Observation of direct processes in photoproduction at HERA

Derrick, M.; Krakauer, D.; Magill, S.; Musgrave, B.; Repond, J.; Repond, S.; Stanek, R. W.; Talaga, R. L.; Thron, J. L.; Arzarello, F.; Ayad, R.; Bari, G.; Basile, M.; Bellagamba, L.; Boscherini, D.; Bruni, A.; Bruni, G.; Bruni, P.; Romeo, G. Cara; Castellini, G.; Chiarini, M.; Cifarelli, L.; Cindolo, F.; Ciralli, F.; Contin, A.; Papa, C. Del; D’Auria, S.; Frasconi, F.; Giusti, P.; Iacobucci, G.; Laurenti, G.; Levi, G.; Lin, Q.; Maccarrone, G.; Margotti, A.; Massam, T.; Nania, R.; Nemoz, C.; Palmonari, F.; Sartorelli, G.; Timellini, R.; Garcia, Y. Zamora; Zichichi, A.; Bargende, A.; Crittenden, J.; Desch, K.; Diekmann, B.; Doeker, T.; Felď, L.; Frey, A.; Geerts, M.; Geitz, G.; Hartmann, H.; Haun, Daniel B. M.; Héinloth, K.; Hilger, E.; Jakob, H.‐P.; Katz, U.; Kramarczyk, S.; Kückes, M.; Mass, A.; Mengel, S.; Mollen, J.; Müsch, H.; Paul, E.; Schattevoy, R.; Schneider, J.-L.; Schramm, David N.; Wedemeyer, R.; Cassidy, A.; Cussans, D.; Dyce, N.; Foster, B.; George, S.; Gilmore, R.; Heath, G. P.; Heath, H. F.; Lancaster, M.; Llewellyn, T.J.; Morgado, Cjs; Omara, Ja; Tapper, R. J.; Wilson, Stephen; Yoshida, R.; Rau, R. R.; Arneodo, M.; Schioppa, M.; Susinno, G.; Bernstein, Adam; Caldwell, A.; Gialas, I.; Parsons, J. A.; Ritz, S.; Sciulli, F.; Straub, P.B.; Wai, L.; Yang, S.; Borzemski, P.; Chwastowski, J. J.; Eskreys, A.; Piotrzkowski, K.; Zachara, M.; Zawiejski, L.; Adamczyk, L.; Bednarek, B.; Eskreys, K.; Jeleń, K.; Kisielewska, D.; Kowalski, T.; Rulikowska-Zarȩbska, E.; Suszycki, L.; Zając, Józef; Kȩdzierski, T.; Kotański, A.; Przybycień, M.; Bauerdick, L. A. T.; Behrens, U.; Bienlein, J. K.; Böttcher, S.; Coldewey, C.; Drews, G.; Flasiński, Mariusz; Fleck, I.; Gilkinson, D. J.; Göttlicher, P.; Gutjahr, B.; Haas, T.; Hagge, Lars; Hain, W.; Hasell, D.; Heßling, H.; Hultschig, H.; Joos, P.; Kasemann, M.; Klanner, R.; Koch, W.; Köpke, L.; Kötz, U.; Kowalski, H.; Kröger, W.; Krüger, J.; Labs, J.; Ladage, A.; Löhr, M.; Löwe, M.; Lüke, D.; Mainusch, J.; Mańczak, O.; Momayezi, M.; Ng, J. S. T.; Nickel, Stefan; Notz, D.; Pösnecker, K. U.; Rohde, M.; Roldán, J.; Schneekloth, U.; Schroeder, J.; Schulz, W.; Selonke, F.; Stiliaris, E.; Tsurugai, T.; Vogel, W.; Westphal, Douglas L.; Wolf, G.; Youngman, C.; Grabosch, H. J.; Leich, A.; Meyer, Andreas Bernhard; Rethfeldt, C.; Schlenstedt, S.; Barbagli, G.; Nuti, Marco; Pelfer, P. G.; Anzivino, G.; Pasquale, S. De; Qian, S. J.; Votano, L.; Bamberger, A.; Freidhof, A.; Poser, T.; Söldner-Rembold, S.; Theisen, G.; Trefzger, T.; Brook, N. H.; Bussey, P.; Doyle, A. T.; Forbes, J.R.; Jamieson, V.A.; Raine, C.; Saxon, D. H.; Stavrianakou, M.; Wilson, A. S.; Brückmann, H.; Dannemann, A.; Holm, U.; Horstmann, D.; Kammerlocher, H.; Krebs, B.; Neumann, T.; Sinkus, Ralph; Wick, K.; Fürtjes, A.; Lohrmann, E.; Milewski, J.; Nakahata, M.; Pavel, N.; Poelz, G.; Schott, W.; Terrón, J.; Zetsche, Frank; Bacon, T. C.; Beuselinck, R.; Butterworth, I.; Gallo, E.; Harris, V. L.; Long, K.; Miller, D. B.; Prinias, A.; Sedgbeer, J. K.; Vorvolakos, A.; Whitfield, A. F.; Bienz, T.; Kreutzmann, H.; Mallik, U.; McCliment, E.; Roco, M.; Wang, M.