Deep exclusive π+ electroproduction off the proton at CLAS

The European Physical Journal A, Jan 2013

The exclusive electroproduction of π + above the resonance region was studied using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Laboratory by scattering a 6GeV continuous electron beam off a hydrogen target. The large acceptance and good resolution of CLAS, together with the high luminosity, allowed us to measure the cross section for the γ * p → nπ + process in 140 (Q 2, x B , t) bins: 0.16 < x B < 0.58, 1.6 GeV2 < Q 2 < 4.5 GeV2 and 0.1 GeV2 < −t < 5.3 GeV2. For most bins, the statistical accuracy is on the order of a few percent. Differential cross sections are compared to four theoretical models, based either on hadronic or on partonic degrees of freedom. The four models can describe the gross features of the data reasonably well, but differ strongly in their ingredients. In particular, the model based on Generalized Parton Distributions (GPDs) contain the interesting potential to experimentally access transversity GPDs.

A PDF file should load here. If you do not see its contents the file may be temporarily unavailable at the journal website or you do not have a PDF plug-in installed and enabled in your browser.

Alternatively, you can download the file locally and open with any standalone PDF reader:

https://link.springer.com/content/pdf/10.1140%2Fepja%2Fi2013-13016-9.pdf

Deep exclusive π+ electroproduction off the proton at CLAS

0 INFN, Sezione di Genova, 16146 Genova, Italy 1 INFN, Sezione di Ferrara, 44100 Ferrara, Italy 2 INFN, Laboratori Nazionali di Frascati, 00044 Frascati, Italy 3 The George Washington University , Washington, D.C. 20052, USA 4 Idaho State University , Pocatello, Idaho 83209, USA 5 Florida State University , Tallahassee, Florida 32306, USA 6 Universit`a di Genova , 16146 Genova, Italy 7 Fairfield University , Fairfield Connecticut 06824, USA 8 Florida International University , Miami, Florida 33199, USA 9 Institut de Physique Nucleaire ORSAY , Orsay, France 10 INFN, Sezione di Roma Tor Vergata, 00133 Rome, Italy 11 Institute of Theoretical and Experimental Physics , Moscow , 117259, Russia 12 James Madison University , Harrisonburg, Virginia 22807, USA 13 Kyungpook National University , Daegu 702-701, Republic of Korea 14 LPSC, Universite Joseph Fourier , CNRS/IN2P3, INPG, Grenoble, France 15 University of New Hampshire , Durham, New Hampshire 03824-3568, USA 16 Norfolk State University , Norfolk, Virginia 23504, USA 17 California State University , Dominguez Hills, Carson, California 90747, USA 18 Arizona State University , Tempe, Arizona 85287-1504, USA 19 Edinburgh University , Edinburgh EH9 3JZ, UK 20 Argonne National Laboratory , Argonne, Illinois 60439, USA 21 CEA, Centre de Saclay, Irfu/Service de Physique Nucleaire , 91191 Gif-sur-Yvette, France 22 Catholic University of America , Washington, D.C. 20064, USA 23 Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, USA 24 Canisius College , Buffalo, New York 14208, USA 25 University of Connecticut , Storrs, Connecticut 06269, USA 26 Christopher Newport University , Newport News, Virginia 23606, USA 27 Thomas Jefferson National Accelerator Facility , Newport News, Virginia 23606, USA 28 Universidad Tecnica Federico Santa Mara , Casilla 110-V Valparaso, Chile 29 Skobeltsyn Nuclear Physics Institute, Skobeltsyn Nuclear Physics Institute , 119899 Moscow, Russia 30 University of South Carolina , Columbia, South Carolina 29208, USA 31 University of Virginia , Charlottesville, Virginia 22901, USA 32 Ohio University , Athens, Ohio 45701, USA 33 University of Glasgow , Glasgow G12 8QQ, UK 34 Old Dominion University , Norfolk, Virginia 23529, USA 35 Virginia Polytechnic Institute and State University , Blacksburg, Virginia 24061-0435, USA 36 Rensselaer Polytechnic Institute , Troy, New York 12180-3590, USA 37 Yerevan Physics Institute , 375036 Yerevan, Armenia 38 Universit`a di Roma Tor Vergata , 00133 Rome, Italy 39 College of William and Mary , Williamsburg, Virginia 23187-8795, USA 40 University of Richmond , Richmond, Virginia 23173, USA - Received: 11 June 2012 / Revised: 7 December 2012 Published online: 30 January 2013 c The Author(s) 2013. This article is published with open access at Springerlink.com Communicated by Z.-E. Meziani Abstract. The exclusive electroproduction of + above the resonance region was studied using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Laboratory by scattering a 6 GeV continuous electron beam off a hydrogen target. The large acceptance and good resolution of CLAS, together with the high luminosity, allowed us to measure the cross section for the p n+ process in 140 (Q2, xB, t) bins: 0.16 < xB < 0.58, 1.6 GeV2 < Q2 < 4.5 GeV2 and 0.1 GeV2 < t < 5.3 GeV2. For most bins, the statistical accuracy is on the order of a few percent. Differential cross sections are compared to four theoretical models, based either on hadronic or on partonic degrees of freedom. The four models can describe the gross features of the data reasonably well, but differ strongly in their ingredients. In particular, the model based on Generalized Parton Distributions (GPDs) contain the interesting potential to experimentally access transversity GPDs. 1 Introduction incoming photon Q2 = (pe pe)2, which effectively rep resents the transverse size of the probe, or the momenOne of the major challenges in contemporary nuclear tum transfer to the nucleon t = (pN pN )2, which effecphysics is the study of the transition between hadronic tively represents the transverse size of the target. Here, pe and partonic pictures of the strong interaction. At asymp- and pe are the initial and scattered electron four-momenta totically short distances, the strong force is actually weak and pN and pN are the initial and final nucleon fourand the appropriate degrees of freedom are the quarks momenta, respectively. Figure 1 sketches the transition and gluons (partons) whose interaction can be quantified regions that have been experimentally explored until now very precisely by perturbative Quantum Chromodynam- (lightly shaded areas) as a function of these two variables, ics (pQCD). However, at larger distances on the order Q2 and |t|. In this figure, we keep, quite arbitrarily, only of one Fermi, effective theories that take hadrons as ele- the experiments for which |t| > 3 GeV2 in photoproducmentary particles whose interactions are described by the t (...truncated)


This is a preview of a remote PDF: https://link.springer.com/content/pdf/10.1140%2Fepja%2Fi2013-13016-9.pdf

K. Park, M. Guidal, R. W. Gothe, J. M. Laget, M. Garçon. Deep exclusive π+ electroproduction off the proton at CLAS, The European Physical Journal A, 2013, pp. 16, Volume 49, Issue 1, DOI: 10.1140/epja/i2013-13016-9