Eur. Phys. J. C (2006) 48: 715-748
https://doi.org/10.1140/epjc/s10052-006-0035-3

Experimental Physics

Measurement and QCD analysis of the diffractive deep-inelastic scattering cross section at HERA

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, Belgium
⁴ Universiteit Antwerpen, Antwerpen, Belgium
⁵ Rutherford Appleton Laboratory, Chilton, Didcot, UK
⁶ Institute for Nuclear Physics, Cracow, Poland
⁷ Institut für Physik, Universität Dortmund, Dortmund, Germany
⁸ Joint Institute for Nuclear Research, Dubna, Russia
⁹ CEA, DSM/DAPNIA, CE-Saclay, Gif-sur-Yvette, France
¹⁰ DESY, Hamburg, Germany
¹¹ Institut für Experimentalphysik, Universität Hamburg, Hamburg, Germany
¹² Max-Planck-Institut für Kernphysik, Heidelberg, Germany
¹³ Physikalisches Institut, Universität Heidelberg, Heidelberg, Germany
¹⁴ Kirchhoff-Institut für Physik, Universität Heidelberg, Heidelberg, Germany
¹⁵ Institut für Experimentelle und Angewandte Physik, Universität Kiel, Kiel, Germany
¹⁶ Institute of Experimental Physics, Slovak Academy of Sciences, Košice, Slovak Republic
¹⁷ Department of Physics, University of Lancaster, Lancaster, UK
¹⁸ Department of Physics, University of Liverpool, Liverpool, UK
¹⁹ Queen Mary and Westfield College, London, UK
²⁰ Physics Department, University of Lund, Lund, Sweden
²¹ Physics Department, University of Manchester, Manchester, UK
²² CPPM, CNRS/IN2P3 – Univ. Mediterranee, Marseille, France
²³ Departamento de Fisica Aplicada, CINVESTAV, Merida, Yucatan, Mexico
²⁴ Departamento de Fisica, CINVESTAV, Merida, Yucatan, Mexico
²⁵ Institute for Theoretical and Experimental Physics, Moscow, Russia
²⁶ Lebedev Physical Institute, Moscow, Russia
²⁷ Max-Planck-Institut für Physik, München, Germany
²⁸ LAL, Université de Paris-Sud 11, IN2P3-CNRS, Orsay, France
²⁹ LLR, Ecole Polytechnique, IN2P3-CNRS, Palaiseau, France
³⁰ LPNHE, Universités Paris VI and VII, IN2P3-CNRS, Paris, France
³¹ Faculty of Science, University of Montenegro, Podgorica, Serbia and Montenegro
³² Institute of Physics, Academy of Sciences of the Czech Republic, Praha, Czech Republic
³³ Faculty of Mathematics and Physics, Charles University, Praha, Czech Republic
³⁴ Dipartimento di Fisica, Università di Roma Tre and INFN Roma 3, Roma, Italy
³⁵ Institute for Nuclear Research and Nuclear Energy, Sofia, Bulgaria
³⁶ Paul Scherrer Institut, Villigen, Switzerland
³⁷ Fachbereich C, Universität Wuppertal, Wuppertal, Germany
³⁸ Yerevan Physics Institute, Yerevan, Armenia
³⁹ DESY, Zeuthen, Germany
⁴⁰ Institut für Teilchenphysik, ETH, Zürich, Switzerland
⁴¹ Physik-Institut, Universität Zürich, Zürich, Switzerland
⁴² Physics Department, National Technical University, Zografou Campus, 15773, Athens, Greece
⁴³ Rechenzentrum, Universität Wuppertal, Wuppertal, Germany
⁴⁴ University of P.J. Šafárik, Košice, Slovak Republic
⁴⁵ CERN, Geneva, Switzerland
⁴⁶ Max-Planck-Institut für Physik, München, Germany
⁴⁷ Comenius University, Bratislava, Slovak Republic

^* e-mail: eperez@hep.saclay.cea.fr

Received: 2 June 2006
Revised: 21 July 2006
Published online: 24 October 2006

Abstract

A detailed analysis is presented of the diffractive deep-inelastic scattering process ep→eXY, where Y is a proton or a low mass proton excitation carrying a fraction 1-x_IP>0.95 of the incident proton longitudinal momentum and the squared four-momentum transfer at the proton vertex satisfies |t|<1 GeV². Using data taken by the H1 experiment, the cross section is measured for photon virtualities in the range 3.5≤Q²≤1600 GeV², triple differentially in x_IP, Q² and β=x/x_IP, where x is the Bjorken scaling variable. At low x_IP, the data are consistent with a factorisable x_IP dependence, which can be described by the exchange of an effective pomeron trajectory with intercept α_IP(0)=1.118±0.008(exp.)^+0.029 _-0.010(model). Diffractive parton distribution functions and their uncertainties are determined from a next-to-leading order DGLAP QCD analysis of the Q² and β dependences of the cross section. The resulting gluon distribution carries an integrated fraction of around 70% of the exchanged momentum in the Q² range studied. Total and differential cross sections are also measured for the diffractive charged current process e⁺p→ν̄_eXY and are found to be well described by predictions based on the diffractive parton distributions. The ratio of the diffractive to the inclusive neutral current ep cross sections is studied. Over most of the kinematic range, this ratio shows no significant dependence on Q² at fixed x_IP and x or on x at fixed Q² and β.