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Diffractive hard photoproduction at HERA and evidence for the gluon content of the pomeron

Physics Letters B 356:1 (1995) 129-146

Authors:

M Derrick, D Krakauer, S Magill, D Mikunas, B Musgrave, J Repond, R Stanek, RL 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, M Grothe, H Hartmann, K Heinloth, E Hilger, HP Jakob, UF Katz, SM Mari, S Mengel, J Mollen, E Paul, M Pfeiffer, C Rembser, D Schramm, J Stamm, R Wedemeyer, S Campbell-Robson, A Cassidy, N Dyce, B Foster, S George, R Gilmore, GP Heath, HF Heath, TJ Llewellyn, CJS Morgado, DJP Norman, JA O'Mara, RJ Tapper, SS Wilson, R Yoshida, RR Rau, M Arneodo, 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:

Inclusive jet cross sections for events with a large rapidity gap with respect to the proton direction from the reaction ep → jet + X with quasi-real photons have been measured with the ZEUS detector. The cross sections refer to jets with transverse energies ETjet> 8 GeV. The data show the characteristics of a diffractive process mediated by pomeron exchange. Assuming that the events are due to the exchange of a pomeron with partonic structure, the quark and gluon content of the pomeron is probed at a scale ∼ (ETjet)2. A comparison of the measurements with model predictions based on QCD plus Regge phenomenology requires a contribution of partons with a hard momentum density in the pomeron. A combined analysis of the jet cross sections and recent ZEUS measurements of the diffractive structure function in deep inelastic scattering gives the first experimental evidence for the gluon content of the pomeron in diffractive hard scattering processes. The data indicate that between 30% and 80% of the momentum of the pomeron carried by partons is due to hard gluons. © 1995.
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Limits on WWZ and WW gamma couplings from WW and WZ production in pp-bar collisions at sqrt s=1.8TeV.

Physical review letters 75:6 (1995) 1017-1022

Authors:

F Abe, MG Albrow, SR Amendolia, D Amidei, J Antos, C Anway-Wiese, G Apollinari, H Areti, M Atac, P Auchincloss, F Azfar, P Azzi, N Bacchetta, W Badgett, MW Bailey, J Bao, de Barbaro P, A Barbaro-Galtieri, VE Barnes, BA Barnett, P Bartalini, G Bauer, T Baumann, F Bedeschi, S Behrends, S Belforte, G Bellettini, J Bellinger, D Benjamin, J Benlloch, J Bensinger, D Benton, A Beretvas, JP Berge, S Bertolucci, A Bhatti, K Biery, M Binkley, F Bird, D Bisello, RE Blair, C Blocker, A Bodek, W Bokhari, V Bolognesi, D Bortoletto, C Boswell, T Boulos, G Brandenburg, C Bromberg, E Buckley-Geer, HS Budd, K Burkett, G Busetto, A Byon-Wagner, KL Byrum, J Cammerata, C Campagnari, M Campbell, A Caner, W Carithers, D Carlsmith, A Castro, Y Cen
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Measurement of the B Meson Differential Cross Section d sigma /dpT in pp-bar Collisions at sqrt s=1.8 TeV.

Physical review letters 75:8 (1995) 1451-1455

Authors:

F Abe, MG Albrow, SR Amendolia, D Amidei, J Antos, C Anway-Wiese, G Apollinari, H Areti, M Atac, P Auchincloss, F Azfar, P Azzi, N Bacchetta, W Badgett, MW Bailey, J Bao, de Barbaro P, A Barbaro-Galtieri, VE Barnes, BA Barnett, P Bartalini, G Bauer, T Baumann, F Bedeschi, S Behrends, S Belforte, G Bellettini, J Bellinger, D Benjamin, J Benlloch, J Bensinger, D Benton, A Beretvas, JP Berge, S Bertolucci, A Bhatti, K Biery, M Binkley, F Bird, D Bisello, RE Blair, C Blocker, A Bodek, W Bokhari, V Bolognesi, D Bortoletto, C Boswell, T Boulos, G Brandenburg, C Bromberg, E Buckley-Geer, HS Budd, K Burkett, G Busetto, A Byon-Wagner, KL Byrum, J Cammerata, C Campagnari, M Campbell, A Caner, W Carithers, D Carlsmith, A Castro, Y Cen
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Search for second generation leptoquarks in pp-bar collisions at sqrt s=1.8 TeV.

Physical review letters 75:6 (1995) 1012-1016

Authors:

F Abe, MG Albrow, SR Amendolia, D Amidei, J Antos, C Anway-Wiese, G Apollinari, H Areti, M Atac, P Auchincloss, F Azfar, P Azzi, N Bacchetta, W Badgett, MW Bailey, J Bao, de Barbaro P, A Barbaro-Galtieri, VE Barnes, BA Barnett, P Bartalini, G Bauer, T Baumann, F Bedeschi, S Behrends, S Belforte, G Bellettini, J Bellinger, D Benjamin, J Benlloch, J Bensinger, D Benton, A Beretvas, JP Berge, S Bertolucci, A Bhatti, K Biery, M Binkley, F Bird, D Bisello, RE Blair, C Blocker, A Bodek, W Bokhari, V Bolognesi, D Bortoletto, C Boswell, T Boulos, G Brandenburg, C Bromberg, E Buckley-Geer, HS Budd, K Burkett, G Busetto, A Byon-Wagner, KL Byrum, J Cammerata, C Campagnari, M Campbell, A Caner, W Carithers, D Carlsmith, A Castro, Y Cen
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Study of the photon remnant in resolved photoproduction at HERA

Physics Letters B 354:1-2 (1995) 163-177

Authors:

M Derrick, D Krakauer, S Magill, D Mikunas, B Musgrave, J Repond, R Stanek, RL 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, K Heinloth, E Hilger, HP Jakob, UF Katz, SM Mari, A Mass, S Mengel, J Mollen, E Paul, C Rembser, D Schramm, J Stamm, R Wedemeyer, S Campbell-Robson, A Cassidy, N Dyce, B Foster, S George, R Gilmore, GP Heath, HF Heath, TJ Llewellyn, CJS Morgado, DJP Norman, JA O'Mara, RJ Tapper, SS Wilson, R Yoshida, RR Rau, M Arneodo, 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 at HERA is studied in ep collisions, with the ZEUS detector, for γp centre-of-mass energies ranging from 130-270 GeV. A sample of events with two high-pTjets (pT> 6 GeV, η < 1.6) and a third cluster in the approximate direction of the electron beam is isolated using a clustering algorithm. These events are mostly due to resolved photoproduction. The third cluster is identified as the photon remnant. Its properties, such as the transverse and longitudinal energy flows around the axis of the cluster, are consistent with those commonly attributed to jets, and in particular with those found for the two jets in these events. The mean value of the photon remnant pTwith respect to the beam axis is measured to be 2.1 ± 0.2 GeV, which demonstrates substantial mean transverse momenta for the photon remnant. © 1995.
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