Eur. Phys. J. C (2012) 72: 1910
https://doi.org/10.1140/epjc/s10052-012-1910-8

Regular Article - Experimental Physics

Measurement of the azimuthal correlation between the most forward jet and the scattered positron in deep-inelastic scattering at HERA

¹ I. Physikalisches Institut der RWTH, Aachen, Germany
² Vinca Institute of Nuclear Sciences, University of Belgrade, 1100, Belgrade, Serbia
³ School of Physics and Astronomy, University of Birmingham, Birmingham, UK
⁴ Inter-University Institute for High Energies ULB-VUB, Brussels and Universiteit Antwerpen, Antwerpen, Belgium
⁵ National Institute for Physics and Nuclear Engineering (NIPNE), Bucharest, Romania
⁶ Rutherford Appleton Laboratory, Chilton, Didcot, UK
⁷ Institute for Nuclear Physics, Cracow, Poland
⁸ Institut für Physik, TU Dortmund, Dortmund, Germany
⁹ Joint Institute for Nuclear Research, Dubna, Russia
¹⁰ CEA, DSM/Irfu, CE-Saclay, Gif-sur-Yvette, France
¹¹ DESY, Hamburg, Germany
¹² Institut für Experimentalphysik, Universität Hamburg, Hamburg, Germany
¹³ Max-Planck-Institut für Kernphysik, Heidelberg, Germany
¹⁴ Physikalisches Institut, Universität Heidelberg, Heidelberg, Germany
¹⁵ Kirchhoff-Institut für Physik, Universität Heidelberg, Heidelberg, 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 CPPM, Aix-Marseille Univ, CNRS/IN2P3, 13288, Marseille, France
²² Departamento de Fisica Aplicada, CINVESTAV, Mérida, Yucatán, Mexico
²³ Departamento de Fisica, CINVESTAV IPN, México City, 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 Paris-Sud, CNRS/IN2P3, Orsay, France
²⁸ LLR, Ecole Polytechnique, CNRS/IN2P3, Palaiseau, France
²⁹ LPNHE, Université Pierre et Marie Curie Paris 6, Université Denis Diderot Paris 7, CNRS/IN2P3, Paris, France
³⁰ Faculty of Science, University of Montenegro, Podgorica, 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, Università di Roma Tre and INFN Roma 3, Roma, Italy
³⁴ Institute for Nuclear Research and Nuclear Energy, Sofia, Bulgaria
³⁵ Institute of Physics and Technology of the Mongolian Academy of Sciences, Ulaanbaatar, Mongolia
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 der Universität Zürich, Zürich, Switzerland

^* e-mail: krueger@mail.desy.de

Received: 17 November 2011
Revised: 27 January 2012
Published online: 6 March 2012

Abstract

Deep-inelastic positron-proton scattering events at low photon virtuality, Q ², with a forward jet, produced at small angles with respect to the proton beam, are measured with the H1 detector at HERA. A subsample of events with an additional jet in the central region is also studied. For both samples, differential cross sections and normalised distributions are measured as a function of the azimuthal angle difference, Δϕ, between the forward jet and the scattered positron in bins of the rapidity distance, Y, between them. The data are compared to predictions of Monte Carlo generators based on different evolution approaches as well as to next-to-leading order calculations in order to test the sensitivity to QCD evolution mechanisms.