Dissociation of virtual photons in events with a leading proton at HERA

The ZEUS detector has been used to study dissociation of virtual photons in events with a leading proton, γp → Xp, in ep collisions at HERA. The data cover photon virtualities in two ranges, 0.03 1.5 GeV, where MX is the mass of the hadronic final state, X. Events were required to have a leading proton, detected in the ZEUS leading proton spectrometer, carrying at least 90% of the incoming proton energy. The cross section is presented as a function of t, the squared four-momentum transfer at the proton vertex, Φ, the azimuthal angle between the positron scattering plane and the proton scattering plane, and Q. The data are presented in terms of the diffractive structure function, F D(3) 2 . A next-to-leading-order QCD fit to the higher-Q data set and to previously published diffractive charm production data is presented. The ZEUS Collaboration S. Chekanov, M. Derrick, J.H. Loizides, S. Magill, S. Miglioranzi, B. Musgrave, J. Repond, R. Yoshida Argonne National Laboratory, Argonne, Illinois 60439-4815, USA n M.C.K. Mattingly Andrews University, Berrien Springs, Michigan 49104-0380, USA N. Pavel Institut fur Physik der Humboldt-Universitat zu Berlin, Berlin, Germany P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, A. Margotti, T. Massam, A. Montanari, R. Nania, F. Palmonari, A. Pesci, A. Polini, L. Rinaldi, G. Sartorelli, A. Zichichi University and INFN Bologna, Bologna, Italy e G. Aghuzumtsyan, D. Bartsch, I. Brock, S. Goers, H. Hartmann, E. Hilger, P. Irrgang, H.P. Jakob, O. Kind, U. Meyer, E. Paul, J. Rautenberg, R. Renner, J. Tandler, K.C. Voss, M. Wang Physikalisches Institut der Universitat Bonn, Bonn, Germany b D.S. Bailey, N.H. Brook, J.E. Cole, G.P. Heath, T. Namsoo, S. Robins, M. Wing H.H. Wills Physics Laboratory, University of Bristol, Bristol, United Kingdom m M. Capua, L. Iannotti, A. Mastroberardino, M. Schioppa, G. Susinno Calabria University, Physics Department and INFN, Cosenza, Italy e J.Y. Kim, I.T. Lim, K.J. Ma, M.Y. Pac Chonnam National University, Kwangju, South Korea g M. Helbich, Y. Ning, Z. Ren, W.B. Schmidke, F. Sciulli Nevis Laboratories, Columbia University, Irvington on Hudson, New York 10027 o J. Chwastowski, A. Eskreys, J. Figiel, A. Galas, K. Olkiewicz, P. Stopa, L. Zawiejski Institute of Nuclear Physics, Cracow, Poland i L. Adamczyk, T. Bo ld, I. Grabowska-Bo ld, D. Kisielewska, A.M. Kowal, J. Lukasik, M. Przybycien, L. Suszycki, D. Szuba, J. Szuba Faculty of Physics and Nuclear Techniques, AGH-University of Science and Technology, Cracow, Poland p A. Kotanski, W. S lominski Department of Physics, Jagellonian University, Cracow, Poland