# Search for large missing transverse momentum in association with one top-quark in proton-proton collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

## TL;DR

This paper reports a search for events with a top-quark and large missing transverse momentum in proton-proton collisions at 13 TeV, using ATLAS data, to probe dark matter and vector-like quark models, setting upper limits on production cross-sections.

## Contribution

It introduces a search strategy for top-quark plus missing energy events at 13 TeV and interprets results within dark matter and vector-like quark models, providing new constraints.

## Key findings

- No significant deviation from Standard Model expectations.
- Set 95% CL upper limits on production cross-sections.
- Constrained parameter space of dark matter and vector-like quark models.

## Abstract

This paper describes a search for events with one top-quark and large missing transverse momentum in the final state. Data collected during 2015 and 2016 by the ATLAS experiment from 13 TeV proton-proton collisions at the LHC corresponding to an integrated luminosity of 36.1 fb$^{-1}$ are used. Two channels are considered, depending on the leptonic or the hadronic decays of the $W$ boson from the top quark. The obtained results are interpreted in the context of simplified models for dark-matter production and for the single production of a vector-like $T$ quark. In the absence of significant deviations from the Standard Model background expectation, 95% confidence-level upper limits on the corresponding production cross-sections are obtained and these limits are translated into constraints on the parameter space of the models considered.