VERTEX 2025 : 33rd International Workshop on Vertex Detectors

25 Aug 2025, 08:00 → 29 Aug 2025, 13:00 America/New_York

Ballroom C (Student Union)

VERTEX '25
August 2025, University of Tennessee, Knoxville

The workshop will begin Monday morning, August 25, and run through a half-day on Friday, August 29. All sessions will be hosted at the UTK Student Union. 

Monday night, there will be a reception and poster session in Knoxville's Sunsphere. Wednesday afternoon will feature a social programme in and around the Knoxville and Great Smoky Mountains area as well as a banquet dinner in the evening.

 

Conference Picture

Reception and group pictures

 

VERTEX2025-Poster-Knoxville-TN

Monday, 25 August

08:00 → 09:00 Registration

Convener: Mathieu Benoit (ORNL)

09:00 → 10:00 Introduction to venue and conference

Convener: Mathieu Benoit (ORNL)

09:00 Conference introduction and logistics

Speaker: Mathieu Benoit (ORNL)

IntroSlides_MB_Vertex25.pdf

ornl_tour_pickup.pdf

09:20 Introduction to UTK

Speaker: Prof. Adrian Del Maestro (UTK)

09:40 Introduction to ORNL

Speaker: Marcel Demarteau (Oak Ridge National Laboratory)

Demarteau-intro-ORNL.pdf

10:00 → 10:30 Coffee break

10:30 → 12:30 Current Vertex Detector performance and status

Convener: Mathieu Benoit (ORNL)

10:30 ATLAS Inner Detector Operational experience at the Large Hadron Collider at CERN

The tracking and vertexing performance of the ATLAS detector relies critically on the silicon and gaseous tracking subsystems that form the ATLAS Inner Detector. They have been operated successfully with high performance in LHC since Run 1 (2010) up to the current date. Those subsystems have undergone significant upgrades to meet the challenges imposed by the higher pileup and luminosity,  that are being delivered by the LHC, well beyond design. Furthermore, the Inner Detector was exposed to a radiation dose higher than what has ever been
experienced in any other detectors in high energy physics experiments. Effects of radiation damage on silicon sensors and front-end ASICs were intensively studied. The key status and performance metrics of the Pixel Detector, the Semi Conductor Tracker, and the Transition Radiation Tracker are summarized, and the operational experience and requirements to ensure optimum data quality and data taking efficiency are described.

Speaker: Daiya Akiyama (Waseda)

dakiyama_20250825.pdf

11:00 CMS Tracker Status, Challenges, and Performance in Run 3

The innermost tracking system of the CMS experiment consists of two tracking devices: the Silicon Pixel and Silicon Strip detectors. The tracker was specifically designed to very accurately determine the trajectory of charged particles or tracks, enabling precise reconstruction of primary and secondary vertices, as well as momentum measurements, in the high-luminosity environment of the LHC. Since the start of Run 3 in 2022, the CMS tracker has operated under increasingly demanding conditions, including higher instantaneous luminosities and increased pileup. In this talk, we present the current status and operational experience of the CMS tracker during Run 3, with a focus on its performance under these new conditions. We review key metrics including hit efficiency, alignment precision, tracking efficiency, and vertex resolution. The tracker has continued to perform at or near design specifications, benefitting from targeted improvements in alignment strategies, calibration workflows, and real-time monitoring. We also discuss the main challenges faced during Run 3, such as radiation-induced effects on sensors and electronics. In particular, aging effects due to cumulative radiation damage are becoming increasingly relevant and require careful monitoring and mitigation to ensure sustained performance.

Speaker: Muti Wulansatiti (Rice University)

VERTEX25_CMSTrackerOps_MW.pdf

11:30 ALICE ITS2: Performance and Operational Experience

ALICE ITS2: Performance and Operational Experience

The ALICE Inner Tracking System (ITS) is the innermost tracking detector at the ALICE experiment, providing vertex reconstruction and tracking of charged particles.
The upgraded version, referred to as ITS2 and currently operating in ALICE, consists of seven cylindrical layers of Monolithic Active Pixel Sensors (MAPS) covering 10 m$^{2}$ of active area.
These so-called ALPIDE sensors, manufactured in 180 nm CMOS technology, feature 27 $\times$ 29 $\mu$m pixel dimensions resulting in a spatial resolution of about 5 $\mu$m and are thinned to 50 $\mu$m (innermost three layers) and 100 $\mu$m (outer four layers), achieving a low material budget of 0.36\% X$_{0}$ per innermost layer.

