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1. Differential cross sections of D*(+/-) photoproduction in ep collisions at HERA

Author

J. Breitweg, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R.L. Talaga, R. Yoshida, H. Zhang, M.C.K. Mattingly, 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, 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, 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, M. Arneodo, R. Ayad, M. Capua, A. Garfagnini, L. Iannotti, M. Schioppa, G. Susinno, J.Y. Kim, J.H. Lee, I.T. Lim, M.Y. Pac, A. Caldwell, N. Cartiglia, Z. Jing, W. Liu, J.A. Parsons, S. Ritz, S. Sampson, F. Sciulli, P.B. Straub, Q. Zhu, P. Borzemski, J. Chwastowski, A. Eskreys, Z. Jakubowski, M.B. Przybycień, M. Zachara, L. Zawiejski, L. Adamczyk, B. Bednarek, K. Jeleń, D. Kisielewska, T. Kowalski, M. Przybycień, E. Rulikowska-Zarȩbska, L. Suszycki, J. Zaja̧c, Z. Duliński, A. Kotański, G. Abbiendi, H. Abramowicz, L.A.T. Bauerdick, U. Behrens, H. Beier, J.K. Bienlein, G. Cases, O. Deppe, K. Desler, G. Drews, D.J. Gilkinson, C. Glasman, P. Göttlicher, J. Große-Knetter, T. Haas, W. Hain, D. Hasell, H. Heßling, Y. Iga, K.F. Johnson, M. Kasemann, W. Koch, U. Kötz, H. Kowalski, J. Labs, L. Lindemann, B. Löhr, M. Löwe, J. Mainusch, 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, A.A. Savin, U. Schneekloth, W. Schulz, F. Selonke, B. Surrow, E. Tassi, T. Voß, D. Westphal, G. Wolf, U. Wollmer, C. Youngman, A.F. Żarnecki, W. Zeuner, B.D. Burow, H.J. Grabosch, A. Meyer, S. Schlenstedt, G. Barbagli, E. Gallo, P. Pelfer, G. Maccarrone, L. Votano, A. Bamberger, S. Eisenhardt, P. Markun, T. Trefzger, S. Wölfle, J.T. Bromley, N.H. Brook, P.J. Bussey, A.T. Doyle, D.H. Saxon, L.E. Sinclair, E. Strickland, M.L. Utley, R. Waugh, A.S. Wilson, I. Bohnet, N. Gendner, U. Holm, A. Meyer-Larsen, H. Salehi, K. Wick, L.K. Gladilin, R. Klanner, E. Lohrmann, G. Poelz, W. Schott, F. Zetsche, T.C. Bacon, I. Butterworth, J.E. Cole, V.L. Harris, G. Howell, B.H.Y. Hung, L. Lamberti, K.R. Long, D.B. Miller, N. Pavel, A. Prinias, J.K. Sedgbeer, D. Sideris, A.F. Whitfield, U. Mallik, S.M. Wang, J.T. Wu, P. Cloth, D. Filges, S.H. An, S.B. Lee, S.W. Nam, H.S. Park, S.K. Park, F. Barreiro, J.P. Fernandez, R. Graciani, J.M. Hernández, L. Hervás, L. Labarga, M. Martinez, J. del Peso, J. Puga, J. Terron, J.F. de Trocóniz, F. Corriveau, D.S. Hanna, J. Hartmann, L.W. Hung, J.N. Lim, W.N. Murray, A. Ochs, M. Riveline, D.G. Stairs, M. St-Laurent, R. Ullmann, T. Tsurugai, V. Bashkirov, B.A. Dolgoshein, A. Stifutkin, G.L. Bashindzhagyan, P.F. Ermolov, Yu.A. Golubkov, V.D. Kobrin, I.A. Korzhavina, V.A. Kuzmin, O.Yu. Lukina, A.S. Proskuryakov, L.M. Shcheglova, A.N. Solomin, N.P. Zotov, C. Bokel, M. Botje, N. Brümmer, F. Chlebana, J. Engelen, M. de Kamps, P. Kooijman, A. Kruse, A. van Sighem, H. Tiecke, W. Verkerke, J. Vossebeld, M. Vreeswijk, L. Wiggers, E. de Wolf, D. Acosta, B. Bylsma, L.S. Durkin, J. Gilmore, C.M. Ginsburg, C.L. Kim, T.Y. Ling, P. Nylander, T.A. Romanowski, H.E. Blaikley, R.J. Cashmore, A.M. Cooper-Sarkar, R.C.E. Devenish, J.K. Edmonds, N. Harnew, M. Lancaster, J.D. McFall, C. Nath, V.A. Noyes, A. Quadt, J.R. Tickner, H. Uijterwaal, R. Walczak, D.S. Waters, T. Yip, A. Bertolin, R. Brugnera, R. Carlin, F. Dal Corso, U. Dosselli, S. Limentani, M. Morandin, M. Posocco, L. Stanco, R. Stroili, C. Voci, J. Bulmahn, R.G. Feild, B.Y. Oh, J.R. Okrasiński, J.J. Whitmore, G. D'Agostini, G. Marini, A. Nigro, J.C. Hart, N.A. McCubbin, T.P. Shah, E. Barberis, T. Dubbs, C. Heusch, M. Van Hook, W. Lockman, J.T. Rahn, H.F.-W. Sadrozinski, A. Seiden, D.C. Williams, O. Schwarzer, A.H. Walenta, G. Briskin, S. Dagan, T. Doeker, A. Levy, T. Abe, J.I. Fleck, M. Inuzuka, T. Ishii, M. Kuze, K. Nagano, M. Nakao, I. Suzuki, K. Tokushuku, K. Umemori, S. Yamada, Y. Yamazaki, R. Hamatsu, T. Hirose, K. Homma, S. Kitamura, T. Matsushita, K. Yamauchi, R. Cirio, M. Costa, M.I. Ferrero, S. Maselli, V. Monaco, C. Peroni, M.C. Petrucci, R. Sacchi, A. Solano, A. Staiano, M. Dardo, D.C. Bailey, M. Brkic, C.-P. Fagerstroem, G.F. Hartner, K.K. Joo, G.M. Levman, J.F. Martin, R.S. Orr, S. Polenz, C.R. Sampson, D. Simmons, R.J. Teuscher, J.M. Butterworth, C.D. Catterall, T.W. Jones, P.B. Kaziewicz, J.B. Lane, R.L. Saunders, J. Shulman, M.R. Sutton, B. Lu, L.W. Mo, J. Ciborowski, G. Grzelak, M. Kasprzak, K. Muchorowski, R.J. Nowak, J.M. Pawlak, R. Pawlak, T. Tymieniecka, A.K. Wróblewski, J.A. Zakrzewski, M. Adamus, C. Coldewey, Y. Eisenberg, D. Hochman, U. Karshon, D. Revel, D. Zer-Zion, W.F. Badgett, D. Chapin, R. Cross, S. Dasu, C. Foudas, R.J. Loveless, S. Mattingly, D.D. Reeder, W.H. Smith, A. Vaiciulis, M. Wodarczyk, S. Bhadra, W.R. Frisken, M. Khakzad, W.B. Schmidke, and Zeus (IHEF, IoP, FNWI)

Subjects
Nuclear and High Energy Physics, Particle physics, Photon, E+E ANNIHILATION, FOS: Physical sciences, 01 natural sciences, High Energy Physics - Experiment, Nuclear physics, High Energy Physics - Experiment (hep-ex), 0103 physical sciences, DISTRIBUTIONS, 010306 general physics, Nuclear Experiment, Quantum chromodynamics, Physics, 010308 nuclear & particles physics, Perturbative QCD, FLAVOR PRODUCTION, ZEUS, ZEUS BARREL CALORIMETER, HERA, CENTRAL TRACKING DETECTOR, Massless particle, PHOTON, HEAVY-QUARK CORRELATIONS, HADRON-COLLISIONS, QCD CORRECTIONS, FRAGMENTATION, High Energy Physics::Experiment
Abstract

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 < 280 GeV and photon virtuality Q**2 < 4 GeV**2. The cross section sigma(ep --> D*X) integrated over the kinematic region pt(D*) > 3 GeV and -1.5 < eta(D*) < 1.0 is (10.6+-1.7(stat.)+1.6(syst.)-1.3(syst.)) nb. Differential cross sections as functions of pt(D*), eta(D*) 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., 18 pages including 4 figures

