Volume 123B, number 1,2 PHYSICS LETTERS 24 March 1983 INVESTIGATION OF T~O PHOTON FINAL STATES IN e+e - ANNIHILATION AT (x/~) = 34.2 GeV CELLO Collaboration I-t.-J. BEHREND, Ch. CHEN 1 , H. FENNER, U. Gi~ClPEL, M.-J. SCHACHTER, V. SCHRODER, H. SINDT Deutsches Elektronen-Synchrotron, DESY, ttamburg, Germany G. D'AGOSTINI, W.-D. APEL, S. BANERJEE, J. BODENKAMP, J. ENGLER, G. FLOGGE, D.C. FRIES, W. FUES, K. GAMERDINGER, G. HOPP, H. K/~ISTER, H. MULLER, H. RANDOLL, G. SCHMIDT, H. SCHNEIDER Kernforsehungszentrum Karlsruhe and Universitgit Karlsruhe, Germany W. De BOER, G. BUSCHHORN, G. GRINDHAMMER, P. GROSSE-WIESMANN, B. GUNDERSON, C. K1ESLING, R. KOTTHAUS, U. KRUSE ~, H. LIERL, D. LUERS, H. OBERLACK, P. SCHACHT Max-Planck-Institut ffir Physik und Astrophysik, Mfinchen, Germany P. COLAS, A. CORDIER, M. DAVIER, D. FOURNIER, J.F. GRIVAZ, J. HAISSINSKI, V. JOURNI~, A. KLARSFELD, F. LAPLANCHE, U. MALLIK, J.-J. VEILLET Laboratoire de I'A ccdl(rateur Lin(aire, Orsay, france J.H. FIELD 3, R. GEORGE, M. GOLDBERG, B. GROSSETI~TE, O. HAMON, F. KAPUSTA, F. KOVACS, G. LONDON, L. POGGIOLI, M. RIVOAL Laboratoire de la Physique Nucl(aire et Hautes Energies, Universitd de PaNs, France and R. ALEKSAN, J. BOUCHEZ, G. CARNESECCHI, G. COZZIKA, Y. DUCROS, A. GAIDOT, Y. LAVAGNE, J. PAMELA, J.P. PANSART and F. PIERRE Centre d 'Etudes Nueldaires, Saclay, France Received 23 December 1982 Two photon final states in e+e-annihilation have been analyzed at CM energies around 34 GeV. Good agreement with QED is observed. Lower limits for the QED cutoff parameters of A+ > 59 GeV and A_> 44 GeV are determined. A search for two photons with missing energy yields an upper limit for the production of neutral particles which decay into a photon and a non-interacting particle. Constraints on the mass and the coupling strength of supersymmetric photinos are discussed. The reaction e+e - ~ 77 provides an important test of quantum electrodynamics (QED) in high energy e+e - reactions. It remains the only classical QED test 1 Visitor from the Institute of High Energy Physics, Chinese Academy of Science, Peking, People's Republic of China. 2 Visitor from the University of Illinois, Urbana, USA. 3 On leave of absence from DESY, Hamburg, Germany. which - in contrast to lepton pair production - is not affected at lowest order by weak interactions and ha- dronic vacuum polarization [1 ]. Furthermore, in two photon final states one can search for pair production of neutral particles which decay into a photon and one non-interacting particle. Experimental setup. The experiment was performed 0 031-9163/83/0000-0000/$ 03.00 © 1983 North-Holland 127