Eur. Phys. J. C (2006) 48: 749-766
https://doi.org/10.1140/epjc/s10052-006-0046-0

Experimental Physics

Diffractive deep-inelastic scattering with a leading proton 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

The cross section for the diffractive deep-inelastic scattering process ep→eXp is measured, with the leading final state proton detected in the H1 Forward Proton Spectrometer. The data analysed cover the range x_IP<0.1 in fractional proton longitudinal momentum loss, 0.08<|t|<0.5 GeV^-2 in squared four-momentum transfer at the proton vertex, 2<Q²<50 GeV² in photon virtuality and 0.004<β=x/x_IP<1, where x is the Bjorken scaling variable. For , the differential cross section has a dependence of approximately dσ/dt∝e^6t, independently of x_IP, β and Q² within uncertainties. The cross section is also measured triple differentially in x_IP, β and Q². The x_IP dependence is interpreted in terms of an effective pomeron trajectory with intercept α_IP(0)=1.114±0.018(stat.)±0.012(syst.)^+0.040 _-0.020(model) and a sub-leading exchange. The data are in good agreement with an H1 measurement for which the event selection is based on a large gap in the rapidity distribution of the final state hadrons, after accounting for proton dissociation contributions in the latter. Within uncertainties, the dependence of the cross section on x and Q² can thus be factorised from the dependences on all studied variables which characterise the proton vertex, for both the pomeron and the sub-leading exchange.