Measurement of the inclusive ep scattering cross section at low Q 2 and x at HERA

F. D. Aaron; C. Alexa; V. Andreev; B. Antunovic; S. Aplin; A. Asmone; A. Astvatsatourov; S. Backovic; A. Baghdasaryan; E. Barrelet; W. Bartel; K. Begzsuren; O. Behnke; O. Behrendt; A. Belousov; J. C. Bizot; V. Boudry; I. Bozovic-Jelisavcic; J. Bracinik; G. Brandt; M. Brinkmann; V. Brisson; D. Bruncko; A. Bunyatyan; G. Buschhorn; L. Bystritskaya; A. J. Campbell; K. B. Cantun Avila; F. Cassol-Brunner; K. Cerny; V. Cerny; V. Chekelian; A. Cholewa; J. G. Contreras; J. A. Coughlan; G. Cozzika; J. Cvach; J. B. Dainton; K. Daum; M. Deák; Y. de Boer; B. Delcourt; M. Del Degan; J. Delvax; A. De Roeck; E. A. De Wolf; C. Diaconu; V. Dodonov; A. Dossanov; A. Dubak; G. Eckerlin; D. Eckstein; V. Efremenko; S. Egli; A. Eliseev; E. Elsen; A. Falkiewicz; P. J. W. Faulkner; L. Favart; A. Fedotov; R. Felst; J. Feltesse; J. Ferencei; D.-J. Fischer; M. Fleischer; A. Fomenko; E. Gabathuler; J. Gayler; S. Ghazaryan; A. Glazov; I. Glushkov; L. Goerlich; N. Gogitidze; M. Gouzevitch; C. Grab; T. Greenshaw; B. R. Grell; G. Grindhammer; S. Habib; D. Haidt; M. Hansson; C. Helebrant; R. C. W. Henderson; E. Hennekemper; H. Henschel; M. Herbst; G. Herrera; M. Hildebrandt; K. H. Hiller; D. Hoffmann; R. Horisberger; T. Hreus; M. Jacquet; M. E. Janssen; X. Janssen; V. Jemanov; L. Jönsson; A. W. Jung; H. Jung; M. Kapichine; J. Katzy; I. R. Kenyon; C. Kiesling; M. Klein; C. Kleinwort; T. Kluge; A. Knutsson; R. Kogler; V. Korbel; P. Kostka; M. Kraemer; K. Krastev; J. Kretzschmar; A. Kropivnitskaya; K. Krüger; K. Kutak; M. P. J. Landon; W. Lange; G. Laštovička-Medin; P. Laycock; T. Laštovička; A. Lebedev; G. Leibenguth; V. Lendermann; S. Levonian; G. Li; K. Lipka; A. Liptaj; B. List; J. List; E. Lobodzinska; N. Loktionova; R. Lopez-Fernandez; V. Lubimov; L. Lytkin; A. Makankine; E. Malinovski; P. Marage; Ll. Marti; H.-U. Martyn; S. J. Maxfield; A. Mehta; K. Meier; A. B. Meyer; H. Meyer; H. Meyer; J. Meyer; V. Michels; S. Mikocki; I. Milcewicz-Mika; F. Moreau; A. Morozov; J. V. Morris; M. U. Mozer; M. Mudrinic; K. Müller; P. Murín; B. Naroska; Th. Naumann; P. R. Newman; C. Niebuhr; A. Nikiforov; G. Nowak; K. Nowak; M. Nozicka; B. Olivier; J. E. Olsson; S. Osman; D. Ozerov; V. Palichik; I. Panagoulias; M. Pandurovic; Th. Papadopoulou; C. Pascaud; G. D. Patel; O. Pejchal; E. Perez; A. Petrukhin; I. Picuric; S. Piec; D. Pitzl; R. Plačakytė; R. Polifka; B. Povh; T. Preda; V. Radescu; A. J. Rahmat; N. Raicevic; A. Raspiareza; T. Ravdandorj; P. Reimer; E. Rizvi; P. Robmann; B. Roland; R. Roosen; A. Rostovtsev; M. Rotaru; J. E. Ruiz Tabasco; Z. Rurikova; S. Rusakov; D. Šálek; D. P. C. Sankey; M. Sauter; E. Sauvan; S. Schmitt; C. Schmitz; L. Schoeffel; A. Schöning; H.-C. Schultz-Coulon; F. Sefkow; R. N. Shaw-West; I. Sheviakov; L. N. Shtarkov; S. Shushkevich; T. Sloan; I. Smiljanic; Y. Soloviev; P. Sopicki; D. South; V. Spaskov; A. Specka; Z. Staykova; M. Steder; B. Stella; G. Stoicea; U. Straumann; D. Sunar; T. Sykora; V. Tchoulakov; G. Thompson; P. D. Thompson; T. Toll; F. Tomasz; T. H. Tran; D. Traynor; T. N. Trinh; P. Truöl; I. Tsakov; B. Tseepeldorj; J. Turnau; K. Urban; A. Valkárová; C. Vallée; P. Van Mechelen; A. Vargas Trevino; Y. Vazdik; S. Vinokurova; V. Volchinski; M. von den Driesch; D. Wegener; Ch. Wissing; E. Wünsch; J. Žáček; J. Zálešák; Z. Zhang; A. Zhokin; T. Zimmermann; H. Zohrabyan; F. Zomer