Published
2016

2. EXTRACTION OF THE GLUON DENSITY OF THE PROTON AT X

Author

M. Derrick, D. Krakauer, S. Magill, B. Musgrave, J. Repond, J. Schlereth, R. Stanek, R.L. Talaga, J. Thron, F. Arzarello, R. Ayad, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, P. Bruni, G. Cara Romeo, G. Castellini, M. Chiarini, L. Cifarelli, F. Cindolo, F. Ciralli, A. Contin, S. D'Auria, F. Frasconi, I. Gialas, P. Giusti, G. Iacobucci, G. Laurenti, G. Levi, A. Margotti, T. Massam, R. Nania, C. Nemoz, F. Palmonari, A. Polini, G. Sartorelli, R. Timellini, Y. Zamora Garcia, A. Zichichi, A. Bargende, J. Crittenden, K. Desch, B. Diekmann, T. Doeker, M. Eckert, L. Feld, A. Frey, M. Geerts, G. Geitz, M. Grothe, H. Hartmann, D. Haun, K. Heinloth, E. Hilger, H.-P. Jakob, U.F. Katz, S.M. Mari, A. Mass, S. Mengel, J. Mollen, E. Paul, Ch. Rembser, R. Schattevoy, D. Schramm, J. Stamm, R. Wedemeyer, S. Campbell-Robson, A. Cassidy, N. Dyce, B. Foster, S. George, R. Gilmore, G.P. Heath, H.F. Heath, T.J. Llewellyn, C.J.S. Morgado, D.J.P. Norman, J.A. O'Mara, R.J. Tapper, S.S. Wilson, R. Yoshida, R.R. Rau, M. Arneodo, L. Iannotti, M. Schioppa, G. Susinno, A. Bernstein, A. Caldwell, J.A. Parsons, S. Ritz, F. Sciulli, P.B. Straub, L. Wai, S. Yang, P. Borzemski, J. Chwastowski, A. Eskreys, K. Piotrzkowski, M. Zachara, L. Zawiejski, L. Adamczyk, B. Bednarek, K. Eskreys, K. Jelén, D. Kisielewska, T. Kowalski, E. Rulikowska-Zarȩbska, L. Suszycki, J. Zaja̧c, T. Kȩdzierski, A. Kotański, M. Przybycień, L.A.T. Bauerdick, U. Behrens, J.K. Bienlein, S. Böttcher, C. Coldewey, G. Drews, M. Flasiński, D.J. Gilkinson, P. Göttlicher, B. Gutjahr, T. Haas, W. Hain, D. Hasell, H. Heβling, H. Hultschig, Y. Iga, P. Joos, M. Kasemann, R. Klanner, W. Koch, L. Köpke, U. Kötz, H. Kowalski, W. Kröger, J. Krüger, J. Labs, A. Ladage, B. Löhr, M. Löwe, D. Lüke, O. Mańczak, J.S.T. Ng, S. Nickel, D. Notz, K. Ohrenberg, M. Roco, M. Rohde, J. Roldán, U. Schneekloth, W. Schulz, F. Selonke, E. Stiliaris, T. Voβ, D. Westphal, G. Wolf, C. Youngman, H.J. Grabosch, A. Leich, A. Meyer, C. Rethfeldt, S. Schlenstedt, G. Barbagli, P. Pelfer, G. Anzivino, G. Maccarrone, S. De Pasquale, S. Qian, L. Votano, A. Bamberger, A. Freidhof, T. Poser, S. Söldner-Rembold, J. Schroeder, G. Theisen, T. Trefzger, N.H. Brook, P.J. Bussey, A.T. Doyle, I. Fleck, V.A. Jamieson, D.H. Saxon, M.L. Utley, A.S. Wilson, A. Dannemann, U. Holm, D. Horstmann, H. Kammerlocher, B. Krebs, T. Neumann, R. Sinkus, K. Wick, E. Badura, B.D. Burow, A. Fürtjes, L. Hagge, E. Lohrmann, J. Mainusch, J. Milewski, M. Nakahata, N. Pavel, G. Poelz, W. Schott, J. Terron, F. Zetsche, T.C. Bacon, R. Beuselinck, I. Butterworth, E. Gallo, V.L. Harris, B.H. Hung, K.R. Long, D.B. Miller, P.P.O. Morawitz, A. Prinias, J.K. Sedgbeer, A.F. Whitfield, U. Mallik, E. McCliment, M.Z. Wang, S.M. Wang, J.T. Wu, Y. Zhang, P. Cloth, D. Filges, S.H. An, S.M. Hong, S.W. Nam, S.K. Park, M.H. Suh, S.H. Yon, R. Imlay, S. Kartik, H.-J. Kim, R.R. McNeil, W. Metcalf, V.K. Nadendla, F. Barreiro, G. Cases, R. Graciani, J.M. Hernández, L. Hervás, L. Labarga, J. del Peso, J. Puga, J.F. de Trocóniz, F. Ikraiam, J.K. Mayer, G.R. Smith, F. Corriveau, D.S. Hanna, J. Hartmann, L.W. Hung, J.N. Lim, C.G. Matthews, P.M. Patel, L.E. Sinclair, D.G. Stairs, M. St.Laurent, R. Ullmann, G. Zacek, V. Bashkirov, B.A. Dolgoshein, A. Stifutkin, G.L. Bashindzhagyan, P.F. Ermolov, L.K. Gladilin, Y.A. Golubkov, V.D. Kobrin, V.A. Kuzmin, A.S. Proskuryakov, A.A. Savin, L.M. Shcheglova, A.N. Solomin, N.P. Zotov, S. Bentvelsen, M. Botje, F. Chlebana, A. Dake, J. Engelen, P. de Jong, M. de Kamps, P. Kooijman, A. Kruse, V. O'Dell, A. Tenner, H. Tiecke, W. Verkerke, M. Vreeswijk, L. Wiggers, E. de Wolf, R. van Woudenberg, D. Acosta, B. Bylsma, L.S. Durkin, K. Honscheid, C. Li, T.Y. Ling, K.W. McLean, W.N. Murray, I.H. Park, T.A. Romanowski, R. Seidlein, D.S. Bailey, G.A. Blair, A. Byrne, R.J. Cashmore, A.M. Cooper-Sarkar, D. Daniels, R.C.E. Devenish, N. Harnew, M. Lancaster, P.E. Luffman, L. Lindemann, J. McFall, C. Nath, A. Quadt, H. Uijterwaal, R. Walczak, F.F. Wilson, T. Yip, G. Abbiendi, A. Bertolin, R. Brugnera, R. Carlin, F. Dal Corso, M. De Giorgi, U. Dosselli, S. Limentani, M. Morandin, M. Posocco, L. Stanco, R. Stroili, C. Voci, J. Bulmahn, J.M. Butterworth, R.G. Feild, B.Y. Oh, J.J. Whitmore, G. D'Agostini, M. Iori, G. Marini, M. Mattioli, A. Nigro, E. Tassi, J.C. Hart, N.A. McCubbin, K. Prytz, T.P. Shah, T.L. Short, E. Barberis, N. Cartiglia, T. Dubbs, C. Heusch, M. Van Hook, B. Hubbard, W. Lockman, J.T. Rahn, H.F.-W. Sadrozinski, A. Seiden, J. Biltzinger, R.J. Seifert, A.H. Walenta, G. Zech, H. Abramowicz, G. Briskin, S. Dagan, A. Levy, T. Hasegawa, M. Hazumi, T. Ishii, M. Kuze, S. Mine, Y. Nagasawa, T. Nagira, M. Nakao, I. Suzuki, K. Tokushuku, S. Yamada, Y. Yamazaki, M. Chiba, R. Hamatsu, T. Hirose, K. Homma, S. Kitamura, S. Nagayama, Y. Nakamitsu, R. Cirio, M. Costa, M.I. Ferrero, L. Lamberti, S. Maselli, C. Peroni, R. Sacchi, A. Solano, A. Staiano, M. Dardo, D.C. Bailey, D. Bandyopadhyay, F. Benard, M. Brkic, M.B. Crombie, D.M. Gingrich, G.F. Hartner, K.K. Joo, G.M. Levman, J.F. Martin, R.S. Orr, C.R. Sampson, R.J. Teuscher, C.D. Catterall, T.W. Jones, P.B. Kaziewicz, J.B. Lane, R.L. Saunders, J. Shulman, K. Blankenship, J. Kochocki, B. Lu, L.W. Mo, W. Bogusz, K. Charchuł, a, J. Ciborowski, J. Gajewski, G. Grzelak, M. Kasprzak, M. Krzyżanowski, K. Muchorowski, R.J. Nowak, J.M. Pawlak, T. Tymieniecka, A.K. Wróblewski, J.A. Zakrzewski, A.F. Zarnecki, M. Adamus, Y. Eisenberg, C. Glasman, U. Karshon, D. Revel, A. Shapira, I. Ali, B. Behrens, S. Dasu, C. Fordham, C. Foudas, A. Goussiou, R.J. Loveless, D.D. Reeder, S. Silverstein, W.H. Smith, T. Tsurugai, S. Bhadra, W.R. Frisken, and K.M. Furutani

Subjects
Nuclear and High Energy Physics, Particle physics, Proton, Nuclear physics, INELASTIC MUON SCATTERING, DEUTERON STRUCTURE FUNCTIONS, ZEUS, NUCLEON STRUCTURE FUNCTIONS, HIGH STATISTICS MEASUREMENT, PARTON DISTRIBUTIONS, LEADING ORDER, HIGH Q2, PERTURBATION-THEORY, SCALING VIOLATIONS, PP COLLISIONS, Quantum chromodynamics, Physics, ZEUS (particle detector), Neutral current, Scattering, High Energy Physics::Phenomenology, HERA, Gluon, High Energy Physics::Experiment, Perturbation theory (quantum mechanics)
Abstract

The gluon momentum density xg ( x , Q 2 ) of the proton was extracted at Q 2 = 20 GeV 2 for small values of x between 4 × 10 −4 and 10 −2 from the scaling violations of the proton structure function F 2 measured recently by ZEUS in deep inelastic neutral current ep scattering at HERA. The extraction was performed in two ways. Firstly, using a global NLO fit to the ZEUS data on F 2 at low x constrained by measurementsfrom NMC at larger x ; and secondly using published approximate methods for the solution of the GLAP QCD evolution equations. Consistent results are obtained. A substantial increase of the gluon density is found at small x in comparison with the NMC result obtained at larger values of x .

Published
2016
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3. Observation of hard scattering in photoproduction events with a large rapidity gap at HERA

Author

M. Derrick, D. Krakauer, S. Magill, B. Musgrave, J. Repond, J. Schlereth, R. Stanek, R.L. Talaga, J. Thron, F. Arzarello, R. Ayad, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, P. Bruni, G. Cara Romeo, G. Castellini, M. Chiarini, L. Cifarelli, F. Cindolo, F. Ciralli, A. Contin, S. D'Auria, F. Frasconi, I. Gialas, P. Giusti, G. Iacobucci, G. Laurenti, G. Levi, A. Margotti, T. Massam, R. Nania, C. Nemoz, F. Palmonari, A. Polini, G. Sartorelli, R. Timellini, Y. Zamora Garcia, A. Zichichi, A. Bargende, J. Crittenden, K. Desch, B. Diekmann, T. Doeker, M. Eckert, L. Feld, A. Frey, M. Geerts, G. Geitz, M. Grothe, H. Hartmann, D. Haun, K. Heinloth, E. Hilger, H.-P. Jakob, U.F. Katz, S.M. Mari, A. Mass, S. Mengel, J. Mollen, E. Paul, Ch. Rembser, R. Schattevoy, D. Schramm, J. Stamm, R. Wedemeyer, S. Campbell-Robson, A. Cassidy, N. Dyce, B. Foster, S. George, R. Gilmore, G.P. Heath, H.F. Heath, T.J. Llewellyn, C.J.S. Morgado, D.J.P. Norman, J.A. O'Mara, R.J. Tapper, S.S. Wilson, R. Yoshida, R.R. Rau, M. Arneodo, L. Iannotti, M. Schioppa, G. Susinno, A. Bernstein, A. Caldwell, J.A. Parsons, S. Ritz, F. Sciulli, P.B. Straub, L. Wai, S. Yang, Q. Zhu, P. Borzemski, J. Chwastowski, A. Eskreys, K. Piotrzkowski, M. Zachara, L. Zawiejski, L. Adamczyk, B. Bednarek, K. Eskreys, K. Jeleń, D. Kisielewska, T. Kowalski, E. Rulikowska-Zarȩbska, L. Suszycki, J. Zaja̧c, A. Kotański, M. Przybycień, L.A.T. Bauerdick, U. Behrens, J.K. Bienlein, S. Böttcher, C. Coldewey, G. Drews, M. Flasiński, D.J. Gilkinson, P. Göttlicher, B. Gutjahr, T. Haas, W. Hain, D. Hasell, H. Heßling, H. Hultschig, Y. Iga, P. Joos, M. Kasemann, R. Klanner, W. Koch, L. Köpke, U. Kötz, H. Kowalski, W. Kröger, J. Krüger, J. Labs, A. Ladage, B. Löhr, M. Löwe, D. Lüke, O. Mańczak, J.S.T. Ng, S. Nickel, D. Notz, K. Ohrenberg, M. Roco, M. Rohde, J. Roldán, U. Schneekloth, W. Schulz, F. Selonke, E. Stiliaris, T. Voß, D. Westphal, G. Wolf, C. Youngman, H.J. Grabosch, A. Leich, A. Meyer, C. Rethfeldt, S. Schlenstedt, G. Barbagli, P. Pelfer, G. Anzivino, G. Maccarrone, S. De Pasquale, S. Qian, L. Votano, A. Bamberger, A. Freidhof, T. Poser, S. Söldner-Rembold, J. Schroeder, G. Theisen, T. Trefzger, N.H. Brook, P.J. Bussey, A.T. Doyle, I. Fleck, V.A. Jamieson, D.H. Saxon, M.L. Utley, A.S. Wilson, A. Dannemann, U. Holm, D. Horstmann, H. Kammerlocher, B. Krebs, T. Neumann, R. Sinkus, K. Wick, E. Badura, B.D. Burow, A. Fürtjes, L. Hagge, E. Lohrmann, J. Mainusch, J. Milewski, M. Nakahata, N. Pavel, G. Poelz, W. Schott, J. Terron, F. Zetsche, T.C. Bacon, R. Beuselinck, I. Butterworth, E. Gallo, V.L. Harris, B.H. Hung, K.R. Long, D.B. Miller, P.P.O. Morawitz, A. Prinias, J.K. Sedgbeer, A.F. Whitfield, U. Mallik, E. McCliment, M.Z. Wang, S.M. Wang, J.T. Wu, Y. Zhang, P. Cloth, D. Filges, S.H. An, S.M. Hong, S.W. Nam, S.K. Park, M.H. Suh, S.H. Yon, R. Imlay, S. Kartik, H.-J. Kim, R.R. McNeil, W. Metcalf, V.K. Nadendla, F. Barreiro, G. Cases, R. Graciani, J.M. Hernández, L. Hervás, L. Labarga, J. del Peso, J. Puga, J.F. de Trocóniz, G.R. Smith, F. Corriveau, D.S. Hanna, J. Hartmann, L.W. Hung, J.N. Lim, C.G. Matthews, P.M. Patel, L.E. Sinclair, D.G. Stairs, M.St. Laurent, R. Ullmann, G. Zacek, V. Bashkirov, B.A. Dolgoshein, A. Stifutkin, G.L. Bashindzhagyan, P.F. Ermolov, L.K. Gladilin, Y.A. Golubkov, V.D. Kobrin, V.A. Kuzmin, A.S. Proskuryakov, A.A. Savin, L.M. Shcheglova, A.N. Solomin, N.P. Zotov, S. Bentvelsen, M. Botje, F. Chlebana, A. Dake, J. Engelen, P. de Jong, M. de Kamps, P. Kooijman, A. Kruse, V. O'Dell, A. Tenner, H. Tiecke, W. Verkerke, M. Vreeswijk, L. Wiggers, E. de Wolf, R. van Woudenberg, D. Acosta, B. Bylsma, L.S. Durkin, K. Honscheid, C. Li, T.Y. Ling, K.W. McLean, W.N. Murray, I.H. Park, T.A. Romanowski, R. Seidlein, D.S. Bailey, G.A. Blair, A. Byrne, R.J. Cashmore, A.M. Cooper-Sarkar, D. Daniels, R.C.E. Devenish, N. Harnew, M. Lancaster, P.E. Luffman, L. Lindemann, J. McFall, C. Nath, A. Quadt, H. Uijterwaal, R. Walczak, F.F. Wilson, T. Yip, G. Abbiendi, A. Bertolin, R. Brugnera, R. Carlin, F. Dal Corso, M. De Giorgi, U. Dosselli, S. Limentani, M. Morandin, M. Posocco, L. Stanco, R. Stroili, C. Voci, J. Bulmahn, J.M. Butterworth, R.G. Feild, B.Y. Oh, J.J. Whitmore, G. D'Agostini, M. Iori, G. Marini, M. Mattioli, A. Nigro, E. Tassi, J.C. Hart, N.A. McCubbin, K. Prytz, T.P. Shah, T.L. Short, E. Barberis, N. Cartiglia, T. Dubbs, C. Heusch, M. Van Hook, B. Hubbard, W. Lockman, J.T. Rahn, H.F.-W. Sadrozinski, A. Seiden, J. Biltzinger, R.J. Seifert, A.H. Walenta, G. Zech, H. Abramowicz, G. Briskin, S. Dagan, A. Levy, T. Hasegawa, M. Hazumi, T. Ishii, M. Kuze, S. Mine, Y. Nagasawa, T. Nagira, M. Nakao, I. Suzuki, K. Tokushuku, S. Yamada, Y. Yamazaki, M. Chiba, R. Hamatsu, T. Hirose, K. Homma, S. Kitamura, S. Nagayama, Y. Nakamitsu, R. Cirio, M. Costa, M.I. Ferrero, L. Lamberti, S. Maselli, C. Peroni, R. Sacchi, A. Solano, A. Staiano, M. Dardo, D.C. Bailey, D. Bandyopadhyay, F. Benard, M. Brkic, M.B. Crombie, D.M. Gingrich, G.F. Hartner, K.K. Joo, G.M. Levman, J.F. Martin, R.S. Orr, C.R. Sampson, R.J. Teuscher, C.D. Catterall, T.W. Jones, P.B. Kaziewicz, J.B. Lane, R.L. Saunders, J. Shulman, K. Blankenship, J. Kochocki, B. Lu, L.W. Mo, W. Bogusz, K. Charchuła, J. Ciborowski, J. Gajewski, G. Grzelak, M. Kasprzak, M. Krzyżanowski, K. Muchorowski, R.J. Nowak, J.M. Pawlak, T. Tymieniecka, A.K. Wróblewski, J.A. Zakrzewski, A.F. Żarnecki, M. Adamus, Y. Eisenberg, C. Glasman, U. Karshon, D. Revel, A. Shapira, I. Ali, B. Behrens, S. Dasu, C. Fordham, C. Foudas, A. Goussiou, R.J. Loveless, D.D. Reeder, S. Silverstein, W.H. Smith, T. Tsurugai, S. Bhadra, W.R. Frisken, K.M. Furutani, and Zeus (IHEF, IoP, FNWI)

