Precision Muon Tracking Detectors for High-Energy Hadron Colliders

Small-diameter muon drift tube (sMDT) chambers with 15 mm tube diameter are a cost-effective technology for high-precision muon tracking over large areas at high background rates as expected at future high-energy hadron colliders including HL-LHC. The chamber design and construction procedures have been optimized for mass production and provide sense wire positioning accuracy of better than 10 ?m. The rate capability of the sMDT chambers has been extensively tested at the CERN Gamma Irradiation Facility. It exceeds the one of the ATLAS muon drift tube (MDT) chambers, which are operated at unprecedentedly high background rates of neutrons and gamma-rays, by an order of magnitude, which is sufficient for almost the whole muon detector acceptance at FCC-hh at maximum luminosity. sMDT operational and construction experience exists from ATLAS muon spectrometer upgrades which are in progress or under preparation for LHC Phase 1 and 2

Optimisation of the Read-out Electronics of Muon Drift-Tube Chambers for Very High Background Rates at HL-LHC and Future Colliders

In the ATLAS Muon Spectrometer, Monitored Drift Tube (MDT) chambers and sMDT chambers with half of the tube diameter of the MDTs are used for precision muon track reconstruction. The sMDT chambers are designed for operation at high counting rates due to neutron and gamma background irradiation expected for the HL-LHC and future hadron colliders. The existing MDT read-out electronics uses bipolar signal shaping which causes an undershoot of opposite polarity and same charge after a signal pulse. At high counting rates and short electronics dead time used for the sMDTs, signal pulses pile up on the undershoot of preceding background pulses leading to a reduction of the signal amplitude and a jitter in the drift time measurement and, therefore, to a degradation of drift tube efficiency and spatial resolution. In order to further increase the rate capability of sMDT tubes, baseline restoration can be used in the read-out electronics to suppress the pile-up effects. A discrete bipolar shaping circuit with baseline restoration has been developed and used for reading out sMDT tubes under irradiation with a 24 MBq 90Sr source. The measurements results show a substantial improvement of the performance of the sMDT tubes at high counting rates

Status of the BELLE II Pixel Detector

The Belle II experiment at the super KEK B-factory (SuperKEKB) in Tsukuba, Japan, has been collecting $e^+e^−$ collision data since March 2019. Operating at a record-breaking luminosity of up to $4.7×10^{34} cm^{−2}s^{−1}$, data corresponding to $424 fb^{−1}$ has since been recorded. The Belle II VerteX Detector (VXD) is central to the Belle II detector and its physics program and plays a crucial role in reconstructing precise primary and decay vertices. It consists of the outer 4-layer Silicon Vertex Detector (SVD) using double sided silicon strips and the inner two-layer PiXel Detector (PXD) based on the Depleted P-channel Field Effect Transistor (DePFET) technology. The PXD DePFET structure combines signal generation and amplification within pixels with a minimum pitch of $(50×55) μm^2$. A high gain and a high signal-to-noise ratio allow thinning the pixels to $75 μm$ while retaining a high pixel hit efficiency of about $99$. As a consequence, also the material budget of the full detector is kept low at $≈0.21$$\frac{X}{X_0}$ per layer in the acceptance region. This also includes contributions from the control, Analog-to-Digital Converter (ADC), and data processing Application Specific Integrated Circuits (ASICs) as well as from cooling and support structures. This article will present the experience gained from four years of operating PXD; the first full scale detector employing the DePFET technology in High Energy Physics. Overall, the PXD has met the expectations. Operating in the intense SuperKEKB environment poses many challenges that will also be discussed. The current PXD system remains incomplete with only 20 out of 40 modules having been installed. A full replacement has been constructed and is currently in its final testing stage before it will be installed into Belle II during the ongoing long shutdown that will last throughout 2023

Searches for new phenomena in final states with 3rd generation quarks using the ATLAS detector

Many theories beyond the Standard Model predict new phenomena, such as heavy vectors or scalar, vector-like quarks, and leptoquarks in final states containing bottom or top quarks. Such final states offer great potential to reduce the Standard Model background, although with significant challenges in reconstructing and identifying the decay products and modelling the remaining background. The recent 13 TeV pp results, along with the associated improvements in identification techniques, will be reported

