Abstract
Observables sensitive to the anomalous production of events containing hadronic jets and missing momentum in the plane transverse to the proton beams at the Large Hadron Collider are presented. The observables are defined as a ratio of cross sections, for events containing jets and large missing transverse momentum to events containing jets and a pair of charged leptons from the decay of a Z/gamma ^* boson. This definition minimises experimental and theoretical systematic uncertainties in the measurements. This ratio is measured differentially with respect to a number of kinematic properties of the hadronic system in two phase-space regions; one inclusive single-jet region and one region sensitive to vector-boson-fusion topologies. The data are found to be in agreement with the Standard Model predictions and used to constrain a variety of theoretical models for dark-matter production, including simplified models, effective field theory models, and invisible decays of the Higgs boson. The measurements use 3.2 fb^{-1} of proton–proton collision data recorded by the ATLAS experiment at a centre-of-mass energy of 13 text {TeV} and are fully corrected for detector effects, meaning that the data can be used to constrain new-physics models beyond those shown in this paper.
Highlights
New physics phenomena at the Large Hadron Collider (LHC) may manifest themselves as events with jets of collimated, mostly hadronic, particles and a momentum imbalance in the plane transverse to the LHC beams, known as missing transverse momentum, pTmiss
New-physics models predicting the existence of weakly interacting massive particles (WIMPs), dark-matter candidates that could be produced at the LHC, could lead to such a signature [5]
The SM predictions do not include NLO electroweak corrections beyond final-state photon radiation. These corrections were studied in Ref. [77] for the Z boson production at a centre-of-mass energy of 8 TeV and are very similar for the numerator and denominator with a residual effect of up to 1% on the ratio
Summary
New physics phenomena at the LHC may manifest themselves as events with jets of collimated, mostly hadronic, particles and a momentum imbalance in the plane transverse to the LHC beams, known as missing transverse momentum, pTmiss. Limits have previously been placed in such models by comparing the number of events in pTmiss + jets final states in LHC data with the number of background events expected to be seen in the detector (the detector level) [6,7] This is a topology similar to that in the invisible decay of a VBF-produced Higgs boson [9,10,11], for which limits have previously been set [12,13] using detectorlevel data.
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