Diffractive photoproduction of ρ mesons with large momentum transfer at HERA
Å. AktasVladimir AndreevLebedev Physical Institute, Moscow, Russia 5T. AnthonisUniversity of Antwerp, Antwerp, BelgiumB. AntunovićMax-Planck-Institut für Physik, München, GermanyS. AplinA. AsmoneDipartimento di Fisica Università di Roma Tre and INFN Roma 3, Roma, ItalyA. AstvatsatourovInter-University Institute for High Energies ULB-VUB, Brussels; Universiteit Antwerpen, Antwerpen; BelgiumA. BabaevInstitute for Theoretical and Experimental Physics, Moscow, Russia 11S. BackovićFaculty of Science, University of Montenegro, Podgorica, Serbia and Montenegro 5A. BaghdasaryanYerevan Physics Institute, Yerevan, ArmeniaP. BaranovLebedev Physical Institute, Moscow, Russia 5E. BarreletSorbonne UniversitéW. BartelS. BaudrandInstitut National de Physique Nucléaire et de Physique des ParticulesS. BaumgartnerInstitut für Teilchenphysik, ETH, Zürich, Switzerland 9J. BeckerPhysik-Institut der Universität Zürich, Zürich, Switzerland 9M. BeckinghamDESY, Hamburg, GermanyO. BehnkePhysikalisches Institut, Universität Heidelberg, Heidelberg, Germany 1O. BehrendtInstitut für Physik, Universität Dortmund, Dortmund, Germany 1A. BelousovLebedev Physical Institute, Moscow, Russia 5N. BergerInstitut für Teilchenphysik, ETH, Zürich, Switzerland 9J.C. BizotCentre National de la Recherche ScientifiqueM.-O. BoenigInstitut für Physik, Universität Dortmund, Dortmund, Germany 1V. BoudryLLR, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, FranceJ. BraciníkMax-Planck-Institut für Physik, München, GermanyG. BrandtPhysikalisches Institut, Universität Heidelberg, Heidelberg, Germany 1V. BrissonLAL, Université de Paris-Sud, IN2P3-CNRS, Orsay, FranceD. BrunckoSlovak Academy of Sciences, Bratislava, SlovakiaF.W. BüsserInstitut für Experimentalphysik, Universität Hamburg, Hamburg, Germany 1A. BunyatyanAlikhanyan National Laboratory, Yerevan, ArmeniaG. BuschhornMax Planck Society, Munich, GermanyL. BystritskayaInstitute for Theoretical and Experimental Physics, Moscow, Russia 11A.J. CampbellF. Cassol-BrunnerCPPM, CNRS/IN2P3 -Univ. Mediterranee, Marseille -FranceK. ČernýFaculty of Mathematics and Physics, Charles University, Praha, Czech Republic 8V. ČernýComenius University Bratislava, Bratislava, SlovakiaV. ChekelianMax-Planck-Institut für Physik, München, GermanyJ.G. ContrerasDepartamento de Fisica Aplicada, CINVESTAV, Mérida, Yucatán, Mexico 10J. A. CoughlanRutherford Appleton Laboratory, Chilton, Didcot, UK 2B. E. CoxPhysics Department, University of Manchester, Manchester, UK 2G. CozzikaDSM (Netherlands), Heerlen, NetherlandsJ. CvachCzech Academy of Sciences, Prague, CzechiaJ.B. DaintonDepartment of Physics, University of Liverpool, Liverpool, UK 2W.D. DauInstitut für Experimentelle und Angewandte Physik, Universität Kiel, Kiel, GermanyK. DaumFachbereich C, Universität Wuppertal, Wuppertal, GermanyY. de BoerYerevan Physics Institute, Yerevan, ArmeniaB. DelcourtLAL, Université de Paris-Sud, IN2P3-CNRS, Orsay, FranceM. Del DeganInstitut für Teilchenphysik, ETH, Zürich, Switzerland 9A. De RoeckCERN, Geneva, SwitzerlandE. A. De WolfUniversity of Antwerp, Antwerp, BelgiumC. DiaconuInstitut de Neurobiologie de la MéditerranéeV. DodonovMax Planck Society, Munich, GermanyA. DubakMax-Planck-Institut für Physik, München, GermanyG. EckerlinV. EfremenkoInstitute for Theoretical and Experimental Physics, Moscow, Russia 11S. EgliPaul Scherrer Institut, Villigen, SwitzerlandR. EichlerPaul