Central exclusive production as a probe of the gluonic component of the η′ and η mesons The KRYSTHAL Collaboration, L. A. Harland-Lang, V. A. Khoze, M. G. Ryskin and W. J. Stirling Eur. Phys. J. C, 73 5 (2013) 2429 Published online: 15 May 2013 DOI: 10.1140/epjc/s10052-013-2429-3