The HARPS search for southern extra-solar planets: XLIV. Eight HARPS multi-planet systems hosting 20 super-Earth and Neptune-mass companions

S. Udry, X. Dumusque, C. Lovis, D. Ségransan, R. F. Diaz, W. Benz, F. Bouchy, A. Coffinet, G. Lo Curto, M. Mayor, C. Mordasini, F. Motalebi, F. Pepe, D. Queloz, N. C. Santos, A. Wyttenbach, R. Alonso, A. Collier Cameron, M. Deleuil, P. FigueiraM. Gillon, C. Moutou, D. Pollacco, E. Pompei