Photoproduction with a leading proton at HERA

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

doi:10.1016/s0550-3213(01)00544-2

Abstract

The total cross section for the photoproduction process with a leading proton in the final state has been measured at γp centre-of-mass energies W of 91, 181 and 231 GeV. The measured cross sections apply to the kinematic range with the transverse momentum of the scattered proton restricted to p T ⩽0.2 GeV and 0.68⩽ z⩽0.88, where z= E p ′/ E p is the scattered proton energy normalised to the beam energy. The cross section d σ γp→ Xp′ ( W, z)/d z is observed to be independent of W and z within the measurement errors and amounts to (8.05±0.06 ( stat)±0.89 ( syst)) μb on average. The data are well described by a Triple Regge model in which the process is mediated by a mixture of exchanges with an effective Regge trajectory of intercept α i(0)=0.33±0.04 ( stat)±0.04 ( syst) . The total cross section for the interaction of the photon with this mixture ( γα i → X) can be described by an effective trajectory of intercept α k(0)=0.99±0.01 ( stat)±0.05 ( syst) . Predictions based on previous triple Regge analyses of pp→ pX data assuming vertex factorisation are broadly consistent with the γp data. The measured cross sections are compared with deep inelastic scattering leading proton data in the same region of z and p T for photon virtuality Q 2>2.5 GeV 2 . The ratio of the cross section for leading proton production to the total cross section is found to rise with Q 2.

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