Invisible Z{sup '} at the CERN LHC
- Physics Department, University of Wisconsin, Madison, WI 53706 (United States)
We study the feasibility of observing an invisibly decaying Z{sup '} at the LHC through the process pp{yields}ZZ{sup '}{yields}l{sup +}l{sup -}XX{sup {dagger}}, 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 {gamma}{sub Z{r_reversible}}{nu}{sub {nu}} and potentially detection of light neutral hidden states. Such particles appear in many models, where the Z{sup '} is a messenger to a hidden sector, and also if dark matter is charged under the U(1){sup '} of the Z{sup '}. We find that with as few as 30 fb{sup -1} of data the invisibly decaying Z{sup '} can be observed at 5{sigma} over standard model background for a 1 TeV Z{sup '} with reasonable couplings. If the Z{sup '} 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{sup '} 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{sup -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.
- OSTI ID:
- 21205117
- Journal Information:
- Physical Review. D, Particles Fields, Vol. 77, Issue 11; Other Information: DOI: 10.1103/PhysRevD.77.115020; (c) 2008 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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