Performance of the ATLAS Level-1 topological trigger in Run 2

During LHC Run 2 (2015–2018) the ATLAS Level-1 topological trigger allowed efficient data-taking by the ATLAS experiment at luminosities up to 2.1$$\times $$ × 10$$^{34}$$ 34 cm$$^{-2}$$ - 2 s$$^{-1}$$ - 1 , which exceeds the design value by a factor of two. The system was installed in 2016 and operated in 2017 and 2018. It uses Field Programmable Gate Array processors to select interesting events by placing kinematic and angular requirements on electromagnetic clusters, jets, $$\tau $$ τ -leptons, muons and the missing transverse energy. It allowed to significantly improve the background event rejection and signal event acceptance, in particular for Higgs and B-physics processes.

Characterization of FBK 3D pixel sensor modules based on RD53A readout chip for the ATLAS ITk

CERN is planning to upgrade its Large Hadron Collider to the High Luminosity phase (HL-LHC), pushing detector technologies to cope with unprecedently demanding performance in terms of particle rate and radiation hardness. The ATLAS experiment decided to equip the innermost layer (L0) of its Inner Tracker (ITk) with small-pitch 3D pixels of two different geometries, i.e., 25 µm × 100 µm for the central barrel and 50 µm × 50 µm for the lateral rings. A new generation of 3D pixels featuring these small-pitch dimensions and reduced active thickness (∼150 µm) has been developed to this purpose within a collaboration of INFN and FBK since 2014. Recently, the R&D activities have been focused on the characterization of modules based on sensors compatible with the RD53A readout chip, which were tested in laboratory and at beam lines. In this paper, we report on the characterization of modules irradiated with protons up to a fluence of 1 × 1016 neq/cm2, including threshold tuning and noise measurements, and results from beam tests performed at DESY. Moreover, we will discuss about the electrical characteristics at wafer level and at module level before and after irradiation.

The trigger and data acquisition system of the FASER experiment

The FASER experiment is a new small and inexpensive experiment that is placed 480 meters downstream of the ATLAS experiment at the CERN LHC. FASER is designed to capture decays of new long-lived particles, produced outside of the ATLAS detector acceptance. These rare particles can decay in the FASER detector together with about 500–1000 Hz of other particles originating from the ATLAS interaction point. A very high efficiency trigger and data acquisition system is required to ensure that the physics events of interest will be recorded. This paper describes the trigger and data acquisition system of the FASER experiment and presents performance results of the system acquired during initial commissioning.

The Detector Control System for the magnetic field sensors in New Small Wheel phase I upgrade of ATLAS detector

In conjunction with the High Luminosity upgrade of the Large Hadron Collider accelerator at CERN, the ATLAS detector is also undergoing an upgrade to handle the significantly higher data rates. The muon end-cap system upgrade in ATLAS, lies with the replacement of the Small Wheel. The New Small Wheel (NSW) is expected to combine high tracking precision with upgraded information for the Level-1 trigger. To accomplish this, small Thin Gap Chamber (sTGC) and MicroMegas detector technologies are being deployed. Due to their installation location in ATLAS, the effects of Barrel Toroid and End-Cap Toroid magnets on NSW must be measured. For the final experiment at ATLAS, each sTGC large double wedge will be equipped with magnetic field Hall effect sensors to monitor the magnetic field near the NSW. The readout is done with an Embedded Local Monitor Board (ELMB) called MDT DCS Module (MDM). For the integration of this hardware in the experiment, first, a detector control system was developed to test the functionality of all sensors before their installation on the detectors. Subsequently, another detector control system was developed for the commissioning of the sensors. Finally, a detector control system based on the above two is under development for the expert panels of ATLAS experiment. In this paper, the sensor readout, the connectivity mapping and the detector control systems will be presented.

Search for R-parity-violating supersymmetry in a final state containing leptons and many jets with the ATLAS experiment using $$\sqrt{s} = 13\hbox { TeV}$$ proton–proton collision data

A search for R-parity-violating supersymmetry in final states characterized by high jet multiplicity, at least one isolated light lepton and either zero or at least three b-tagged jets is presented. The search uses $${139}\,{\text {fb}^{-1}}$$ 139 fb - 1 of $$\sqrt{s} = {13}\hbox { TeV}$$ s = 13 TeV proton–proton collision data collected by the ATLAS experiment during Run 2 of the Large Hadron Collider. The results are interpreted in the context of R-parity-violating supersymmetry models that feature gluino production, top-squark production, or electroweakino production. The dominant sources of background are estimated using a data-driven model, based on observables at medium jet multiplicity, to predict the b-tagged jet multiplicity distribution at the higher jet multiplicities used in the search. Machine-learning techniques are used to reach sensitivity to electroweakino production, extending the data-driven background estimation to the shape of the machine-learning discriminant. No significant excess over the Standard Model expectation is observed and exclusion limits at the 95% confidence level are extracted, reaching as high as 2.4 TeV in gluino mass, 1.35 TeV in top-squark mass, and 320 (365) GeV in higgsino (wino) mass.

