The Invisible Z' at the LHC

Understand

We study the feasibility of observing an invisibly decaying Z' at the LHC through the process pp -> ZZ' -> l+l-XX*, where X is any neutral, (quasi-) stable particle, whether a Standard Model (SM) neutrino or a new state.

• The measurement of the invisible width through this process facilitates both a model independent measurement of Gamma_{Z' -> \bar{nu} nu} and potentially detection of light neutral hidden states.
• Such particles appear in many models where the Z' is a messenger to a hidden sector, and also if dark matter is charged under the U(1)' of the Z'.
• We find that with as few as 30 fb^-1 of data the invisibly decaying Z' can be observed at 5 sigma over SM background for a 1 TeV Z' with reasonable couplings.