Eur. Phys. J. C (2006) 47: 597-610
https://doi.org/10.1140/epjc/s2006-02616-5

Experimental Physics

Measurement of charm and beauty dijet cross sections in photoproduction at HERA using the H1 vertex detector

¹ I. Physikalisches Institut, RWTH, Aachen, Germany
² School of Physics and Astronomy, University of Birmingham, Birmingham, UK
³ Inter-University Institute for High Energies ULB-VUB, Brussels, Universiteit Antwerpen, Antwerpen, Belgium
⁴ Rutherford Appleton Laboratory, Chilton, Didcot, UK
⁵ Institute for Nuclear Physics, Cracow, Poland
⁶ Institut für Physik, Universität Dortmund, Dortmund, Germany
⁷ Joint Institute for Nuclear Research, Dubna, Russia
⁸ CEA, DSM/DAPNIA, CE-Saclay, Gif-sur-Yvette, France
⁹ DESY, Hamburg, Germany
¹⁰ Institut für Experimentalphysik, Universität Hamburg, Hamburg, Germany
¹¹ Max-Planck-Institut für Kernphysik, Heidelberg, Germany
¹² Physikalisches Institut, Universität Heidelberg, Heidelberg, Germany
¹³ Kirchhoff-Institut für Physik, Universität Heidelberg, Heidelberg, Germany
¹⁴ Institut für Experimentelle und Angewandte Physik, Universität Kiel, Kiel, Germany
¹⁵ Institute of Experimental Physics, Slovak Academy of Sciences, Kosice, Slovak Republic
¹⁶ Department of Physics, University of Lancaster, Lancaster, UK
¹⁷ Department of Physics, University of Liverpool, Liverpool, UK
¹⁸ Queen Mary and Westfield College, London, UK
¹⁹ Physics Department, University of Lund, Lund, Sweden
²⁰ Physics Department, University of Manchester, Manchester, UK
²¹ CPPM, CNRS/IN2P3, Univ. Mediterranee, Marseille, France
²² Departamento de Fisica Aplicada, CINVESTAV, Merida, Yucatan, Mexico
²³ Departamento de Fisica, CINVESTAV, Merida, Mexico
²⁴ Institute for Theoretical and Experimental Physics, Moscow, Russia
²⁵ Lebedev Physical Institute, Moscow, Russia
²⁶ Max-Planck-Institut für Physik, München, Germany
²⁷ LAL, Université de Paris-Sud 11, IN2P3-CNRS, Orsay, France
²⁸ LLR, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, France
²⁹ LPNHE, Universités Paris VI and VII, IN2P3-CNRS, Paris, France
³⁰ Faculty of Science, University of Montenegro, Podgorica, Serbia and Montenegro
³¹ Institute of Physics, Academy of Sciences of the Czech Republic, Praha, Czech Republic
³² Faculty of Mathematics and Physics, Charles University, Praha, Czech Republic
³³ Dipartimento di Fisica, Universitá di Roma Tre and INFN Roma 3, Roma, Italy
³⁴ Institute for Nuclear Research and Nuclear Energy, Sofia, Bulgaria
³⁵ Paul Scherrer Institut, Villigen, Switzerland
³⁶ Fachbereich C, Universität Wuppertal, Wuppertal, Germany
³⁷ Yerevan Physics Institute, Yerevan, Armenia
³⁸ DESY, Zeuthen, Germany
³⁹ Institut für Teilchenphysik, ETH, Zürich, Switzerland
⁴⁰ Physik-Institut, Universität Zürich, Zürich, Switzerland
⁴¹ Physics Department, National Technical University, Zografou Campus, 15773, Athens, Greece
⁴² Rechenzentrum, Universität Wuppertal, Wuppertal, Germany
⁴³ University of P.J. Safárik, Kosice, Slovak Republic
⁴⁴ CERN, Geneva, Switzerland
⁴⁵ Max-Planck-Institut für Physik, München, Germany
⁴⁶ Comenius University, Bratislava, Slovak Republic

Received: 9 May 2006
Revised: 13 June 2006
Published online: 26 July 2006

Abstract

A measurement of charm and beauty dijet photoproduction cross sections at the ep collider HERA is presented. Events are selected with two or more jets of transverse momentum p_t ^jet1(2)>11(8) GeV in the central range of pseudo-rapidity -0.9<η^jet1(2)<1.3. The fractions of events containing charm and beauty quarks are determined using a method based on the impact parameter, in the transverse plane, of tracks to the primary vertex, as measured by the H1 central vertex detector. Differential dijet cross sections for charm and beauty, and their relative contributions to the flavour inclusive dijet photoproduction cross section, are measured as a function of the transverse momentum of the leading jet, the average pseudo-rapidity of the two jets and the observable x_γ ^obs. Taking into account the theoretical uncertainties, the charm cross sections are consistent with a QCD calculation in next-to-leading order, while the predicted cross sections for beauty production are somewhat lower than the measurement.