Professor Amanda Cooper-Sarkar: Publications

Determination of the ratio rv=dvuv of the valence quark distributions in the proton from neutrino and antineutrino reactions on hydrogen and deuterium

Zeitschrift Fur Physik C Particles and Fields 62:4 (1994) 601-607

Authors:

GT Jones, RWL Jones, BW Kennedy, H Klein, DRO Morrison, H Wachsmuth, DB Miller, MM Mobayyen, S Wainstein, M Aderholz, D Hantke, UF Katz, J Kern, N Schmitz, W Wittek, HP Borner, G Myatt, AM Cooper-Sarkar, J Guy, W Venus, FW Bullock, S Burke

Abstract:

Based on a QCD analysis of the parton momentum distributions in the proton, the ratio rv=dv/uv of the d and u valence quark distributions is determined as function of x in the range 0.01v mainly depends on the deuterium/hydrogen ratios of the normalised x-y-Q²-distributions many systematic effects cancel. It is found that rv decreases with increasing x, and drops below the naive SU(6) expectation of 0.5 for x≳0.3. An extrapolation of rv to x=1 is consistent with the hypothesis rv(1)=0. © 1994 Springer-Verlag.

Comparison of energy flows in deep inelastic scattering events with and without a large rapidity gap

Physics Letters B 338:4 (1994) 483-496

Authors:

M Derrick, D Krakauer, S Magill, B Musgrave, J Repond, J Schlereth, R Stanek, RL Talaga, J Thron, F Arzarello, R Ayad, G Bari, M Basile, L Bellagamba, D Boscherini, A Bruni, G Bruni, P Bruni, GC Romeo, G Castellini, M Chiarini, L Cifarelli, F Cindolo, F Ciralli, A Contin, S D'Auria, C Del Papa, F Frasconi, P Giusti, G Iacobucci, G Laurenti, G Levi, G Maccarrone, A Margotti, T Massam, R Nania, C Nemoz, F Palmonari, A Polini, G Sartorelli, R Timellini, YZ Garcia, A Zichichi, A Bargende, J Crittenden, K Desch, B Diekmann, T Doeker, L Feld, A Frey, M Geerts, G Geitz, M Grothe, H Hartmann, D Haun, K Heinloth, E Hilger, HP Jakob, UF Katz, SM Mari, A Mass, S Mengel, J Mollen, E Paul, C Rembser, R Schattevoy, JL Schneider, 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, I Gialas, JA Parsons, S Ritz, F Sciulli, PB Straub, L Wai, S Yang, P Borzemski

Abstract:

Energy flows in deep inelastic electron-proton scattering are investigated at a centre-of-mass energy of 269 GeV for the range Q2 ≥ 10 GeV2 using the ZEUS detector. A comparison is made between events with and without a large rapidity gap between the hadronic system and the proton direction. The energy flows, corrected for detector acceptance and resolution, are shown for these two classes of events in both the HERA laboratory frame and the Breit frame. From the differences in the shapes of these energy flows we conclude that QCD radiation is suppressed in the large-rapidity-gap eents compared to the events without a large rapidity gap. © 1994.

Measurement of total and partial photon proton cross sections at 180 GeV center of mass energy

Zeitschrift Fur Physik C Particles and Fields 63:3 (1994) 391-408

Authors:

M Derrick, D Krakauer, S Magill, B Musgrave, J Repond, J Schlereth, R Stanek, RL Talaga, J Thron, F Arzarello, R Ayad, G Bari, M Basile, L Bellagamba, D Boscherini, A Bruni, G Bruni, P Bruni, GC Romeo, G Castellini, M Chiarini, L Cifarelli, F Cindolo, F Ciralli, A Contin, S D'Auria, C Del Papa, F Frasconi, P Giusti, G Iacobucci, G Laurenti, G Levi, G Maccarrone, A Margotti, T Massam, R Nania, C Nemoz, F Palmonari, G Sartorelli, R Timellini, Y Zamora Garcia, A Zichichi, A Bargende, J Crittenden, K Desch, B Diekmann, T Doeker, L Feld, A Frey, M Geerts, G Geitz, H Hartmann, D Haun, K Heinloth, E Hilger, HP Jakob, UF Katz, S Kramarczyk, A Mass, S Mengel, J Mollen, E Paul, C Rembser, R Schattevoy, JL Schneider, D Schramm, R Wedemeyer, A Cassidy, DG Cussans, N Dyce, B Foster, S George, R Gilmore, GP Heath, HF Heath, M Lancaster, TJ Llewellyn, CJS Morgado, JA O'Mara, RJ Tapper, SS Wilson, R Yoshida, RR Rau, M Arneodo, M Schioppa, G Susinno, A Bernstein, A Caldwell, I Gialas, JA Parsons, S Ritz, F Sciulli, PB Straub, L Wai, S Yang, P Borzemski, J Chwastowski, A Eskreys, K Piotrzkowski, M Zachara

