Measurement of the longitudinal proton structure function at HERA

Article history: Received 15 April 2009 Received in revised form 16 October 2009 Accepted 19 October 2009 Available online 21 October 2009 Editor: L. Rolandi The reduced cross sections for ep deep inelastic scattering have been measured with the ZEUS detector at HERA at three different centre-of-mass energies, 318, 251 and 225 GeV. From the cross sections, measured double differentially in Bjorken x and the virtuality, Q 2, the proton structure functions F L and F2 have been extracted in the region 5 × 10−4 < x < 0.007 and 20 < Q 2 < 130 GeV2. © 2009 Elsevier B.V. All rights reserved. * Corresponding author. E-mail address: tobias.haas@desy.de (T. Haas). 1 Also affiliated with University College London, United Kingdom. 2 Supported by the US Department of Energy. 3 Supported by the Italian National Institute for Nuclear Physics (INFN). 4 Now at University of Salerno, Italy. 5 Supported by the German Federal Ministry for Education and Research (BMBF), under contract Nos. 05 HZ6PDA, 05 HZ6GUA, 05 HZ6VFA and 05 HZ4KHA. 6 Supported by the Science and Technology Facilities Council, UK. 7 Also working at Max Planck Institute, Munich, Germany. 8 Supported by an FRGS grant from the Malaysian government. 9 Supported by the US National Science Foundation. Any opinion, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. 10 Supported by the Polish State Committee for Scientific Research, project No. DESY/256/2006-154/DES/2006/03. 11 Now at Institute of Aviation, Warsaw, Poland. 12 Supported by the Polish Ministry of Science and Higher Education as a scientific project (2006–2008). 13 Supported by the research grant No. 1 P03B 04529 (2005–2008). 14 This work was supported in part by the Marie Curie Actions Transfer of Knowledge project COCOS (contract MTKD-CT-2004-517186). 15 Now at DESY group FEB, Hamburg, Germany. 16 Also at Moscow State University, Russia. 17 Now at University of Liverpool, UK. 18 On leave of absence at CERN, Geneva, Switzerland. 19 Now at CERN, Geneva, Switzerland. 20 Also at Institut of Theoretical and Experimental Physics, Moscow, Russia. 21 Also at INP, Cracow, Poland. 22 Also at FPACS, AGH-UST, Cracow, Poland. 23 Partially supported by Warsaw University, Poland. 24 Partially supported by Moscow State University, Russia. 25 Also affiliated with DESY, Germany. 26 Also at University of Tokyo, Japan. 27 Now at Kobe University, Japan. 28 Supported by the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT) and its grants for Scientific Research. 29 Supported by DESY, Germany. 30 Supported by the Korean Ministry of Education and Korea Science and Engineering Foundation. 31 Supported by FNRS and its associated funds (IISN and FRIA) and by an InterUniversity Attraction Poles Programme subsidised by the Belgian Federal Science Policy Office. 32 Supported by the Spanish Ministry of Education and Science through funds provided by CICYT. 33 Supported by the Natural Sciences and Engineering Research Council of Canada (NSERC). 34 Partially supported by the German Federal Ministry for Education and Research (BMBF). 35 Deceased. 36 Partially supported by Russian Foundation for Basic Research grant No. 05-0239028-NSFC-a. 37 Supported by RF Presidential grant No. 1456.2008. 2 for the leading scientific schools and by the Russian Ministry of Education and Science through its grant for Scientific Research on High Energy Physics. 38 Supported by the Netherlands Foundation for Research on Matter (FOM). 39 STFC Advanced Fellow. 40 Nee Korcsak-Gorzo. 41 This material was based on work supported by the National Science Foundation, while working at the Foundation. 42 Now at University of Kansas, Lawrence, USA. 43 Also at Max Planck Institute, Munich, Germany, Alexander von Humboldt Research Award. 44 Supported by the Israel Science Foundation.