Eur. Phys. J. C (2007) 51: 1-23
https://doi.org/10.1140/epjc/s10052-007-0299-2

Regular Article - Experimental Physics

Measurement of K⁰ _S, Λ and Λ̄ production 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, UK
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, UK
¹⁹ Department of Engineering in Management and Finance, University of Aegean, Mytilene, Greece
²⁰ Institute of Exp. Physics, Hamburg University, Hamburg, Germany
²¹ High Energy Nuclear Physics Group, Imperial College London, London, UK
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, H3A 2T8, Canada
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, UK
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, UK
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, M5S 1A7, Canada
⁴⁷ Physics and Astronomy Department, University College London, London, UK
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, M3J 1P3, Canada
⁵³ also affiliated with University College London, London, UK
⁵⁴ Alexander von Humboldt Fellow, also at University of Hamburg, Hamburg, Germany
⁵⁵ now at Univ. of Wuppertal, Wuppertal, Germany
⁵⁶ now at University of Regina, Regina, Canada
⁵⁷ now at DESY group FEB, Hamburg, Germany
⁵⁸ also at Institut of Theoretical and Experimental Physics, Moscow, Russia
⁵⁹ also at INP, Cracow, Poland
⁶⁰ on leave of absence from FPACS AGH-UST, Cracow, Poland
⁶¹ now at CERN, Geneva, Switzerland
⁶² also at University of Tokyo, Tokyo, Japan
⁶³ Alexander von Humboldt Research Award, Munich, Germany
⁶⁴ now at KEK, Tsukuba, Japan
⁶⁵ now at Nagoya University, Nagoya, Japan
⁶⁶ also at Łódź University, Łódź, Poland
⁶⁷ Łódź University, Łódź, Poland

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

Received: 12 December 2006
Revised: 19 March 2007
Published online: 1 June 2007

Abstract

The production of the neutral strange hadrons K⁰ _S, Λ and Λ̄ has been measured in ep collisions at HERA using the ZEUS detector. Cross sections, baryon-to-meson ratios, relative yields of strange and charged light hadrons, Λ (Λ̄) asymmetry and polarization have been measured in three kinematic regions: Q² > 25 GeV²; 5 < Q² < 25 GeV²; and in photoproduction (Q²≃0). In photoproduction the presence of two hadronic jets, each with at least 5 GeV transverse energy, was required. The measurements agree in general with Monte Carlo models and are consistent with measurements made at e⁺e^- colliders, except for an enhancement of baryon relative to meson production in photoproduction.