Measurement of di-jet cross-sections in photoproduction and photon structure

C Adloff,J.E Turney,L Janauschek,L Hajduk,F Moreau,N Keller,S Kermiche,A Bunyatyan,R Demirchyan,P Höting,V Efremenko,M Winde,K Rybicki,I Ayyaz,D Lüke,H Spitzer,W.J Haynes,W Braunschweig,S Von Dombrowski,U Straumann,P Truöl,A Astvatsatourov,P Bruel,J Gassner,S Schleif,K.T Donovan,G Franke,A Beglarian,J Feltesse,P Kostka,A Glazov,M Kapichine,T Nunnemann,W Hoprich,W Lachnit,T Greenshaw,H.K Kästli,B Delcourt,V Lubimov,F Niebergall,B Naroska,T Benisch,K Wacker,B Koblitz,N Loktionova,I Négri,R Roosen,A Droutskoi,E Gabathuler,S Wiesand,E Malinovski,F Sefkow,J Martyniak,L Goerlich,H.-B Bröker,T Wilksen,J Garvey,Y Vazdik,W Struczinski,C Wissing,D Haidt,T Berndt,G Heinzelmann,G Siegmon,F Ferrarotto,V Brisson,L Lytkin,V Nagovizin,J Žáček,O Karschnick,I Malinovski,H Krehbiel,W.D Dau,Ç İşsever,G Grindhammer,M Ellerbrock,E Barrelet,R Eichler,H Wollatz,M Swart,C Vallée,F Metlica,S Mikocki,N Tobien,R Heremans,J Stiewe,S Levonian,G Bertrand-Coremans,D Wegener,R Gerhards,B Leißner,A Stellberger,J Ferencei,D Kant,K Müller,I Herynek,G Buschhorn,J Scheins,J Naumann,J Zsembery,R Maraček,H Grässler,E Eisenhandler,A Usik,A Meyer,T Kuhr,S Hurling,R Pöschl,J Formánek,I Foresti,G Rädel,M Zur Nedden,J Gayler,J Bähr,O Behnke,C Kiesling,G Cozzika,E Tzamariudaki,J Steinhart,M Fleischer,H Mahlke-Krüger,A Burrage,T Hadig,V Solochenko,S Passaggio,S Ferron,O Nix,V Schröder,C Niebuhr,S Mohrdieck,M Jacquet,J Marks,V Jemanov,M Kausch,R Lemrani,J Cvach,F Eisele,D Traynor,I Sheviakov,V Spaskov,Ch Berger,V Arkadov,N Malden,M Hilgers,C Duprel,V Lendermann,A Valkárová,A Küpper,S Egli,S Hengstmann,N Gogitidze,J Ebert,I Potachnikova,K Gabathuler,V Panassik,R Marshall,P Zini,B Reisert,A Rostovtsev,V Dodonov,M Ibbotson,M Taševský,P Van Mechelen,V Korbel,J.C Bizot,P Dixon,E Wünsch,C.D Hilton,J Kroseberg,B Stella,G Knies,V Haustein,W Brückner,G Villet,Y Soloviev,A Wegner,R Felst,G Lobo,M Lindstroem,N Magnussen,U Bassler,J Turnau,C Pascaud,J Rauschenberger,V Tchernyshov,A De Roeck,W Bartel,K Daum,H Henschel,A Lebedev,G Herrera,A Specka,S Ghazaryan,S Tchetchelnitski,D Ozerov,G Weber,G G Winter ,S Bürke ,L Jönsson,V Lemaı̂tre ,M Weber,C Grab,J E Olsson ,Junpeng Cao ,M Goldberg,P R Newman ,S.K Kotelnikov,E A De Wolf ,V Andreev,S Caron,B Łobodziński ,R.K Griffiths,S Lüders,D Hoffmann,M Jaffré ,B Clerbaux,A Fomenko,C Collard,D Müller,R Wallny,T Mkrtchyan,W Lange,H.‐C Schultz‐Coulon ,C Royon,R Horisberger,J G Contreras ,T Walter,L.R West,H Jung,J Meyer,K Rabbertz,Y Sirois,O Kaufmann,T Kurča,M N Mondragón ,T C Nicholls ,L Favart,P.-O Meyer,F.W Büsser,P Merkel,G White,T Naumann ,F Zomer,K Meier,S Rieß ,V Shekelyan,A Fedotov,Z Zhang,J P Phillips ,G Tsipolitis,D Eckstein,M N K Smith ,A Babaev,R.kh Kutuev ,P Schleper,P Reimer,B Heinemann,D Brown ,F P Schilling ,G D Patel ,J D Dowell ,E Elsen,J P Sutton ,D Reyna,D Krücker,J Zálešâk ,G Eckerlin,K H Hiller ,M David,E Rizvi,R Stamen,P Smirnov,Peter Faulkner ,D Clarke,Bernard Andrieu ,A Schöning,H U Martyn ,J Bürger,K Borras,T Wengler,A Mehta,M Werner,R Casanova Mohr ,H Meyer,Bogdan Povh ,T Laštovička ,D Pitzl,E Lobodzinska,Benedict Martin Waugh ,Martin Karlsson ,G Nowak,G Flügge,C Diaconu,H K Nguyen ,C Kleinwort,J Kennedy,P Baranov,Nicolas Delerue ,J Hladký ,T Schörner,C Beier,D M Jansen ,S D Kolya ,K Krüger,M Erdmann,M P J Landon ,A Morozov,A Campbell ,M Wobisch,D P C Sankey ,P Sievers,X Janssen,П Мурін ,R Lahmann,H Kolanoski,M Klein,H Burkhardt,Frerich J Keil ,L N Shtarkov ,D Johnson ,P Marage,Pete S Bate ,Kamil Sedlák ,Peter Thompson ,Š Valkár ,R C W Henderson ,D Milstead,D Bruncko,Christopher J Goodwin ,J V Morris ,D Schmidt,J B Dainton ,V Boudry,J A Coughlan ,P Robmann,A Belousov,Steffen Udluft ,I Gorelov,L Schoeffel,S V Rusakov ,David C Lamb ,Marcus Davidsson ,G Bernardi,M Jones ,J M Foster ,M W Krasny ,T Carli,E Pérez ,G Thompson,I R Kenyon ,S J Maxfield ,T Sloan,M C Cousinou ,T R Mcmahon ,E C Chabert ,A Zhokin,B E Cox

doi:10.1016/s0370-2693(00)00576-1

Abstract

The production of hard di-jet events in photoproduction at HERA is dominated by resolved photon processes in which a parton in the photon with momentum fraction x γ is scattered from a parton in the proton. These processes are sensitive to the quark and gluon content of the photon. The differential di-jet cross-section d σ/dlog( x γ ) is presented here, measured in tagged photoproduction at HERA using data taken with the H1 detector, corresponding to an integrated luminosity of 7.2 pb −1. Using a restricted data sample at high transverse jet energy, E T,jet>6 GeV, the effective parton density f γ ,eff (x γ)= q(x γ)+ q ̄ (x γ)+9/4 g(x γ) in the photon in leading order QCD is measured down to x γ = 0.05 from which the gluon density in the photon is derived.

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