Scherrer Institut, Villigen, SwitzerlandF. EiselePhysikalisches Institut, Universität Heidelberg, Heidelberg, Germany 1A. EliseevLebedev Physical Institute, Moscow, Russia 5E. ElsenS. EssenovInstitute for Theoretical and Experimental Physics, Moscow, Russia 11A. FalkewiczInstitute for Nuclear Physics, Cracow, Poland 4Peter FaulknerUniversity of BirminghamL. FavartInter-University Institute for High Energies ULB-VUB, and Universiteit Antwerpen, Antwerpen, Belgium 3A. FedotovI. Physikalisches Institut der RWTH, Aachen, GermanyR. FelstDESY, Hamburg, GermanyJ. FeltesseUniversity of Birmingham, Birmingham, United KingdomJ. FerenceiInstitute of Experimental Physics, Slovak Academy of Sciences, Košice, Slovak RepublicL. FinkeInstitut für Experimentalphysik, Universität Hamburg, Hamburg, Germany 1M. FleischerP. FleischmannI. Physikalisches Institut der RWTH, Aachen, GermanyG. FluckeA. FomenkoLebedev Physical Institute, Moscow, Russia 5G. FrankeT. FrissonLLR, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, FranceE. GabathulerDepartment of Physics, University of Liverpool, Liverpool, UK 2E. GaruttiJoint Institute for Nuclear Research, Dubna, RussiaJ. GaylerDESY, Hamburg, GermanyC. GerlichPhysikalisches Institut, Universität Heidelberg, Heidelberg, Germany 1S. GhazaryanYerevan Physics Institute, Yerevan, ArmeniaS. GinzburgskayaSchool of Physics and Astronomy, University of Birmingham, Birmingham, UKA. GlazovI. Physikalisches Institut der RWTH, Aachen, GermanyI. GlushkovDESY, Zeuthen, GermanyL. GoerlichSchool of Physics and Astronomy, University of Birmingham, Birmingham, UKM. GoettlichN. GogitidzeLebedev Physical Institute, Moscow, Russia 5S. GorbounovDESY, Zeuthen, GermanyC. GrabInstitut für Teilchenphysik, ETH, Zürich, Switzerland 9T. GreenshawDepartment of Physics, University of Liverpool, Liverpool, UK 2M. GregoriQueen Mary and Westfield College, London, UK 2B.R. GrellDESY, Hamburg, GermanyG. GrindhammerMax Planck Institute for PhysicsC. B. GwilliamPhysics Department, University of Manchester, Manchester, UK 2D. HaidtDESY, Hamburg, GermanyL. HajdukInstitute for Nuclear Physics, Cracow, Poland 4M. HanssonPhysics Department, University of Lund, Lund, Sweden 7G. HeinzelmannInstitut für Experimentalphysik, Universität Hamburg, Hamburg, Germany 1R. C. W. HendersonDepartment of Physics, University of Lancaster, Lancaster, UK 2H. HenschelI. Physikalisches Institut der RWTH, Aachen, GermanyG. HerreraDepartamento de Fisica, CINVESTAV, Mexico 10
2006en
ABI
Abstract
The diffractive photoproduction of ρ mesons, e p → e ρ Y , with large momentum transfer squared at the proton vertex, |t|, is studied with the H1 detector at HERA using an integrated luminosity of 20.1 pb −1 . The photon–proton centre of mass energy spans the range 75 < W < 95 GeV , the photon virtuality is restricted to Q 2 < 0.01 GeV 2 and the mass M Y of the proton remnant is below 5 GeV. The t dependence of the cross section is measured for the range 1.5 < | t | < 10.0 GeV 2 and is well described by a power law, d σ / d | t | ∝ | t | − n . The spin density matrix elements, which provide information on the helicity structure of the interaction, are extracted using measurements of angular distributions of the ρ decay products. The data indicate a violation of s -channel helicity conservation, with contributions from both single and double helicity-flip being observed. The results are compared to the predictions of perturbative QCD models.