Mass composition working group report E. Barcikowski, J. Bellido, J. Belz, Y. Egorov, S. Knurenko, V. de Souza, Y. Tameda, Y. Tsunesada and M. Unger EPJ Web of Conferences, 53 (2013) 01006 Published online: 25 June 2013 DOI: 10.1051/epjconf/20135301006