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1. The ATLAS experiment at the CERN Large Hadron Collider: a description of the detector configuration for Run 3

   https://doi.org/10.1088/1748-0221/19/05/P05063  

   Aad, G; Abbott, B; Abbott, DC; Abdallah, J; Abeling, K; Abidi, SH; Aboulhorma, A; Abovyan, S; Abramowicz, H; Abreu, H; et al (May 2024, Journal of Instrumentation)

   Abstract The ATLAS detector is installed in its experimental cavern at Point 1 of the CERN Large Hadron Collider. During Run 2 of the LHC, a luminosity of  ℒ = 2 × 10³⁴cm^-2s^-1was routinely achieved at the start of fills, twice the design luminosity. For Run 3, accelerator improvements, notably luminosity levelling, allow sustained running at an instantaneous luminosity of  ℒ = 2 × 10³⁴cm^-2s^-1, with an average of up to 60 interactions per bunch crossing. The ATLAS detector has been upgraded to recover Run 1 single-lepton trigger thresholds while operating comfortably under Run 3 sustained pileup conditions. A fourth pixel layer 3.3 cm from the beam axis was added before Run 2 to improve vertex reconstruction and b-tagging performance. New Liquid Argon Calorimeter digital trigger electronics, with corresponding upgrades to the Trigger and Data Acquisition system, take advantage of a factor of 10 finer granularity to improve triggering on electrons, photons, taus, and hadronic signatures through increased pileup rejection. The inner muon endcap wheels were replaced by New Small Wheels with Micromegas and small-strip Thin Gap Chamber detectors, providing both precision tracking and Level-1 Muon trigger functionality. Trigger coverage of the inner barrel muon layer near one endcap region was augmented with modules integrating new thin-gap resistive plate chambers and smaller-diameter drift-tube chambers. Tile Calorimeter scintillation counters were added to improve electron energy resolution and background rejection. Upgrades to Minimum Bias Trigger Scintillators and Forward Detectors improve luminosity monitoring and enable total proton-proton cross section, diffractive physics, and heavy ion measurements. These upgrades are all compatible with operation in the much harsher environment anticipated after the High-Luminosity upgrade of the LHC and are the first steps towards preparing ATLAS for the High-Luminosity upgrade of the LHC. This paper describes the Run 3 configuration of the ATLAS detector. 

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2. Development of the CMS detector for the CERN LHC Run 3

   https://doi.org/10.1088/1748-0221/19/05/P05064  

   Hayrapetyan, A; Tumasyan, A; Adam, W; Andrejkovic, JW; Arnold, B; Bergauer, H; Bergauer, T; Chatterjee, S; Damanakis, K; Dragicevic, M; et al (May 2024, Journal of Instrumentation)

   Abstract Since the initial data taking of the CERN LHC, the CMS experiment has undergone substantial upgrades and improvements. This paper discusses the CMS detector as it is configured for the third data-taking period of the CERN LHC, Run 3, which started in 2022. The entire silicon pixel tracking detector was replaced. A new powering system for the superconducting solenoid was installed. The electronics of the hadron calorimeter was upgraded. All the muon electronic systems were upgraded, and new muon detector stations were added, including a gas electron multiplier detector. The precision proton spectrometer was upgraded. The dedicated luminosity detectors and the beam loss monitor were refurbished. Substantial improvements to the trigger, data acquisition, software, and computing systems were also implemented, including a new hybrid CPU/GPU farm for the high-level trigger. 

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3. Characterization of a high bandwidth readout chain for the CMS phase-2 pixel upgrade

   https://doi.org/10.1088/1748-0221/17/08/C08017  

   Smith, C. (August 2022, Journal of Instrumentation)

   Abstract The CMS collaboration is building a new inner tracking pixel detector for the High-Luminosity LHC. Each pixel readout chip will be controlled with a single serial input stream at 160 Mb/s and will send out data via four current mode logic (CML) 1.28 Gb/s outputs. The readout chips will be grouped in modules and connected with up to 1.6 meters long low-mass electrical links to Low-Power Gigabit Transceivers (lpGBT) and Versatile Link PLUS Transceiver (VTRx+) modules that send the data optically to off-detector electronics at 10 Gb/s. The characterization of these components and system tests of the readout chain are presented. 

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4. Smart pixel sensors: towards on-sensor filtering of pixel clusters with deep learning

   https://doi.org/10.1088/2632-2153/ad6a00  

   Yoo, Jieun; Dickinson, Jennet; Swartz, Morris; Di_Guglielmo, Giuseppe; Bean, Alice; Berry, Douglas; Blanco_Valentin, Manuel; DiPetrillo, Karri; Fahim, Farah; Gray, Lindsey; et al (August 2024, Machine Learning: Science and Technology)

   Abstract Highly granular pixel detectors allow for increasingly precise measurements of charged particle tracks. Next-generation detectors require that pixel sizes will be further reduced, leading to unprecedented data rates exceeding those foreseen at the High- Luminosity Large Hadron Collider. Signal processing that handles data incoming at a rate of $O$(40 MHz) and intelligently reduces the data within the pixelated region of the detectorat ratewill enhance physics performance at high luminosity and enable physics analyses that are not currently possible. Using the shape of charge clusters deposited in an array of small pixels, the physical properties of the traversing particle can be extracted with locally customized neural networks. In this first demonstration, we present a neural network that can be embedded into the on-sensor readout and filter out hits from low momentum tracks, reducing the detector’s data volume by 57.1%–75.7%. The network is designed and simulated as a custom readout integrated circuit with 28 nm CMOS technology and is expected to operate at less than 300  $\mu W$with an area of less than 0.2 mm². The temporal development of charge clusters is investigated to demonstrate possible future performance gains, and there is also a discussion of future algorithmic and technological improvements that could enhance efficiency, data reduction, and power per area. 

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5. The CMS Fast Beam Condition Monitor for HL-LHC

   https://doi.org/10.1088/1748-0221/19/03/C03048  

   Auzinger, G.; Bakhshiansohi, H.; Dabrowski, A.; Delannoy, A.G.; Dierlamm, A.; Dragicevic, M.; Gholami, A.; Gomez, G.; Guthoff, M.; Haranko, M.; et al (March 2024, Journal of Instrumentation)

   Abstract The high-luminosity upgrade of the LHC brings unprecedented requirements for real-time and precision bunch-by-bunch online luminosity measurement and beam-induced background monitoring. A key component of the CMS Beam Radiation, Instrumentation and Luminosity system is a stand-alone luminometer, the Fast Beam Condition Monitor (FBCM), which is fully independent from the CMS central trigger and data acquisition services and able to operate at all times with a triggerless readout. FBCM utilizes a dedicated front-end application-specific integrated circuit (ASIC) to amplify the signals from CO₂-cooled silicon-pad sensors with a timing resolution of a few nanoseconds, which enables the measurement of the beam-induced background. FBCM uses a modular design with two half-disks of twelve modules at each end of CMS, with four service modules placed close to the outer edge to reduce radiation-induced aging. The electronics system design adapts several components from the CMS Tracker for power, control and read-out functionalities. The dedicated FBCM23 ASIC contains six channels and adjustable shaping time to optimize the noise with regards to sensor leakage current. Each ASIC channel outputs a single binary high-speed asynchronous signal carrying time-of-arrival and time-over-threshold information. The chip output signal is digitized,encoded, and sent via a radiation-hard gigabit transceiverand an optical link to the back-end electronics for analysis. This paper reports on the updated design of the FBCM detector and the ongoing testing program. 

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