doi:10.1140/epjc/s10052-009-1128-6

2023 Impact factor 4.2

Particles and Fields

Open Access

Eur. Phys. J. C (2009) 63: 625-678
https://doi.org/10.1140/epjc/s10052-009-1128-6

Regular Article - Experimental Physics

Measurement of the inclusive ep scattering cross section at low Q ² and x at HERA

The H1 Collaboration
F. D. Aaron⁶, C. Alexa⁶, V. Andreev²⁶, B. Antunovic¹², S. Aplin¹², A. Asmone³⁴, A. Astvatsatourov⁴^,5, S. Backovic³¹, A. Baghdasaryan³⁹, E. Barrelet³⁰, W. Bartel¹², K. Begzsuren³⁶, O. Behnke¹⁵, O. Behrendt⁹, A. Belousov²⁶, J. C. Bizot²⁸, V. Boudry²⁹, I. Bozovic-Jelisavcic², J. Bracinik³, G. Brandt¹², M. Brinkmann¹², V. Brisson²⁸, D. Bruncko¹⁷, A. Bunyatyan¹⁴^,39, G. Buschhorn²⁷, L. Bystritskaya²⁵, A. J. Campbell¹², K. B. Cantun Avila²³, F. Cassol-Brunner²², K. Cerny³³, V. Cerny¹⁷, V. Chekelian²⁷, A. Cholewa¹², J. G. Contreras²³, J. A. Coughlan⁷, G. Cozzika¹¹, J. Cvach³², J. B. Dainton¹⁹, K. Daum³⁸, M. Deák¹², Y. de Boer¹², B. Delcourt²⁸, M. Del Degan⁴¹, J. Delvax⁴^,5, A. De Roeck¹², E. A. De Wolf⁴^,5, C. Diaconu²², V. Dodonov¹⁴, A. Dossanov²⁷, A. Dubak³¹, G. Eckerlin¹², D. Eckstein⁴⁰, V. Efremenko²⁵, S. Egli³⁷, A. Eliseev²⁶, E. Elsen¹², A. Falkiewicz⁸, P. J. W. Faulkner³, L. Favart⁴^,5, A. Fedotov²⁵, R. Felst¹², J. Feltesse¹¹, J. Ferencei¹⁷, D.-J. Fischer¹², M. Fleischer¹², A. Fomenko²⁶, E. Gabathuler¹⁹, J. Gayler¹², S. Ghazaryan³⁹, A. Glazov¹², I. Glushkov⁴⁰, L. Goerlich⁸, N. Gogitidze²⁶, M. Gouzevitch²⁹, C. Grab⁴¹, T. Greenshaw¹⁹, B. R. Grell¹², G. Grindhammer²⁷, S. Habib¹³, D. Haidt¹², M. Hansson²¹, C. Helebrant¹², R. C. W. Henderson¹⁸, E. Hennekemper¹⁶, H. Henschel⁴⁰, M. Herbst¹⁶, G. Herrera²⁴, M. Hildebrandt³⁷, K. H. Hiller⁴⁰, D. Hoffmann²², R. Horisberger³⁷, T. Hreus⁴^,5, M. Jacquet²⁸, M. E. Janssen¹², X. Janssen⁴^,5, V. Jemanov¹³, L. Jönsson²¹, A. W. Jung¹⁶, H. Jung¹², M. Kapichine¹⁰, J. Katzy¹², I. R. Kenyon³, C. Kiesling²⁷, M. Klein¹⁹, C. Kleinwort¹², T. Kluge¹⁹, A. Knutsson¹², R. Kogler²⁷, V. Korbel¹², P. Kostka⁴⁰, M. Kraemer¹², K. Krastev¹², J. Kretzschmar¹⁹, A. Kropivnitskaya²⁵, K. Krüger¹⁶, K. Kutak¹², M. P. J. Landon²⁰, W. Lange⁴⁰, G. Laštovička-Medin³¹, P. Laycock¹⁹, T. Laštovička⁴⁰, A. Lebedev²⁶, G. Leibenguth⁴¹, V. Lendermann¹⁶, S. Levonian¹², G. Li²⁸, K. Lipka¹³, A. Liptaj²⁷, B. List¹³, J. List¹², E. Lobodzinska⁴⁰, N. Loktionova²⁶, R. Lopez-Fernandez²⁴, V. Lubimov²⁵, L. Lytkin¹⁴, A. Makankine¹⁰, E. Malinovski²⁶, P. Marage⁴^,5, Ll. Marti¹², H.-U. Martyn¹, S. J. Maxfield¹⁹, A. Mehta¹⁹, K. Meier¹⁶, A. B. Meyer¹², H. Meyer¹², H. Meyer³⁸, J. Meyer¹², V. Michels¹², S. Mikocki⁸, I. Milcewicz-Mika⁸, F. Moreau²⁹, A. Morozov¹⁰, J. V. Morris⁷, M. U. Mozer⁴^,5, M. Mudrinic², K. Müller⁴², P. Murín¹⁷, B. Naroska¹³, Th. Naumann⁴⁰, P. R. Newman³, C. Niebuhr¹², A. Nikiforov¹², G. Nowak⁸, K. Nowak⁴², M. Nozicka¹², B. Olivier²⁷, J. E. Olsson¹², S. Osman²¹, D. Ozerov²⁵, V. Palichik¹⁰, I. Panagoulias¹², M. Pandurovic², Th. Papadopoulou¹², C. Pascaud²⁸, G. D. Patel¹⁹, O. Pejchal³³, E. Perez¹¹, A. Petrukhin²⁵, I. Picuric³¹, S. Piec⁴⁰, D. Pitzl¹², R. Plačakytė¹², R. Polifka³³, B. Povh¹⁴, T. Preda⁶, V. Radescu¹², A. J. Rahmat¹⁹, N. Raicevic³¹, A. Raspiareza²⁷, T. Ravdandorj³⁶, P. Reimer³², E. Rizvi²⁰, P. Robmann⁴², B. Roland⁴^,5, R. Roosen⁴^,5, A. Rostovtsev²⁵, M. Rotaru⁶, J. E. Ruiz Tabasco²³, Z. Rurikova¹², S. Rusakov²⁶, D. Šálek³³, D. P. C. Sankey⁷, M. Sauter⁴¹, E. Sauvan²², S. Schmitt¹²^*, C. Schmitz⁴², L. Schoeffel¹¹, A. Schöning¹²^,42, H.-C. Schultz-Coulon¹⁶, F. Sefkow¹², R. N. Shaw-West³, I. Sheviakov²⁶, L. N. Shtarkov²⁶, S. Shushkevich²⁷, T. Sloan¹⁸, I. Smiljanic², Y. Soloviev²⁶, P. Sopicki⁸, D. South⁹, V. Spaskov¹⁰, A. Specka²⁹, Z. Staykova¹², M. Steder¹², B. Stella³⁴, G. Stoicea⁶, U. Straumann⁴², D. Sunar⁴^,5, T. Sykora⁴^,5, V. Tchoulakov¹⁰, G. Thompson²⁰, P. D. Thompson³, T. Toll¹², F. Tomasz¹⁷, T. H. Tran²⁸, D. Traynor²⁰, T. N. Trinh²², P. Truöl⁴², I. Tsakov³⁵, B. Tseepeldorj³⁶, J. Turnau⁸, K. Urban¹⁶, A. Valkárová³³, C. Vallée²², P. Van Mechelen⁴^,5, A. Vargas Trevino¹², Y. Vazdik²⁶, S. Vinokurova¹², V. Volchinski³⁹, M. von den Driesch¹², D. Wegener⁹, Ch. Wissing¹², E. Wünsch¹², J. Žáček³³, J. Zálešák³², Z. Zhang²⁸, A. Zhokin²⁵, T. Zimmermann⁴¹, H. Zohrabyan³⁹ and F. Zomer²⁸

