Dijet angular distributions in photoproduction of charm at HERA
Sergei ChekanovArgonne National Laboratory , Argonne , IL 60439-4815 , USAM. DerrickArgonne National Laboratory , Argonne , IL 60439-4815 , USAD. KrakauerNIKHEF and University of Amsterdam, Amsterdam, Netherlands3737Supported by the Netherlands Foundation for Research on Matter (FOM)J.H. LoizidesAlso affiliated with University College London S. MagillArgonne National Laboratory , Argonne , IL 60439-4815 , USAB. MusgraveArgonne National Laboratory , Argonne , IL 60439-4815 , USAJ. RepondArgonne National Laboratory , Argonne , IL 60439-4815 , USAR. YoshidaArgonne National Laboratory , Argonne , IL 60439-4815 , USAM.C.K. MattinglyAndrews University, Berrien Springs, MI 49104-0380, USAP. AntonioliUniversity andG. BariUniversity andM. BasileUniversity andL. BellagambaAndrews University , Berrien Springs , MI 49104-0380 , USAD. BoscheriniAndrews University , Berrien Springs , MI 49104-0380 , USAA. BruniAndrews University , Berrien Springs , MI 49104-0380 , USAG. BruniNIKHEF and University of Amsterdam, Amsterdam, Netherlands3737Supported by the Netherlands Foundation for Research on Matter (FOM)G. Cara RomeoUniversity andL. CifarelliUniversity andF. CindoloUniversity andA. ContinAndrews University , Berrien Springs , MI 49104-0380 , USAM. CorradiAndrews University , Berrien Springs , MI 49104-0380 , USAS. De PasqualeNIKHEF and University of Amsterdam, Amsterdam, Netherlands3737Supported by the Netherlands Foundation for Research on Matter (FOM)P. GiustiUniversity andG. IacobucciUniversity andA. MargottiR. NaniaINFN Bologna , Bologna , ItalyF. PalmonariINFN Bologna , Bologna , ItalyA. PesciINFN Bologna , Bologna , ItalyG. SartorelliNIKHEF and University of Amsterdam, Amsterdam, Netherlands3737Supported by the Netherlands Foundation for Research on Matter (FOM)A. ZichichiG. AghuzumtsyanUniversity andD. BartschUniversity andI. BrockUniversity andS. GoersINFN Bologna , Bologna , ItalyH. HartmannNIKHEF and University of Amsterdam, Amsterdam, Netherlands3737Supported by the Netherlands Foundation for Research on Matter (FOM)E. HilgerNIKHEF and University of Amsterdam, Amsterdam, Netherlands3737Supported by the Netherlands Foundation for Research on Matter (FOM)P. IrrgangINFN Bologna , Bologna , ItalyH.‐P. JakobA. KappesOn leave of absence at University of Erlangen- Nürnberg , GermanyU. KatzOn leave of absence at University of Erlangen- Nürnberg , GermanyO. KindPhysikalisches Institut der Universität Bonn , Bonn , GermanyU. MeyerINFN Bologna , Bologna , ItalyE. PaulNIKHEF and University of Amsterdam, Amsterdam, Netherlands3737Supported by the Netherlands Foundation for Research on Matter (FOM)J. RautenbergNIKHEF and University of Amsterdam, Amsterdam, Netherlands3737Supported by the Netherlands Foundation for Research on Matter (FOM)R. RennerUniversity andA. StifutkinJ. TandlerPhysikalisches Institut der Universität Bonn , Bonn , GermanyK.C. VossPhysikalisches Institut der Universität Bonn , Bonn , GermanyMeng WangPhysikalisches Institut der Universität Bonn , Bonn , GermanyA. WeberINFN Bologna , Bologna , ItalyDS BaileyN. H. BrookJ. E. ColePhysikalisches Institut der Universität Bonn , Bonn , GermanyB. FosterPhysikalisches Institut der Universität Bonn , Bonn , GermanyG.P. HeathPhysics Laboratory , University of Bristol , Bristol , UKH. F. HeathPhysics Laboratory , University of Bristol , Bristol , UKS. RobinsNIKHEF and University of Amsterdam, Amsterdam, Netherlands3737Supported by the Netherlands Foundation for Research on Matter (FOM)E. RodriguesNIKHEF and University of Amsterdam, Amsterdam, Netherlands3737Supported by the Netherlands Foundation for Research on Matter (FOM)J. ScottNIKHEF and University of Amsterdam, Amsterdam, Netherlands3737Supported by the Netherlands Foundation for Research on Matter (FOM)R.J. TapperPhysics Laboratory , University of Bristol , Bristol , UKM. WingPhysics Laboratory , University of Bristol , Bristol , UKM. CapuaCalabria University , Physics Department and INFN , Cosenza , ItalyA. MastroberardinoCalabria University , Physics Department and INFN , Cosenza , ItalyM. SchioppaPhysics Laboratory , University of Bristol , Bristol , UKG. SusinnoNIKHEF and University of