Exploring the Structure of the Bound Proton with Deeply Virtual Compton Scattering

Journal Article · 16 July 2019 · Physical Review Letters

DOI: https://doi.org/10.1103/PhysRevLett.123.032502 · OSTI ID:1543328

Hattawy, M.; Baltzell, N. A.; Dupré, R.; Bültmann, S.; De Vita, R.; El Alaoui, A.; El Fassi, L.; Egiyan, H.; Girod, F. X.; Guidal, M.; Hafidi, K.; Jenkins, D.; Liuti, S.; Perrin, Y.; Stepanyan, S.; Torayev, B.; Voutier, E.; Adhikari, S.; Angelini, Giovanni; Ayerbe Gayoso, C. ; Barion, L.; Battaglieri, M.; Bedlinskiy, I.; Biselli, A. S.; Bossù, F.; Brooks, W.; Cao, F.; Carman, D. S.; Celentano, A.; Chatagnon, P.; Chetry, T.; Ciullo, G.; Clark, L.; Cole, P. L.; Contalbrigo, M.; Crede, V.; D’Angelo, A.; Dashyan, N.; De Sanctis, E.; Defurne, M.; Deur, A.; Diehl, S.; Djalali, C.; Ehrhart, M.; Eugenio, P.; Fegan, S.; Filippi, A.; Forest, T. A.; Fradi, A.; Garçon, M.; Gavalian, G.; Gevorgyan, N.; Gilfoyle, G. P.; Giovanetti, K. L.; Golovatch, E.; Gothe, R. W.; Griffioen, K. A.; Harrison, N.; Hauenstein, F.; Hayward, T. B.; Heddle, D.; Hicks, K.; Holtrop, M.; Ilieva, Y.; Ireland, D. G.; Isupov, E. L.; Jo, H. S.; Johnston, S.; Keller, D.; Khachatryan, G.; Khachatryan, M.; Khanal, A.; Khandaker, M.; Kim, C. W.; Kim, W.; Klein, F. J.; Kubarovsky, V.; Kuhn, S. E.; Lanza, L.; L. Kabir, M.; Lenisa, P.; Livingston, K.; MacGregor, I. J. D.; Marchand, D.; Markov, N.; Mayer, M.; McKinnon, B.; Meziani, Z. E.; Mineeva, T.; Mirazita, M.; Montgomery, R. A.; Munoz Camacho, C.; Nadel-Turonski, P.; Niccolai, S.; Ostrovidov, A. I.; Pappalardo, L. L.; Paremuzyan, R.; Pasyuk, E.; Pogorelko, O.; Poudel, J.; Prok, Y.; Protopopescu, D.; Ripani, M.; Riser, D.; Rizzo, A.; Rosner, G.; Rossi, P.; Sabatié, F.; Salgado, C.; Schumacher, R. A.; Sharabian, Y. G.; Skorodumina, Iu.; Sokhan, D.; Soto, O.; Sparveris, N.; Strauch, S.; Taiuti, M.; Tan, J. A.; Tyler, N.; Ungaro, M.; Voskanyan, H.; Wang, R.; Watts, D. P.; Wei, X.; Weinstein, L. B.; Wood, M. H.; Zachariou, N.; Zhang, J.; Zhao, Z. W.

In the past two decades, deeply virtual Compton scattering of electrons has been successfully used to advance our knowledge of the partonic structure of the free proton and investigate correlations between the transverse position and the longitudinal momentum of quarks inside the nucleon. Meanwhile, the structure of bound nucleons in nuclei has been studied in inclusive deep-inelastic lepton scattering experiments off nuclear targets, showing a significant difference in longitudinal momentum distribution of quarks inside the bound nucleon, known as the EMC effect. In this work, we report the first beam spin asymmetry (BSA) measurement of exclusive deeply virtual Compton scattering (DVCS) off a proton bound in $^4$He. The data used here were accumulated using a $$6$$ GeV longitudinally polarized electron beam incident on a pressurized $^4$He gaseous target placed within the CLAS spectrometer in Hall-B at the Thomas Jefferson National Accelerator Facility. Here, the azimuthal angle ($$\phi$$) dependence of the BSA was studied in a wide range of virtual photon and scattered proton kinematics. The $Q^2$, $$x_B$$, and t dependencies of the BSA on the bound proton are compared with those on the free proton. In the whole kinematical region of our measurements, the BSA on the bound proton is smaller by 20\% to 40\%, indicating possible medium modification of its partonic structure.

• Research Organization: Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
• Contributing Organization: CLAS Collaboration
• Grant/Contract Number: AC02-06CH11357; AC05-06OR23177
• OSTI ID: 1543328
• Alternate ID(s): OSTI ID: 1543180; OSTI ID: 1566121; OSTI ID: 1656753; OSTI ID: 1656756; OSTI ID: 1593818
• Report Number(s): JLAB-PHY--19-2819; DOE/OR/23177--4617; arXiv:1812.07628
• Journal Information: Physical Review Letters, Journal Name: Physical Review Letters Journal Issue: 3 Vol. 123; ISSN 0031-9007; ISSN PRLTAO
• Publisher: American Physical Society (APS)Copyright Statement
• Country of Publication: United States
• Language: English