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 ΓZ'→ν¯ν 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 30fb-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 100fb-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.
- Publication:
-
Physical Review D
- Pub Date:
- June 2008
- DOI:
- 10.1103/PhysRevD.77.115020
- arXiv:
- arXiv:0803.4005
- Bibcode:
- 2008PhRvD..77k5020P
- Keywords:
-
- 12.60.Cn;
- 12.60.Jv;
- 14.70.Pw;
- Extensions of electroweak gauge sector;
- Supersymmetric models;
- Other gauge bosons;
- High Energy Physics - Phenomenology
- E-Print:
- 18 pages, 11 figures. References added