https://doi.org/10.1140/epjc/s10052-011-1836-6
Regular Article - Experimental Physics
Measurement of the diffractive longitudinal structure function 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 Université, CNRS/IN2P3, 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: daum@mail.desy.de
Received:
18
July
2011
Revised:
26
October
2011
Published online:
22
December
2011
First measurements are presented of the diffractive cross section σ ep→eXY at centre-of-mass energies of 225 and , together with a precise new measurement at of , using data taken with the H1 detector in the years 2006 and 2007. Together with previous H1 data at of , the measurements are used to extract the diffractive longitudinal structure function in the range of photon virtualities and fractional proton longitudinal momentum loss 5×10−4≤x ℙ≤3×10−3. The measured is compared with leading twist predictions based on diffractive parton densities extracted in NLO QCD fits to previous measurements of diffractive Deep-Inelastic Scattering and with a model which additionally includes a higher twist contribution derived from a colour dipole approach. The ratio of the diffractive cross section induced by longitudinally polarised photons to that for transversely polarised photons is extracted and compared with the analogous quantity for inclusive Deep-Inelastic Scattering.
© Springer-Verlag / Società Italiana di Fisica, 2011