Title

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

Authors

M. Hattawy, Argonne National Laboratory
N. A. Baltzell, Argonne National Laboratory
R. Dupré, Argonne National Laboratory
S. Bültmann, Old Dominion University
R. De Vita, Istituto Nazionale di Fisica Nucleare, Sezione di Genova
A. El Alaoui, Argonne National Laboratory
L. El Fassi, Argonne National Laboratory
H. Egiyan, Thomas Jefferson National Accelerator Facility
F. X. Girod, Thomas Jefferson National Accelerator Facility
M. Guidal, Institut de Physique Nucléaire Orsay
K. Hafidi, Argonne National Laboratory
D. Jenkins, Virginia Polytechnic Institute and State University
S. Liuti, University of Virginia
Y. Perrin, Universite Grenoble Alpes
S. Stepanyan, Thomas Jefferson National Accelerator Facility
B. Torayev, Old Dominion University
E. Voutier, Institut de Physique Nucléaire Orsay
S. Adhikari, Florida International University
Giovanni Angelini, The George Washington University
C. Ayerbe Gayoso, The College of William and Mary
L. Barion, Istituto Nazionale di Fisica Nucleare, Sezione di Ferrara
M. Battaglieri, Istituto Nazionale di Fisica Nucleare, Sezione di Genova
I. Bedlinskiy, Alikhanov Institute for Theoretical and Experimental Physics
A. S. Biselli, Fairfield University
F. Bossù, Universite Paris-Saclay
W. Brooks, Universidad Técnica Federico Santa María
F. Cao, University of Connecticut
D. S. Carman, Thomas Jefferson National Accelerator Facility
T. Chetry, Ohio University
C. Djalali, Ohio University
K. Hicks, Ohio University
D. Keller, Ohio University

Document Type

Article

Publication Date

7-17-2019

Abstract

© 2019 American Physical Society. 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 Letter, we report the first beam spin asymmetry (BSA) measurement of exclusive deeply virtual Compton scattering off a proton bound in He4. The data used here were accumulated using a 6 GeV longitudinally polarized electron beam incident on a pressurized He4 gaseous target placed within the CLAS spectrometer in Hall-B at the Thomas Jefferson National Accelerator Facility. The azimuthal angle (φ) dependence of the BSA was studied in a wide range of virtual photon and scattered proton kinematics. The Q2, xB, 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.

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