-Z.; Cloth, P.; Filges, D.; An, S. H.; Hong, S.; Kim, C. O.; Kim, T. Y.; Nam, S.; Park, S. K.; Suh, M. H.; Yon, S. H.; Imlay, R.; Kartik, S.; Kim, H. J.; McNeil, R. R.; Metcalf, W.; Nadendla, V. K.; Barreiro, F.; Cases, G.; Hervás, L.; Labarga, L.; Peso, J. Del; Trocóniz, Jorge F de; Ikraiam, F.; Mayer, J.; Smith, G. R.; Corriveau, F.; Hanna, D.; Hartmann, J.; Hung, L. W.; Lim, J.; Matthews, C. G.; Mitchell, J. W.; Patel, P. M.; Sinclair, L.E.; Stairs, D. G.; St.Laurent, M.; Ullmann, R.; Bashindzhagyan, G. L.; Ermolov, P.; Gladilin, L. K.; Golubkov, Yu. A.; Kuzmin, V. A.; Kuznetsov, E.; Savin, A.A.; Voronin, A.; Zotov, N. P.; Bentvelsen, S.; Botje, M.; Dake, A.; Engelen, J.; Jong, P. de; Kamps, Marc de; Kooijman, P.; Kruse, A.; Lugt, H. van der; O’Dell, V.; Tenner, A.; Tiecke, H.; Uijterwaal, H.; Vreeswijk, M.; Wiggers, L.; Wolf, E. de; Woudenberg, R. van; Bylsma, B.; Durkin, L. S.; Honscheid, K.; Li, C.; Ling, T. Y.; McLean, K. W.; Murray, W. N.; Park, I. H.; Romanowski, T. A.; Seidlein, R.; Blair, G.A.; Byrne, A.; Cashmore, R. J.; Cooper-Sarkar, A. M.; Devenish, R.C.E.; Harnew, N.; Khatri, T.; Luffman, P.; Morawitz, P.; Nash, J.A.; Roocroft, N.C.; Walczak, R.; Wilson, F. F.; Yip, T.; Abbiendi, G.; Bertolin, A.; Brugnera, R.; Carlin, R.; Corso, F. Dal; Giorgi, M. De; Dosselli, U.; Gasparini, F.; Limentani, S.; Morandin, M.; Posocco, M.; Stančo, L.; Stroili, R.; Voci, C.; Bulmahn, J.; Butterworth, J. M.; Feild, R. G.; Oh, B.Y.; Whitmore, J. J.; Contino, U.; D’Agostini, G.; Guida, M.; Iori, M.; Mari, S. M.; Marini, G.; Mattioli, M.; Nigro, A.; Hart, J. C.; McCubbin, N. A.; Prytz, Kjell; Shah, T.; Short, T.L.; Barberis, E.; Cartiglia, N.; Heusch, C. A.; Hook, M. Van; Hubbard, B.; Lockman, W. S.; Sadrozinski, H. F-W.; Seiden, A.; Zer-Zion, D.; Badura, E.; Biltzinger, J.; Seifert, R. J.; Walenta, A.H.; Zech, G.; Dagan, S.; Levy, A.; Hasegawa, T.; Hazumi, M.; Ishii, T.; Kasai, S.; Kuze, M.; Mine, S.; Nagasawa, Yutaka; Nagira, T.; Nakao, M.; Okuno, Hiroshi; Suzuki, I.; Tokushuku, K.; Yamada, S.; Yamazaki, Y.; Chiba, M.; Hamatsu, R.; Hirose, T.; Homma, K.; Kitamura, S.; Nagayama, S.; Nakamitsu, Y.; Cirio, R.; Costa, M.; Ferrero, M. I.; Lamberti, Luciano; Maselli, S.; Peroni, C.; Solano, A.; Sacchi, R.; Staiano, A.; Dardo, M.; Bailey, D. C.; Bandyopadhyay, Debades; Bénard, F.; Bhadra, S.; Brkić, M.; Burow, B.D.; Chlebana, F.; Crombie, M.B.; Gingrich, D. M.; Hartner, G.; Levman, G.; Martin, J. F.; Orr, R. S.; Sampson, C. R.; Teuscher, R. J.; Bullock, F. W.; Catterall, C. D.; Giddings, J. Calvin; Jones, T. W.; Khan, A.; Lane, J.B.; Makkar, P.L.; Shaw, D.; Shulman, J.; Blankenship, Kevin; Kochocki, J.; Lu, B.; Mo, L. W.; Charchuła, K.; Ciborowski, J.; Gajewski, J.; Grzelak, G.; Kasprzak, M.; Krzyżanowski, M.; Muchorowski, K.; Nowak, R. J.; Pawlak, J. M.; Tymieniecka, T.; Wróblewski, A.; Zakrzewski, J.; Żarnecki, A. F.; Adamus, M.; Abramowicz, H.; Eisenberg, Y.; Glasman, C.; Karshon, U.; Montag, A.; Revel, D.; Shapira, A.; Foudas, C.; Fordham, C.; Loveless, R.; Goussiou, A. G.; Ali, I.; Behrens, B. H.; Dasu, S.; Reeder, D.D.; Smith, W. H.; Silverstein, S.; Frisken, W. R.; Furutani, K.M.; Iga, Y.

