Measurement of top quark-antiquark pair production in association with a W or Z boson in pp collisions at sqrt(s) = 8 TeV

Understand

A measurement of the cross section for the production of top quark-antiquark pairs (t tbar) in association with a vector boson V (W or Z) in proton-proton collisions at sqrt(s) = 8 TeV is presented.

• The results are based on a dataset corresponding to an integrated luminosity of 19.5 inverse femtobarns recorded with the CMS detector at the LHC.
• The measurement is performed in three leptonic (e and mu) channels: a same-sign dilepton analysis targeting t tbar W events, and trilepton and four-lepton analyses designed for t tbar Z events.
• In the same-sign dilepton channel, the t tbar W cross section is measured as sigma[t tbar W] = 170 +90/-80 (stat) +/- 70 (syst) fb, corresponding to a significance of 1.6 standard deviations over the background-only hypothesis.