Performance of the LHCb RICH photodetectors in a charged particle beam by Adinolfi, M, Rinella, G, Albrecht, E, Ameri, M, Arnaboldi, C, Bellunato, T, Bibby, J, Blake, T, Cuneo, S, Dickens, J, Easo, S, Egede, U, Fontanelli, F, Gibson, V, Gys, T, Hallam, R, Harnew, N, Howard, A, Kanaya, N, Katvars, S, Matteuzzi, C, McCarron, J, Minic, G, Muheim, F, Panzeri, E