Experimental proposal demonstrates high beam luminosity in lepton-proton elastic scattering, highlighting improved precision for testing two-photon exchange effects.
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 2.12× 10³⁵ 2.12 × 10 35 cm ⁻²· - 2 · s ⁻¹ - 1 ( ≈ 200 ≈ 200 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 Q²=4.6 Q 2 = 4.6 (GeV/ c ) ² 2 (twice the range of current measurements). We present and discuss the proposed experimental setup, run plan, and expectations.
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Alarcón et al. (2024) studied this question.
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