Beam asymmetry Σ in η′ photoproduction off the proton at the GRAAL experiment G. Mandaglio, V. Bellini, J. P. Bocquet, M. Capogni, F. Curciarello, A. D'Angelo, V. De Leo, J.P. Didelez, R. Di Salvo, A. Fantini et al. (21 more) EPJ Web of Conferences, 73 (2014) 04006 Published online: 09 June 2014 DOI: 10.1051/epjconf/20147304006