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Measurement of deeply virtual Compton scattering off Helium-4 with CLAS at Jefferson Lab

We report on the measurement of the beam spin asymmetry in the deeply virtual Compton scattering off \(^4\)He using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab using a 6 GeV longitudinally polarized electron beam incident on a pressurized \(^4\)He gaseous target. We detail the me...

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Published in:arXiv.org 2021-08
Main Authors: Baltzell, N A, Bültmann, S, De Vita, R, L El Fassi, Girod, F X, Guidal, M, Hafidi, K, Liuti, S, Perrin, Y, Stepanyan, S, Torayev, B, Amaryan, M J, Armstrong, W R, Atac, H, C Ayerbe Gayoso, Barion, L, Battaglieri, M, Bedlinskiy, I, Boiarinov, S, Briscoe, W J, Burkert, V, Carman, D S, Carvajal, J C, Chatagnon, P, Chesnokov, V, Chetry, T, Ciullo, G, Costantini, G, Crede, V, D'Angelo, A, Dashyan, N, Defurne, M, Deur, A, Diehl, S, Djalali, C, Ehrhart, M, Elouadrhiri, L, Filippi, A, est, T A, Ghandilyan, Y, Gilfoyle, G P, Gothe, R W, Hakobyan, H, Hayward, T B, Hicks, K, Hobart, A, Holtrop, M, Ilieva, Y, Ireland, D G, Jo, H S, Joosten, S, Khachatryan, G, Kim, A, Kim, W, Lanza, L, Livingston, K, Kabir, M L, Lenisa, P, MacGregor, I J D, Mascagna, V, McKinnon, B, Mirazita, M, Mokeev, V I, Neupane, K, Niccolai, S, O'Connell, T R, Osipenko, M, Paolone, M, Pappalardo, L L, Paremuzyan, R, Payette, D, Phelps, W, Pivnyuk, N, Pogorelko, O, Poudel, J, Prok, Y, Ritman, J, Rizzo, A, Rosner, G, Rossi, P, Sabatié, F, Salgado, C, Schmidt, A, Schumacher, R, Sharabian, Y, Shrestha, U, Sokhan, D, Soto, O, Sparveris, N, Strakovsky, I I, Strauch, S, Tyler, N, Ungaro, M, Venturelli, L, Voskanyan, H, Watts, D, Wei, X, Weinstein, L B, Wood, M H, Yale, B
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Language:English
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Summary:We report on the measurement of the beam spin asymmetry in the deeply virtual Compton scattering off \(^4\)He using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab using a 6 GeV longitudinally polarized electron beam incident on a pressurized \(^4\)He gaseous target. We detail the method used to ensure the exclusivity of the measured reactions, in particular the upgrade of CLAS with a radial time projection chamber to detect the low-energy recoiling \(^4\)He nuclei and an inner calorimeter to extend the photon detection acceptance at forward angles. Our results confirm the theoretically predicted enhancement of the coherent (\(e^4\)He$~\to~e'$$^4\(He\)'\gamma'\() beam spin asymmetries compared to those observed on the free proton, while the incoherent (\)e^4\(He\)~\to~e'\(p\)'\gamma'\(X\)'\() asymmetries exhibit a 30\)\%\( suppression. From the coherent data, we were able to extract, in a model-independent way, the real and imaginary parts of the only \)^4\(He Compton form factor, \)\cal H_A$, leading the way toward 3D imaging of the partonic structure of nuclei.
ISSN:2331-8422
DOI:10.48550/arxiv.2102.07419