Eur. Phys. J. C (1999) 6: 371-384
https://doi.org/10.1007/s100529801044

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

⁴⁸ Department of Physics and Astronomy, Iowa State University, 50011-3160, Ames, IA, USA
²⁹ Physics Department, Univ. Instelling Antwerpen, Universiteitsplein 1, BE-2610, Wilrijk, Belgium
³⁰ IIHE, ULB-VUB, Pleinlaan 2, BE-1050, Brussels, Belgium
³¹ Faculté des Sciences, Univ. de l’Etat Mons, Av. Maistriau 19, BE-7000, Mons, Belgium
¹¹ Physics Laboratory, University of Athens, Solonos Str. 104, GR-10680, Athens, Greece
³⁷ Department of Physics, University of Bergen, Allégaten 55, NO-5007, Bergen, Norway
²⁸ Dipartimento di Fisica, Università di Bologna and INFN, Via Irnerio 46, IT-40126, Bologna, Italy
²³ Centro Brasileiro de Pesquisas Físicas, rua Xavier Sigaud 150, BR-22290, Rio de Janeiro, Brazil
²⁴ Depto. de Física, Pont. Univ. Católica, C.P. 38071 BR-22453, Rio de Janeiro, Brazil
²⁵ Inst. de Física, Univ. Estadual do Rio de Janeiro, rua São Francisco Xavier 524, Rio de Janeiro, Brazil
⁴⁶ Faculty of Mathematics and Physics, Comenius University, Mlynska Dolina, SK-84215, Bratislava, Slovakia
²⁶ Collège de France, Lab. de Physique Corpusculaire, IN2P3-CNRS, FR-75231, Paris Cedex 05, France
⁹ CERN, CH-1211, 23, Geneva, Switzerland
³⁴ Institut de Recherches Subatomiques, IN2P3 — CNRS/ULP — BP20, FR-67037, Strasbourg, Cedex, France
³ Institute of Nuclear Physics, N.C.S.R. Demokritos, P.O. Box 60228, GR-15310, Athens, Greece
⁶⁰ FZU, Inst. of Phys. of the C.A.S. High Energy Physics Division, Na Slovance 2, CZ-180 40, 8, Praha, Czech Republic
⁴⁰ Dipartimento di Fisica, Università di Genova and INFN, Via Dodecaneso 33, IT-16146, Genova, Italy
¹⁵ Institut des Sciences Nucléaires, IN2P3-CNRS, Université de Grenoble 1, FR-38026, Grenoble, Cedex, France
²⁰ Helsinki Institute of Physics, HIP, P.O. Box 9, FI-00014, Helsinki, Finland
⁵ Joint Institute for Nuclear Research, Dubna, Head Post Office, P.O. Box 79, RU-101 000, Moscow, Russian Federation
¹⁴ Institut für Experimentelle Kernphysik, Universität Karlsruhe, 6980 DE-76128, Postfach, Karlsruhe, Germany
⁴¹ Institute of Nuclear Physics and University of Mining and Metalurgy, Ul. Kawiory 26a, PL-30055, Krakow, Poland
¹⁶ Lab. de l’Accélérateur Linéaire, Université de Paris-Sud, IN2P3-CNRS, Bât. 200, FR-91405, Orsay, Cedex, France
⁵⁹ School of Physics and Chemistry, University of Lancaster, LA1 4YB, Lancaster, UK
¹ LIP, IST, FCUL — Av. Elias Garcia, 14-1o, PT-1000, Lisboa, Codex, Portugal
⁷ Department of Physics, University of Liverpool, P.O. Box 147, L69 3BX, Liverpool, UK
²¹ LPNHE, IN2P3-CNRS, Univ. Paris VI et VII, Tour 33 (RdC), 4 place Jussieu, FR-75252, Paris, Cedex, 05, France
⁸ Department of Physics, University of Lund, Sölvegatan 14, SE-223 63, Lund, Sweden
¹³ Université Claude Bernard de Lyon, IPNL, IN2P3-CNRS, FR-69622, Villeurbanne, Cedex, France
⁵¹ Univ. d’ Aix – Marseille II — CPP, IN2P3-CNRS, FR-13288, Marseille, Cedex 09, France
