Low Q(2) weak mixing angle measurements and rare Higgs decays

Abstract

A weighted average weak mixing angle theta(W) derived from relatively low Q(2) experiments is compared with the standard model prediction obtained from precision measurements. The approximate 1.8 sigma discrepancy is fit with an intermediate mass (similar to 10- 35 GeV) "dark" Z boson Z(d), corresponding to a U(1)(d) gauge symmetry of hidden dark matter, which couples to our world via kinetic and Z-Z(d) mass mixing. Constraints on such a scenario are obtained from precision electroweak bounds and searches for the rare Higgs decays H -> ZZ(d) -> 4 charged leptons at the LHC. The sensitivity of future anticipated low Q(2) measurements of sin(2) theta(W)(Q(2)) to intermediate mass Z(d) is also illustrated. This dark Z scenario can provide interesting concomitant signals in low energy parity violating measurements and rare Higgs decays at the LHC over the next few years.