Search for dark matter and unparticles produced in association with a Z boson in proton-proton collisions at sqrt(s) = 8 TeV

TL;DR

This paper reports a search for dark matter and unparticles produced with a Z boson in proton-proton collisions at 8 TeV, setting new limits on their properties based on CMS data.

Contribution

It provides the first limits on dark matter and unparticle production in association with a Z boson at the LHC at 8 TeV.

Findings

No significant excess observed above standard model expectations.

Set 90% CL limits on DM-nucleon cross section and effective cutoff scale.

Established the most stringent 95% CL limits on unparticle parameters.

Abstract

A search for evidence of particle dark matter (DM) and unparticle production at the LHC has been performed using events containing two charged leptons, consistent with the decay of a Z boson, and large missing transverse momentum. This study is based on data collected with the CMS detector corresponding to an integrated luminosity of 19.7 inverse femtobarns of pp collisions at the LHC at a center-of-mass energy of 8 TeV. No significant excess of events is observed above the number expected from the standard model contributions. The results are interpreted in terms of 90% confidence level limits on the DM-nucleon scattering cross section, as a function of the DM particle mass, for both spin-dependent and spin-independent scenarios. Limits are set on the effective cutoff scale Lambda, and on the annihilation rate for DM particles, assuming that their branching fraction to quarks is 100%. Additionally, the most stringent 95% confidence level limits to date on the unparticle model parameters are obtained.