Subjects
Nuclear and High Energy Physics, Particle physics, Photon, Proton, Astrophysics::High Energy Astrophysical Phenomena, Hadron, FOS: Physical sciences, Astronomy & Astrophysics, DIFFRACTION, 01 natural sciences, High Energy Physics - Experiment, Physics, Particles & Fields, law.invention, COLLIDER, Nuclear physics, High Energy Physics - Experiment (hep-ex), 0202 Atomic, Molecular, Nuclear, Particle And Plasma Physics, DESIGN, law, 0103 physical sciences, Rapidity, CALORIMETER, Nuclear Experiment, 010306 general physics, Collider, DETECTOR, Physics, Research Groups and Centres\Physics\Low Temperature Physics, Science & Technology, ZEUS (particle detector), Faculty of Science\Physics, hep-ex, 010308 nuclear & particles physics, Scattering, ZEUS, diffractive scattering, HERA, photoproduction, Nuclear & Particles Physics, POMERON STRUCTURE, Physics, Nuclear, PHOTON, Physical Sciences, JETS, High Energy Physics::Experiment
Abstract

Events with a large rapidity gap and total transverse energy greater than 5 GeV have been observed in quasi-real photoproduction at HERA with the ZEUS detector. The distribution of these events as a function of the $\gamma p$ centre of mass energy is consistent with diffractive scattering. For total transverse energies above 12 GeV, the hadronic final states show predominantly a two-jet structure with each jet having a transverse energy greater than 4 GeV. For the two-jet events, little energy flow is found outside the jets. This observation is consistent with the hard scattering of a quasi-real photon with a colourless object in the proton., Comment: 19 pages, latex, 4 figures appended as uuencoded file

Published
1995
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4. Measurement of elastic $\phi$ photoproduction at HERA

Author

M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J.R. Okrasinski, J. Repond, R. Stanek, R.L. Talaga, H. Zhang, M.C.K. Mattingly, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, P. 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, A. Polini, G. Sartorelli, Y. Zamora Garcia, A. Zichichi, A. Bornheim, J. Crittenden, T. Doeker, M. Eckert, L. Feld, A. Frey, M. Geerts, M. Grothe, H. Hartmann, K. Heinloth, L. Heinz, E. Hilger, H.-P. Jakob, U.F. Katz, S. Mengel, J. Mollen, E. Paul, M. Pfeiffer, Ch. Rembser, D. Schramm, J. Stamm, R. Wedemeyer, S. Campbell-Robson, A. Cassidy, W.N. Cottingham, N. Dyce, B. Foster, S. George, M.E. Hayes, G.P. Heath, H.F. Heath, D. Piccioni, D.G. Roff, R.J. Tapper, R. Yoshida, M. Arneodo, R. Ayad, M. Capua, A. Garfagnini, L. Iannotti, M. Schioppa, G. Susinno, A. Caldwell, N. Cartiglia, Z. Jing, W. Liu, J.A. Parsons, S. Ritz, F. Sciulli, P.B. Straub, L. Wai, S. Yang, Q. Zhu, P. Borzemski, J. Chwastowski, A. Eskreys, M. Zachara, L. Zawiejski, L. Adamczyk, B. Bednarek, K. Jeleń, D. Kisielewska, T. Kowalski, M. Przybycień, E. Rulikowska-Zarȩbska, L. Suszycki, J. Zaja̧c, A. Kotański, L.A.T. Bauerdick, U. Behrens, H. Beier, J.K. Bienlein, O. Deppe, K. Desler, G. Drews, M. Flasiński, D.J. Gilkinson, C. Glasman, P. Göttlicher, J. Große-Knetter, T. Haas, W. Hain, D. Hasell, H. Heßling, Y. Iga, K.F. Johnson, P. Joos, M. Kasemann, R. Klanner, W. Koch, U. Kötz, H. Kowalski, J. Labs, A. Ladage, B. Löhr, M. Löwe, D. Lüke, J. Mainusch, O. Mańczak, T. Monteiro, J.S.T. Ng, D. Notz, K. Ohrenberg, K. Piotrzkowski, M. Roco, M. Rohde, J. Roldán, U. Schneekloth, W. Schulz, F. Selonke, B. Surrow, T. Voß, D. Westphal, G. Wolf, C. Youngman, W. Zeuner, H.J. Grabosch, A. Kharchilava, S.M. Mari, A. Meyer, S. Schlenstedt, N. Wulff, G. Barbagli, E. Gallo, P. Pelfer, G. Maccarrone, S. De Pasquale, L. Votano, A. Bamberger, S. Eisenhardt, T. Trefzger, S. Wölfle, J.T. Bromley, N.H. Brook, P.J. Bussey, A.T. Doyle, D.H. Saxon, L.E. Sinclair, M.L. Utley, A.S. Wilson, A. Dannemann, U. Holm, D. Horstmann, R. Sinkus, K. Wick, B.D. Burow, L. Hagge, E. Lohrmann, J. Milewski, N. Pavel, G. Poelz, W. Schott, F. Zetsche, T.C. Bacon, N. Brümmer, I. Butterworth, V.L. Harris, G. Howell, B.H.Y. Hung, L. Lamberti, K.R. Long, D.B. Miller, A. Prinias, J.K. Sedgbeer, D. Sideris, A.F. Whitfield, U. Mallik, M.Z. Wang, S.M. Wang, J.T. Wu, P. Cloth, D. Filges, S.H. An, G.H. Cho, B.J. Ko, S.B. Lee, S.W. Nam, H.S. Park, S.K. Park, S. Kartik, H.-J. Kim, R.R. McNeil, W. Metcalf, V.K. Nadendla, F. Barreiro, G. Cases, J.P. Fernandez, R. Graciani, J.M. Hernández, L. Hervás, L. Labarga, M. Martinez, J. del Peso, J. Puga, J. Terron, J.F. de Trocóniz, F. Corriveau, D.S. Hanna, J. Hartmann, L.W. Hung, J.N. Lim, C.G. Matthews, P.M. Patel, M. Riveline, D.G. Stairs, M. St-Laurent, R. Ullmann, G. Zacek, T. Tsurugai, V. Bashkirov, B.A. Dolgoshein, A. Stifutkin, G.L. Bashindzhagyan, P.F. Ermolov, L.K. Gladilin, Yu.A. Golubkov, V.D. Kobrin, I.A. Korzhavina, V.A. Kuzmin, O.Yu. Lukina, A.S. Proskuryakov, A.A. Savin, L.M. Shcheglova, A.N. Solomin, N.P. Zotov, M. Botje, F. Chlebana, J. Engelen, M. de Kamps, P. Kooijman, A. Kruse, A. van Sighem, H. Tiecke, W. Verkerke, J. Vossebeld, M. Vreeswijk, L. Wiggers, E. de Wolf, R. van Woudenberg, D. Acosta, B. Bylsma, L.S. Durkin, J. Gilmore, C. Li, T.Y. Ling, P. Nylander, I.H. Park, T.A. Romanowski, D.S. Bailey, R.J. Cashmore, A.M. Cooper-Sarkar, R.C.E. Devenish, N. Harnew, M. Lancaster, L. Lindemann, J.D. McFall, C. Nath, V.A. Noyes, A. Quadt, J.R. Tickner, H. Uijterwaal, R. Walczak, D.S. Waters, F.F. Wilson, T. Yip, G. Abbiendi, A. Bertolin, R. Brugnera, R. Carlin, F. Dal Corso, M. De Giorgi, U. Dosselli, S. Limentani, M. Morandin, M. Posocco, L. Stanco, R. Stroili, C. Voci, F. Zuin, J. Bulmahn, R.G. Feild, B.Y. Oh, J.J. Whitmore, G. D'Agostini, G. Marini, A. Nigro, E. Tassi, J.C. Hart, N.A. McCubbin, T.P. Shah, E. Barberis, T. Dubbs, C. Heusch, M. Van Hook, W. Lockman, J.T. Rahn, H.F.-W. Sadrozinski, A. Seiden, D.C. Williams, J. Biltzinger, R.J. Seifert, O. Schwarzer, A.H. Walenta, G. Zech, H. Abramowicz, G. Briskin, S. Dagan, A. Levy, J.I. Fleck, M. Inuzuka, T. Ishii, M. Kuze, S. Mine, M. Nakao, I. Suzuki, K. Tokushuku, K. Umemori, S. Yamada, Y. Yamazaki, M. Chiba, R. Hamatsu, T. Hirose, K. Homma, S. Kitamura, T. Matsushita, K. Yamauchi, R. Cirio, M. Costa, M.I. Ferrero, S. Maselli, C. Peroni, R. Sacchi, A. Solano, A. Staiano, M. Dardo, D.C. Bailey, F. Benard, M. Brkic, G.F. Hartner, K.K. Joo, G.M. Levman, J.F. Martin, R.S. Orr, S. Polenz, C.R. Sampson, D. Simmons, R.J. Teuscher, J.M. Butterworth, C.D. Catterall, T.W. Jones, P.B. Kaziewicz, J.B. Lane, R.L. Saunders, J. Shulman, M.R. Sutton, B. Lu, L.W. Mo, W. Bogusz, J. Ciborowski, J. Gajewski, G. Grzelak, M. Kasprzak, M. Krzyżanowski, K. Muchorowski, R.J. Nowak, J.M. Pawlak, T. Tymieniecka, A.K. Wróblewski, J.A. Zakrzewski, A.F. Żarnecki, M. Adamus, C. Coldewey, Y. Eisenberg, U. Karshon, D. Revel, D. Zer-Zion, W.F. Badgett, J. Breitweg, D. Chapin, R. Cross, S. Dasu, C. Foudas, R.J. Loveless, S. Mattingly, D.D. Reeder, S. Silverstein, W.H. Smith, A. Vaiciulis, M. Wodarczyk, S. Bhadra, M.L. Cardy, C.-P. Fagerstroem, W.R. Frisken, M. Khakzad, W.N. Murray, W.B. Schmidke, and ZEUS at HERA (IHEF, IoP, FNWI)

