Z-boson production with two unobserved, back-to-back, hard photons at LEP

III. Physikalisches Institut, RWTH, D-52056 Aachen, Germany11Supported by the German Bundesministerium für Bildung, Wissenschaft, Forschung und Technologie.; National Institute for High Energy Physics, NIKHEF, and University of Amsterdam, NL-1009 DB Amsterdam, The Netherlands; University of Michigan, Ann Arbor, MI 48109, USA; Laboratoire d'Annecy-le-Vieux de Physique des Particules, LAPP, IN2P3-CNRS, BP 110, F-74941 Annecy-le-Vieux cedex, France; Institute of Physics, University of Basel, CH-4056 Basel, Switzerland; Louisiana State University, Baton Rouge, LA 70803, USA; Institute of High Energy Physics, IHEP, 100039 Beijing, China66Supported by the National Natural Science Foundation of China.; University of Bologna and INFN, Sezione di Bologna, I-40126 Bologna, Italy; Tata Institute of Fundamental Research, Mumbai (Bombay) 400 005, India; Northeastern University, Boston, MA 02115, USA; Institute of Atomic Physics and University of Bucharest, R-76900 Bucharest, Romania; Central Research Institute for Physics of the Hungarian Academy of Sciences, H-1525 Budapest 114, Hungary22Supported by the Hungarian OTKA fund under contract Nos. T019181, F023259 and T037350.; Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Panjab University, Chandigarh 160 014, India; KLTE-ATOMKI, H-4010 Debrecen, Hungary33Also supported by the Hungarian OTKA fund under contract No. T026178.; Department of Experimental Physics, University College Dublin, Belfield, Dublin 4, Ireland; INFN, Sezione di Firenze and University of Florence, I-50125 Florence, Italy; European Laboratory for Particle Physics, CERN, CH-1211 Geneva 23, Switzerland; World Laboratory, FBLJA Project, CH-1211 Geneva 23, Switzerland; University of Geneva, CH-1211 Geneva 4, Switzerland; University of Hamburg, D-22761 Hamburg, Germany; Chinese University of Science and Technology, USTC, Hefei, Anhui 230 029, China6; University of Lausanne, CH-1015 Lausanne, Switzerland; Institut de Physique Nucléaire de Lyon, IN2P3-CNRS, Université Claude Bernard, F-69622 Villeurbanne, France; Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, CIEMAT, E-28040 Madrid, Spain44Supported also by the Comisión Interministerial de Ciencia y Tecnología.; Florida Institute of Technology, Melbourne, FL 32901, USA; INFN, Sezione di Milano, I-20133 Milan, Italy; Institute of Theoretical and Experimental Physics, ITEP, Moscow, Russia; INFN, Sezione di Napoli and University of Naples, I-80125 Naples, Italy; Department of Physics, University of Cyprus, Nicosia, Cyprus; Radboud University and NIKHEF, NL-6525 ED Nijmegen, The Netherlands; California Institute of Technology, Pasadena, CA 91125, USA; INFN, Sezione di Perugia and Università Degli Studi di Perugia, I-06100 Perugia, Italy; Nuclear Physics Institute, St. Petersburg, Russia; Carnegie Mellon University, Pittsburgh, PA 15213, USA; INFN, Sezione di Napoli and University of Potenza, I-85100 Potenza, Italy; Princeton University, Princeton, NJ 08544, USA; University of Californa, Riverside, CA 92521, USA; INFN, Sezione di Roma and University of Rome, “La Sapienza”, I-00185 Rome, Italy; University and INFN, Salerno, I-84100 Salerno, Italy; University of California, San Diego, CA 92093, USA; Bulgarian Academy of Sciences, Central Lab. of Mechatronics and Instrumentation, BU-1113 Sofia, Bulgaria; The Center for High Energy Physics, Kyungpook National University, 702-701 Taegu, Republic of Korea; National Central University, Chung-Li, Taiwan; Department of Physics, National Tsing Hua University, Taiwan; Purdue University, West Lafayette, IN 47907, USA; Paul Scherrer Institut, PSI, CH-5232 Villigen, Switzerland; DESY, D-15738 Zeuthen, Germany; Eidgenössische Technische Hochschule, ETH Zürich, CH-8093 Zürich, Switzerland; Received 1 March 2005. Revised 11 March 2005. Accepted 15 March 2005. Available online 21 March 2005. Editor: L. Rolandi.
Physics Research Publications DOI: 10.1016/j.physletb.2005.03.039
Source: OAI

ABSTRACT The double-radiative process e(+)e(-) → Zγγ → q $(q) over bar $ γγ where the two hard photons escape detection at low polar angles into opposite directions, is studied in 0.62 fb(-1) of data collected with the L3 detector at LEP at centre-of-mass energies between 188.6 and 209.2 GeV. The cross sections are measured and found to be consistent with the Standard Model expectations. © 2005 Published by Elsevier B.V.

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