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Published June 1, 2008 | Published + Accepted Version
Journal Article Open

Invisible Z′ at the CERN LHC

Abstract

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 neutrino or a new state. The measurement of the invisible width through this process facilitates both a model-independent measurement of Γ_(Z′→ṽν 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 5σ over standard model background for a 1 TeV Z′ with reasonable couplings. If the Z′ does not couple to leptons and therefore cannot be observed in the Drell-Yan channel, this process becomes a discovery mode. For reasonable hidden sector couplings, masses up to 2 TeV can be probed at the LHC. If the Z′ does couple to leptons, then the rate for this invisible decay is predicted by on-peak data and the presence of additional hidden states can be searched for. With 100 fb^(−1) of data, the presence of excess decays to hidden states can be excluded at 95% C.L., if they comprise 20–30% of the total invisible cross section.

Additional Information

© 2008 American Physical Society. (Received 9 April 2008; published 24 June 2008) The authors are supported by the DOE grant DE-FG02-95ER40896 by the University of Wisconsin Research Committee with funds provided by the Wisconsin Alumni Research Foundation, and by the Alfred P. Sloan Foundation.

Attached Files

Published - PhysRevD.77.115020.pdf

Accepted Version - 0803.4005.pdf

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August 19, 2023
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