The ep charged-current deep inelastic scattering cross sections, dσ/dQ for Q between 200 and 60000 GeV, and dσ/dx and dσ/dy for Q > 200 GeV, have been measured with the ZEUS detector at HERA. A data sample of 47.7 pb, collected at a center-of-mass energy of 300 GeV, has been used. The cross section dσ/dQ falls by a factor of about 50000 as Q increases from 280 to 30000 GeV. The double differential cross section dσ/dxdQ has also been measured. A comparison between the data and Standard Model (SM) predictions shows that contributions from antiquarks (u and c) and quarks (d and s) are both required by the data. The predictions of the SM give a good description of the full body of the data presented here. A comparison of the charged-current cross section dσ/dQ with the recent ZEUS results for neutral-current scattering shows that the weak and electromagnetic forces have similar strengths for Q above M W ,M 2 Z . A fit to the data for dσ/dQ 2 with the Fermi constant GF and MW as free parameters yields GF = ( 1.171±0.034 (stat.) −0.032 (syst.) +0.016 −0.015 (PDF) ) ×10−5 GeV and MW = 80.8 +4.9 −4.5 (stat.) +5.0 −4.3 (syst.) +1.4 −1.3 (PDF) GeV. Results for MW , where the propagator effect alone or the SM constraint between GF and MW have been considered, are also presented. The ZEUS Collaboration J. Breitweg, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Stanek, R. Yoshida Argonne National Laboratory, Argonne, IL, USA p M.C.K. Mattingly Andrews University, Berrien Springs, MI, USA G. Abbiendi, 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, N. Coppola, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Laurenti, G. Levi, A. Margotti, T. Massam, R. Nania, F. Palmonari, 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, H. Hartmann, K. Heinloth, E. Hilger, H.-P. Jakob, A. Kappes, U.F. Katz, R. Kerger, E. Paul, J. Rautenberg, H. Schnurbusch, A. Stifutkin, J. Tandler, A. Weber, H. Wieber Physikalisches Institut der Universität Bonn, Bonn, Germany c D.S. Bailey, O. Barret, W.N. Cottingham, B. Foster, G.P. Heath, H.F. Heath, J.D. McFall, D. Piccioni, J. Scott, R.J. Tapper H.H. Wills Physics Laboratory, University of Bristol, Bristol, U.K. o r M. Capua, A. Mastroberardino, M. Schioppa, G. Susinno Calabria University, Physics Dept.and INFN, Cosenza, Italy f H.Y. Jeoung, J.Y. Kim, J.H. Lee, I.T. Lim, K.J. Ma, M.Y. Pac Chonnam National University, Kwangju, Korea h A. Caldwell, N. Cartiglia, Z. Jing, W. Liu, B. Mellado, J.A. Parsons, S. Ritz, R. Sacchi, S. Sampson, F. Sciulli, Q. Zhu Columbia University, Nevis Labs., Irvington on Hudson, N.Y., USA q J. Chwastowski, A. Eskreys, J. Figiel, K. Klimek, K. Olkiewicz, M.B. Przybycień, P. Stopa, L. Zawiejski Inst. of Nuclear Physics, Cracow, Poland j L. Adamczyk, B. Bednarek, K. Jeleń, D. Kisielewska, A.M. Kowal, 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

Charged particle production has been measured in deep inelastic scattering (DIS) events over a large range of x and Q using the ZEUS detector. The evolution of the scaled momentum, xp, with Q , in the range 10 to 1280 GeV, has been investigated in the current fragmentation region of the Breit frame. The results show clear evidence, in a single experiment, for scaling violations in scaled momenta as a function of Q. DESY 97-183

Exclusive production of 0 and J== mesons in e + p collisions has been studied with the ZEUS detector in the kinematic range 0:25 < Q 2 < 50 GeV 2 , 20 < W < 167 GeV for the 0 data and 2 < Q 2 < 40 GeV 2 , 50 < W < 150 GeV for the J== data. Cross sections for exclusive 0 and J== production have been measured as a function of Q 2 , W and t. The spin-density matrix elements r 04 00 , r 1 1?1 and Re r 5 10 have been determined for exclusive 0 production as well as r 04 00 and r 04 1?1 for exclusive J== production. The results are discussed in the context of theoretical models invoking soft and hard phenomena.

