Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Electronics Design and Layout Complexity of the ATLAS New Small Wheels

The upgrades of the LHC accelerator and the experiments in 2019/20 and 2023/24 will allow to increase the luminosity to 2×1034 cm−2s−1 and 5×1034 cm−2s−1, respectively. For the ultimate HL-LHC phase the expected mean number of interactions per bunch crossing will increase from 55 at 2×1034 cm−2s−1 to ∼140 at 5×1034 cm−2s−1. This increase, drastically impacts the ATLAS trigger and trigger rates. For the ATLAS Muon Spectrometer, a replacement of the innermost endcap stations, the so called “Small Wheels” operating in a magnetic field, is therefore planned for 2019/20 to be able to maintain a low pT threshold for single muon and excellent tracking capability in the HL-LHC regime. The New Small Wheels will feature two new detector technologies, Resistive Micromegas and small strip Thin Gap Chambers conforming a system of ~2.4 million readout channels. Both detector technologies will provide trigger and tracking primitives fully compliant with the post-2024 HL-LHC operation. To allow for some safety margin, the design studies assume a maximum instantaneous luminosity of 7×1034 cm−2 s−1, 200 pile-up events, trigger rates of 1 MHz at Level-0 and 400 KHz at Level-1. A radiation dose of ~ 1700 Gy (inner radius) is expected. The electronics design of such a system will be implemented in some 8000 front-end boards including the design of 4 different custom front-end ASICs. Among them the 64 channels VMM, a common frontend ASIC for both detector technologies and charge-interpolating trackers, providing amplitude, timing measurements, per channel analog-to-digital conversions and in parallel direct trigger outputs. The candidate selection is designed within the budget latency of 1 us, and 6 us after 2024. Moreover, the design integrates the GBTx (Gigabit transceiver) ASIC and a Slow Control ASIC developed at CERN. The data flow is designed through a high-throughput network approach. The overall design will be presented.

Trigger and readout electronics for the Phase-I upgrade of the ATLAS forward muon spectrometer

The upgrades of the LHC accelerator and the experiments in 2019/20 and 2023/24 will increase the instantaneous and integrated luminosity, but also will drastically increase the data and trigger rates. To cope with the huge data flow while maintaining high muon detection efficiency and reducing fake muons found at Level-1, the present ATLAS small wheel muon detector will be replaced with a New Small Wheel (NSW) detector for high luminosity LHC runs. The NSW will feature two new detector technologies: resistive micromegas and small strip Thin Gap Chambers conforming a system of ~2.4 million readout channels. Both detector technologies will provide trigger and tracking primitives. A common readout path and a separate trigger path are developed for each detector technology. The electronics design of such a system will be implemented in about 8000 front-end boards, including the design of a number of custom radiation tolerant Application Specific Integrated Circuits (ASICs), capable of driving trigger and tracking primitives to the backend trigger processor and readout system. The large number of readout channels, the short period of time available to prepare and transmit trigger data, the high-speed output data rate, the harsh radiation environment, and the low power consumption, all impose great challenges to the system design. The overall design, development and performance of various prototypes and integration efforts will be presented