Subjects
Diffraction, Nuclear and High Energy Physics, Particle physics, Meson, 7. Clean energy, 01 natural sciences, High Energy Physics - Experiment, Nuclear physics, PHYSICS, Cross section (physics), DESIGN, 0103 physical sciences, 010306 general physics, DETECTOR, ZEUS, ZEUS BARREL CALORIMETER, CONSTRUCTION, Physics, Range (particle radiation), ZEUS (particle detector), 010308 nuclear & particles physics, HERA, Helicity, Exponential function, High Energy Physics::Experiment
Abstract

The production of $\phi$ mesons in the reaction $e^{+}p \rightarrow e^{+} \phi p$ ($\phi \rightarrow K^{+}K^{-}$) at a median $Q^{2}$ of $10^{-4} \ \rm{GeV^2}$ has been studied with the ZEUS detector at HERA. The differential $\phi$ photoproduction cross section $d\sigma/dt$ has an exponential shape and has been determined in the kinematic range $0.1, Comment: 23 pages, including 6 post script figures

Published
1996

5. Rapidity gaps between jets in photoproduction at HERA

Author

M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R.L. Talaga, H. Zhang, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, P. Bruni, G. Cara Romeo, G. Castellini, M. Chiarini, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, I. Gialas, P. Giusti, G. Iacobucci, G. Laurenti, G. Levi, A. Margotti, T. Massam, R. Nania, C. Nemoz, F. Palmonari, A. Polini, G. Sartorelli, R. Timellini, Y. Zamora Garcia, A. Zichichi, A. Bornheim, J. Crittenden, K. Desch, B. Diekmann, T. Doeker, M. Eckert, L. Feld, A. Frey, M. Geerts, M. Grothe, H. Hartmann, K. Heinloth, L. Heinz, E. Hilger, H.-P. Jakob, U.F. Katz, S. Mengel, J. Mollen, E. Paul, M. Pfeiffer, Ch. Rembser, D. Schramm, J. Stamm, R. Wedemeyer, S. Campbell-Robson, A. Cassidy, W.N. Cottingham, N. Dyce, B. Foster, S. George, M.E. Hayes, G.P. Heath, H.F. Heath, C.J.S. Morgado, J.A. O'Mara, D. Piccioni, D.G. Roff, R.J. Tapper, R. Yoshida, R.R. Rau, M. Arneodo, R. Ayad, M. Capua, A. Garfagnini, L. Iannotti, M. Schioppa, G. Susinno, A. Bernstein, A. Caldwell, N. Cartiglia, J.A. Parsons, S. Ritz, F. Sciulli, P.B. Straub, L. Wai, S. Yang, Q. Zhu, P. Borzemski, J. Chwastowski, A. Eskreys, K. Piotrzkowski, M. Zachara, L. Zawiejski, L. Adamczyk, B. Bednarek, K. Jeleń, D. Kisielewska, T. Kowalski, M. Przybycień, E. Rulikowska-Zarȩbska, L. Suszycki, J. Zaja̧c, A. Kotański, L.A.T. Bauerdick, U. Behrens, H. Beier, J.K. Bienlein, C. Coldewey, O. Deppe, K. Desler, G. Drews, M. Flasiński, D.J. Gilkinson, C. Glasman, P. Göttlicher, J. Groß-Knetter, B. Gutjahr, T. Haas, W. Hain, D. Hasell, H. Heßling, Y. Iga, K.F. Johnson, P. Joos, M. Kasemann, R. Klanner, W. Koch, L. Köpke, U. Kötz, H. Kowalski, J. Labs, A. Ladage, B. Löhr, M. Löwe, D. Lüke, J. Mainusch, O. Mańczak, T. Monteiro, J.S.T. Ng, S. Nickel, D. Notz, K. Ohrenberg, M. Roco, M. Rohde, J. Roldán, U. Schneekloth, W. Schulz, F. Selonke, E. Stiliaris, B. Surrow, T. Voß, D. Westphal, G. Wolf, C. Youngman, W. Zeuner, J.F. Zhou, H.J. Grabosch, A. Kharchilava, A. Leich, S.M. Mari, M.C.K. Mattingly, A. Meyer, S. Schlenstedt, N. Wulff, G. Barbagli, E. Gallo, P. Pelfer, G. Anzivino, G. Maccarrone, S. De Pasquale, L. Votano, A. Bamberger, S. Eisenhardt, A. Freidhof, S. Söldner-Rembold, J. Schroeder, T. Trefzger, N.H. Brook, P.J. Bussey, A.T. Doyle, D.H. Saxon, M.L. Utley, A.S. Wilson, A. Dannemann, U. Holm, D. Horstmann, T. Neumann, R. Sinkus, K. Wick, E. Badura, B.D. Burow, L. Hagge, E. Lohrmann, J. Milewski, M. Nakahata, N. Pavel, G. Poelz, W. Schott, F. Zetsche, T.C. Bacon, N. Bruemmer, I. Butterworth, V.L. Harris, B.Y.H. Hung, K.R. Long, D.B. Miller, P.P.O. Morawitz, A. Prinias, J.K. Sedgbeer, A.F. Whitfield, U. Mallik, E. McCliment, M.Z. Wang, S.M. Wang, J.T. Wu, P. Cloth, D. Filges, S.H. An, S.M. Hong, S.V. Nam, S.K. Park, M.H. Suh, S.H. Yon, R. Imlay, S. Kartik, H.-J. Kim, R.R. McNeil, W. Metcalf, V.K. Nadendla, F. Barreiro, G. Cases, J.P. Fernandez, R. Graciani, J.M. Hernández, L. Hervás, L. Labarga, M. Martinez, J. del Peso, J. Puga, J. Terron, J.F. de Trocóniz, G.R. Smith, F. Corriveau, D.S. Hanna, J. Hartmann, L.W. Hung, J.N. Lim, C.G. Matthews, P.M. Patel, L.E. Sinclair, D.G. Stairs, M. St.Laurent, R. Ullmann, G. Zacek, V. Bashkirov, B.A. Dolgoshein, A. Stifutkin, G.L. Bashindzhagyan, P.F. Ermolov, L.K. Gladilin, Yu.A. Golubkov, V.D. Kobrin, I.A. Korzhavina, V.A. Kuzmin, O.Yu. Lukina, A.S. Proskuryakov, A.A. Savin, L.M. Shcheglova, A.N. Solomin, N.P. Zotov, M. Botje, F. Chlebana, A. Dake, J. Engelen, M. de Kamps, P. Kooijman, A. Kruse, H. Tiecke, W. Verkerke, M. Vreeswijk, L. Wiggers, E. de Wolf, R. van Woudenberg, D. Acosta, B. Bylsma, L.S. Durkin, J. Gilmore, K. Honscheid, C. Li, T.Y. Ling, K.W. McLean, P. Nylander, I.H. Park, T.A. Romanowski, R. Seidlein, D.S. Bailey, A. Byrne, R.J. Cashmore, A.M. Cooper-Sarkar, R.C.E. Devenish, N. Harnew, M. Lancaster, L. Lindemann, J.D. McFall, C. Nath, V.A. Noyes, A. Quadt, J.R. Tickner, H. Uijterwaal, R. Walczak, D.S. Waters, F.F. Wilson, T. Yip, G. Abbiendi, A. Bertolin, R. Brugnera, R. Carlin, F. Dal Corso, M. De Giorgi, U. Dosselli, S. Limentani, M. Morandin, M. Posocco, L. Stanco, R. Stroili, C. Voci, J. Bulmahn, J.M. Butterworth, R.G. Feild, B.Y. Oh, J.R. Okrasinski, J.J. Whitmore, G. D'Agostini, G. Marini, A. Nigro, E. Tassi, J.C. Hart, N.A. McCubbin, K. Prytz, T.P. Shah, T.L. Short, E. Barberis, T. Dubbs, C. Heusch, M. Van Hook, W. Lockman, J.T. Rahn, H.F.-W. Sadrozinski, A. Seiden, D.C. Williams, J. Biltzinger, R.J. Seifert, O. Schwarzer, A.H. Walenta, G. Zech, H. Abramowicz, G. Briskin, S. Dagan, C. Händel-Pikielny, A. Levy, J.I. Fleck, T. Hasegawa, M. Hazumi, T. Ishii, M. Kuze, S. Mine, Y. Nagasawa, M. Nakao, I. Suzuki, K. Tokushuku, S. Yamada, Y. Yamazaki, M. Chiba, R. Hamatsu, T. Hirose, K. Homma, S. Kitamura, Y. Nakamitsu, K. Yamauchi, R. Cirio, M. Costa, M.I. Ferrero, L. Lamberti, S. Maselli, C. Peroni, R. Sacchi, A. Solano, A. Staiano, M. Dardo, D.C. Bailey, D. Bandyopadhyay, F. Benard, M. Brkic, D.M. Gingrich, G.F. Hartner, K.K. Joo, G.M. Levman, J.F. Martin, R.S. Orr, S. Polenz, C.R. Sampson, R.J. Teuscher, C.D. Catterall, T.W. Jones, P.B. Kaziewicz, J.B. Lane, R.L. Saunders, J. Shulman, K. Blankenship, B. Lu, L.W. Mo, W. Bogusz, K. Charchuła, J. Ciborowski, J. Gajewski, G. Grzelak, M. Kasprzak, M. Krzyżanowski, K. Muchorowski, R.J. Nowak, J.M. Pawlak, T. Tymieniecka, A.K. Wróblewski, J.A. Zakrzewski, A.F. Żarnecki, M. Adamus, Y. Eisenberg, U. Karshon, D. Revel, D. Zer-Zion, I. Ali, W.F. Badgett, B. Behrens, S. Dasu, C. Fordham, C. Foudas, A. Goussiou, R.J. Loveless, D.D. Reeder, S. Silverstein, W.H. Smith, A. Vaiciulis, M. Wodarczyk, T. Tsurugai, S. Bhadra, M.L. Cardy, C.-P. Fagerstroem, W.R. Frisken, K.M. Furutani, M. Khakzad, W.N. Murray, W.B. Schmidke, and ZEUS at HERA (IHEF, IoP, FNWI)