doi:10.1016/0370-2693(94)91121-5

Cited by 69 publications

(25 citation statements)

References 25 publications

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“…Photoproduction events were selected by requiring that no scattered electron with energy of greater than 5 GeV be identified in the CAL [39]. The photon-proton centreof-mass energy, W , was reconstructed using the Jacquet-Blondel [40] estimator of W , W JB = 2E p i E i (1 − cos θ i ).…”

Section: Jhep09(2013)058mentioning

confidence: 99%

“…Here E i and θ i denote the energy and polar angle of the i th energy-flow object (EFO) [41], respectively, and the sum i runs over all final-state energyflow objects built from CTD-MVD tracks and energy clusters measured in the CAL. After correcting for detector effects, the most important of which were energy losses in inactive material in front of the CAL and particle interactions in the beam pipe [39,42], events were selected in the interval 130 < W JB < 300 GeV. The lower limit was set by the trigger requirements, while the upper limit was imposed to suppress remaining DIS events with an unidentified low-energy scattered electron in the CAL [39].…”

Section: Jhep09(2013)058mentioning

confidence: 99%

“…After correcting for detector effects, the most important of which were energy losses in inactive material in front of the CAL and particle interactions in the beam pipe [39,42], events were selected in the interval 130 < W JB < 300 GeV. The lower limit was set by the trigger requirements, while the upper limit was imposed to suppress remaining DIS events with an unidentified low-energy scattered electron in the CAL [39].…”

Section: Jhep09(2013)058mentioning

confidence: 99%

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Measurement of charm fragmentation fractions in photoproduction at HERA