³⁶ Dipartimento di Fisica, Università di Milano and INFN, Via Celoria 16, IT-20133, Milan, Italy
⁵⁰ Niels Bohr Institute, Blegdamsvej 17, DK-2100, Copenhagen Ø, Denmark
⁴⁷ NC, Nuclear Centre of MFF, Charles University, Areal MFF, V Holesovickach 2, CZ-180 00, Praha 8, Czech Republic
³⁵ NIKHEF, Postbus 41882, NL-1009 DB, Amsterdam, The Netherlands
⁵³ Physics Department, Zografou Campus, National Technical University, GR-15773, Athens, Greece
⁴² Physics Department, University of Oslo, Blindem, NO-1000, 3, Oslo, Norway
⁴⁹ Dpto. Fisica, Univ. Oviedo, Avda. Calvo Sotelo s/n, ES-33007, Oviedo, Spain
⁵⁸ Department of Physics, University of Oxford, Keble Road, OX1 3RH, Oxford, UK
⁴⁵ Dipartimento di Fisica, Università di Padova and INFN, Via Marzolo 8, IT-35131, Padua, Italy
² Rutherford Appleton Laboratory, OX11 OQX, Chilton, Didcot, UK
⁴⁴ Dipartimento di Fisica, Università di Roma II and INFN, Tor Vergata, IT-00173, Rome, Italy
¹⁹ Dipartimento di Fisica, Università di Roma III and INFN, Via délia Vasca Navale 84, IT-00146, Rome, Italy
³² DAPNIA/Service de Physique des Particules, CEA-Saclay, FR-91191, Gif-sur-Yvette, Cedex, France
⁴³ Instituto de Fisica de Cantabria (CSIC-UC), Avda. los Castros s/n, ES-39006, Santander, Spain
³⁸ Dipartimento di Fisica, Università degli Studi di Roma La Sapienza, Piazzale Aldo Moro 2, IT-00185, Rome, Italy
⁴ Inst. for High Energy Physics, Serpukov P.O. Box 35, Protvino, (Moscow Region), Russian Federation
⁵⁴ Slovenia and Department of Astroparticle Physics, School of Environmental Sciences, J. Stefan Institute Jamova 39, SI-1000 Ljubljana, Kostanjeviska 16a, SI-5000, Nova, Gorica, Slovenia
⁵⁵ Department of Physics, University of Ljubljana, SI-1000, Ljubljana, Slovenia
¹² Fysikum, Stockholm University, Box 6730, SE-113 85, Stockholm, Sweden
³³ Dipartimento di Fisica Sperimentale, Università di Torino and INFN, Via P. Giuria 1, IT-10125, Turin, Italy
¹⁷ Dipartimento di Fisica, Università di Trieste and INFN, Via A. Valerio 2, IT-34127, Trieste, Italy
¹⁸ Istituto di Fisica, Università di Udine, IT-33100, Udine, Italy
¹⁰ Univ. Federal do Rio de Janeiro, C.P. 68528 Cidade Univ., Ilha do Fundão, BR-21945-970, Rio de Janeiro, Brazil
³⁹ Department of Radiation Sciences, University of Uppsala, P.O. Box 535, SE-751 21, Uppsala, Sweden
⁶ IFIC, Valencia-CSIC, and D.F.A.M.N., U. de Valencia, Avda. Dr. Moliner 50, ES-46100, Burjassot (Valencia), Spain
⁵⁶ Institut für Hochenergiephysik, Österr. Akad. d. Wissensch., Nikolsdorfergasse 18, AT-1050, Vienna, Austria
⁵² Inst. Nuclear Studies and University of Warsaw, Ul. Hoza 69, PL-00681, Warsaw, Poland
²² Fachbereich Physik, University of Wuppertal, Postfach 100 127, DE-42097, Wuppertal, Germany
²⁷ On leave of absence from IHEP Serpukhov, Russia
⁵⁷ Now at University of Florida, United States

Received: 11 September 1998
Published online: 17 September 2013

Abstract

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.