Online program Overview Session: NSS-19

Abstract

The Silicon Tracker of the Compact Muon Solenoid (CMS) is the innermost sub-detector, measuring charged particles produced in high-energy collisions at the Large Hadron Collider (LHC), and is the world’s largest silicon tracking system operational today. The High-Luminosity LHC (HL LHC) will increase luminosity by up to an order of magnitude, delivering 3000–4000 fb⁻¹ of data with up to 200 simultaneous interactions per bunch crossing. To cope with these extreme conditions, CMS will replace its entire tracking system during the Phase-2 Upgrade. The new tracker will feature enhanced radiation tolerance, finer granularity, and extended coverage, significantly improving tracking efficiency, vertex resolution, and momentum measurement. A key innovation is the inclusion of tracking information at the Level-1 trigger. This is enabled by pₜ-modules in the Outer Tracker, each consisting of two closely spaced sensors that correlate hits to identify high-pₜ track candidates in real time. The Outer Tracker will comprise over 13,000 such modules, produced worldwide, with a large-scale production underway since 2025. This contribution will detail the Outer Tracker design and the ongoing module production and integration efforts leading up to the installation and commissioning of the new tracker during the upcoming LHC Long Shutdown 3.

Abstract

The ATLAS Liquid Argon (LAr) calorimeter provides electromagnetic calorimetry for |η|<3.2 and hadronic and forward calorimetry up to |η|=4.9, playing a central role in the reconstruction and triggering of electrons, photons, jets, and missing transverse momentum at the Large Hadron Collider. During LHC Run 3, the detector operated under increased instantaneous luminosity and pileup conditions reaching up to approximately 65 interactions per bunch crossing. A major evolution during this period was the commissioning and operation of the Phase-I Digital Trigger readout system based on longitudinally segmented supercells and real-time FPGA processing. The upgraded trigger path provides finer granularity and improved trigger performance compared to the legacy trigger architecture. In addition, the Digital Trigger enables advanced online detector monitoring and demonstrates strong potential for luminosity measurements using statistical properties of digitized supercell signals. Run 3 data show stable detector operation, excellent trigger-readout agreement, and enhanced trigger efficiency for physics objects.

Abstract

The TRISTAN detector, an array of 9 modules based on monolithic arrays of 166 Silicon Drift Detectors (SDD) pixels is being realized for high accuracy (1 ppm) beta spectroscopy. It will be installed in the KATRIN focal plane by the end of 2026 in order to extend the use of the KATRIN Tritium facility for searching the sterile neutrino in the keV mass range. Each detection module is 4-side buttable and has an area of 4 by 4 cm². Here, the progress in detectors assembly is reported. Currently, more than 25 modules have been realized and tested, allowing to select the best 7 modules, out of the final set of 9. They are being characterized in a chamber replicating the operating conditions in terms of vacuum, electric and magnetic fields. Out of the final target value of 1494 pixels, currently a total of 981 pixels are operational, making this system the largest array of spectroscopic SDD detectors ever commissioned. The challenges of this phase are mostly related to production yield and reliability of the complex assembly phase. All pixels show an average FWHM energy resolution below 300 eV for electrons of 20 keV.

Abstract

The ALICE collaboration is currently developing a new vertex detector ("ITS3"), scheduled for installation in 2028 - 2029 during LHC long shutdown 3 to replace the three innermost layers (Inner Barrel) of the existing Inner Tracking System as from Run 4 onwards. ITS3 comprises the use of ultra-thin (down to 50 micrometers) silicon wafers and stitching technologies in 65nm CMOS imaging process , enabling the production of large area (9.8cm x 26.7cm) Monolithic Active Pixels Sensors sensors which will be bent to half-cylindrical shapes of 19, 25.2 and 31.5 mm bending radii for layer 0, 1 and 2 respectively, and supported by carbon foam structures. The very low power consumption of about 40mV/cm² allows for air cooling, and the bent shape allows for a minimum of mechanical support using carbon foam only. The very low material budget of less than 0.09% of a radiation length per layer ensures extremely good tracking and vertexing performance. Following an extensive R\&D program for the ITS3,  large area stitched prototype structures (MOSAIX) with a final pixel pitch of 20.8µm x 22.8µm, matrix sizes and all other features have been produced and will be tested throughout this year before and after irradiation with TID and NIEL in order to validate the final design for production. In this contribution we present and discuss an overview of detection performance measurements in various test beams.

Abstract

The LHCb Upgrade II program aims to operate at an instantaneous luminosity of up to 1.0x10³⁴ cm⁻² s⁻¹, during the High-Luminosity LHC Run 5, targeting an integrated dataset of 300 fb⁻¹. This ambitious goal requires a complete redesign of the electromagnetic calorimeter (ECAL), leading to the development of the PicoCal detector. The upgrade addresses the challenges of extreme pile-up, high particle densities, and severe radiation levels—reaching up to 1 MGy in the innermost regions—by introducing enhanced transverse granularity and precision timing capabilities at the level of O(10) picoseconds. The PicoCal design combines different technologies optimized for distinct detector regions. The central, high-radiation zones will employ Spaghetti Calorimeter (SpaCal) modules, based on dense absorbers coupled with fast scintillating materials. The
outer regions will be instrumented with upgraded Shashlik calorimeters with fast wavelength-shifting fibers to improve timing performance. Extensive R&D efforts have focused on scintillators, photodetectors, and front-end electronics, with several photomultiplier tube (PMT) candidates evaluated for their timing precision and radiation tolerance. Prototype modules of both SpaCal and Shashlik technologies have been successfully designed, constructed, and tested. Test beam campaigns demonstrate that the calorimeter achieves an energy resolution with a stochastic term of about 10% sampling contribution and 1% constant term, while timing resolutions better than 20 ps are achieved at high energies across different scintillator options. In parallel, the SPIDER ASIC prototype has been validated in beam tests, achieving timing performance comparable to standard digitizer-based readout systems. These results collectively demonstrate that the PicoCal concept meets the stringent performance requirements of LHCb Upgrade II, ensuring precise energy and time measurements
under extreme HL-LHC conditions.

Abstract

Planned upgrades to Ring Imaging Cherenkov (RICH) detectors in the LHCb, Belle II, and ALICE 3 high energy physics experiments require photodetectors capable of single-photon detection at high event rates and neutron fluences up to a few 10¹³ 1-MeV equivalent/cm². The spadRICH project develops a CMOS-based single-photon avalanche diode (SPAD) array optimized for radiation hardness and cryogenic operation to meet these requirements.
This paper presents a decision-maker (DM) circuit architecture for use in digital silicon photomultiplier (dSiPM) readout. The DM identifies the first-firing SPAD along with its address among competing channels and disables both the winning and losing SPADs immediately after the decision, thus suppressing subsequent avalanches. Combined with fast quenching, this reduces afterpulsing and lowers power consumption in multi-channel readout — critical for operation in high-radiation cryogenic environments. The DM can be cascaded into a binary tree topology to implement full dSiPM functionality. dSiPMs with varying aspect ratios and SPAD sizes are fabricated in the GlobalFoundries 55 nm BCDLite® process. In addition to dSiPMs, we have also implemented analog SiPMs (aSiPMs) to compare the advantage of its high fill factor with selective deactivation of SPADs and time-gating features of dSiPMs in high radiation environments.