Eur. Phys. J. C (2007) 51: 289-299
https://doi.org/10.1140/epjc/s10052-007-0310-y

Regular Article - Experimental Physics

Measurement of azimuthal asymmetries in neutral current deep inelastic scattering at HERA

¹ Argonne National Laboratory, Argonne, Illinois, 60439-4815, USA
² Andrews University, Berrien Springs, Michigan, 49104-0380, USA
³ Institut für Physik der Humboldt-Universität zu Berlin, Berlin, Germany
⁴ University and INFN Bologna, Bologna, Italy
⁵ Physikalisches Institut der Universität Bonn, Bonn, Germany
⁶ H.H. Wills Physics Laboratory, University of Bristol, Bristol, U.K.
⁷ Physics Department and INFN, Calabria University, Cosenza, Italy
⁸ Chonnam National University, Kwangju, South Korea
⁹ Jabatan Fizik, Universiti Malaya, 50603, Kuala Lumpur, Malaysia
¹⁰ Nevis Laboratories, Columbia University, Irvington on Hudson, New York, 10027, USA
¹¹ The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Cracow, Poland
¹² Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, Cracow, Poland
¹³ Department of Physics, Jagellonian University, Cracow, Poland
¹⁴ Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany
¹⁵ Deutsches Elektronen-Synchrotron DESY, Zeuthen, Germany
¹⁶ University and INFN, Florence, Italy
¹⁷ Fakultät für Physik der Universität Freiburg i.Br., Freiburg i.Br., Germany
¹⁸ Department of Physics and Astronomy, University of Glasgow, Glasgow, U.K.
¹⁹ Department of Engineering in Management and Finance, Univ. of Aegean, Aegean, Greece
²⁰ Institute of Exp. Physics, Hamburg University, Hamburg, Germany
²¹ High Energy Nuclear Physics Group, Imperial College London, London, U.K.
²² Institute of Particle and Nuclear Studies, KEK, Tsukuba, Japan
²³ Institute of Physics and Technology of Ministry of Education and Science of Kazakhstan, Almaty, Kazakhstan
²⁴ Center for High Energy Physics, Kyungpook National University, Daegu, South Korea
²⁵ Institut de Physique Nucléaire, Université Catholique de Louvain, Louvain-la-Neuve, Belgium
²⁶ Departamento de Física Teórica, Universidad Autónoma de Madrid, Madrid, Spain
²⁷ Department of Physics, McGill University, Montréal, Québec, Canada H3A 2T8,
²⁸ Faculty of General Education, Meiji Gakuin University, Yokohama, Japan
²⁹ Moscow Engineering Physics Institute, Moscow, Russia
³⁰ Institute of Nuclear Physics, Moscow State University, Moscow, Russia
³¹ Max-Planck-Institut für Physik, München, Germany
³² NIKHEF and University of Amsterdam, Amsterdam, Netherlands
³³ Physics Department, Ohio State University, Columbus, Ohio, 43210, USA
³⁴ Department of Physics, University of Oxford, Oxford, U.K.
³⁵ Dipartimento di Fisica dell’ Università and INFN, Padova, Italy
³⁶ Department of Physics, Pennsylvania State University, University Park, Pennsylvania, 16802, USA
³⁷ Polytechnic University, Sagamihara, Japan
³⁸ Dipartimento di Fisica, Università ”La Sapienza” and INFN, Rome, Italy
³⁹ Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, U.K.
⁴⁰ Raymond and Beverly Sackler Faculty of Exact Sciences, School of Physics, Tel-Aviv University, Tel-Aviv, Israel
⁴¹ Department of Physics, Tokyo Institute of Technology, Tokyo, Japan
⁴² Department of Physics, University of Tokyo, Tokyo, Japan
⁴³ Department of Physics, Tokyo Metropolitan University, Tokyo, Japan
⁴⁴ Università di Torino and INFN, Torino, Italy
⁴⁵ Università del Piemonte Orientale, Novara, and INFN, Torino, Italy
⁴⁶ Department of Physics, University of Toronto, Toronto, Ontario, Canada M5S 1A7,
⁴⁷ Physics and Astronomy Department, University College London, London, U.K.
⁴⁸ Institute of Experimental Physics, Warsaw University, Warsaw, Poland
⁴⁹ Institute for Nuclear Studies, Warsaw, Poland
⁵⁰ Department of Particle Physics, Weizmann Institute, Rehovot, Israel
⁵¹ Department of Physics, University of Wisconsin, Madison, Wisconsin, 53706, USA
⁵² Department of Physics, York University, Ontario, Canada M3J 1P3,

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

Received: 18 August 2006
Revised: 13 February 2007
Published online: 8 May 2007

Abstract

The distribution of the azimuthal angle of charged and neutral hadrons relative to the lepton plane has been studied for neutral current deep inelastic ep scattering using an integrated luminosity of 45 pb^-1 taken with the ZEUS detector. The kinematic range is 100<Q²<8000 GeV², 0.2<y<0.8 and 0.01<x<0.1 where Q² is the virtuality of the exchanged boson, y is the inelasticity and x is the Bjorken variable. The measurements were made in the hadronic centre-of-mass system. The analysis exploits the energy-flow method, which allows the measurement to be made over a larger range of pseudorapidity compared to previous results. The dependence of the moments of the azimuthal distributions on the pseudorapidity and minimum transverse energy of the final-state hadrons are presented. Although the predictions from next-to-leading-order QCD describe the data better than do the Monte Carlo models incorporating leading-logarithm parton showers, they still fail to describe the magnitude of the asymmetries. This suggests that higher-order calculations may be necessary to describe these data.