Eur. Phys. J. A (2021) 57: 261
https://doi.org/10.1140/epja/s10050-021-00564-y

Regular Article - Experimental Physics

An experimental program with high duty-cycle polarized and unpolarized positron beams at Jefferson Lab

¹ Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405, Orsay, France
² Thomas Jefferson National Accelerator Facility, 23606, Newport News, VA, USA
³ INFN, Sezione di Genova, 16146, Genova, Italy
⁴ The George Washington University, 20052, Washington, DC, USA
⁵ Ohio University, 45701, Athens, OH, USA
⁶ Fermi National Accelerator Laboratory, 60510, Batavia, IL, USA
⁷ Lamar University, 77710, Beaumont, TX, USA
⁸ Lawrence Berkeley National Laboratory, 94720, Berkeley, CA, USA
⁹ University of Colorado, 80309, Boulder, CO, USA
¹⁰ Università degli Studi di Brescia, 25121, Brescia, Italy
¹¹ Canisius College, 14208, Buffalo, NY, USA
¹² Massachusetts Institute of Technology, 02139, Cambridge, MA, USA
¹³ INFN, Sezione di Catania, 95123, Catania, Italy
¹⁴ University of Virginia, 22904, Charlottesville, VA, USA
¹⁵ Kavli Institute for Cosmological Physics, University of Chicago, 60637, Chicago, IL, USA
¹⁶ Università degli Studi dell’Insubria, 22100, Como, Italy
¹⁷ The University of North Georgia, 30597, Dahlonega, GA, USA
¹⁸ Energy Systems, 95616, Davis, CA, USA
¹⁹ Duke University, 27708, Durham, NC, USA
²⁰ Triangle Universities Nuclear Laboratory, 27708, Durham, NC, USA
²¹ University of New Hampshire, 03824, Durham, NH, USA
²² Facility for Rare Isotope Beams, Michigan State University, 48824, East Lansing, MI, USA
²³ INFN, Sezione di Ferrara, 44122, Ferrara, Italy
²⁴ Università degli Studi di Ferrara, 44121, Ferrara, Italy
²⁵ INFN, Laboratori Nazionali di Frascati, 00044, Frascati, Italy
²⁶ Università degli Studi di Genova, 16146, Genova, Italy
²⁷ Universität Gießen, 35390, Gießen, Germany
²⁸ IRFU, CEA, Université Paris-Saclay, 91191, Gif-sur-Yvette, France
²⁹ University of Glasgow, G12 8QQ, Glasgow, UK
³⁰ North Carolina A&T State University, 27411, Greensboro, NC, USA
³¹ Hampton University, 23668, Hampton, VA, USA
³² James Madison University, 22807, Harrisonburg, VA, USA
³³ Los Alamos National Laboratory, 87545, Los Alamos, NM, USA
³⁴ Faculty of Mathematics and Physics, University of Ljubljana, 1000, Ljubljana, Slovenia
³⁵ Akdeniz Üniversitesi, 07070, Konyaalti/Antalya, Turkey
³⁶ PRISMA+ Cluster of Excellence, Institut für Kernphysik, Johannes Gutenberg Universität, 55099, Mainz, Germany
³⁷ PRISMA+ Cluster of Excellence, Institut für Physik, Johannes Gutenberg Universität, 55099, Mainz, Germany
³⁸ Florida International University, 33199, Miami, FL, USA
³⁹ Institute for Nuclear Problems, Belarusian State University, 220040, Minsk, Belarus
⁴⁰ Mississippi State University, Mississippi State, 39762, Mississippi, MS, USA
⁴¹ Faculté des Sciences de Monastir, Monastir, Tunisia
⁴² Old Dominion University, 23529, Norfolk, VA, USA
⁴³ Università degli Studi di Pavia, 27100, Pavia, Italy
⁴⁴ INFN, Sezione di Pavia, 27100, Pavia, Italy
⁴⁵ University of West Florida, 32514, Pensacola, FL, USA
⁴⁶ INFN, Sezione di Perugia, 06123, Perugia, Italy
⁴⁷ Università degli studi di Perugia, 06123, Perugia, Italy
⁴⁸ Physics Department, Temple University, 19122-180, Philadelphia, PA, USA
⁴⁹ Idaho State University, 83209, Pocatello, ID, USA
⁵⁰ INFN, Sezione di Roma, 00185, Rome, Italy
⁵¹ INFN, Sezione di Roma Tor Vergata, 00133, Rome, Italy
⁵² Sapienza Università di Roma, 00185, Rome, Italy
⁵³ Università degli Studi di Roma Tor Vergata, 00133, Rome, Italy
⁵⁴ University of Sofia, Faculty of Physics, 1164, Sofia, Bulgaria
⁵⁵ Center for Frontiers in Nuclear Science, Stony Brook University, 11794, Stony Brook, NY, USA
⁵⁶ Stony Brook University, 11794, Stony Brook, NY, USA
⁵⁷ University of Connecticut, 06269-3046, Storrs, CT, USA
⁵⁸ Syracuse University, 13244, Syracuse, NY, USA
⁵⁹ Florida State University, 32306, Tallahassee, FL, USA
⁶⁰ INFN, Sezione di Torino, 10125, Torino, Italy
⁶¹ RIKEN BNL Research Center, 11973, Upton, NY, USA
⁶² National Centre for Nuclear Research (NCBJ), 02-093, Warsaw, Poland
⁶³ The Catholic University of America, 20064, Washington, DC, USA
⁶⁴ University of Manitoba, R3T 2N2, Winnipeg, MB, Canada
⁶⁵ A. Alikhanyan National Laboratory, Yerevan Physics Institute, 375036, Yerevan, Armenia
⁶⁶ CSSM, Department of Physics, University of Adelaide, 5005, Adelaide, SA, Australia
⁶⁷ Tsinghua University, 100084, Beijing, People’s Republic of China
⁶⁸ Fairfield University, 06824, Fairfield, CT, USA
⁶⁹ Cairo University, 12613, Giza, Egypt
⁷⁰ New Mexico State University, 88003, Las Cruces, NM, USA
⁷¹ Argonne National Laboratory, 60439, Lemont, IL, USA
⁷² Duquesne University, 15282, Pittsburgh, PA, USA
⁷³ Virginia Union University, 23220, Richmond, VA, USA
⁷⁴ Louisiana Tech University, 71272, Ruston, LA, USA
⁷⁵ The College of William & Mary, 23185, Williamsburg, VA, USA

^jg voutier@ijclab.in2p3.fr

Received: 19 May 2021
Accepted: 3 August 2021
Published online: 28 August 2021

Abstract

Positron beams, both polarized and unpolarized, are identified as important ingredients for the experimental programs at the next generation of lepton accelerators. In the context of the hadronic physics program at Jefferson Lab (JLab), positron beams are complementary, even essential, tools for a precise understanding of the electromagnetic structure of nucleons and nuclei, in both the elastic and deep-inelastic regimes. For instance, elastic scattering of polarized and unpolarized electrons and positrons from the nucleon enables a model independent determination of its electromagnetic form factors. Also, the deeply-virtual scattering of polarized and unpolarized electrons and positrons allows unambiguous separation of the different contributions to the cross section of the lepto-production of photons and of lepton-pairs, enabling an accurate determination of the nucleons and nuclei generalized parton distributions, and providing an access to the gravitational form factors of the energy-momentum tensor. Furthermore, positron beams offer the possibility of alternative tests of the Standard Model of particle physics through the search of a dark photon, the precise measurement of electroweak couplings, and the investigation of charged lepton flavor violation. This document discusses the perspectives of an experimental program with high duty-cycle positron beams at JLab.