A. Andresen a, A. Bamberger ', A. Baigende c, F. Barreiro `', U. Behrens `, S. Bentvelsen f, M. Brkic 9, B. Burow 9, A. CaldwelI h, G . Cases d°§§, F. Corriveau ',', J .A . Crittenden c, A. Dake f, A. Dannemann °, J. Dawson ', K. Dierks ', G. Drews 1 , J. Engelen f, H . Fawcett W. Fiisken k, A. Fürtjes ', D . Gilkinson ', L. Hagge ', R . Hamatsu in, D. Hanna I, J . Hartmann e, T. Hasegawa ", D . Hasell k , M. Hazumi ", L. Hervás `', E. Hilgei c, U. Holm e, T. Ishii ", P. de Jong f, H. Kammerlocher c, S . Kasai ", S. Kitamuia ', R. Manner ', P . Kooijman f, U. Kötz ', M. Kriimer c, B . Krebs e, W. Krüger a, J. Krüger a, M. Kuze ", G. Levman 9, T. Lindenberg b, H. v.d . Lugt f, J. Martin 9, J. Mayer P, J . Mitchell ', P. Patel ', T. Poser b, K. Prange `, S . Ritz h , M. Rohde ', T. Romanowski °, E. Ros °, H.-L. Schneider `, D. Schäcke b, W. Schulz ', F. Selorike ', W. Sippach h, G. Smith P, G. Stairs 9, J. Straver f, G. Theisen 6, H. Tiecke f, K. Tokushuku ", B. Trdndle b, T. Tsurugai a, H. Uijterwaal ', R . Ullmann b, W. Vogel ', K. Wick e, T. Woeriiger `', S . Yamada ", C. Youngman ' University of Hamburg, II. Institute for Experimental Physics . Germany n University of Freiburg, Germany ` University of Bonn, Germany " Unn ersidad Autónoma de Madrid, Spain `' University of Hamburg, I. Institute for Experimental Physics, Germany i NIKHEF-H, Amsterdam, The Netherlands x University of Toronto, Canada + i' Columbia University, USA + ' Argonne National Laboratory, USA ° ' DESY, Hamburg, Germany York University, Canada i McGill University, Canada "' Tokyo Metropolitan Unn ersity, Japan " INS, University of Tokyo, Japan " Ohio State Unit ersity, USA P University of Manitoba, Canada +

Elastic and proton-dissociative ρ photoproduction (γp → ρp, γp → ρN , respectively, with ρ → π+π−) has been studied in ep interactions at HERA for photon-proton centre-of-mass energies in the range 50 < W < 100 GeV and for |t| < 0.5 GeV, where t is the square of the four-momentum transfer at the proton vertex; the results on the protondissociative reaction are presented for masses of the dissociated proton system in the range M N < 0.1W . For the elastic process, the π+π− invariant mass spectrum has been investigated as a function of t. As in fixed target experiments, the ρ resonance shape is asymmetric; this asymmetry decreases with increasing |t|, as expected in models in which the asymmetry is ascribed to the interference of resonant and non-resonant π+π− production. The cross section has been studied as a function of W ; a fit to the resonant part with the form W a gives a = 0.16± 0.06 (stat.) +0.11 −0.15 (syst.). The resonant part of the γp → π+π−p cross section is 11.2 ± 0.1 (stat.) +1.1 −1.2 (syst.) μb at 〈W 〉 = 71.7 GeV. The t dependence of the cross section can be described by a function of the type Aρ exp (−bρ|t| + cρt) with bρ = 10.9 ± 0.3 (stat.) +1.0 −0.5 (syst.) GeV−2 and cρ = 2.7 ± 0.9 (stat.) +1.9 −1.7 (syst.) GeV−4. The t dependence has also been studied as a function of W and a value of the slope of the pomeron trajectory α IP ′ = 0.23 ± 0.15 (stat.) +0.10 −0.07 (syst.) GeV−2 has been deduced. The ρ spin density matrix elements r 00, r 04 1−1 and Re[r04 10 ] have been measured and found to be consistent with expectations based on s-channel helicity conservation. For proton-dissociative π+π− photoproduction in the ρ mass range, the distributions of the two-pion invariant mass, W and the polar and azimuthal angles of the pions in the helicity frame are the same within errors as those for the elastic process. The t distribution has been fitted to an exponential function with a slope parameter 5.8 ± 0.3 (stat.) ± 0.5 (syst.) GeV−2. The ratio of the elastic to proton-dissociative ρ photoproduction cross section is 2.0 ± 0.2 (stat.) ± 0.7 (syst.). DESY 97-237 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