¹ I. Physikalisches Institut der RWTH, Aachen, Germany
² Vinca Institute of Nuclear Sciences, Belgrade, Serbia
³ School of Physics and Astronomy, University of Birmingham, Birmingham, UK
⁴ Inter-University Institute for High Energies ULB-VUB, Brussels, Belgium
⁵ Universiteit Antwerpen, Antwerpen, Belgium
⁶ National Institute for Physics and Nuclear Engineering (NIPNE), Bucharest, Romania
⁷ Rutherford Appleton Laboratory, Chilton, Didcot, UK
⁸ Institute for Nuclear Physics, Cracow, Poland
⁹ Institut für Physik, TU Dortmund, Dortmund, Germany
¹⁰ Joint Institute for Nuclear Research, Dubna, Russia
¹¹ CEA, DSM/Irfu, CE-Saclay, Gif-sur-Yvette, France
¹² DESY, Hamburg, Germany
¹³ Institut für Experimentalphysik, Universität Hamburg, Hamburg, Germany
¹⁴ Max-Planck-Institut für Kernphysik, Heidelberg, Germany
¹⁵ Physikalisches Institut, Universität Heidelberg, Heidelberg, Germany
¹⁶ Kirchhoff-Institut für Physik, Universität Heidelberg, Heidelberg, Germany
¹⁷ Institute of Experimental Physics, Slovak Academy of Sciences, Košice, Slovak Republic
¹⁸ Department of Physics, University of Lancaster, Lancaster, UK
¹⁹ Department of Physics, University of Liverpool, Liverpool, UK
²⁰ Queen Mary and Westfield College, London, UK
²¹ Physics Department, University of Lund, Lund, Sweden
²² CPPM, CNRS/IN2P3, Univ. Mediterranee, Marseille, France
²³ Departamento de Fisica Aplicada, CINVESTAV, Mérida, Yucatán, México
²⁴ Departamento de Fisica, CINVESTAV, Mérida, México
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, Univ Paris-Sud, CNRS/IN2P3, 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, 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 Institute of Physics and Technology of the Mongolian Academy of Sciences, Ulaanbaatar, Mongolia
³⁷ Paul Scherrer Institut, Villigen, Switzerland
³⁸ Fachbereich C, Universität Wuppertal, Wuppertal, Germany
³⁹ Yerevan Physics Institute, Yerevan, Armenia
⁴⁰ DESY, Zeuthen, Germany
⁴¹ Institut für Teilchenphysik, ETH, Zürich, Switzerland
⁴² Physik-Institut der Universität Zürich, Zürich, Switzerland

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

Received: 7 April 2009
Revised: 20 July 2009
Published online: 12 September 2009

Abstract

A measurement of the inclusive ep scattering cross section is presented in the region of low momentum transfers, 0.2 GeV² ≤Q ²≤12 GeV², and low Bjorken x, 5⋅10⁻⁶≤x≤0.02. The result is based on two data sets collected in dedicated runs by the H1 Collaboration at HERA at beam energies of 27.6 GeV and 920 GeV for positrons and protons, respectively. A combination with data previously published by H1 leads to a cross section measurement of a few percent accuracy. A kinematic reconstruction method exploiting radiative ep events extends the measurement to lower Q ² and larger x. The data are compared with theoretical models which apply to the transition region from photoproduction to deep inelastic scattering.