Constraints on a Light Leptophobic Mediator from LEP Data

Manuel Drees; Zhongyi Zhang

doi:10.1007/JHEP08(2018)194

paper

Constraints on a Light Leptophobic Mediator from LEP Data

arXiv:1805.02780 · doi:10.1007/JHEP08(2018)194

Abstract

We apply data taken at the $e^{+} e^{-}$ collider LEP in the 1990's at center-of-mass energy up to 209 GeV to constrain Dark Matter models with a light leptophobic spin-1 mediator $R$ . We assume that the dark sector particle (DSP) is a spin-1/2 fermion $χ$ . This scenario is well studied in the context of LHC searches for mediator mass from 100 GeV to several TeV. Emission of the mediator off a quark or antiquark at LEP gives rise to di-jet plus missing energy and 4-jet signatures, which we use to limit the relevant couplings. We focus on scenarios with $2 m_{χ} > m_{R}$ , which are poorly constrained by LHC data. We recast published searches by the ALEPH collaboration. For $m_{χ} < 20$ GeV the best bounds result from an analysis at $s ≃ M_{Z}$ of di-jet plus missing energy events. For heavier DSP but $m_{R} < 70$ GeV meaningful bounds can be derived from a four jet analysis at $s = 183$ GeV. Unfortunately published searches using four jet final states at $s ≃ M_{Z}$ use only a small fraction of the total data sample. Moreover, all published searches for di-jet plus missing energy final states at $s \geq 130$ GeV have poor efficiency for our model; we therefore design new cuts that combine good background rejection with higher efficiency. Re-analyzing the higher energy data using our new cuts, and an analysis of the complete four jet data sample taken at $s ≃ M_{Z}$ , can explore new regions of parameter space.

arXiv comment28 pages, 16 figures

Constraints on a Light Leptophobic Mediator from LEP Data

Abstract

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