Exclusive production of ρ0 and J/ψ mesons in e+p collisions has been studied with the ZEUS detector in the kinematic range 0.25 < Q2 < 50 GeV, 20 < W < 167 GeV for the ρ0 data and 2 < Q2 < 40 GeV, 50 < W < 150 GeV for the J/ψ data. Cross sections for exclusive ρ0 and J/ψ production have been measured as a function of Q2, W and t. The spin-density matrix elements r04 00, r 1 1−1 and Re r 5 10 have been determined for exclusive ρ0 production as well as r04 00 and r 04 1−1 for exclusive J/ψ production. The results are discussed in the context of theoretical models invoking soft and hard phenomena. The ZEUS Collaboration J. Breitweg, S. Chekanov, 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, N. Coppola, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Laurenti, G. Levi, A. Margotti, T. Massam, R. Nania, F. Palmonari, 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, M. Grothe, H. Hartmann, K. Heinloth, L. Heinz, E. Hilger, H.-P. Jakob, A. Kappes, U.F. Katz, R. Kerger, E. Paul, M. Pfeiffer, H. Schnurbusch, A. Weber, H. Wieber Physikalisches Institut der Universität Bonn, Bonn, Germany c D.S. Bailey, W.N. Cottingham, B. Foster, R. Hall-Wilton, G.P. Heath, H.F. Heath, J.D. McFall, D. Piccioni, D.G. Roff, J. Scott, R.J. Tapper H.H. Wills Physics Laboratory, University of Bristol, Bristol, U.K. o M. Capua, L. Iannotti, A. Mastroberardino, 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.M. 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

Using the ZEUS detector at the HERA electronproton collider, we have searched for lepton flavor violation in ep collisions at a center–of–mass energy ( √ s) of 300 GeV. Events of the typee + p → ` + X with a final–state lepton of high transverse momentum, ` = μ or τ , were sought. No evidence was found for lepton flavor violation in the combined 1993 and 1994 data samples, for which the integrated luminosities were 0.84 pb−1 for e−p collisions and 2.94pb−1 for e+p collisions. Limits on couplingvs.mass are provided for leptoquarks and R–parity violating squarks. For flavor violating couplings of electromagnetic strength, we set 95% confidence level lower limits on leptoquark masses between 207 GeV and 272 GeV, depending on the leptoquark species and final–state lepton. For leptoquark masses larger than 300 GeV, limits on flavor–changing couplings are determined, many of which supersede prior limits from rare decay processes. 29 also at University of Hamburg, Alexander von Humboldt Research Award 30 now at Lawrence Berkeley Laboratory, Berkeley 31 now at Yale University, New Haven, CT 32 supported by a MINERVA Fellowship 33 supported by the Japan Society for the Promotion of Science (JSPS) 34 present address: Tokyo Metropolitan College of Allied Medical Sciences, Tokyo 116, Japan 35 supported by the Polish State Committee for Scientific Research, grant No. 2P03B09308 36 supported by the Polish State Committee for Scientific Research, grant No. 2P03B09208 37 now at TECMAR Incorporated, Toronto a supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) b supported by the FCAR of Qu ébec, Canada c supported by the German Federal Ministry for Education and Science, Research and Technology (BMBF), under contract numbers 057BN19P, 057FR19P, 057HH19P, 057HH29P, 057SI75I d supported by the MINERVA Gesellschaft f ür Forschung GmbH, the Israel Academy of Science and the U.S.-Israel Binational Science Foundation e supported by the German Israeli Foundation, and by the Israel Academy of Science f supported by the Italian National Institute for Nuclear Physics (INFN) g supported by the Japanese Ministry of Education, Science and Culture (the Monbusho) and its grants for Scientific Research h supported by the Korean Ministry of Education and Korea Science and Engineering Foundation i supported by the Netherlands Foundation for Research on Matter (FOM) j supported by the Polish State Committee for Scientific Research, grants No. 115/E-343/SPUB/P03/109/95, 2P03B 244 08p02, p03, p04 and p05, and the Foundation for Polish-German Collaboration (proj. No. 506/92) k supported by the Polish State Committee for Scientific Research (grant No. 2 P03B 083 08) and Foundation for Polish-German Collaboration l partially supported by the German Federal Ministry for Education and Science, Research and Technology (BMBF) m supported by the German Federal Ministry for Education and Science, Research and Technology (BMBF), and the Fund of Fundamental Research of Russian Ministry of Science and Education and by INTAS-Grant No. 93-63 n supported by the Spanish Ministry of Education and Science through funds provided by CICYT o supported by the Particle Physics and Astronomy Research Council p supported by the US Department of Energy q supported by the US National Science Foundation