Subjects
Nuclear and High Energy Physics, Particle physics, COLLISIONS, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, 01 natural sciences, High Energy Physics - Experiment, Nuclear physics, EVENTS, High Energy Physics - Experiment (hep-ex), MONTE-CARLO, DESIGN, 0103 physical sciences, Rapidity, 010306 general physics, Nuclear Experiment, Physics, Research Groups and Centres\Physics\Low Temperature Physics, ZEUS (particle detector), CONSTRUCTION, 010308 nuclear & particles physics, Faculty of Science\Physics, ZEUS, PARTON ELASTIC-SCATTERING, ZEUS BARREL CALORIMETER, HERA, diffractive scattering, photoproduction, High Energy Physics::Experiment
Abstract

Photoproduction events which have two or more jets have been studied in the $W_{\gamma p}$ range 135~GeV $< W_{\gamma p}, Comment: 19 pages, latex, 3 figures appended as uuencoded file. Author list corrected

Published
1996

6. Measurement of Alpha(s) From Jet Rates In Deep-inelastic Scattering At Hera

Author

M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R.L. Talaga, H. Zhang, R. Ayad, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, P. Bruni, G. Cara Romeo, G. Castellini, M. Chiarini, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, I. Gialas, P. Giusti, G. Iacobucci, G. Laurenti, G. Levi, A. Margotti, T. Massam, R. Nania, C. Nemoz, F. Palmonari, A. Polini, G. Sartorelli, R. Timellini, Y. Zamora Garcia, A. Zichichi, A. Bargende, A. Bornheim, J. Crittenden, K. Desch, B. Diekmann, T. Doeker, M. Eckert, L. Feld, A. Frey, M. Geerts, M. Grothe, H. Hartmann, K. Heinloth, E. Hilger, H.-P. Jakob, U.F. Katz, S. Mengel, J. Mollen, E. Paul, M. Pfeiffer, Ch. Rembser, D. Schramm, J. Stamm, R. Wedemeyer, S. Campbell-Robson, A. Cassidy, W.N. Cottingham, N. Dyce, B. Foster, S. George, M.E. Hayes, G.P. Heath, H.F. Heath, C.J.S. Morgado, J.A. O'Mara, D. Piccioni, D.G. Roff, R.J. Tapper, R. Yoshida, R.R. Rau, M. Arneodo, M. Capua, A. Garfagnini, L. Iannotti, M. Schioppa, G. Susinno, A. Bernstein, A. Caldwell, N. Cartiglia, J.A. Parsons, S. Ritz, F. Sciulli, P.B. Straub, L. Wai, S. Yang, Q. Zhu, P. Borzemski, J. Chwastowski, A. Eskreys, K. Piotrzkowski, M. Zachara, L. Zawiejski, L. Adamczyk, B. Bednarek, K. Jeleń, D. Kisielewska, T. Kowalski, E. Rulikowska-Zarȩbska, L. Suszycki, J. Zaja̧c, A. Kotański, M. Przybycień, L.A.T. Bauerdick, U. Behrens, H. Beier, J.K. Bienlein, C. Coldewey, O. Deppe, K. Desler, G. Drews, M. Flasiński, D.J. Gilkinson, C. Glasman, P. Göttlicher, J. Große-Knetter, B. Gutjahr, T. Haas, W. Hain, D. Hasell, H. Heßling, Y. Iga, K.F. Johnson, P. Joos, M. Kasemann, R. Klanner, W. Koch, L. Köpke, U. Kötz, H. Kowalski, J. Labs, A. Ladage, B. Löhr, M. Löwe, D. Lüke, J. Mainusch, O. Mańczak, T. Monteiro, J.S.T. Ng, S. Nickel, D. Notz, K. Ohrenberg, M. Roco, M. Rohde, J. Roldán, U. Schneekloth, W. Schulz, F. Selonke, E. Stiliaris, B. Surrow, T. Voß, D. Westphal, G. Wolf, C. Youngman, W. Zeuner, J.F. Zhou, H.J. Grabosch, A. Kharchilava, A. Leich, M.C.K. Mattingly, S.M. Mari, A. Meyer, S. Schlenstedt, N. Wulff, G. Barbagli, P. Pelfer, G. Anzivino, G. Maccarrone, S. De Pasquale, L. Votano, A. Bamberger, S. Eisenhardt, A. Freidhof, S. Söldner-Rembold, J. Schroeder, T. Trefzger, N.H. Brook, P.J. Bussey, A.T. Doyle, D.H. Saxon, M.L. Utley, A.S. Wilson, A. Dannemann, U. Holm, D. Horstmann, T. Neumann, R. Sinkus, K. Wick, E. Badura, B.D. Burow, L. Hagge, E. Lohrmann, J. Milewski, M. Nakahata, N. Pavel, G. Poelz, W. Schott, F. Zetsche, T.C. Bacon, N. Bruemmer, I. Butterworth, E. Gallo, V.L. Harris, B.Y.H. Hung, K.R. Long, D.B. Miller, P.P.O. Morawitz, A. Prinias, J.K. Sedgbeer, A.F. Whitfield, U. Mallik, E. McCliment, M.Z. Wang, S.M. Wang, J.T. Wu, P. Cloth, D. Filges, S.H. An, S.M. Hong, S.W. Nam, S.K. Park, M.H. Suh, S.H. Yon, R. Imlay, S. Kartik, H.-J. Kim, R.R. McNeil, W. Metcalf, V.K. Nadendla, F. Barreiro, G. Cases, J.P. Fernandez, R. Graciani, J.M. Hernández, L. Hervás, L. Labarga, M. Martinez, J. del Peso, J. Puga, J. Terron, J.F. de Trocóniz, G.R. Smith, F. Corriveau, D.S. Hanna, J. Hartmann, L.W. Hung, J.N. Lim, C.G. Matthews, P.M. Patel, L.E. Sinclair, D.G. Stairs, M. St.Laurent, R. Ullmann, G. Zacek, V. Bashkirov, B.A. Dolgoshein, A. Stifutkin, G.L. Bashindzhagyan, P.F. Ermolov, L.K. Gladilin, Yu.A. Golubkov, V.D. Kobrin, I.A. Korzhavina, V.A. Kuzmin, O.Yu. Lukina, A.S. Proskuryakov, A.A. Savin, L.M. Shcheglova, A.N. Solomin, N.P. Zotov, M. Botje, F. Chlebana, A. Dake, J. Engelen, M. de Kamps, P. Kooijman, A. Kruse, H. Tiecke, W. Verkerke, M. Vreeswijk, L. Wiggers, E. de Wolf, R. van Woudenberg, D. Acosta, B. Bylsma, L.S. Durkin, J. Gilmore, K. Honscheid, C. Li, T.Y. Ling, K.W. McLean, W.N. Murray, P. Nylander, I.H. Park, T.A. Romanowski, R. Seidlein, D.S. Bailey, A. Byrne, R.J. Cashmore, A.M. Cooper-Sarkar, R.C.E. Devenish, N. Harnew, M. Lancaster, L. Lindemann, J.D. McFall, C. Nath, V.A. Noyes, A. Quadt, J.R. Tickner, H. Uijterwaal, R. Walczak, D.S. Waters, F.F. Wilson, T. Yip, G. Abbiendi, A. Bertolin, R. Brugnera, R. Carlin, F. Dal Corso, M. De Giorgi, U. Dosselli, S. Limentani, M. Morandin, M. Posocco, L. Stanco, R. Stroili, C. Voci, J. Bulmahn, J.M. Butterworth, R.G. Feild, B.Y. Oh, J.R. Okrasinski, J.J. Whitmore, G. D'Agostini, G. Marini, A. Nigro, E. Tassi, J.C. Hart, N.A. McCubbin, K. Prytz, T.P. Shah, T.L. Short, E. Barberis, T. Dubbs, C. Heusch, M. Van Hook, W. Lockman, J.T. Rahn, H.F.-W. Sadrozinski, A. Seiden, D.C. Williams, J. Biltzinger, R.J. Seifert, O. Schwarzer, A.H. Walenta, G. Zech, H. Abramowicz, G. Briskin, S. Dagan, C. Händel-Pikielny, A. Levy, J.I. Fleck, T. Hasegawa, M. Hazumi, T. Ishii, M. Kuze, S. Mine, Y. Nagasawa, M. Nakao, I. Suzuki, K. Tokushuku, S. Yamada, Y. Yamazaki, M. Chiba, R. Hamatsu, T. Hirose, K. Homma, S. Kitamura, Y. Nakamitsu, K. Yamauchi, R. Cirio, M. Costa, M.I. Ferrero, L. Lamberti, S. Maselli, C. Peroni, R. Sacchi, A. Solano, A. Staiano, M. Dardo, D.C. Bailey, D. Bandyopadhyay, F. Benard, M. Brkic, D.M. Gingrich, G.F. Hartner, K.K. Joo, G.M. Levman, J.F. Martin, R.S. Orr, S. Polenz, C.R. Sampson, R.J. Teuscher, C.D. Catterall, T.W. Jones, P.B. Kaziewicz, J.B. Lane, R.L. Saunders, J. Shulman, K. Blankenship, B. Lu, L.W. Mo, W. Bogusz, K. Charchuła, J. Ciborowski, J. Gajewski, G. Grzelak, M. Kasprzak, M. Krzyżanowski, K. Muchorowski, R.J. Nowak, J.M. Pawlak, T. Tymieniecka, A.K. Wróblewski, J.A. Zakrzewski, A.F. Żarnecki, M. Adamus, Y. Eisenberg, U. Karshon, D. Revel, D. Zer-Zion, I. Ali, W.F. Badgett, B. Behrens, S. Dasu, C. Fordham, C. Foudas, A. Goussiou, R.J. Loveless, D.D. Reeder, S. Silverstein, W.H. Smith, A. Vaiciulis, M. Wodarczyk, T. Tsurugai, S. Bhadra, M.L. Cardy, C.-P. Fagerstroem, W.R. Frisken, K.M. Furutani, M. Khakzad, and W.B. Schmidke

Subjects
Nuclear and High Energy Physics, Particle physics, jet production, ENERGIES, Astrophysics::High Energy Astrophysical Phenomena, Parton, PROTON SCATTERING, 01 natural sciences, perturbative QCD, High Energy Physics - Experiment, CROSS-SECTIONS, Nuclear physics, EVENT GENERATOR, MONTE-CARLO, QCD JETS, ZEUS, CALORIMETER, FRAGMENTATION, DEPENDENCE, 0103 physical sciences, determination of alpha_s, 010306 general physics, Quantum chromodynamics, Physics, 010308 nuclear & particles physics, High Energy Physics::Phenomenology, Perturbative QCD, HERA, Deep inelastic scattering, High Energy Physics::Experiment
Abstract

Jet production in deep inelastic scattering for $120, Comment: 22 pages, latex, 4 figures appended as uuencoded file

