Eur. Phys. J. A (2020) 56: 126
https://doi.org/10.1140/epja/s10050-020-00135-7

Regular Article - Experimental Physics

Dispersive corrections in elastic electron-nucleus scattering: an investigation in the intermediate energy regime and their impact on the nuclear matter

¹ National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI, 48824, USA
² Hampton University, Hampton, VA, 23668, USA
³ Kent State University, Kent, OH, 44242, USA
⁴ Florida State University, Tallahassee, FL, 32306, USA
⁵ Saint Mary’s University, Halifax, NS, B3H 3C3, Canada
⁶ Dalhousie University, Halifax, NS, B3H 3J5, Canada
⁷ Weizmann Institute of Science, Rehovot, 76100, Israel
⁸ Seoul National University, Seoul, 151-747, South Korea
⁹ Rutgers, The State University of New Jersey, Piscataway, NJ, 08855, USA
¹⁰ Thomas Jefferson National Accelerator Facility, Newport News, VA, 23606, USA
¹¹ Tel Aviv University, Tel Aviv, 69978, Israel
¹² University of South Carolina, Columbia, SC, 29208, USA
¹³ University of Kentucky, Lexington, KY, 40506, USA
¹⁴ Temple University, Philadelphia, PA, 19122, USA
¹⁵ Argonne National Laboratory, Argonne, IL, 60439, USA
¹⁶ Institut für Kernphysik, Johannes Gutenberg-Universität, 55099, Mainz, Germany
¹⁷ NRCN, P.O. Box 9001, Beer-Sheva, 84190, Israel
¹⁸ Duquesne University, Pittsburgh, PA, 15282, USA
¹⁹ George Washington University, Washington D.C., 20052, USA
²⁰ Florida International University, Miami, FL, 33199, USA
²¹ Christopher Newport University, Newport News, VA, 23606, USA
²² University of New Hampshire, Durham, NH, 03824, USA
²³ University of Virginia, Charlottesville, VA, 22094, USA
²⁴ Laboratorio di Fisica, INFN, Sezione Sanitá, Istituto Superiore di Sanitá, 00161, Rome, Italy
²⁵ Longwood University, Farmville, VA, 23909, USA
²⁶ Old Dominion University, Norfolk, VA, 23508, USA
²⁷ Université Blaise Pascal/CNRS-IN2P3, 63177, Aubière, France
²⁸ Cairo University, Giza, 12613, Egypt
²⁹ University of Western Ontario, London, ON, N6A 3K7, Canada
³⁰ College of William and Mary, Williamsburg, VA, 23187, USA
³¹ Saint Norbert College, Greenbay, WI, 54115, USA
³² Jožef Stefan Institute, 1000, Ljubljana, Slovenia
³³ NSC Kharkov Institute of Physics and Technology, Kharkov, 61108, Ukraine
³⁴ Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
³⁵ Norfolk State University, Norfolk, VA, 23504, USA
³⁶ Duke University, Durham, NC, 27708, USA
³⁷ Ohio University, Athens, OH, 45701, USA
³⁸ Yerevan Physics Institute, 375036, Yerevan, Armenia
³⁹ Department of Physics, University of Ljubljana, 1000, Ljubljana, Slovenia

^* e-mail: gueye@nscl.msu.edu

Received: 24 November 2019
Accepted: 23 March 2020
Published online: 18 May 2020

Abstract

Measurements of elastic electron scattering data within the past decade have highlighted two-photon exchange contributions as a necessary ingredient in theoretical calculations to precisely evaluate hydrogen elastic scattering cross sections. This correction can modify the cross section at the few percent level. In contrast, dispersive effects can cause significantly larger changes from the Born approximation. The purpose of this experiment is to extract the carbon-12 elastic cross section around the first diffraction minimum, where the Born term contributions to the cross section are small to maximize the sensitivity to dispersive effects. The analysis uses the LEDEX data from the high resolution Jefferson Lab Hall A spectrometers to extract the cross sections near the first diffraction minimum of C at beam energies of 362 MeV and 685 MeV. The results are in very good agreement with previous world data, although with less precision. The average deviation from a static nuclear charge distribution expected from linear and quadratic fits indicate a 30.6% contribution of dispersive effects to the cross section at 1 GeV. The magnitude of the dispersive effects near the first diffraction minimum of C has been confirmed to be large with a strong energy dependence and could account for a large fraction of the magnitude for the observed quenching of the longitudinal nuclear response. These effects could also be important for nuclei radii extracted from parity-violating asymmetries measured near a diffraction minimum.