Abramowicz¹,

Abt²,

Adamczyk³

et al. 2013

J. High Energ. Phys.

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The production of D 0 , D * + , D + , D + s and Λ + c charm hadrons and their antiparticles in ep scattering at HERA has been studied with the ZEUS detector, using a total integrated luminosity of 372 pb −1 . The fractions of charm quarks hadronising into a particular charm hadron were derived. In addition, the ratio of neutral to charged D-meson production rates, the fraction of charged D mesons produced in a vector state, and the stangenesssuppression factor have been determined. The measurements have been performed in the photoproduction regime. The charm hadrons were reconstructed in the range of transverse momentum p T > 3.8 GeV and pseudorapidity |η| < 1.6. The charm fragmentation fractions are compared to previous results from HERA and from e + e − experiments. The data support the hypothesis that fragmentation is independent of the production process. 6 Charm-hadron production cross sections 11 The ZEUS collaboration 24 IntroductionThe fragmentation fractions of charm quarks into specific charm hadrons cannot be predicted by Quantum Chromodynamics (QCD) and have to be measured. It is usually assumed that they are universal, i.e. the same for charm quarks produced in e + e − annihilation, in ep collisions and also in pp or other hadronic collisions, even though the charm production mechanisms are not the same: in e + e − collisions, cc pairs are produced dominantly by QED pair production, whereas in ep collisions, the main production mechanism is the QCD boson-gluon fusion process γg → cc. The fragmentation universality can be tested by measuring the fragmentation fractions at HERA and comparing the results with those obtained with e + e − collisions. Additionally, the values of the fragmentation fractions are crucial parameters used in comparisons of perturbative QCD (pQCD) calculations with measurements of charm production at HERA and elsewhere.-1 - JHEP09(2013)058In this paper, measurements of the photoproduction of charm hadrons in ep collisions at HERA are presented. The relative production rates of the most copiously produced charm ground states, the D In addition, the ratio of neutral to charged D-meson production rates, the fraction of charged D mesons produced in a vector state, and the strangeness-suppression factor were determined.The analysis presented here is based on an independent data set with an integrated luminosity over 4.5 times larger than the previous ZEUS measurement [1]. The new measurement benefits also from the ZEUS microvertex detector (MVD), which made it possible to identify the secondary decay vertices of the charm ground states and thereby to suppress background significantly. The new results are compared to the previous ZEUS measurement [1] in photoproduction, other HERA results from H1 [2] and ZEUS [3,4] in deep inelastic scattering, and to results from experiments at the e + e − storage rings CLEO [5,6], ARGUS [7][8][9] and the LEP experiments [10][11][12][13][14][15]. A summary is given in [16], with an update to 2010 branching ratios [17].

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Section: Jhep09(2013)058mentioning

confidence: 99%

Section: Jhep09(2013)058mentioning

confidence: 99%

Section: Jhep09(2013)058mentioning

confidence: 99%

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Measurement of charm fragmentation fractions in photoproduction at HERA

Abramowicz¹,

Abt²,

Adamczyk³

et al. 2013

J. High Energ. Phys.

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“…The upper cut rejects possible background from DIS events in which the scattered positron had not been recognised. A systematic shift in the reconstructed values of W JB with respect to the true W of the event, due to energy losses in inactive material in front of the calorimeter and particles lost in the beam pipe, was corrected [12,19], using the MC simulation of the detector described in section 4. The centre of mass energy range covered by the photoproduction sample is then 130 < W < 280 GeV, corresponding to 0.19 < y < 0.87.…”

Section: Offline Data Selectionmentioning

confidence: 99%

“…In such events, the fraction x OBS γ of the photon momentum which participates in the dijet production can be measured [3]. This quantity is sensitive to the relative contributions of resolved and direct processes [12]. In LO QCD direct photon events at the parton level have x OBS γ =1, while resolved photon events populate low values of x OBS γ .…”

Section: Introductionmentioning

confidence: 99%

Measurement of inclusive $D^{\ast\pm}$ and associated dijet cross sections in photoproduction at HERA

Breitweg

1999

Eur. Phys. J. C

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Inclusive photoproduction of D * ± mesons has been measured for photon-proton centre-of-mass energies in the range 130 < W < 280 GeV and photon virtuality Q 2 < 1 GeV 2 . The data sample used corresponds to an integrated luminosity of 37 pb −1 . Total and differential cross sections as functions of the D * transverse momentum and pseudorapidity are presented in restricted kinematical regions and the data are compared with next-to-leading order (NLO) perturbative QCD calculations using the "massive charm" and "massless charm" schemes. The measured cross sections are generally above the NLO calculations, in particular in the forward (proton) direction. The large data sample also allows the study of dijet production associated with charm. A significant resolved as well as a direct photon component contribute to the cross section. Leading order QCD Monte Carlo calculations indicate that the resolved contribution arises from a significant charm component in the photon. A massive charm NLO parton level calculation yields lower cross sections compared to the measured results in a kinematic region where the resolved photon contribution is significant.

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Hard Photoproduction and the Structure of the Photon

Sinclair

New Trends in HERA Physics 1999

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Observation of direct processes in photoproduction at HERA

Cited by 69 publications

References 25 publications

Measurement of charm fragmentation fractions in photoproduction at HERA

Measurement of charm fragmentation fractions in photoproduction at HERA

Measurement of inclusive $D^{\ast\pm}$ and associated dijet cross sections in photoproduction at HERA

Hard Photoproduction and the Structure of the Photon

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