1 v 1 2 1 A pr 1 99 7 Differential Cross Sections of D ∗ ± Photoproduction in ep Collisions at HERA ZEUS

Inclusive photoproduction of D in ep collisions at HERA has been measured with the ZEUS detector for photon-proton centre of mass energies in the range 115 < W < 280GeV and photon virtuality Q < 4GeV. The cross section σep→D∗X integrated over the kinematic region p D ⊥ > 3GeV and −1.5 < ηD∗ < 1.0 is (10.6 ± 1.7(stat .) ± 1.3 (syst .)) nb. Differential cross sections as functions of p ∗ ⊥ , η ∗ and W are given. The data are compared with two next-to-leading order perturbative QCD predictions. For a calculation using a massive charm scheme the predicted cross sections are smaller than the measured ones. A recent calculation using a massless charm scheme is in agreement with the data. DESY-97-026 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, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, I. Gialas, P. Giusti, G. Iacobucci, G. Laurenti, G. Levi, A. Margotti, T. Massam, R. Nania, F. Palmonari, S. De Pasquale, A. Pesci, A. Polini, 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, L. Feld, M. Grothe, H. Hartmann, K. Heinloth, L. Heinz, E. Hilger, H.-P. Jakob, U.F. Katz, E. Paul, M. Pfeiffer, Ch. Rembser, J. Stamm, R. Wedemeyer 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, 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, 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, Z. Jakubowski, M.B. Przybycień, M. Zachara, L. Zawiejski Inst. of Nuclear Physics, Cracow, Poland j L. Adamczyk, B. Bednarek, K. Jeleń, D. Kisielewska, T. Kowalski, M. Przybycień, E. RulikowskaZarȩbska, L. Suszycki, J. Zaja̧c Faculty of Physics and Nuclear Techniques, Academy of Mining and Metallurgy, Cracow, Poland j Z. Duliński, A. Kotański A. Kotański Jagellonian Univ., Dept. of Physics, Cracow, Poland k