The Micromegas Surface Commissioning For the ATLAS New Small Wheel

In order to cope with the required precision tracking and trigger capabilities from Run III onward in the ATLAS experiment, the innermost layer of the Muon Spectrometer end-cap (Small Wheels) will be upgraded. Each of the two New Small Wheels (NSW) will be equipped with eight layers of MicroMegas (MM) detectors and eight layers of small-strip Thin Gap Chambers (sTGC), both arranged in two quadruplets. MM detectors of large size (up to 3m2) will be employed for the first time in HEP experiments. Four different types of MM quadruplet modules (SM1, SM2, LM1, LM2), built by different Institutes, compose the NSW. The modules are then sent to CERN, integrated into double wedges (DW), tested and sent for commissioning on the wheel itself. At the commissioning stage the MM double wedges along with the sTGC wedges are assembled together into sectors which are then installed and tested on the wheel. Each wheel comprises 8 small (made of SM1 and SM2 modules) and 8 large (made of LM1 and LM2 modules) sectors, in order to provide full coverage of the end caps. The first of the two wheels (NSW-A) has been fully commissioned, installed in ATLAS and the first tests are currently ongoing. The second wheel (NSW-C) is currently under commissioning and is expected to be ready by October this year.

A program to drive the ATLAS Local Trigger Interface (ALTI) at the ATLAS experiment

During the High Luminosity upgrade of the Large Hadron Collider at CERN, the LHC experiments will undergo a series of upgrades in order to maintain high physics performance following an increased data rate. The largest Phase 1 upgrade project at the ATLAS muon system is the replacement of the current inner station (end-cap regions) with the New Small Wheels. In addition, the ATLAS Local Trigger Interface (ALTI), a part of the Timing, Trigger and Control (TTC) system, will replace the four existing TTC modules. In normal operation, the detectors, along with the surrounding electronics, will receive TTC related signals from the Central Trigger Processor (CTP). This information is forwarded to the front-end electronics of each of the ATLAS sub-detectors through an optical network via the ALTI. The interface currently produces an artificially generated pulse pattern that contains the TTC information. This paper will summarize the creation of a program that generates pulse pattern files which are used to drive ALTI. Various tests have been conducted in order to study the performance of the NSW trigger electronics while using these files. Software development and data analysis using ROOT framework were used to validate the results of these tests.

Methods used for Gas Tightness Test and percent Oxygen Monitoring of the NSW Micromegas Detectors of LHC-ATLAS Experiment

In the frame of the LHC-ATLAS Upgrade of phase I, the New Small Wheel detector system is under integration and commissioning at CERN Laboratories. One of the detector type, the Micromegas detectors, during their integration are tested in several stages for gas tightness validation. In particular, the novel method we are using for the gas tightness test, that we called “Flow Rate Loss”, has been realized in several semi-automatic fixed, portable and stand-alone setups for testing either the Micromegas Quads or the final Double Wedges. The obtained measurements up-to-date are presented as well as their obtained statistical distribution. Additionally, during the performance evaluation of the detectors, a percent oxygen monitoring is also performed in 24-hour base. The methods and techniques we developed and used are presented analytically in this work.

The Detector Control System of the New Small Wheel for the ATLAS experiment

The ATLAS Muon Spectrometer is going through an extensive Phase I upgrade to cope up with the future LHC runs of high luminosity of up to instantaneous luminosity of 7.5 × 1034cm−2s−1. The luminosity increase drastically impacts the ATLAS trigger and readout data rates. The present ATLAS Small Wheel Muon detector will be replaced with a New Small Wheel (NSW) detector which is expected to be installed in the ATLAS underground cavern by the end of the Long Shutdown 2 of the LHC. Due to its complexity and long-term operation, the NSW requires the development of a sophisticated Detector Control System (DCS). The use of such a system is necessary to allow the detector to function consistently and safely as well as to function as a seamless interface to all sub-detectors and the technical infrastructure of the experiment. The central system handles the transition between the probe’s possible operating states while ensuring continuous monitoring and archiving of the system’s operating parameters. Any abnormality in any subsystem of the detector triggers a signal or alert (alarm), which alerts the user and either adapts to automatic processes or allows manual actions to reset the system to function properly.