In this contribution, the operational experience during LHC Run 3 as well as performance results are summarized.
This includes threshold stability, fake-hit rate, fraction of noisy pixels, detector efficiency, and impact-parameter resolution as well as beam background effects.
Moreover, selected curiosities, such as the measurement of energy loss achieved by detuning the detector front-end circuitry and oversampling its response, will also be presented.

Speaker: Jiyoung Kim (Inha University)

20250825_Vertex2025_ITS-overview_JiyoungKim_ver5.pdf

12:00 Belle II Vertex Detector: Run Performance (PXD + SVD) and Upgrade Developments (VTX)

Since 2019, the Belle II experiment at the SuperKEKB ($B$-factory) in Tsukuba, Japan has been collecting data from asymmetric-energy $e^-e^+$ collisions at the $\Upsilon({4S})$ resonance. It holds the world luminosity record of $5.1 \times 10^{34}\ \mathrm{cm}^{-2}\ \mathrm{s}^{-1}$ recorded in 2024, with the goal of collecting a data set 50 times larger than the predecessor experiments Belle and BaBar.
The Vertex Detector (VXD) provides a vertex resolution of approximately 10 $\mu$m, allowing highly precise tracking and vertex reconstruction, which is essential for time-dependent measurements. The VXD is designed to achieve this performance through two complementary subsystems: closest to the interaction point (IP), the Pixel Detector (PXD), which consists of two layers of thin DEpleted P-channel Field Effect Transistor (DEPFET)-based silicon sensors, and four outer layers of double-sided silicon strip sensors (DSSD), known as the Silicon Vertex Detector (SVD).
During Run 1 (2019-2022), a single layer of PXD and the full SVD, consisting of 172 DSSD modules, were installed and delivered the excellent performance which included high hit efficiency $(> 99 \%)$. In 2023, during the first long shutdown (LS1), a new fully populated two-layer PXD (PXD2) was installed with the same SVD. PXD2 has 40 modules, each consisting of an array of 250 × 768 pixels, with pixel sizes ranging from 50 $\mu$m × 55 $\mu$m to 50 $\mu$m × 85 $\mu$m. PXD utilizes DEPFET sensors, allowing an average material budget of 0.21% $X_0$ per layer.
Since February 2024, Belle II has resumed data-taking for Run 2, and the VXD performed within specifications until May 2024, when PXD2 was temporarily shut down due to partial damage from two uncontrolled beam losses. The following talk will discuss the details and performance of both the PXD and SVD during Runs 1 and 2. In addition, we present the development of a next-generation pixelated vertex detector (VTX), based entirely on depleted monolithic active pixel sensors (DMAPS), specifically the OBELIX sensor, which aims to collect 50 $\mathrm{ab}^{-1}$ of data and increase the luminosity up to $6 \times 10^{35}\ \mathrm{cm}^{-2}\ \mathrm{s}^{-1}$ during upcoming run periods. This new system will replace the full VXD and promises improved spatial resolution, reduced readout integration time, reduced material budget, and lower power consumption. It is designed to operate at high hit rates and high radiation levels. This transition marks a strategic shift toward ensuring continued high-performance vertexing as Belle II advances its search for new physics at the intensity frontier.

