Abstract
A search for dark matter (DM) particles produced in association with a hadronically decaying vector boson is performed using pp collision data at a centre-of-mass energy of sqrt{s}=13 TeV corresponding to an integrated luminosity of 36.1 fb−1, recorded by the ATLAS detector at the Large Hadron Collider. This analysis improves on previous searches for processes with hadronic decays of W and Z bosons in association with large missing transverse momentum (mono-W/Z searches) due to the larger dataset and further optimization of the event selection and signal region definitions. In addition to the mono-W/Z search, the as yet unexplored hypothesis of a new vector boson Z′ produced in association with dark matter is considered (mono-Z′ search). No significant excess over the Standard Model prediction is observed. The results of the mono-W/Z search are interpreted in terms of limits on invisible Higgs boson decays into dark matter particles, constraints on the parameter space of the simplified vector-mediator model and generic upper limits on the visible cross sections for W/Z+DM production. The results of the mono-Z′ search are shown in the framework of several simplified-model scenarios involving DM production in association with the Z′ boson.
Highlights
Background estimationThe dominant background contribution in the signal region originates from ttand V +jets production
Compared to the analysis presented in ref. [1], the results are obtained from a larger data sample, and event selection and definition of the signal regions are further optimized, including new signal regions based on the tagging of jets from heavy-flavour hadrons and on jet topologies
No sideband regions are employed for the mono-Z search and only categories with the resolved topology are considered for mZ > 100 GeV
Summary
The ATLAS detector [16] is a general-purpose detector with forward-backward symmetric cylindrical geometry. It consists of an inner tracking detector (ID), electromagnetic (EM) and hadronic calorimeters and a muon spectrometer (MS) surrounding the interaction point. The ATLAS detector [16] is a general-purpose detector with forward-backward symmetric cylindrical geometry.. The ATLAS detector [16] is a general-purpose detector with forward-backward symmetric cylindrical geometry.1 It consists of an inner tracking detector (ID), electromagnetic (EM) and hadronic calorimeters and a muon spectrometer (MS) surrounding the interaction point. The electromagnetic calorimeter is a lead/liquid-argon (LAr) sampling calorimeter with an accordion geometry covering the pseudorapidity range |η| < 3.2. The calorimeter coverage is extended to |η| < 4.9 by copper/LAr and tungsten/LAr forward calorimeters providing both electromagnetic and hadronic energy measurements. The first-level trigger selects events based on custom-made hardware and uses information from muon detectors and calorimeters with coarse granularity. The second-level trigger is based on software algorithms similar to those applied in the offline event reconstruction and uses the full detector granularity
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