9 v 1 1 5 D ec 1 99 7 Measurement of the t Distribution in Diffractive Photoproduction at HERA

Photon diffractive dissociation, γp → Xp, has been studied at HERA with the ZEUS detector using ep interactions where the virtuality Q of the exchanged photon is smaller than 0.02 GeV. The squared four-momentum t exchanged at the proton vertex was determined in the range 0.073 < |t| < 0.40 GeV by measuring the scattered proton in the ZEUS Leading Proton Spectrometer. In the photon-proton centre-of-mass energy interval 176 < W < 225 GeV and for masses of the dissociated photon system 4 < MX < 32 GeV, the t distribution has an exponential shape, dN/d|t| ∝ exp (−b|t|), with a slope parameter b = 6.8± 0.9 (stat.) +1.2 −1.1 (syst.) GeV−2. DESY 97-238 November 1997 The ZEUS Collaboration J. Breitweg, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R.L. Talaga, R. Yoshida, H. Zhang Argonne National Laboratory, Argonne, IL, USA p M.C.K. Mattingly Andrews University, Berrien Springs, MI, USA F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, M. Chiarini, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, I. Gialas, P. Giusti, G. Iacobucci, G. Laurenti, G. Levi, A. Margotti, T. Massam, R. Nania, C. Nemoz, F. Palmonari, A. Pesci, A. Polini, F. Ricci, G. Sartorelli, Y. Zamora Garcia, A. Zichichi University and INFN Bologna, Bologna, Italy f C. Amelung, A. Bornheim, I. Brock, K. Coböken, J. Crittenden, R. Deffner, M. Eckert, M. Grothe, H. Hartmann, K. Heinloth, L. Heinz, E. Hilger, H.-P. Jakob, U.F. Katz, R. Kerger, E. Paul, M. Pfeiffer, Ch. Rembser, J. Stamm, R. Wedemeyer, H. Wieber Physikalisches Institut der Universität Bonn, Bonn, Germany c D.S. Bailey, S. Campbell-Robson, W.N. Cottingham, B. Foster, R. Hall-Wilton, M.E. Hayes, G.P. Heath, H.F. Heath, J.D. McFall, D. Piccioni, D.G. Roff, R.J. Tapper H.H. Wills Physics Laboratory, University of Bristol, Bristol, U.K. o M. Arneodo, R. Ayad, M. Capua, A. Garfagnini, L. Iannotti, M. Schioppa, G. Susinno Calabria University, Physics Dept.and INFN, Cosenza, Italy f J.Y. Kim, J.H. Lee, I.T. Lim, M.Y. Pac Chonnam National University, Kwangju, Korea h A. Caldwell, N. Cartiglia, Z. Jing, W. Liu, B. Mellado, J.A. Parsons, S. Ritz, S. Sampson, F. Sciulli, P.B. Straub, Q. Zhu Columbia University, Nevis Labs., Irvington on Hudson, N.Y., USA q P. Borzemski, J. Chwastowski, A. Eskreys, J. Figiel, K. Klimek, M.B. Przybycień, L. Zawiejski Inst. of Nuclear Physics, Cracow, Poland j L. Adamczyk, B. Bednarek, M. Bukowy, A. Czermak, K. Jeleń, D. Kisielewska, T. Kowalski, M. Przybycień, E. Rulikowska-Zarȩbska, L. Suszycki, J. Zaja̧c Faculty of Physics and Nuclear Techniques, Academy of Mining and Metallurgy, Cracow, Poland j Z. Duliński, A. Kotański Jagellonian Univ., Dept. of Physics, Cracow, Poland k G. Abbiendi, L.A.T. Bauerdick, U. Behrens, H. Beier, J.K. Bienlein, G. Cases, O. Deppe, K. Desler, G. Drews, U. Fricke, D.J. Gilkinson, C. Glasman, P. Göttlicher, T. Haas, W. Hain, D. Hasell, K.F. Johnson, M. Kasemann, W. Koch, U. Kötz, H. Kowalski, J. Labs, L. Lindemann, B. Löhr, M. Löwe, O. Mańczak, J. Milewski, T. Monteiro, J.S.T. Ng, D. Notz, K. Ohrenberg, I.H. Park, A. Pellegrino, F. Pelucchi, K. Piotrzkowski, M. Roco, M. Rohde, J. Roldán, J.J. Ryan, A.A. Savin, U. Schneekloth, O. Schwarzer, F. Selonke, B. Surrow, E. Tassi, T. Voß, D. Westphal, G. Wolf, U. Wollmer, C. Youngman, A.F. Żarnecki, W. Zeuner Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany B.D. Burow, H.J. Grabosch, A. Meyer, S. Schlenstedt DESY-IfH Zeuthen, Zeuthen, Germany G. Barbagli, E. Gallo, P. Pelfer University and INFN, Florence, Italy f G. Anzivino, G. Maccarrone, L. Votano INFN, Laboratori Nazionali di Frascati, Frascati, Italy f A. Bamberger, S. Eisenhardt, P. Markun, T. Trefzger, S. Wölfle Fakultät für Physik der Universität Freiburg i.Br., Freiburg i.Br., Germany c J.T. Bromley, N.H. Brook, P.J. Bussey, A.T. Doyle, N. Macdonald, D.H. Saxon, L.E. Sinclair, E. Strickland, R. Waugh Dept. of Physics and Astronomy, University of Glasgow, Glasgow, U.K. o I. Bohnet, N. Gendner, U. Holm, A. Meyer-Larsen, H. Salehi, K. Wick Hamburg University, I. Institute of Exp. Physics, Hamburg, Germany c L.K. Gladilin, D. Horstmann, D. Kçira, R. Klanner, E. Lohrmann, G. Poelz, W. Schott, F. Zetsche Hamburg University, II. Institute of Exp. Physics, Hamburg, Germany c T.C. Bacon, I. Butterworth, J.E. Cole, G. Howell, B.H.Y. Hung, L. Lamberti, K.R. Long, D.B. Miller, N. Pavel, A. Prinias, J.K. Sedgbeer, D. Sideris, R. Walker Imperial College London, High Energy Nuclear Physics Group, London, U.K. o U. Mallik, S.M. Wang, J.T. Wu University of Iowa, Physics and Astronomy Dept., Iowa City, USA p P. Cloth, D. Filges Forschungszentrum Jülich, Institut für Kernphysik, Jülich, Germany J.I. Fleck, T. Ishii, M. Kuze, I. Suzuki, K. Tokushuku, S. Yamada, K. Yamauchi, Y. Yamazaki Institute of Particle and Nuclear Studies, KEK, Tsukuba, Japan g S.J. Hong, S.B. Lee, S.W. Nam, S.K. Park Korea University, Seoul, Korea h F. Barreiro, J.P. Fernández, G. Garćıa, R. Graciani, J.M. Hernández, L. Hervás, L. Labarga, M. Mart́ınez, J. del Peso, J. Puga, J. Terrón, J.F. de Trocóniz Univer. Autónoma Madrid, Depto de F́ısica Teórica, Madrid, Spain n