Search for invisibly decaying Higgs bosons produced in vector boson fusion with ATLASin Run 2

Dark matter is one of the remaining puzzles of the Standard Model. This poster presents preliminary results of a search for dark matter candidates in invisible Higgs boson decays with the ATLAS experiment using 139 fb-1 of proton-proton collision data. The search targets vector boson fusion Higgs boson production, which is expected to be the most sensitive channel. This presentation highlights the background estimates for V+jets and multijet processes, the event categorisation, limit setting as well as the interpretation of the result in terms of Higgs portal models

Search for Dark Matter in Invisible Higgs Boson Decays with the ATLAS Detector at the LHC

The nature of dark matter is one of the biggest open questions in modern physics. While dark matter accountsfor roughly 25% of the energy density in the Universe, its particle nature remains unknown so far. In thisthesis a search for dark matter at the Large Hadron Collider with the Atlas experiment is presented usingproton-proton collision data collected at a center-of-mass energy of 13 TeV. Furthermore, the absoluteMonte Carlo based jet energy scale calibration of particle flow jets is presented.The dark matter search targets vector boson fusion Higgs boson production, which is expected to be the mostsensitive channel. For the full Run II data set, the background estimates with a focus on multijet processes, theevent categorisation, limit setting as well as the interpretation of the result are presented.In absence of a signal excess over the background-only hypothesis, an upper limit is set on the invisibleHiggs boson branching fraction. The observed (expected) 95%CL limit is 0.145 (0.103), which is the bestlimit ever achieved so far for invisible Higgs boson decays.The result is interpreted in terms of Higgs portal models to set upper limits on the WIMP-nucleon cross section.Moreover, also limits on potential other scalar mediators than the Higgs boson of the Standard Model areset

Operation and performance of the ATLAS semiconductor tracker in LHC Run 2

Abstract The semiconductor tracker (SCT) is one of the tracking systems for charged particles in the ATLAS detector. It consists of 4088 silicon strip sensor modules. During Run 2 (2015–2018) the Large Hadron Collider delivered an integrated luminosity of 156 fb-1 to the ATLAS experiment at a centre-of-mass proton-proton collision energy of 13 TeV. The instantaneous luminosity and pile-up conditions were far in excess of those assumed in the original design of the SCT detector. Due to improvements to the data acquisition system, the SCT operated stably throughout Run 2. It was available for 99.9% of the integrated luminosity and achieved a data-quality efficiency of 99.85%. Detailed studies have been made of the leakage current in SCT modules and the evolution of the full depletion voltage, which are used to study the impact of radiation damage to the modules.</jats:p