Design of the front-end detector control system of the ATLAS New Small Wheels

The ATLAS experiment will be upgraded during the next LHC Long Shutdown (LS2). The flagship upgrade is the New Small Wheel (NSW) [1], which consists of 2 disks of Muon Gas detectors. The detector technologies used are Micromegas (MM) and sTGC, providing a total of 16 layers of tracking and trigger. The Slow Control Adapter (SCA) is part of the Gigabit Transceiver (GBT) - “Radiation Hard Optical Link Project” family of chips designed at CERN, EP-ESE department [2,3], which will be used at the NSW upgrade. The SCA offers several interfaces to read analogue and digital inputs, and configure front-end Readout ASICs, FPGAs, or other chips. The design of the NSW Detector Control System (DCS) takes advantage of this functionality, as described in this paper.The foreseen upgrades of the LHC accelerator and the experiments will drastically increase the data and trigger rates. To cope with the vast and low latency data flow, the ATLAS small wheel muon detector will be replaced with a New Small Wheel. Among the upgrades needed, is a radiation tolerant Slow Control Adapter (GBT-SCA) ASIC dedicated for the on-detector control and monitoring. The ASIC employs various interfaces, making it flexible to match the needs of the different operations. On the backend, the Front-End Link eXchange system will be the interface between the data handling system and the detector front-end and trigger electronics. A dedicated slow control data component was developed as the middleware from FELIX to the end users. It is based on the OPC Unified Architecture protocol and it is comprised of an OPC-UA server, that will handle the slow control traffic from the control room to the GBT-SCA and vice versa. Ultimately, various scope-oriented OPC-UA clients, connected to the OPC-UA server, will be employed to configure and calibrate the ASICs, program the FPGAs, oversee the well-functioning of the boards and monitor the environmental parameters of the detector

quasar : The Full-Stack Solution for Creation of OPC-UA Middleware

Quasar (Quick OPC-UA Server Generation Framework) enables efficient development of OPC-UA servers. The project evolved into a software ecosystem providing complete OPC-UA support for Detector Control Systems. OPC-UA servers can be modeled and generated and profit from tooling to aid development, deployment and maintenance. OPC-UA client libraries can be generated and published to users. Client-server chaining is supported. quasar was used to build OPC-UA servers for different computing platforms including server machines, credit-card computers as well as System-on-a-chip solutions. Quasar generated servers can be integrated as slave modules into other software projects written in higher-level programming languages (such as Python) to provide OPC-UA information exchange. quasar supports quick and efficient integration of OPC-UA servers into a control system based on the WinCC OA SCADA platform. The ecosystem can work with different OPC-UA stacks including 100% free and open-source ones. Thus it’s not restricted by licensing constraints. The contribution will present an overview and the evolution of the ecosystem along with example applications from ATLAS DCS and beyond

WinCC OA project limit studies

In preparation of Phase-2 upgrade of ATLAS experiment, for the high luminosity era, the subsystems are required to develop the Detecror Control System (DCS) based on their unique needs. A key consideration for this upgrade is the size of WinCC OA projects in terms of various parameters. Understanding how large a WinCC OA project can be, without compromising performance is critical for ensuring the stability and efficiency of the DCS. The current internal note presents studies conducted on WinCC OA projects in order to assess the limits of the servers that are being used by ATLAS experiment. The results provide practical guidance for detector groups, helping them determine how to structure their control systems, in terms of datapoint elements and eventually how many WinCC OA projects will be needed based on their detectors' needs

ATLAS Muon DCS Upgrades and Optimizations

The Muon subsystem is comprised of four detector types: Resistive Plate Chambers (RPC) and Thin Gap Chambers (TGC) for trigger purposes, and Cathode Strip Chambers (CSC) and Muon Drift Tubes (MDT) for muon track reconstruction. The MDTs cover a large area at the outer part of the detector. In total, there are over a 1’000 MDT chambers, which are made of about 350’000 tubes. The luminosity upgrade of the HL-LHC is expected to pose a serious challenge to the MDTs. The expected increase of particle flux will set new, higher standards regarding the operation and control of the chambers. A step towards optimizing the ATLAS Muon Detector Control System (DCS) was to develop several DCS tools, namely a High Luminosity vs Trip Limit panel with its accompanying scripts and managers. The ultimate goal of this tool is to protect the MDT chambers from the rising particle flux and its associated increase in chamber current. In addition to optimizing the ATLAS Muon DCS, several tasks to accommodate the newly installed BMG chambers in the DCS infrastructure have been carried out as well. The BMGs, which are similar to the original MDTs but have a smaller tube diameter, required the creation of new Finite State Machine (FSM) JTAG and Power Supply nodes, and the addition of their corresponding Data Point Elements (DPEs) to Oracle's PVSS2COOL archiving scheme. Finally, maintenance work has been conducted to the CSCs of the ATLAS small wheel, and further DCS upgrades have been implemented to their subsystem as well