Published
1995

7. Measurement of the Cross-section For the Reaction Gamma-p-]j/psi-p With the Zeus Detector At Hera

Author

M Derrick, D Krakauer, S Magill, D Mikunas, B Musgrave, J Repond, R Stanek, R.L Talaga, H Zhang, R Ayad, G Bari, M Basile, L Bellagamba, D Boscherini, A Bruni, G Bruni, P Bruni, G Cara Romeo, G Castellini, M Chiarini, L Cifarelli, F Cindolo, A Contin, M Corradi, I Gialas, P Giusti, G Iacobucci, G Laurenti, G Levi, A Margotti, T Massam, R Nania, C Nemoz, F Palmonari, A Polini, G Sartorelli, R Timellini, Y Zamora Garcia, A Zichichi, A Bargende, J Crittenden, K Desch, B Diekmann, T Doeker, M Eckert, L Feld, A Frey, M Geerts, G Geitz, M Grothe, T Haas, H Hartmann, D Haun, K Heinloth, E Hilger, H.-P Jakob, U.F Katz, S.M Mari, A Mass, S Mengel, J Mollen, E Paul, Ch Rembser, R Schattevoy, D Schramm, J Stamm, R Wedemeyer, S Campbell-Robson, A Cassidy, N Dyce, B Foster, S George, R Gilmore, G.P Heath, H.F Heath, T.J Llewellyn, C.J.S Morgado, D.J.P Norman, J.A O'Mara, R.J Tapper, S.S Wilson, R Yoshida, R.R Rau, M Arneodo, L Iannotti, M Schioppa, G Susinno, A Bernstein, A Caldwell, N Cartiglia, J.A Parsons, S Ritz, F Sciulli, P.B Straub, L Wai, S Yang, Q Zhu, P Borzemski, J Chwastowski, A Eskreys, K Piotrzkowski, M Zachara, L Zawiejski, L Adamczyk, B Bednarek, K Jeleń, D Kisielewska, T Kowalski, E Rulikowska-Zarȩbska, L Suszycki, J Zaja̧c, A Kotański, M Przybycień, L.A.T Bauerdick, U Behrens, H Beier, J.K Bienlein, C Coldewey, O Deppe, K Desler, G Drews, M Flasiński, D.J Gilkinson, C Glasman, P Göttlicher, J Große-Knetter, B Gutjahr, W Hain, D Hasell, H Heßling, Y Iga, P Joos, M Kasemann, R Klanner, W Koch, L Köpke, U Kötz, H Kowalski, J Labs, A Ladage, B Löhr, M Löwe, D Lüke, O Mańczak, T Monteiro, J.S.T Ng, S Nickel, D Notz, K Ohrenberg, M Roco, M Rohde, J Roldán, U Schneekloth, W Schulz, F Selonke, E Stiliaris, B Surrow, T Voß, D Westphal, G Wolf, C Youngman, J.F Zhou, H.J Grabosch, A Kharchilava, A Leich, M.C.K Mattingly, A Meyer, S Schlenstedt, N Wulff, G Barbagli, P Pelfer, G Anzivino, G Maccarrone, S De Pasquale, L Votano, A Bamberger, S Eisenhardt, A Freidhof, S Söldner-Rembold, J Schroeder, T Trefzger, N.H Brook, P.J Bussey, A.T Doyle, J.I Fleck, D.H Saxon, M.L Utley, A.S Wilson, A Dannemann, U Holm, D Horstmann, T Neumann, R Sinkus, K Wick, E Badura, B.D Burow, L Hagge, E Lohrmann, J Mainusch, J Milewski, M Nakahata, N Pavel, G Poelz, W Schott, F Zetsche, T.C Bacon, I Butterworth, E Gallo, V.L Harris, B.Y.H Hung, K.R Long, D.B Miller, P.P.O Morawitz, A Prinias, J.K Sedgbeer, A.F Whitfield, U Mallik, E McCliment, M.Z Wang, S.M Wang, J.T Wu, Y Zhang, P Cloth, D Filges, S.H An, S.M Hong, S.W Nam, S.K Park, M.H Suh, S.H Yon, R Imlay, S Kartik, H.-J Kim, R.R McNeil, W Metcalf, V.K Nadendla, F Barreiro, G Cases, R Graciani, J.M Hernández, L Hervás, L Labarga, J del Peso, J Puga, J Terron, J.F de Trocóniz, G.R Smith, F Corriveau, D.S Hanna, J Hartmann, L.W Hung, J.N Lim, C.G Matthews, P.M Patel, L.E Sinclair, D.G Stairs, M St.Laurent, R Ullmann, G Zacek, V Bashkirov, B.A Dolgoshein, A Stifutkin, G.L Bashindzhagyan, P.F Ermolov, L.K Gladilin, Y.A Golubkov, V.D Kobrin, V.A Kuzmin, A.S Proskuryakov, A.A Savin, L.M Shcheglova, A.N Solomin, N.P Zotov, M Botje, F Chlebana, A Dake, J Engelen, M de Kamps, P Kooijman, A Kruse, H Tiecke, W Verkerke, M Vreeswijk, L Wiggers, E de Wolf, R van Woudenberg, D Acosta, B Bylsma, L.S Durkin, K Honscheid, C Li, T.Y Ling, K.W McLean, W.N Murray, I.H Park, T.A Romanowski, R Seidlein, D.S Bailey, G.A Blair, A Byrne, R.J Cashmore, A.M Cooper-Sarkar, D Daniels, R.C.E Devenish, N Harnew, M Lancaster, P.E Luffman, L Lindemann, J.D McFall, C Nath, V.A Noyes, A Quadt, H Uijterwaal, R Walczak, F.F Wilson, T Yip, G Abbiendi, A Bertolin, R Brugnera, R Carlin, F Dal Corso, M De Giorgi, U Dosselli, S Limentani, M Morandin, M Posocco, L Stanco, R Stroili, C Voci, J Bulmahn, J.M Butterworth, R.G Feild, B.Y Oh, J.J Whitmore, G D'Agostini, G Marini, A Nigro, E Tassi, J.C Hart, N.A McCubbin, K Prytz, T.P Shah, T.L Short, E Barberis, T Dubbs, C Heusch, M Van Hook, B Hubbard, W Lockman, J.T Rahn, H.F.-W Sadrozinski, A Seiden, J Biltzinger, R.J Seifert, A.H Walenta, G Zech, H Abramowicz, G Briskin, S Dagan, A Levy, T Hasegawa, M Hazumi, T Ishii, M Kuze, S Mine, Y Nagasawa, M Nakao, I Suzuki, K Tokushuku, S Yamada, Y Yamazaki, M Chiba, R Hamatsu, T Hirose, K Homma, S Kitamura, Y Nakamitsu, K Yamauchi, R Cirio, M Costa, M.I Ferrero, L Lamberti, S Maselli, C Peroni, R Sacchi, A Solano, A Staiano, M Dardo, D.C Bailey, D Bandyopadhyay, F Benard, M Brkic, M.B Crombie, D.M Gingrich, G.F Hartner, K.K Joo, G.M Levman, J.F Martin, R.S Orr, C.R Sampson, R.J Teuscher, C.D Catterall, T.W Jones, P.B Kaziewicz, J.B Lane, R.L Saunders, J Shulman, K Blankenship, B Lu, L.W Mo, W Bogusz, K Charchuła, J Ciborowski, J Gajewski, G Grzelak, M Kasprzak, M Krzyżanowski, K Muchorowski, R.J Nowak, J.M Pawlak, T Tymieniecka, A.K Wróblewski, J.A Zakrzewski, A.F Żarnecki, M Adamus, Y Eisenberg, U Karshon, D Revel, D Zer-Zion, I Ali, W.F Badgett, B Behrens, S Dasu, C Fordham, C Foudas, A Goussiou, R.J Loveless, D.D Reeder, S Silverstein, W.H Smith, A Vaiciulis, M Wodarczyk, T Tsurugai, S Bhadra, M.L Cardy, C.-P Fagerstroem, W.R Frisken, K.M Furutani, M Khakzad, and W.B Schmidke

Subjects
Nuclear and High Energy Physics, Particle physics, Proton, LUND MONTE-CARLO, ZEUS, ELASTIC-SCATTERING, BARREL CALORIMETER, PHOTOPRODUCTION, J/PSI, DESIGN, 01 natural sciences, 7. Clean energy, High Energy Physics - Experiment, Nuclear physics, Cross section (physics), 0103 physical sciences, photoproduction, J/ψ cross section measurement, 010306 general physics, Nuclear Experiment, Quantum chromodynamics, Physics, Elastic scattering, ZEUS (particle detector), Luminosity (scattering theory), 010308 nuclear & particles physics, HERA, Gluon, High Energy Physics::Experiment
Abstract

This paper reports the cross section measurements for the process ep $\rightarrow$ e~\jpsi~p for $Q^2 < 4$ GeV$^2$ at $\sqrt s = 296$ GeV, based on an integrated luminosity of about 0.5~pb$^{-1}$, using the ZEUS detector. The \jpsi~was detected in its $\rm e^{+}e^{-}$ and $\rm \mu^{+}\mu^{-}$ decay modes. The photoproduction cross section was measured to be $52^{ \ +7}_{-12}\pm 10$~nb at an average $\gamma$p centre of mass energy of 67 GeV and $71^{+13}_{-20}\pm 12$~nb at 114 GeV. The significant rise of the cross section compared to lower energy measurements is not in agreement with VDM models, but can be described by QCD inspired models if a rise in the gluon momentum density at low $x$ in the proton is assumed., Comment: 21 pages, latex, 4 figures appended as uuencoded file

