Search for new phenomena in events with two $Z$ bosons and missing transverse momentum in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV

TL;DR

This paper searches for new physics involving two Z bosons and missing energy in proton-antiproton collisions, setting upper limits on potential new particle production consistent with models like supersymmetry.

Contribution

It presents the first search for specific new phenomena involving Z bosons and missing energy at the Tevatron, providing constraints on new particle models.

Findings

No significant excess over standard model backgrounds.

Set 95% CL upper limits on cross sections from 50 fb to 1 pb.

Constraints on models with fourth generation neutrinos or supersymmetric particles.

Abstract

We present a search for new phenomena in events with two reconstructed $Z$ bosons and large missing transverse momentum, sensitive to processes $p\bar{p}\rightarrow X_2X_2 \rightarrow Z Z X_1 X_1$, where $X_2$ is an unstable particle decaying as $X_2\rightarrow ZX_1$ and $X_1$ is undetected. The particles $X_1$ and $X_2$ 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 $p\bar{p}\rightarrow X_2X_2 \rightarrow Z Z X_1 X_1$ ranging from 50 fb to 1 pb, depending on the masses of $X_1$ and $X_2$.