Amsterdam, Amsterdam, Netherlands3737Supported by the Netherlands Foundation for Research on Matter (FOM)J.Y. KimChonnam National University , Kwangju , South KoreaY.K. KimChonnam National University , Kwangju , South KoreaJ.H. LeeChonnam National University , Kwangju , South KoreaI.T. LimCalabria University , Physics Department and INFN , Cosenza , ItalyM.Y. PacCalabria University , Physics Department and INFN , Cosenza , ItalyA. CaldwellNow at Max-Planck-Institut für Physik , München , GermanyM. HelbichNevis Laboratories , Columbia University , Irvington on Hudson , NY 10027 , USAXiang LiuNevis Laboratories , Columbia University , Irvington on Hudson , NY 10027 , USAB. MelladoNevis Laboratories , Columbia University , Irvington on Hudson , NY 10027 , USAY. NingAndrews University, Berrien Springs, MI 49104-0380, USAE. PaganisNIKHEF and University of Amsterdam, Amsterdam, Netherlands3737Supported by the Netherlands Foundation for Research on Matter (FOM)Z. RenNevis Laboratories , Columbia University , Irvington on Hudson , NY 10027 , USAW.B. SchmidkeNevis Laboratories , Columbia University , Irvington on Hudson , NY 10027 , USAF. SciulliNIKHEF and University of Amsterdam, Amsterdam, Netherlands3737Supported by the Netherlands Foundation for Research on Matter (FOM)J. J. ChwastowskiInstitute of Nuclear Physics , Cracow , PolandA. EskreysInstitute of Nuclear Physics , Cracow , PolandJ. FigielNIKHEF and University of Amsterdam, Amsterdam, Netherlands3737Supported by the Netherlands Foundation for Research on Matter (FOM)K. OlkiewiczNevis Laboratories , Columbia University , Irvington on Hudson , NY 10027 , USAP. StopaNIKHEF and University of Amsterdam, Amsterdam, Netherlands3737Supported by the Netherlands Foundation for Research on Matter (FOM)L. ZawiejskiNevis Laboratories , Columbia University , Irvington on Hudson , NY 10027 , USAL. AdamczykNIKHEF and University of Amsterdam, Amsterdam, Netherlands3737Supported by the Netherlands Foundation for Research on Matter (FOM)T. BołdNIKHEF and University of Amsterdam, Amsterdam, Netherlands3737Supported by the Netherlands Foundation for Research on Matter (FOM)I. Grabowska-BołdInstitute of Nuclear Physics , Cracow , PolandD. KisielewskaInstitute of Nuclear Physics , Cracow , PolandA.M. KowalInstitute of Nuclear Physics , Cracow , PolandM. KowalNIKHEF and University of Amsterdam, Amsterdam, Netherlands3737Supported by the Netherlands Foundation for Research on Matter (FOM)T. Z. KowalskiNIKHEF and University of Amsterdam, Amsterdam, Netherlands3737Supported by the Netherlands Foundation for Research on Matter (FOM)M. PrzybycieńFaculty of Physics and Nuclear Techniques , University of Mining and Metallurgy , Cracow , PolandL. SuszyckiNIKHEF and University of Amsterdam, Amsterdam, Netherlands3737Supported by the Netherlands Foundation for Research on Matter (FOM)D. SzubaFaculty of Physics and Nuclear Techniques , University of Mining and Metallurgy , Cracow , PolandJ. SzubaNIKHEF and University of Amsterdam, Amsterdam, Netherlands3737Supported by the Netherlands Foundation for Research on Matter (FOM)A. KotańskiFaculty of Physics and Nuclear Techniques , University of Mining and Metallurgy , Cracow , PolandW. SłomińskiMember of Department of Computer Science . 12 Now at Fermilab , Batavia , IL , USAL. A. T. BauerdickDepartment of Physics , Jagellonian University , Cracow , PolandU. BehrensNIKHEF and University of Amsterdam, Amsterdam, Netherlands3737Supported by the Netherlands Foundation for Research on Matter (FOM)
2003en
ABI
Abstract
Dijet angular distributions of photoproduction events in which a D∗± meson is produced in association with one of two energetic jets have been measured with the ZEUS detector at HERA, using an integrated luminosity of 120 pb−1. Differential cross sections as a function of the angle between the charm-jet and the proton-beam direction in the dijet rest frame have been measured for samples enriched in direct or resolved photon events. The results are compared with predictions from leading-order parton-shower Monte Carlo models and with next-to-leading-order QCD calculations. The angular distributions show clear evidence for the existence of charm originating from the photon.
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