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Measurement of elastic φ photoproduction at HERA

Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 377:4 (1996) 259-272

Authors:

M Derrick, D Krakauer, S Magill, D Mikunas, B Musgrave, JR Okrasinski, J Repond, R Stanek, RL Talaga, H Zhang, MCK Mattingly, G Bari, M Basile, L Bellagamba, D Boscherini, A Bruni, G Bruni, R 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, HP Jakob, UF Katz, S Mengel, J Mollen, E Paul, M Pfeiffer, C Rembser, D Schramm, J Stamm, R Wedemeyer, S Campbell-Robson, A Cassidy, WN Cottingham, N Dyce, B Foster, S George, ME Hayes, GP Heath, HF Heath, D Piccioni, DG Roff, RJ 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, JA Parsons, S Ritz, F Sciulli, PB 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

Abstract:

The production of φ mesons in the reaction e+p → e+φp (φ → K+K-) at a median Q2 of 10-4 GeV2 has been studied with the ZEUS detector at HERA. The differential φ photoproduction cross section dσ/dt has an exponential shape and has been determined in the kinematic range 0.1 < |t| < 0.5 GeV2 and 60 < W < 80 GeV. An integrated cross section of σγp→φp = 0.96 ± 0.19+0.21-.18 μb has been obtained by extrapolating to t = 0. When compared to lower energy data, the results show a weak energy dependence of both σγp→φp and the slope of the t distribution. The φ decay angular distributions are consistent with s-channel helicity conservation. From lower energies to HERA energies, the features of φ photoproduction are compatible with those of a soft diffractive process.
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Rapidity gaps between jets in photoproduction at HERA

Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 369:1 (1996) 55-68

Authors:

M Derrick, D Krakauer, S Magill, D Mikunas, B Musgrave, J Repond, R Stanek, RL Talaga, H Zhang, G Bari, M Basile, L Bellagamba, D Boscherini, A Bruni, G Bruni, R Bruni, G Cara Romeo, G Castellini, M Chiarini, L Cifarelli, F Cindolo, A Contin, M Corradi, I Gialas, R 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, HP Jakob, UF Katz, S Mengel, J Mollen, E Paul, M Pfeiffer, C Rembser, D Schramm, J Stamm, R Wedemeyer, S Campbell-Robson, A Cassidy, WN Cottingham, N Dyce, B Foster, S George, ME Hayes, GP Heath, HF Heath, CJS Morgado, JA O'Mara, D Piccioni, DG Roff, RJ Tapper, R Yoshida, RR Rau, M Arneodo, R Ayad, M Capua, A Garfagnini, L Iannotti, M Schioppa, G Susinno, A Bernstein, A Caldwell, N Cartiglia, JA Parsons, S Ritz, F Sciulli, PB Straub, L Wai, S Yang, Q Zhu, P Borzemski, J Chwastowski, A Eskreys, K Piotrzkowski, M Zachara

Abstract:

Photoproduction events which have two or more jets have been studied in the Wγp range 135 GeV < Wγp < 280 GeV with the ZEUS detector at HERA. A class of events is observed with little hadronic activity between the jets. The jets are separated by pseudorapidity intervals (Δη) of up to four units and have transverse energies greater than 6 GeV. A gap is defined as the absence between the jets of particles with transverse energy greater than 300 MeV. The fraction of events containing a gap is measured as a function of Δη. It decreases exponentially as expected for processes in which colour is exchanged between the jets, up to a value of Δη ∼ 3, then reaches a constant value of about 0.1. The excess above the exponential fall-off can be interpreted as evidence for hard diffractive scattering via a strongly interacting colour singlet object.
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Inclusive charged particle distributions in deep inelastic scattering events at HERA

Zeitschrift fur Physik C-Particles and Fields 70:1 (1996) 1-15

Authors:

M Derrick, D Krakauer, S Magill, D Mikunas, B Musgrave, J Repond, R Stanek, RL Talaga, H Zhang, 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, K Desch, B Diekmann, T Doeker, M Eckert, L Feld, A Frey, M Geerts, M Grothe, H Hartmann, K Heinloth, L Heinz, E Hilger, HP Jakob, UF Katz, S Mengel, J Mollen, E Paul, M Pfeiffer, C Rembser, D Schramm, J Stamm, R Wedemeyer, S Campbell-Robson, A Cassidy, WN Cottingham, N Dyce, B Foster, S George, ME Hayes, GP Heath, HF Heath, CJS Morgado, JA O'Mara, D Piccioni, DG Roff, RJ Tapper, R Yoshida, RR Rau, M Arneodo, R Ayad, M Capua, A Garfagnini, L Iannotti, M Schioppa, G Susinno, A Bernstein, A Caldwell, N Cartiglia, JA Parsons, S Ritz, F Sciulli, PB Straub, L Wai, S Yang, Q Zhu, P Borzemski, J Chwastowski, A Eskreys, K Piotrzkowski, M Zachara, L Zawiejski, L Adamczyk, B Bednarek

Abstract:

A measurement of inclusive charged particle distributions in deep inelastic ep scattering for γ*p centre-of-mass energies 75 < W < 175 GeV and momentum transfer squared 10 < Q2 < 160 GeV2 from the ZEUS detector at HERA is presented. The differential charged particle rates in the γ*p centre-of-mass system as a function of the scaled longitudinal momentum, xF, and of the transverse momentum, pt* and , as a function of xF, W and Q2 are given. Separate distributions are shown for events with (LRG) and without (NRG) a rapidity gap with respect to the proton direction. The data are compared with results from experiments at lower beam energies, with the naive quark parton model and with parton models including perturbative QCD corrections. The comparison shows the importance of the higher order QCD processes. Significant differences of the inclusive charged particle rates between NRG and LRG events at the same W are observed. The value of for LRG events with a hadronic mass MX, which excludes the forward produced baryonic system, is similar to the
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Measurement of the diffractive cross section in deep inelastic scattering

Zeitschrift Fur Physik C Particles and Fields 70:3 (1996) 391-412

Authors:

M Derrick, D Krakauer, S Magill, D Mikunas, B Musgrave, JR Okrasinski, J Repond, R Stanek, RL Talaga, H Zhang, MCK 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, T Doeker, M Eckert, L Feld, A Frey, M Geerts, M Grothe, H Hartmann, K Heinloth, L Heinz, E Hilger, HP Jakob, UF Katz, S Mengel, J Mollen, E Paul, M Pfeiffer, C Rembser, D Schramm, J Stamm, R Wedemeyer, S Campbell-Robson, A Cassidy, WN Cottingham, N Dyce, B Foster, S George, ME Hayes, GP Heath, HF Heath, D Piccioni, DG Roff, RJ 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, JA Parsons, S Ritz, F Sciulli, PB Straub, L Wai, S Yang, Q Zhu, P Borzemski, J Chwastowski, A Eskreys, M Zachara, L Zawiejski, L Adamczyk, B Bednarek, K Jelén, D Kisielewska

Abstract:

Diffractive scattering of γ∗p → X + N, where N is either a proton or a nucleonic system with MN < 4 GeV has been measured in deep inelastic scattering (DIS) at HERA. The cross section was determined by a novel method as a function of the γ∗p c.m. energy W between 60 and 245 GeV and of the mass MX of the system X up to 15 GeV at average Q2 values of 14 and 31 GeV2. The diffractive cross section dσdi f f /dMX is, within errors, found to rise linearly with W. Parameterizing the W dependence by the form dσdi f f /dMX ∞ (W2)(2αIP - 2) the DIS data yield for the pomeron trajectory αIP = 1.23±0.02(stat)±0.04(syst) averaged over t in the measured kinematic range assuming the longitudinal photon contribution to be zero. This value for the pomeron trajectory is substantially larger than αIP extracted from soft interactions. The value of αIP measured in this analysis suggests that a substantial part of the diffractive DIS cross section originates from processes which can be described by perturbative QCD. From the measured diffractive cross sections the diffractive structure function of the proton F2 D(3) (β,Q2, xIP) has been determined, where β is the momentum fraction of the struck quark in the pomeron. The form F2 D(3) = constant·(1/xIP)a gives a good fit to the data in all β and Q2 intervals with a = 1.46 ± 0.04(stat) ± 0.08(syst).
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Dijet angular distributions in direct and resolved photoproduction at HERA

PHYSICS LETTERS B 384:1-4 (1996) 401-413

Authors:

M Derrick, D Krakauer, S Magill, D Mikunas, B Musgrave, JR Okrasinski, J Repond, R Stanek, RL Talaga, H Zhang, MCK Mattingly, G Bari, M Basile, L Bellagamba, D Boscherini, A Bruni, G Bruni, P Bruni, GC 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, YZ 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, HP Jakob, UF Katz, S Mengel, E Paul, M Pfeiffer, C Rembser, D Schramm, J Stamm, R Wedemeyer, S CampbellRobson, A Cassidy, WN Cottingham, N Dyce, B Foster, S George, ME Hayes, GP Heath, HF Heath, D Piccioni, DG Roff, RJ 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, JA Parsons, S Ritz, F Sciulli, PB Straub, L Wai, S Yang, Q Zhu, P Borzemski, J Chwastowski, A Eskreys, Z Jakubowski, MB Przybycien, M Zachara, L Zawiejski, L Adamczyk, B Bednarek, K Jelen, D Kisielewska, T Kowalski, M Przybycien, E RulikowskaZarebska, L Suszycki, J Zajac, Z Dulinski, A Kotanski, G Abbiendi, LAT Bauerdick, U Behrens, H Beier, JK Bienlein, G Cases, O Deppe, K Desler, G Drews, M Flasinski, DJ Gilkinson, C Glasman, P Gottlicher, J GrosseKnetter, T Haas, W Hain, D Hasell, A Hessling, Y Iga, KF Johnson, P Joos, M Kasemann, R Klanner, W Koch, U Kotz, H Kowalski, J Labs, A Ladage, B Lohr, M Lowe, D Luke, J Mainusch, O Manczak, J Milewski, T Monteiro, JST Ng, D Notz, K Ohrenberg, K Piotrzkowski, M Roco, M Rohde, J Roldan, U Schneekloth, W Schulz, F Selonke, B Surrow, T Voss, D Westphal, G Wolf, U Wollmer, C Youngman, W Zeuner, HJ Grabosch, A Kharchilava, SM Mari, A Meyer, S Schlenstedt, N Wulff, G Barbagli, E Gallo, P Pelfer, G Maccarrone, S DePasquale, L Votano, A Bamberger, S Eisenhardt, T Trefzger, S Wolfle, JT Bromley, NH Brook, PJ Bussey, AT Doyle, DH Saxon, LE Sinclair, ML Utley, AS Wilson, A Dannemann, U Holm, D Horstmann, R Sinkus, K Wick, BD Burow, L Hagge, E Lohrmann, G Poelz, W Schott, F Zetsche, TC Bacon, N Brummer, I Butterworth, VL Harris, G Howell, BHY Hung, L Lamberti, KR Long, DB Miller, N Pavel, A Prinias, JK Sedgbeer, D Sideris, AF Whitfield, U Mallik, MZ Wang, SM Wang, JT Wu, SH An, GH Cho, BJ Ko, SB Lee, SW Nam, HS Park, SK Park, S Kartik, HJ Kim, RR McNeil, W Metcalf, VK Nadendla, F Barreiro, JP Fernandez, R Graciani, JM Hernandez, L Hervas, L Labarga, M Martinez, J delPeso, J Puga, J Terron, JF deTroconiz, F Corriveau, DS Hanna, J Hartmann, LW Hung, JN Lim, CG Matthews, PM Patel, M Riveline, DG Stairs, M StLaurent, R Ullmann, G Zacek, T Tsurugai, V Bashkirov, BA Dolgoshein, A Stifutkin, GL Bashindzhagyan, PF Ermolov, LK Gladilin, YA Golubkov, VD Kobrin, IA Korzhavina, VA Kuzmin, OY Lukina, AS Proskuryakov, AA Savin, LM Shcheglova, AN Solomin, NP Zotov, M Botje, F Chlebana, J Engelen, M deKamps, P Kooijman, A Kruse, A vanSighem, H Tiecke, W Verkerke, J Vossebeld, M Vreeswijk, L Wiggers, E deWolf, R vanWoudenberg, D Acosta, B Bylsma, LS Durkin, J Gilmore, C Li, TY Ling, P Nylander, IH Park, TA Romanowski, DS Bailey, RJ Cashmore, AM CooperSarkar, RCE Devenish, N Harnew, M Lancaster, L Lindemann, JD McFall, C Nath, VA Noyes, A Quadt, JR Tickner, H Uijterwaal, R Walczak, DS Waters, FF Wilson, T Yip, A Bertolin, R Brugnera, R Carlin, F DalCorso, M DeGiorgi, U Dosselli, S Limentani, M Morandin, M Posocco, L Stanco, R Stroili, C Voci, F Zuin, G DAgostini, G Marini, A Nigro, E Tassi, JC Hart, NA McCubbin, TP Shah, E Barberis, T Dubbs, C Heusch, M VanHook, W Lockman, JT Rahn, HFW Sadrozinski, A Seiden, DC Williams, J Biltzinger, RJ Seifert, O Schwarzer, AH Walenta, G Zech, H Abramowicz, G Briskin, S Dagan, A Levy, JI 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 Yamuchi, R Cirio, M Costa, MI Ferrero, S Maselli, C Peroni, R Sacchi, A Solano, A Staiano, M Dardo, DC Bailey, F Benard, M Brkic, CP Fagerstroem, GF Hartner, KK Joo, GM Levman, JF Martin, RS Orr, S Polenz, CR Sampson, D Simmons, RJ Teuscher, JM Butterworth, CD Catterall, TW Jones, PB Kaziewicz, JB Lane, RL Saunders, J Shulman, MR Sutton, B Lu, LW Mo, W Bogusz, J Ciborowski, J Gajewski, G Grzelak, M Kasprzak, M Krzyzanowski, K Muchorowski, RJ Nowak, JM Pawlak, T Tymieniecka, AK Wroblewski, JA Zakrzewski, AF Zarnecki, C Coldewey, Y Eisenberg, D Hochman, U Karshon, D Revel, D ZerZion, WF Badgett, J Breitweg, D Chapin, R Cross, S Dasu, C Foudas, RJ Loveless, S Mattingly, DD Reeder, S Silverstein, WH Smith, A Vaiciulis, M Wodarczyk, S Bhadra, ML Cardy, WR Frisken, M Khakzad, WN Murray, WB Schmidke
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