https://doi.org/10.1140/epja/s10050-024-01299-2
Regular Article - Experimental Physics
The two-photon exchange experiment at DESY
1
Department of Physics and Astronomy, Arizona State University, Tempe, AZ, USA
2
Department of Physics and Astronomy, Friedrich Wilhelms Universität, Bonn, Germany
3
Center for Frontiers in Nuclear Science, Stony Brook University, Stony Brook, NY, USA
4
Riken BNL Research Center, Brookhaven National Laboratory, Upton, NY, USA
5
Laboratory for Nuclear Science, Massachusetts Institute of Technology, Cambridge, MA, USA
6
Department of Physics and Astronomy, Hampton University, Hampton, VA, USA
7
Department of Low Temperature Physics, Charles University, Prague, Czech Republic
8
Department of Physics, Faculty of Science, University of Zagreb, Zagreb, Croatia
9
Department of Physics, The George Washington University, Washington, DC, USA
10
Department of Physics, Catholic University of America, Washington, DC, USA
11
Randall Laboratory of Physics, University of Michigan, Ann Arbor, MI, USA
12
Institute of Nuclear Physics, Johannes Gutenberg Universität, Mainz, Germany
13
Deutsches Elektronen-Synchrotron DESY, Hamburg, Germany
14
Department of Physics and Astronomy, University of Glasgow, Glasgow, Scotland
f
ewcline@mit.edu
z
ievgen@umich.edu
Received:
10
August
2023
Accepted:
13
March
2024
Published online:
5
April
2024
We propose a new measurement of the ratio of positron-proton to electron-proton elastic scattering at DESY. The purpose is to determine the contributions beyond single-photon exchange, which are essential for the Quantum Electrodynamic (QED) description of the most fundamental process in hadronic physics. By utilizing a 20 cm long liquid hydrogen target in conjunction with the extracted beam from the DESY synchrotron, we can achieve an average luminosity of 
cm
s
(
times the luminosity achieved by OLYMPUS). The proposed two-photon exchange experiment (TPEX) entails a commissioning run at a beam energy of 2 GeV, followed by measurements at 3 GeV, thereby providing new data up to 
(GeV/c)
(twice the range of current measurements). We present and discuss the proposed experimental setup, run plan, and expectations.
© The Author(s) 2024
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