Published
1995

8. Measurement of the reaction γ*p→φp in deep inelastic e+p scattering at HERA

Author

M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J.R. Okrasinski, J. Repond, R. Stanek, R.L. Talaga, H. Zhang, M.C.K. Mattingly, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, P. 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, A. Polini, G. Sartorelli, Y.Zamora Garcia, A. Zichichi, C. Amelung, A. Bornheim, J. Crittenden, R. Deffner, T. Doeker, M. Eckert, L. Feld, A. Frey, M. Geerts, M. Grothe, H. Hartmann, K. Heinloth, L. Heinz, E. Hilger, H.-P. Jakob, U.F. Katz, S. Mengel, E. Paul, M. Pfeiffer, Ch. Rembser, D. Schramm, J. Stamm, R. Wedemeyer, S. Campbell-Robson, A. Cassidy, W.N. Cottingham, N. Dyce, B. Foster, S. George, M.E. Hayes, G.P. Heath, H.F. Heath, D. Piccioni, D.G. Roff, R.J. Tapper, R. Yoshida, M. Arneodo, R. Ayad, M. Capua, A. Garfagnini, L. Iannotti, M. Schioppa, G. Susinno, A. Caldwell, N. Cartiglia, Z. Jing, W. Liu, J.A. Parsons, S. Ritz, F. Sciulli, P.B. Straub, L. Wai, S. Yang, Q. Zhu, P. Borzemski, J. Chwastowski, A. Eskreys, Z. Jakubowski, M.B. Przybycień, M. Zachara, L. Zawiejski, L. Adamczyk, B. Bednarek, K. Jeleń, D. Kisielewska, T. Kowalski, M. Przybycień, E. Rulikowska-Zarȩbska, L. Suszycki, J. Zaja̧c, Z. Duliński, A. Kotański, G. Abbiendi, L.A.T. Bauerdick, U. Behrens, H. Beier, J.K. Bienlein, G. Cases, O. Deppe, K. Desler, G. Drews, M. Flasiński, D.J. Gilkinson, C. Glasman, P. Göttlicher, J. Große-Knetter, T. Haas, W. Hain, D. Hasell, H. Heßling, Y. Iga, K.F. Johnson, P. Joos, M. Kasemann, R. Klanner, W. Koch, U. Kötz, H. Kowalski, J. Labs, A. Ladage, B. Löhr, M. Löwe, D. Lüke, J. Mainusch, O. Mańczak, J. Milewski, T. Monteiro, J.S.T. Ng, D. Notz, K. Ohrenberg, K. Piotrzkowski, M. Roco, M. Rohde, J. Roldán, U. Schneekloth, W. Schulz, F. Selonke, B. Surrow, T. Voß, D. Westphal, G. Wolf, U. Wollmer, C. Youngman, W. Zeuner, H.J. Grabosch, A. Kharchilava, S.M. Mari, A. Meyer, S. Schlenstedt, N. Wulff, G. Barbagli, E. Gallo, P. Pelfer, G. Maccarrone, S. De Pasquale, L. Votano, A. Bamberger, S. Eisenhardt, T. Trefzger, S. Wölfle, J.T. Bromley, N.H. Brook, P.J. Bussey, A.T. Doyle, D.H. Saxon, L.E. Sinclair, M.L. Utley, A.S. Wilson, A. Dannemann, U. Holm, D. Horstmann, R. Sinkus, K. Wick, B.D. Burow, L. Hagge, E. Lohrmann, N. Pavel, G. Poelz, W. Schott, F. Zetsche, T.C. Bacon, N. Brümmer, I. Butterworth, V.L. Harris, G. Howell, B.H.Y. Hung, L. Lamberti, K.R. Long, D.B. Miller, A. Prinias, J.K. Sedgbeer, D. Sideris, A.F. Whitfield, U. Mallik, M.Z. Wang, S.M. Wang, J.T. Wu, P. Cloth, D. Filges, S.H. An, G.H. Cho, B.J. Ko, S.B. Lee, S.W. Nam, H.S. Park, S.K. Park, S. Kartik, H.-J. Kim, R.R. McNeil, W. Metcalf, V.K. Nadendla, F. Barreiro, J.P. Fernandez, R. Graciani, J.M. Hernández, L. Hervás, L. Labarga, M. Martinez, J. del Peso, J. Puga, J. Terron, J.F. de Trocóniz, F. Corriveau, D.S. Hanna, J. Hartmann, L.W. Hung, J.N. Lim, C.G. Matthews, P.M. Patel, M. Riveline, D.G. Stairs, M. St-Laurent, R. Ullmann, G. Zacek, T. Tsurugai, V. Bashkirov, B.A. Dolgoshein, A. Stifutkin, G.L. Bashindzhagyan, P.F. Ermolov, L.K. Gladilin, Yu.A. Golubkov, V.D. Kobrin, I.A. Korzhavina, V.A. Kuzmin, O.Yu. Lukina, A.S. Proskuryakov, A.A. Savin, L.M. Shcheglova, A.N. Solomin, N.P. Zotov, M. Botje, F. Chlebana, J. Engelen, M. de Kamps, P. Kooijman, A. Kruse, A. van Sighem, H. Tiecke, W. Verkerke, J. Vossebeld, M. Vreeswijk, L. Wiggers, E. de Wolf, R. van Woudenberg, D. Acosta, B. Bylsma, L.S. Durkin, J. Gilmore, C. Li, T.Y. Ling, P. Nylander, I.H. Park, T.A. Romanowski, D.S. Bailey, R.J. Cashmore, A.M. Cooper-Sarkar, R.C.E. Devenish, N. Harnew, M. Lancaster, L. Lindemann, J.D. McFall, C. Nath, V.A. Noyes, A. Quadt, J.R. Tickner, H. Uijterwaal, R. Walczak, D.S. Waters, F.F. Wilson, T. Yip, A. Bertolin, R. Brugnera, R. Carlin, F. Dal Corso, M. De Giorgi, U. Dosselli, S. Limentani, M. Morandin, M. Posocco, L. Stanco, R. Stroili, C. Voci, F. Zuin, J. Bulmahn, R.G. Feild, B.Y. Oh, J.J. Whitmore, G. D'Agostini, G. Marini, A. Nigro, E. Tassi, J.C. Hart, N.A. McCubbin, T.P. Shah, E. Barberis, T. Dubbs, C. Heusch, M. Van Hook, W. Lockman, J.T. Rahn, H.F.-W. Sadrozinski, A. Seiden, D.C. Williams, J. Biltzinger, R.J. Seifert, O. Schwarzer, A.H. Walenta, G. Zech, H. Abramowicz, G. Briskin, S. Dagan, A. Levy, J.I. Fleck, M. Inuzuka, T. Ishii, M. Kuze, S. Mine, M. Nakao, I. Suzuki, K. Tokushuku, K. Umemori, S. Yamada, Y. Yamazaki, M. Chiba, R. Hamatsu, T. Hirose, K. Homma, S. Kitamura, T. Matsushita, K. Yamauchi, R. Cirio, M. Costa, M.I. Ferrero, S. Maselli, C. Peroni, R. Sacchi, A. Solano, A. Staiano, M. Dardo, D.C. Bailey, F. Benard, M. Brkic, C.-P. Fagerstroem, G.F. Hartner, K.K. Joo, G.M. Levman, J.F. Martin, R.S. Orr, S. Polenz, C.R. Sampson, D. Simmons, R.J. Teuscher, J.M. Butterworth, C.D. Catterall, T.W. Jones, P.B. Kaziewicz, J.B. Lane, R.L. Saunders, J. Shulman, M.R. Sutton, B. Lu, L.W. Mo, W. Bogusz, J. Ciborowski, J. Gajewski, G. Grzelak, M. Kasprzak, M. Krzyżanowski, K. Muchorowski, R.J. Nowak, J.M. Pawlak, T. Tymieniecka, A.K. Wróblewski, J.A. Zakrzewski, A.F. Żarnecki, M. Adamus, C. Coldewey, Y. Eisenberg, D. Hochman, U. Karshon, D. Revel, D. Zer-Zion, W.F. Badgett, J. Breitweg, D. Chapin, R. Cross, S. Dasu, C. Foudas, R.J. Loveless, S. Mattingly, D.D. Reeder, S. Silverstein, W.H. Smith, A. Vaiciulis, M. Wodarczyk, S. Bhadra, M.L. Cardy, W.R. Frisken, M. Khakzad, W.N. Murray, and W.B. Schmidke

Subjects
Quark, Physics, Nuclear and High Energy Physics, Particle physics, Meson, Proton, 010308 nuclear & particles physics, Perturbative QCD, HERA, 7. Clean energy, 01 natural sciences, Zeus (malware), Gluon, Nuclear physics, Pomeron, 0103 physical sciences, High Energy Physics::Experiment, Nuclear Experiment, 010306 general physics
Abstract

The production of φ mesons in the reaction e+p → e+φp (φ → K+K−), for 7 Q 2 GeV 2 and virtual photon-proton centre of mass energies (W) in the range 42–134 GeV, has been studied with the ZEUS detector at HERA. When compared to lower energy data at similar Q 2, the results show that the γ ∗ p → φp cross section rises strongly with W. This behaviour is similar to that previously found for the γ ∗ p → ϱ 0 p cross section. This strong dependence cannot be explained by production through soft pomeron exchange. It is, however, consistent with perturbative QCD expectations, where it reflects the rise of the gluon momentum density in the proton at small x. The ratio of σ(φ) σ(ϱ 0 ) , which has previously been determined by ZEUS to be 0.065 ± 0.013 (stat.) in photoproduction at a mean W of 70 GeV, is measured to be 0.18 ± 0.05 (stat.) ± 0.03 (syst.) at a mean Q 2 of 12.3 GeV2 and mean W of ≈ 100 GeV and is thus approaching at large Q 2 the value of 2 9 predicted from the quark charges of the vector mesons and a flavour independent production mechanism.

9. Observation of scaling violations in scaled momentum distributions at HERA

Author

J Breitweg, M Derrick, D Krakauer, S Magill, D Mikunas, B Musgrave, J Repond, R Stanek, R.L Talaga, R Yoshida, H Zhang, M.C.K Mattingly, 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, F Ricci, G Sartorelli, Y Zamora Garcia, A Zichichi, 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, 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, M Arneodo, R Ayad, M Capua, A Garfagnini, L Iannotti, M Schioppa, G Susinno, J.Y Kim, J.H Lee, I.T Lim, M.Y Pac, A Caldwell, N Cartiglia, Z Jing, W Liu, B Mellado, J.A Parsons, S Ritz, S Sampson, F Sciulli, P.B Straub, Q Zhu, P Borzemski, J Chwastowski, A Eskereys, J Figiel, K Klimek, M.B Przybycień, L Zawiejski, L Adamczyk, B Bednarek, M Bukowy, K Jeleń, D Kisielewska, T Kowalski, M Przybycień, E Rulikowska-Zarȩbska, L Suszycki, J Zaja̧c, Z Duliński, A Kotański, 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, F Selonke, B Surrow, E Tassi, T Voß, D Westphal, G Wolf, U Wollmer, C Youngman, A.F Żarnecki, W Zeuner, B.D Burow, H.J Grabosch, A Meyer, S Schlenstedt, G Barbagli, E Gallo, P Pelfer, G Maccarrone, L Votano, A Bamberger, S Eisenhardt, P Markun, T Trefzger, S Wölfle, J.T Bromley, N.H Brook, P.J Bussey, A.T Doyle, N Macdonald, D.H Saxon, L.E Sinclair, E Strickland, R Waugh, I Bohnet, N Gendner, U Holm, A Meyer-Larsen, H Salehi, K Wick, L.K Gladilin, D Horstmann, D Kçira, R Klanner, E Lohrmann, G Poelz, W Schott, F Zetsche, 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, U Mallik, S.M Wang, J.T Wu, P Cloth, D Filges, J.I Fleck, T Ishii, M Kuze, I Suzuki, K Tokushuku, S Yamada, K Yamauchi, Y Yamazaki, S.J Hong, S.B Lee, S.W Nam, S.K Park, F Barreiro, J.P Fernándeza, G García, R Graciani, J.M Hernández, L Hervás, L Labarga, M Martínez, J del Peso, J Puga, J Terrón, J.F de Trocóniz, F Corriveau, D.S Hanna, J Hartmann, L.W Hung, W.N Murray, A Ochs, M Riveline, D.G Stairs, M St-Laurent, R Ullmann, T Tsurugai, V Bashkirov, B.A Dolgoshein, A Stifutkin, G.L Bashindzhagyan, P.F Ermolov, Yu.A Golubkov, L.A Khein, N.A Korotkova, I.A Korzhavina, V.A Kuzmin, O.Yu Lukina, A.S Proskuryakov, L.M Shcheglova, A.N Solomin, S.A Zotkin, C Bokel, M Botje, N Brümmer, F Chlebana, J Engelen, E Koffeman, P Kooijman, A van Sighem, H Tiecke, N Tuning, W Verkerke, J Vossebeld, M Vreeswijk, L Wiggers, E de Wolf, D Acosta, B Bylsma, L.S Durkin, J Gilmore, C.M Ginsburg, C.L Kim, T.Y Ling, P Nylander, T.A Romanowski, H.E Blaikley, R.J Cashmore, A.M Cooper-Sarkar, R.C.E Devenish, J.K Edmonds, J Große-Knetter, N Harnew, M Lancaster, C Nath, V.A Noyes, A Quadt, O Ruske, J.R Tickner, H Uijterwaal, R Walczak, D.S Waters, A Bertolin, R Brugnera, R Carlin, F Dal Corso, U Dosselli, S Limentani, M Morandin, M Posocco, L Stanco, R Stroili, C Voci, J Bulmahn, B.Y Oh, J.R Okrasiński, W.S Toothacker, J.J Whitmore, Y Iga, G D'Agostini, G Marini, A Nigro, M Raso, J.C Hart, N.A McCubbin, T.P Shah, D Epperson, C Heusch, J.T Rahn, H.F.-W Sadrozinski, A Seiden, R Wichmann, D.C Williams, O Schwarzer, A.H Walenta, H Abramowicz, G Briskin, S Dagan, S Kananov, A Levy, T Abe, T Fusayasu, M Inuzuka, K Nagano, K Umemori, T Yamashita, R Hamatsu, T Hirose, K Homma, S Kitamura, T Matsushita, R Cirio, M Costa, M.I Ferrero, S Maselli, V Monaco, C Peroni, M.C Petrucci, M Ruspa, R Sacchi, A Solano, A Staiano, M Dardo, D.C Bailey, C.-P Fagerstroem, R Galea, G.F Hartner, K.K Joo, G.M Levman, J.F Martin, R.S Orr, S Polenz, A Sabetfakhri, D Simmons, R.J Teuscher, J.M Butterworth, C.D Catterall, T.W Jones, J.B Lane, R.L Saunders, J Shulman, M.R Sutton, M Wing, J Ciborowski, G Grzelak, M Kasprzak, K Muchorowski, R.J Nowak, J.M Pawlak, R Pawlak, T Tymieniecka, A.K Wróblewski, J.A Zakrzewski, M Adamus, C Coldewey, Y Eisenberg, D Hochman, U Karshon, W.F Badgett, D Chapin, R Cross, S Dasu, C Foudas, R.J Loveless, S Mattingly, D.D Reeder, W.H Smith, A Vaiciulis, M Wodarczyk, S Bhadra, W.R Frisken, M Khakzad, W.B Schmidke, and Zeus (IHEF, IoP, FNWI)