Searches for new phenomena in final states with 3rd generation quarks using the ATLAS detector

Many theories beyond the Standard Model predict new phenomena, such as heavy vectors or scalar, vector-like quarks, and leptoquarks in final states containing bottom or top quarks. Such final states offer great potential to reduce the Standard Model background, although with significant challenges in reconstructing and identifying the decay products and modelling the remaining background. The recent 13 TeV pp results, along with the associated improvements in identification techniques, will be reported

Development of a Concept for the Muon Trigger of the ATLAS Detector at the HL-LHC

Highly selective first level triggers are essential to exploit the full physics potential of the ATLAS experiment at the High Luminosity-Large Hadron Collider, where the instantaneous luminosity will exceed the LHC Run 1 instantaneous luminosity by almost an order of magnitude. The ATLAS experiment plans to increase the rate of the first trigger level to 1 MHz at 6 µs latency. The momentum resolution of the existing first level muon trigger is limited by the moderate position resolution of the trigger chambers. Including the data of the precision Monitored Drift Tube (MDT) chambers in the first level muon trigger decision will increase the selectivity of the first level muon trigger substantially. Run 1 LHC data with a centre-of-mass energy of $\sqrt{s} = 8\, \textrm{TeV}$ and a bunch spacing of 25 ns was used to study the achievable selectivity of a muon trigger making use of the MDT data. It could be shown that it is not necessary to fully reconstruct the muon trajectory. The position and direction information of the straight track segments reconstructed in the MDT chambers is sufficient to measure the momentum with a precision that allows for a rate reduction compared to the expected Phase-I trigger rate of over 70 % for the whole ATLAS muon spectrometer. Fast algorithms employed in the trigger electronics are required for the reconstruction of the track segments within the trigger latency. For the end-cap ($1.05 < |\eta| < 2.4$) the ATLAS collaboration considered a 1-dimensional Hough transform algorithm, which is seeded by the trigger chamber data. The algorithm is not applicable in the barrel region ($0 < |\eta| < 1.05$) because of the lower spatial resolution of the trigger chambers in the barrel region than in the end-cap region. Extending the algorithm to a Binned 2D-Hough Transform, which improves the track segment reconstruction quality sufficiently for all regions apart from the outer barrel MDT chambers. In this thesis, a new track segment finding algorithm, that makes use of tangents to drift radii, was developed and shown to be applicable to the entire muon spectrometer ($|\eta| < 2.4$)

ATLAS Highlights on DM Searches in Exotic Models

Dark matter could be produced at the LHC if it interacts weakly with the Standard Model. The search for dark matter can be performed directly, by looking for a signature of large missing transverse momentum coming from the dark matter candidates escaping the detector, measured against an accompanying visible object (jet, photon, vector boson). It can also be performed indirectly, by looking for the intermediate mediators which would couple the dark matter particles to the Standard Model. The mediator could indeed decay to jets or leptons, leading to a resonant signature which can be probed. A broad and systematic search program covering these various possibilities with the ATLAS detector is in place: the talk will review the latest results of these searches, excluding the searches involving a Higgs boson which will be covered in a dedicated talk

Search for Dark Matter in association with a hadronically decaying Z' vector boson with the ATLAS detector in pp collisions at 13 TeV

A search for dark matter pair production in association with a Z' boson in pp collisions, at 13 TeV, using 36.1 fb−1 of LHC pp collision data recorded with the ATLAS detector is presented. Events are characterised by large missing transverse momentum and a hadronically decaying vector boson reconstructed as either a pair of small-radius jets, or as a single large-radius jet with substructure. Results are interpreted in terms of simplified models which describe the interaction of dark matter and standard model particles

Search for dark matter produced in association with a hadronically decaying Z’ vector boson with the ATLAS detector at the LHC

A search for dark matter pair production in association with a $Z'$ boson is performed using 36.1$\,$fb$^{-1}$ of LHC $pp$ collision data at $\sqrt{s} = 13\,$TeV recorded with the ATLAS detector.Events are characterised by large missing transverse momentum and a hadronically decaying vector boson reconstructed as either a pair of small-radius jets, or as a single large-radius jet with a two-body decay substructure.Results are interpreted in terms of simplified models which describe the interaction of dark matter and Standard Model particles