Observation of top quark pairs produced in association with a vector boson in pp collisions at sqrt(s) = 8 TeV

CMS Collaboration, Shimaa Abu Zeid, Freya Blekman, Jorgen D'Hondt, Nadir Daci, Isabelle Helena De Bruyn, Kevin Deroover, Natalie Heracleous, James Keaveney, Steven Lowette, Lieselotte Moreels, Annik Olbrechts, Quentin Python, Derek Strom, Stefaan Tavernier, Walter Van Doninck, Petra Van Mulders, Gerrit Van Onsem, Isis Marina Van Parijs