Subjects
ZEUS, CENTRAL TRACKING DETECTOR, ZEUS BARREL CALORIMETER, FRAGMENTATION FUNCTIONS, E+E-ANNIHILATION, MASS-ENERGY, QCD, PROTON, CONSTRUCTION, DESIGN, SCATTERING, Nuclear and High Energy Physics, Particle physics, FOS: Physical sciences, Large range, 01 natural sciences, High Energy Physics - Experiment, Nuclear physics, High Energy Physics - Experiment (hep-ex), 0103 physical sciences, 010306 general physics, Scaling, Quantum chromodynamics, Physics, 010308 nuclear & particles physics, Scattering, Detector, HERA, Deep inelastic scattering, Charged particle, High Energy Physics::Experiment
Abstract

Charged particle production has been measured in deep inelastic scattering (DIS) events over a large range of $x$ and $Q^2$ using the ZEUS detector. The evolution of the scaled momentum, $x_p$, with $Q^2,$ in the range 10 to 1280 $GeV^2$, 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 $Q^2$., Comment: 21 pages including 4 figures, to be published in Physics Letters B. Two references added

10. Dijet angular distributions in direct and resolved photoproduction at HERA

Author

M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J.R. Okrasinski, J. Repond, R. Stanek, R.L. Talaga, H. Zhang, M.C.K. Mattingly, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, P. 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, A. Polini, G. Sartorelli, Y. Zamora Garcia, A. Zichichi, C. Amelung, A. Bornheim, J. Crittenden, R. Deffner, T. Doeker, M. Eckert, L. Feld, A. Frey, M. Geerts, M. Grothe, H. Hartmann, K. Heinloth, L. Heinz, E. Hilger, H.-P. Jakob, U.F. Katz, S. Mengel, E. Paul, M. Pfeiffer, Ch. Rembser, D. Schramm, J. Stamm, R. Wedemeyer, S. Campbell-Robson, A. Cassidy, W.N. Cottingham, N. Dyce, B. Foster, S. George, M.E. Hayes, G.P. Heath, H.F. Heath, D. Piccioni, D.G. Roff, R.J. Tapper, R. Yoshida, M. Arneodo, R. Ayad, M. Capua, A. Garfagnini, L. Iannotti, M. Schioppa, G. Susinno, A. Caldwell, N. Cartiglia, Z. Jing, W. Liu, J.A. Parsons, S. Ritz, F. Sciulli, P.B. Straub, L. Wai, S. Yang, Q. Zhu, P. Borzemski, J. Chwastowski, A. Eskreys, Z. Jakubowski, M.B. Przybycień, M. Zachara, L. Zawiejski, L. Adamczyk, B. Bednarek, K. Jeleń, D. Kisielewska, T. Kowalski, M. Przybycień, E. Rulikowska-Zarȩbska, L. Suszycki, J. Zaja̧c, Z. Duliński, A. Kotański, G. Abbiendi, L.A.T. Bauerdick, U. Behrens, H. Beier, J.K. Bienlein, G. Cases, O. Deppe, K. Desler, G. Drews, M. Flasiński, D.J. Gilkinson, C. Glasman, P. Göttlicher, J. Große-Knetter, T. Haas, W. Hain, D. Hasell, H. Heßling, Y. Iga, K.F. Johnson, P. Joos, M. Kasemann, R. Klanner, W. Koch, U. Kötz, H. Kowalski, J. Labs, A. Ladage, B. Löhr, M. Löwe, D. Lüke, J. Mainusch, O. Mańczak, J. Milewski, T. Monteiro, J.S.T. Ng, D. Notz, K. Ohrenberg, K. Piotrzkowski, M. Roco, M. Rohde, J. Roldán, U. Schneekloth, W. Schulz, F. Selonke, B. Surrow, T. Voß, D. Westphal, G. Wolf, U. Wollmer, C. Youngman, W. Zeuner, H.J. Grabosch, A. Kharchilava, S.M. Mari, A. Meyer, S. Schlenstedt, N. Wulff, G. Barbagli, E. Gallo, P. Pelfer, G. Maccarrone, S. De Pasquale, L. Votano, A. Bamberger, S. Eisenhardt, T. Trefzger, S. Wölfle, J.T. Bromley, N.H. Brook, P.J. Bussey, A.T. Doyle, D.H. Saxon, L.E. Sinclair, M.L. Utley, A.S. Wilson, A. Dannemann, U. Holm, D. Horstmann, R. Sinkus, K. Wick, B.D. Burow, L. Hagge, E. Lohrmann, G. Poelz, W. Schott, F. Zetsche, T.C. Bacon, N. Brümmer, I. Butterworth, V.L. Harris, G. Howell, B.H.Y. Hung, L. Lamberti, K.R. Long, D.B. Miller, N. Pavel, A. Prinias, J.K. Sedgbeer, D. Sideris, A.F. Whitfield, U. Mallik, M.Z. Wang, S.M. Wang, J.T. Wu, P. Cloth, D. Filges, S.H. An, G.H. Cho, B.J. Ko, S.B. Lee, S.W. Nam, H.S. Park, S.K. Park, S. Kartik, H.-J. Kim, R.R. McNeil, W. Metcalf, V.K. Nadendla, F. Barreiro, J.P. Fernandez, R. Graciani, J.M. Hernández, L. Hervás, L. Labarga, M. Martinez, J. del Peso, J. Puga, J. Terron, J.F. de Trocóniz, F. Corriveau, D.S. Hanna, J. Hartmann, L.W. Hung, J.N. Lim, C.G. Matthews, P.M. Patel, M. Riveline, D.G. Stairs, M. St-Laurent, R. Ullmann, G. Zacek, T. Tsurugai, V. Bashkirov, B.A. Dolgoshein, A. Stifutkin, G.L. Bashindzhagyan, P.F. Ermolov, L.K. Gladilin, Yu.A. Golubkov, V.D. Kobrin, I.A. Korzhavina, V.A. Kuzmin, O.Yu. Lukina, A.S. Proskuryakov, A.A. Savin, L.M. Shcheglova, A.N. Solomin, N.P. Zotov, M. Botje, F. Chlebana, J. Engelen, M. de Kamps, P. Kooijman, A. Kruse, A. van Sighem, H. Tiecke, W. Verkerke, J. Vossebeld, M. Vreeswijk, L. Wiggers, E. de Wolf, R. van Woudenberg, D. Acosta, B. Bylsma, L.S. Durkin, J. Gilmore, C. Li, T.Y. Ling, P. Nylander, I.H. Park, T.A. Romanowski, D.S. Bailey, R.J. Cashmore, A.M. Cooper-Sarkar, R.C.E. Devenish, N. Harnew, M. Lancaster, L. Lindemann, J.D. McFall, C. Nath, V.A. Noyes, A. Quadt, J.R. Tickner, H. Uijterwaal, R. Walczak, D.S. Waters, F.F. Wilson, T. Yip, A. Bertolin, R. Brugnera, R. Carlin, F. Dal Corso, M. De Giorgi, U. Dosselli, S. Limentani, M. Morandin, M. Posocco, L. Stanco, R. Stroili, C. Voci, F. Zuin, J. Bulmahn, R.G. Feild, B.Y. Oh, J.J. Whitmore, G. D'Agostini, G. Marini, A. Nigro, E. Tassi, J.C. Hart, N.A. McCubbin, T.P. Shah, E. Barberis, T. Dubbs, C. Heusch, M. Van Hook, W. Lockman, J.T. Rahn, H.F.-W. Sadrozinski, A. Seiden, D.C. Williams, J. Biltzinger, R.J. Seifert, O. Schwarzer, A.H. Walenta, G. Zech, H. Abramowicz, G. Briskin, S. Dagan, A. Levy, J.I. Fleck, M. Inuzuka, T. ishii, M. Kuze, S. Mine, M. Nakao, I. Suzuki, K. Tokushuku, K. Umemori, S. Yamada, Y. Yamazaki, M. Chiba, R. Hamatsu, T. Hirose, K. Homma, S. Kitamura, T. Matsushita, K. Yamauchi, R. Cirio, M. Costa, M.I. Ferrero, S. Maselli, C. Peroni, R. Sacchi, A. Solano, A. Staino, M. Dardo, D.C. Bailey, F. Benard, M. Brkic, C.-P. Fagerstroem, G.F. Hartner, K.K. Joo, G.M. Levman, J.F. Martin, R.S. Orr, S. Polenz, C.R. Sampson, D. Simmons, R.J. Teuscher, J.M. Butterworth, C.D. Catterall, T.W. Jones, P.B. Kaziewicz, J.B. Lane, R.L. Saunders, J. Shulman, M.R. Sutton, B. Lu, L.W. Mo, W. Bogusz, J. Ciborowski, J. Gajewski, G. Grzelak, M. Kasprzak, M. Krzyżanowski, K. Muchorowski, R.J. Nowak, J.M. Pawlak, T. Tymieniecka, A.K. Wróblewski, J.A. Zakrzewski, A.F. Żarnecki, M. Adamus, C. Coldewey, Y. Eisenberg, D. Hochman, U. Karshon, D. Revel, D. Zer-Zion, W.F. Badgett, J. Breitweg, D. Chapin, R. Cross, S. Dasu, C. Foudas, R.J. Loveless, S. Mattingly, D.D. Reeder, S. Silverstein, W.H. Smith, A. Vaiciulis, M. Wodarczyk, S. Bhadra, M.L. Cardy, W.R. Frisken, M. Khakzad, W.N. Murray, W.B. Schmidke, and ZEUS at HERA (IHEF, IoP, FNWI)

Subjects
Nuclear and High Energy Physics, Particle physics, COLLISIONS, Astrophysics::High Energy Astrophysical Phenomena, Nuclear Theory, FOS: Physical sciences, Jet (particle physics), PPBAR COLLIDER, PROTON, 01 natural sciences, 7. Clean energy, law.invention, CROSS-SECTIONS, High Energy Physics - Experiment, Nuclear physics, EVENTS, High Energy Physics - Experiment (hep-ex), GAMMA-P INTERACTIONS, MONTE-CARLO, law, 0103 physical sciences, Invariant mass, 010306 general physics, Collider, Nuclear Experiment, Quantum chromodynamics, Physics, ZEUS (particle detector), 010308 nuclear & particles physics, High Energy Physics::Phenomenology, ZEUS, ZEUS BARREL CALORIMETER, HERA, Rest frame, Gluon, PARTON DISTRIBUTIONS, HARD SCATTERING, High Energy Physics::Experiment
Abstract

Jet photoproduction, where the two highest transverse energy ($\ETJ$) jets have $\ETJ$ above 6 GeV and a jet-jet invariant mass above 23~GeV, has been studied with the ZEUS detector at the HERA $ep$ collider. Resolved and direct photoproduction samples have been separated. The cross section as a function of the angle between the jet-jet axis and the beam direction in the dijet rest frame has been measured for the two samples. The measured angular distributions differ markedly from each other. They agree with the predictions of QCD calculations, where the different angular distributions reflect the different spins of the quark and gluon exchanged in the hard subprocess., 20 pages including 4 figures

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