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1. 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

2. 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

3. Kinematic fitting of neutral current events at HERA

Author

R.J. Seifert, G. Zech, and H. Chaves

Subjects
Physics, Nuclear and High Energy Physics, Particle physics, Neutral current, Hadron, Electron, HERA, Kinematics, Deep inelastic scattering, Nuclear physics, High Energy Physics::Experiment, Instrumentation, Scaling, Computer Science::Databases, Beam (structure)
Abstract

The measurement of the scaling variables in deep inelastic scattering at HERA can be improved considerably by constraining the scattered electrons and the produced hadrons to energy-momentum conservation. It is shown how unobserved particles moving down the beam pipe and initial state radiation can be included in the kinematics. The particle momenta are adjusted in a linear least squares fit.

Published
1993

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. 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.

6. 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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