This paper presents measurements of D∗± production in deep inelastic scattering from collisions between 27.5GeV positrons and 820GeV protons. The data have been taken with the ZEUS detector at HERA. The decay channel D∗+ → (D → K−π+)π+ (+ c.c.) has been used in the study. The ep cross section for inclusive D∗± production with 5 < Q < 100GeV and y < 0.7 is 5.3± 1.0± 0.8 nb in the kinematic region 1.3 < pT(D ∗±) < 9.0GeV and | η(D∗±) | < 1.5. Differential cross sections as functions of pT(D ∗±), η(D∗±), W and Q are compared with next-to-leading order QCD calculations based on the photon-gluon fusion production mechanism. After an extrapolation of the cross section to the full kinematic region in pT(D ∗±) and η(D∗±), the charm contribution F cc̄ 2 (x,Q ) to the proton structure function is determined for Bjorken x between 2 · 10−4 and 5 · 10−3. 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, S. De Pasquale, I. Gialas, P. Giusti, G. Iacobucci, G. Laurenti, G. Levi, A. Margotti, T. Massam, R. Nania, F. Palmonari, 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 Jagellonian Univ., Dept. of Physics, Cracow, Poland k

The forward and rear calorimeters of the ZEUS experiment are made of 48 modules with maximum active dimensions of 4.6 m height, 0.2 m width, 7 λ depth and maximum weight of 12 t. It consists of 1 X0 uranium plates interleaved with plastic scintillator tiles read out via wavelength shifters and photomultipliers. The mechanical construction, the achieved tolerances as well as the optical and electronics readout are described. Ten of these modules have been tested with electrons, hadrons and muons in the momentum range 15–100 GeV/c. Results on resolution, uniformity and calibration are presented. Our main result is the achieved calibration accuracy of about 1% obtained by using the signal from the uranium radioactivity.

In einer prospektiv randomisierten Studie wurde der Einfluß auf die Wundheilungsstörung bei bedingt aseptischen Operationen durch lokale Gabe von Grammaxin und Totocillin verglichen. Bei 121 mit Grammaxin behandelten Patienten gab es 6 Wundinfektionen (4,9%); bei 129 mit Totocillin behandelten Patienten kam es zu 10 Sekundärheilungen (7,8%). Die Differenz ist statistisch nicht signifikant.

