Eur. Phys. J. A (2009) 39: 5-31
https://doi.org/10.1140/epja/i2008-10683-5

Regular Article - Experimental Physics

Exclusive ρ⁰ electroproduction on the proton at CLAS

¹ Institut de Physique Nucleaire ORSAY, Orsay, France
² CEA-Saclay, Service de Physique Nucléaire, 91191, Gif-sur-Yvette, France
³ Thomas Jefferson National Accelerator Facility, 23606, Newport News, VA, USA
⁴ Rensselaer Polytechnic Institute, 12180-3590, Troy, NY, USA
⁵ Old Dominion University, 23529, Norfolk, VA, USA
⁶ INFN, Laboratori Nazionali di Frascati, 00044, Frascati, Italy
⁷ INFN, Sezione di Genova, 16146, Genova, Italy
⁸ Yerevan Physics Institute, 375036, Yerevan, Armenia
⁹ College of William and Mary, 23187-8795, Williamsburg, VA, USA
¹⁰ Arizona State University, 85287-1504, Tempe, AZ, USA
¹¹ University of South Carolina, 29208, Columbia, SC, USA
¹² Florida State University, 32306, Tallahassee, FL, USA
¹³ Institute of Theoretical and Experimental Physics, 117259, Moscow, Russia
¹⁴ Ohio University, 45701, Athens, OH, USA
¹⁵ Carnegie Mellon University, 15213, Pittsburgh, PA, USA
¹⁶ The George Washington University, 20052, Washington, DC, USA
¹⁷ Fairfield University, 06824, Fairfield, CT, USA
¹⁸ Rice University, 77005-1892, Houston, TX, USA
¹⁹ Edinburgh University, EH9 3JZ, Edinburgh, UK
²⁰ Universidad Técnica Federico Santa María, 110-V, Casilla, Valparaíso, Chile
²¹ University of New Hampshire, 03824-3568, Durham, NH, USA
²² Catholic University of America, 20064, Washington, DC, USA
²³ Idaho State University, 83209, Pocatello, ID, USA
²⁴ University of Virginia, 22901, Charlottesville, VA, USA
²⁵ University of Pittsburgh, 15260, Pittsburgh, PA, USA
²⁶ Florida International University, 33199, Miami, FL, USA
²⁷ Christopher Newport University, 23606, Newport News, VA, USA
²⁸ Argonne National Laboratory, 60439, Argonne, IL, USA
²⁹ Moscow State University, General Nuclear Physics Institute, 119899, Moscow, Russia
³⁰ University of Richmond, 23173, Richmond, VA, USA
³¹ James Madison University, 22807, Harrisonburg, VA, USA
³² University of California at Los Angeles, 90095-1547, Los Angeles, CA, USA
³³ University of Connecticut, 06269, Storrs, CT, USA
³⁴ University of Glasgow, G12 8QQ, Glasgow, UK
³⁵ Virginia Polytechnic Institute and State University, 24061-0435, Blacksburg, VA, USA
³⁶ Norfolk State University, 23504, Norfolk, VA, USA
³⁷ Kyungpook National University, 702-701, Daegu, Republic of Korea
³⁸ University of Massachusetts, 01003, Amherst, MA, USA
³⁹ California State University, 90747, Dominguez Hills, Carson, CA, USA
⁴⁰ Massachusetts Institute of Technology, 02139-4307, Cambridge, MA, USA
⁴¹ Union College, 12308, Schenectady, NY, USA

^* e-mail: guidal@ipno.in2p3.fr

Received: 28 July 2008
Published online: 5 December 2008

Abstract

The ep → e ^′ pρ⁰ reaction has been measured using the 5.754GeV electron beam of Jefferson Lab and the CLAS detector. This represents the largest ever set of data for this reaction in the valence region. Integrated and differential cross-sections are presented. The W , Q² and t dependences of the cross-section are compared to theoretical calculations based on the t -channel meson-exchange Regge theory, on the one hand, and on quark handbag diagrams related to Generalized Parton Distributions (GPDs) on the other hand. The Regge approach can describe at the 30% level most of the features of the present data while the two GPD calculations that are presented in this article which succesfully reproduce the high-energy data strongly underestimate the present data. The question is then raised whether this discrepancy originates from an incomplete or inexact way of modelling the GPDs or the associated hard scattering amplitude or whether the GPD formalism is simply inapplicable in this region due to higher-twists contributions, incalculable at present.