Abstract:

Photon proton cross sections for elastic light vector meson production, σel^ν��, inelastic diffractive production, σnd^ν��, non-diffractive production, σd^ν��, as well as the total cross section, σtot^ν��, have been measured at an average υp center of mass energy of 180 GeV with the ZEUS detector at HERA. The resulting values are σel^ν�� = 18 ± 7 μb, σd^ν�� = 33 ± 8 μb, σnd^ν�� = 91 ± 11 μb, and σtot^ν�� 143 ± 17 μb, where the errors include statistical and systematic errors added in quadrature. © 1994 Springer-Verlag.

Observation of jet production in deep inelastic scattering with a large rapidity gap at HERA

Physics Letters B 332:1-2 (1994) 228-243

Authors:

M Derrick, D Krakauer, S Magill, B Musgrave, J Repond, J Schlereth, R Stanek, RL Talaga, J Thron, F Arzarello, R Ayad, G Bari, M Basile, L Bellagamba, D Boscherini, A Bruni, G Bruni, P Bruni, GC Romeo, G Castellini, M Chiarini, L Cifarelli, F Cindolo, F Ciralli, A Contin, S D'Auria, C Del Papa, F Frasconi, P Giusti, G Iacobucci, G Laurenti, G Levi, G Maccarrone, A Margotti, T Massam, R Nania, C Nemoz, F Palmonari, G Sartorelli, R Timellini, YZ Garcia, A Zichichi, A Bargende, J Crittenden, K Desch, B Diekmann, T Doeker, L Feld, A Frey, M Geerts, G Geitz, H Hartmann, D Haun, K Heinloth, E Hilger, HP Jakob, UF Katz, S Kramarczyk, A Mass, S Mengel, J Mollen, E Paul, C Rembser, R Schattevoy, JL Schneider, 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 Schioppa, G Susinno, A Bernstein, A Caldwell, I Gialas, JA Parsons, S Ritz, F Sciulli, PB Straub, L Wai, S Yang, P Borzemski, J Chwastowski, A Eskreys, K Piotrzkowski

Abstract:

Events with a large rapidity gap in deep inelastic scattering with Q2 ≥ 10 GeV2 have been studied in the ZEUS detector. The properties of these events with W > 140 GeV are consistent with a leading twist diffractive production mechanism. In the laboratory frame, with ETjet ≥ 4 GeV, 15% of the events are of the 1-jet type with negligible 2-jet production. The single jet is back-to-back in azimuth with the scattered electron. No energy flow is observed between the jet and the proton direction. With a lower jet transverse energy cut 2-jet production is observed both in the laboratory and the γ* p centre-of-mass systems, demonstrating the presence of hard scattering in the virtual photon proton interactions that give rise to large rapidity gap events. © 1994.

Observation of direct processes in photoproduction at HERA

Physics Letters B 322:3 (1994) 287-300

Authors:

M Derrick, D Krakauer, S Magill, B Musgrave, J Repond, S Repond, R Stanek, RL 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, C Del Papa, S D'Auria, F Frasconi, P Giusti, G Iacobucci, G Laurenti, G Levi, Q Lin, G Maccarrone, A Margotti, T Massam, R Nania, C Nemoz, F Palmonari, G Sartorelli, R Timellini, Y Zamora Garcia, A Zichichi, A Bargende, J Crittenden, K Desch, B Diekmann, T Doeker, L Feld, A Frey, M Geerts, G Geitz, H Hartmann, D Haun, K Heinloth, E Hilger, HP Jakob, UF Katz, S Kramarczyk, M Kückes, A Mass, S Mengel, J Mollen, H Müsch, E Paul, R Schattevoy, JL Schneider, D Schramm, R Wedemeyer, A Cassidy, DG Cussans, N Dyce, B Foster, S George, R Gilmore, GP Heath, HF Heath, M Lancaster, TJ Llewellyn, CJS Morgado, JA O'Mara, RJ Tapper, SS Wilson, R Yoshida, RR Rau, M Arneodo, M Schioppa, G Susinno, A Bernstein, A Caldwell, I Gialas, JA Parsons, S Ritz, F Sciulli, PB Straub, L Wai, S Yang, P Borzemski, J Chwastowski, A Eskreys

Abstract:

Jets in photoproduction events have been studied with the ZEUS detector for γp centre-of-mass energies ranging from 130 to 250 GeV. The inclusive jet distributions give evidence for the dominance of resolved photon interactions. In the di-jet sample the direct processes are for the first time clearly isolated. Di-jet cross sections for the resolved and direct processes are given in a restricted kinematic range. © 1994.

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