C
• Format: Article
• Language: English
• Subjects: Beam interactions; Fermions; Neutral particles; Particle decay; Photons; Searching
• ISSN: 1434-6044; 1434-6052
• DOI: 10.1007/s100529801044

The events with two photons and missing (transverse) energy collected by the DELPHI detector at centre-of-mass energies between 130 GeV and 183 GeV have been studied to search for processes of the type e+e- → YY with the subsequent decay Y → X7, where X is an undetectable neutral particle. Reactions of this kind are expected in supersymmetric models, where the Y particle can be either the lightest neutralino, decaying to a photon and a gravitino, or the next-to-lightest neutralino, decaying to a photon and the lightest neutralino. To study the case of long-lived Y particles, a search for single-photon events with the reconstructed photon axis pointing far from the beam interaction region has also been performed. No evidence for a deviation from Standard Model expectations has been observed in the data and upper limits have been derived on the signal cross-section as a function of the the X and Y masses and of the Y mean decay path.