We present a search for new phenomena in events with two
reconstructed Z bosons and large missing transverse momentum, sensitive
to processes pp̅ →X2X2→ZZX1X1, where X2 is an unstable particle
decaying as X2→ZX1 and X1 is undetected. The particles X1 and X2 may be,
among other possibilities, fourth-generation neutrinos or supersymmetric
particles. We study the final state in which one Z boson decays to two
charged leptons and the second decays hadronically. In data corresponding
to an integrated luminosity of 4.2 fb-1 from proton-antiproton
collisions recorded by the CDF II detector at the Tevatron, with
center-of-mass energy of 1.96 TeV, we find agreement between data and
standard-model backgrounds. We calculate 95% confidence level upper limits
on the cross section of the process pp̅ →X2X2→ZZX1X1 ranging from
50 fb to 1 pb, depending on the masses of X1 and X2.
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Updated: Friday, 2012 January 27 10:36:36 CST automatically from input from "Stephanie A. Schuler"