Photoproduction events which have two or more jets have been studied in the W,, range 135 GeV < W,, < 280 GeV with the ZEUS detector at HERA. A class of events is observed with little hadronic activity between the jets. The jets are separated by pseudorapidity intervals (Ar]) of up to four units and have transverse energies greater than 6 GeV. A gap is defined as the absence between the jets of particles with transverse energy greater than 300 MeV. The fraction of events containing a gap is measured as a function of AT. It decreases exponentially as expected for processes in which colour is exchanged between the jets, up to a value of AT 3, then reaches a constant value of about 0.1. The excess above the exponential fall-off can be interpreted as evidence for hard diffractive scattering via a strongly interacting colour singlet object. ’ Also at IROE Florence, Italy. * Now at Univ. of Salerno and INFN Napoli, Italy. 3 Supported by EU HCM contract ERB-CHRX-CT93-0376. 4 Supported by Worldlab, Lausanne, Switzerland. 5 Now a self-employed consultant. 6 Now at ELEKLUFT, Bonn. ’ Now also at University of Torino. * Alexander von Humboldt Fellow. g Alfred P. Sloan Foundation Fellow. lo Now at Inst. of Computer Science, Jagellonian Univ., Cracow. l1 Now at Comma-Soft, Bonn. ‘* Visitor from Florida State University. I3 Now at Univ. of Mainz. I4 Now at DESY Computer Center. I5 Supported by European Community Program PRAXIS XXI. l6 Now at Dr. Seidel Informationssysteme, Frankfurt/M. ” Now at Inst. of Accelerating Systems & Applications (IASA), Athens. l8 Now at Mercer Management Consulting, Munich. lg Now at Univ. de Strasbourg. ” Now at Andrews University, Barrien Springs, USA. *’ Now with OPAL Collaboration, Faculty of Physics at Univ. of Freiburg. ** Now at SAS-Institut GmbH, Heidelberg. u Now at GSI Darmstadt. 24 Also supported by NSERC. Z Now at Institute for Cosmic Ray Research, University of Tokyo. 26 Partially supported by CAM. ” Partially supported by DESY. 28 Now at Philips Natlab, Eindhoven, NL. 2g Now at Carleton University, Ottawa, Canada. 3o Now at Department of Energy, Washington. 31 Now at HEP Div., Argonne National Lab., Argonne, IL, USA. 32 Now at Oxford Magnet Technology, Eynsham, Oxon. 33 In part supported by Argonne National Laboratory. 34 Supported by a MINERVA Fellowship. 35 Now at Centre for Subatomic Research, Univ.of Alberta, Canada and TRIUMF, Vancouver, Canada. 36 Supported by the Polish State Committee for Scientific Research, grant No. 2P03B09308. 37 Supported by the Polish State Committee for Scientific Research, grant No. 2P03B09208. 38 Now at University of Colorado, USA. 3g Now at High Energy Group of State University of New York, 60 ZEUS Collaboration/Physics Letters B 369 (1996) 55-68

Differential dijet cross sections have been measured with the ZEUS detector for photoproduction events in which the hadronic final state containing the jets is separated with respect to the outgoing proton direction by a large rapidity gap. The cross section has been measured as a function of the fraction of the photon (xOBS γ ) and pomeron (β OBS) momentum participating in the production of the dijet system. The observed xOBS γ dependence shows evidence for the presence of a resolvedas well as a direct-photon component. The measured cross section dσ/dβOBS increases as βOBS increases indicating that there is a sizeable contribution to dijet production from those events in which a large fraction of the pomeron momentum participates in the hard scattering. These cross sections and the ZEUS measurements of the diffractive structure function can be described by calculations based on parton densities in the pomeron which evolve according to the QCD evolution equations and include a substantial hard momentum component of gluons in the pomeron. DESY 98-045 April 1998 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, N. Coppola, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Laurenti, G. Levi, A. Margotti, T. Massam, R. Nania, F. Palmonari, 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, M. Grothe, H. Hartmann, K. Heinloth, L. Heinz, E. Hilger, H.-P. Jakob, A. Kappes, U.F. Katz, R. Kerger, E. Paul, M. Pfeiffer, J. Stamm, H. Wieber Physikalisches Institut der Universität Bonn, Bonn, Germany c D.S. Bailey, S. Campbell-Robson, W.N. Cottingham, B. Foster, R. Hall-Wilton, 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 R. Ayad, M. Capua, 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.M. 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, K. Desler, G. Drews, U. Fricke, I. Gialas, F. Goebel, P. Göttlicher, R. Graciani, T. Haas, W. Hain, D. Hasell, K. Hebbel, K.F. Johnson, M. Kasemann, W. Koch, U. Kötz, H. Kowalski, L. Lindemann, B. Löhr, J. Milewski, M. Milite, T. Monteiro, J.S.T. Ng, D. Notz, I.H. Park, A. Pellegrino, F. Pelucchi, K. Piotrzkowski, M. Rohde, J. Roldán, J.J. Ryan, A.A. Savin, U. Schneekloth, O. Schwarzer, F. Selonke, S. Stonjek, B. Surrow, E. Tassi, D. Westphal, G. Wolf, U. Wollmer, C. Youngman, W. Zeuner Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany