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Events with large E-T(tot) in photoproduction at HERA

J PHYS G NUCL PARTIC 25:7 (1999) 1440-1443

Authors:

C Nath, R Walczak, Y Yamazaki

Abstract:

Hard photoproduction events observed at HERA have a large excesses of transverse energy how with respect to theoretical predictions. For this paper events with total transverse energy greater than 45 GeV were selected. Jet cross sections and the dependence of the event rate on the photon-proton centre of mass energy W were measured. A multi-parton interaction model can describe the jet cross section but probably not the W distribution while a model without multi-parton interactions describes the W dependence well but not the jet cross section. At the moment, there is no model that describes data satisfactorily in the measured kinematic range.
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High E-T, exotics and rare processes

J PHYS G NUCL PARTIC 25:7 (1999) 1411-1411

Authors:

J Kalinowski, MW Krasny, R Walczak
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Exclusive electroproduction of ρ0 and J/ψ mesons at HERA

European Physical Journal C 6:4 (1999) 603-627

Authors:

J Breitweg, S Chekanov, M Derrick, D Krakauer, S Magill, D Mikunas, B Musgrave, J Repond, R Stanek, RL Talaga, R Yoshida, H Zhang, MCK 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, N Coppola, M Corradi, S de Pasquale, P Giusti, G Iacobucci, G Laurenti, G Levi, A Margotti, T Massam, R Nania, F Palmonari, A Pesci, A Polini, G Sartorelli, Y Zamora Garcia, A Zichichi, C Amelung, A Bornheim, I Brock, K Coböken, J Crittenden, R Deffner, M Eckert, M Grothe, H Hartmann, K Heinloth, L Heinz, E Hilger, HP Jakob, A Kappes, UF Katz, R Kerger, E Paul, M Pfeiffer, H Schnurbusch, A Weber, H Wieber, DS Bailey, WN Cottingham, B Foster, R Hall-Wilton, GP Heath, HF Heath, JD McFall, D Piccioni, DG Roff, J Scott, RJ Tapper, M Capua, L Iannotti, A Mastroberardino, M Schioppa, G Susinno, JY Kim, JH Lee, IT Lim, MY Pac, A Caldwell, N Cartiglia, Z Jing, W Liu, B Mellado, JA Parsons, S Ritz, S Sampson, F Sciulli, PB Straub, Q Zhu, P Borzemski, J Chwastowski, A Eskreys, J Figiel, K Klimek, MB Przybycień

Abstract:

Exclusive production of ρ0 and J/ψ mesons in e+p collisions has been studied with the ZEUS detector in the kinematic range 0.25 < Q2 < 50 GeV2, 20 < W < 167 GeV for the ρ0 data and 2 < Q2 < 40 GeV2, 50 < W < 150 GeV for the J/ψ data. Cross sections for exclusive ρ0 and J/ψ production have been measured as a function of Q2, W and t. The spin-density matrix elements r04 00, r1 1-1i and Re r5 10 have been determined for exclusive ρ0 production as well as r04 00 and r04 1-1 for exclusive J/ψ production. The results are discussed in the context of theoretical models invoking soft and hard phenomena.
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Forward jet production in deep inelastic scattering at HERA

European Physical Journal C 6:2 (1999) 239-252

Authors:

J Breitweg, M Derrick, D Krakauer, S Magill, D Mikunas, B Musgrave, J Repond, R Stanek, RL Talaga, R Yoshida, H Zhang, MCK 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, N Coppola, M Corradi, S de Pasquale, P Giusti, G Iacobucci, G Laurenti, G Levi, A Margotti, T Massam, R Nania, F Palmonari, A Pesci, A Polini, G Sartorelli, Y Zamora Garcia, A Zichichi, C Amelung, A Bornheim, I Brock, K Coböken, J Crittenden, R Deffner, M Eckert, M Grothe, H Hartmann, K Heinloth, L Heinz, E Hilger, HP Jakob, A Kappes, UF Katz, R Kerger, E Paul, M Pfeiffer, J Stamm, H Wieber, DS Bailey, S Campbell-Robson, WN Cottingham, B Foster, R Hall-Wilton, GP Heath, HF Heath, JD McFall, D Piccioni, DG Roff, RJ Tapper, R Ayad, M Capua, L Iannotti, M Schioppa, G Susinno, JY Kim, JH Lee, IT Lim, MY Pac, A Caldwell, N Cartiglia, Z Jing, W Liu, B Mellado, JA Parsons, S Ritz, S Sampson, F Sciulli, PB Straub, Q Zhu, P Borzemski, J Chwastowski, A Eskreys, J Figiel, K Klimek, MB Przybycień, L Zawiejski, L Adamczyk

Abstract:

The inclusive forward jet cross section in deep inelastic e+p scattering has been measured in the region of cursive Greek chi-Bjorken, 4.5 · 10-4 to 4.5 · 10-2. This measurement is motivated by the search for effects of BFKL-like parton shower evolution. The cross section at hadron level as a function of cursive Greek chi is compared to cross sections predicted by various Monte Carlo models. An excess of forward jet production at small cursive Greek chi is observed, which is not reproduced by models based on DGLAP parton shower evolution. The Colour Dipole model describes the data reasonably well. Predictions of perturbative QCD calculations at the parton level based on BFKL and DGLAP parton evolution are discussed in the context of this measurement.
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Investigation of a discharge-ablated capillary waveguide for high-intensity laser pulses

Institute of Electrical and Electronics Engineers (IEEE) (1999) 410-411

Authors:

SM Hooker, DJ Spence, RA Smith
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