2008/03/31 by Frank Petriello, Frank J. Petriello, Seth Quackenbush +1
Physics and Astronomy · #Dark Matter and Cosmic Phenomena #Neutrino Physics Research #Particle physics theoretical and experimental studies #hep-ph
paper · pdf · doi:10.1103/physrevd.77.115020
published as Phys.Rev.D77:115020,2008 · 18 pages, 11 figures. References added
arxiv created 2008/06/12 · openalex publication_date 2008/06/24 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We study the feasibility of observing an invisibly decaying Z^\ensuremath' at the LHC through the process pp\ensuremath→ZZ^\ensuremath'\ensuremath→\ensuremathℓ+\ensuremathℓ^\ensuremath-XX^\ifmmode†\else\textdagger\fi, 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 \ensuremathΓ_Z^\ensuremath'\ensuremath→\ensuremathν\ensuremathν and potentially detection of light neutral hidden states. Such particles appear in many models, where the Z^\ensuremath' is a messenger to a hidden sector, and also if dark matter is charged under the U(1)^\ensuremath' of the Z^\ensuremath'. We find that with as few as 30 fb^\ensuremath-1 of data the invisibly decaying Z^\ensuremath' can be observed at 5\ensuremathσ over standard model background for a 1 TeV Z^\ensuremath' with reasonable couplings. If the Z^\ensuremath' 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^\ensuremath' 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^\ensuremath-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.