Beam Charge Asymmetries for Deeply Virtual Compton Scattering on the Proton at CLAS12

Author:

E. Voutier, V. Burkert, S. Niccolai, R. Paremuzyan, A. Afanasev, J. -S. Alvarado-Galeano, M. Atoui, L. Barion, M. Battaglieri, J. Bernauer, A. Bianconi, M. Bondi, W. Briscoe, A. Camsonne, R. Capobianco, A. Celentano, P. Chatagnon, T. Chetry, G. Ciullo, P. Cole, M. Contalbrigo, G. Costantini, M. Defurne, A. Deur, R. De Vita, S. Diehl, R. Dupré, L. Elouadrhiri, I. Fernando, A. Filippi, T. Forest, F. -X. Girod, G. Gosta, J. Grames, P. Gueye, S. Habet, M. Hattawy, D. Higinbotham, A. Hobart, C. Hyde, K. Joo, A. Kim, V. Klimenko, V. Kubarovsky, M. Leali, P. Lenisa, D. Marchand, L. Marsicano, V. Mascagna, D. Matamoros, M. McCaughan, B. McKinnon, S. Migliorati, H. S. Mitra, A. Movsisyan, C. Muñoz-Camacho, M. Osipenko, M. Ouillon, L. Pappalardo, B. Pasquini, E. Pasyuk, N. Pilleux, M. Poelker, B. Raue, M. Ripani, R. Santos, A. Schmidt, R. Singh, D. Sokhan, M. Spreafico, P. Stoler, I. Strakovsky, M. Taiuti, L. Venturelli, P. -K. Wang, X. Wei, Z. Zhao, the CLAS Collaboration, the Jefferson Lab Positron Working Group

Keyword:

Nuclear Experiment, Nuclear Experiment (nucl-ex), High Energy Physics - Experiment (hep-ex)

journal:

date:

2023-09-24 16:00:00

Abstract

The parameterization of the nucleon structure through Generalized Parton Distributions (GPDs) shed a new light on the nucleon internal dynamics. For its direct interpretation, Deeply Virtual Compton Scattering (DVCS) is the golden channel for GPDs investigation. The DVCS process interferes with the Bethe-Heitler (BH) mechanism to constitute the leading order amplitude of the $eN \to eN\gamma$ process. The study of the $ep\gamma$ reaction with polarized positron and electron beams gives a complete set of unique observables to unravel the different contributions to the $ep \gamma$ cross section. This separates the different reaction amplitudes, providing a direct access to their real and imaginary parts which procures crucial constraints on the model dependences and associated systematic uncertainties on GPDs extraction. The real part of the BH-DVCS interference amplitude is particularly sensitive to the $D$-term which parameterizes the Gravitational Form Factors of the nucleon. The separation of the imaginary parts of the interference and DVCS amplitudes provides insights on possible higher-twist effects. We propose to measure the unpolarized and polarized Beam Charge Asymmetries (BCAs) of the $\vec{e}^{\pm}p \to e^{\pm}p \gamma$ process on an unpolarized hydrogen target with {\tt CLAS12}, using polarized positron and electron beams at 10.6 GeV. The azimuthal and $t$-dependences of the unpolarized and polarized BCAs will be measured over a large $(x_B,Q^2)$ phase space using a 100 day run with a luminosity of 0.66$\times 10^{35}$cm$^{-2}\cdot$s$^{-1}$.

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