Speaker: Ravinder Dhayal (Charles University, Prague)

Vertex2025_BelleII_Dhayal.pdf

12:30 → 14:00 Lunch

Free lunch around Student Union

14:00 → 14:30 Current Vertex Detector performance and status

Convener: Mathieu Benoit (ORNL)

14:00 Operation and performance of the sPHENIX MAPS vertex detector

The sPHENIX detector at the Relativistic Heavy Ion Collider is the newest experiment at a hadron collider since the switch on of the LHC. It completed its commissioning in October 2024 and is dedicated to precision probes of Quark-Gluon Plasma. To achieve this goal, sPHENIX utilises a monolithic active pixel vertex detector (MVTX). This detector enables precision measurements of beauty and charm hadrons produced in proton-proton and gold-gold collisions. The MVTX contains 432 MAPS ASICs, each 50 microns thick and reading out at 600 MB/s. The MVTX is capable of operating in a streaming mode which allows for the collection of high statistics open heavy flavor data without a trigger bias, enriching the low pT reach of sPHENIX. This presentation will discuss the design, operation and performance of the detector, including overcoming challanges faced from backgrounds in the harsh conditions experienced from heavy ion beams.

Speaker: Michael Peters (Massachusetts Institute of Technology (MIT))

Peters_MVTX_VERTEX2025.pdf

14:30 → 15:30 Vertex detector upgrade at the LHC

Convener: Oskar Hartbrich (Oak Ridge National Lab)

14:30 Phase-2 Upgrade of the ATLAS Inner Tracker

The ATLAS experiment is currently preparing for an upgrade of the Inner Tracking for High-Luminosity LHC operation, scheduled to start in 2030. The radiation damage at the maximum integrated luminosity of 4000/fb implies integrated hadron fluencies over 2x1016neq/cm2 and tracking in a very dense environment call for a replacement of the existing Inner Detector. An all-silicon Inner Tracker (ITk) is proposed with a pixel detector surrounded by a strip detector. After an extensive prototyping phase, all the institutes involved in the ITk are currently in pre-production phase, moving toward production mode. In this contribution we present the design of the ITk Detector and its expected performance. An overview of the current status of the various detector components, both pixel, strip and the other common items, focusing on the preparation for production, with its more challenging aspects, will be summarized.

Speaker: Caterina Vernieri (SLAC)

CV-ITK-Vertex-Talk-2025-v2.pdf

15:00 ALICE Inner Tracking System 3 overview: from MOSS and MOST to the full-size MOSAIX sensor prototype

The Inner Tracking System 3 (ITS3) for the ALICE experiment at CERN, to be installed during the LHC Long Shutdown 3 (2026-2030), will replace the current three innermost ITS2 layers. ITS3 introduces a novel ultra-light and high-precision vertex detector based on monolithic active pixel sensors that are thinned to 50 µm, bent to radii of 19, 25, and 32 mm to form truly cylindrical layers, and extended to unprecedented lengths of 27 cm through a wafer-scale stitching process. Stitching multiple reticle-sized blocks into a single large sensor eliminates the need for flexible printed circuits, reducing complexity and mass. These design choices aim to meet the stringent ITS3 requirements of minimal material budget (< 0.09 % X$_0$ per layer), low power consumption (∼ 40 mW/cm$^2$ ), a lightweight mechanical support structure based on carbon foam, air-cooled mechanics, and high spatial resolution (∼ 5 µm). The core of this upgrade is the development of a new family of stitched CMOS sensors — MOSS, MOST, and MOSAIX — fabricated in the 65 nm Tower Semiconductor (TPSCo) process.
MOSS and MOST prototypes have demonstrated the feasibility of this approach, achieving excellent performance in laboratory and beam tests: detection efficiency above 99%, low fake-hit rate (< 10$^{−2}$ /pixel/s), and radiation tolerance up to 4 × 10$^{12}$ 1 MeV n$_{eq}$ /cm$^2$ and 4 krad. Building on these results, the final full-size full-functionality ITS3 sensor prototype, MOSAIX, is under development.
This contribution will present the development path from MOSS and MOST to MOSAIX with focus on the sensor performance validation and highlighting key technological breakthroughs such as large-area sensor stitching, sensor bending and thinning, radiation-tolerant design, and integration using carbon foam and air cooling.

Speaker: Livia Terlizzi (CERN)

ALICE_Inner_Tracking_System_3_overview:from_MOSS_and_MOST_to_the_full-size_MOSAIX_sensor_prototype.pdf

15:30 → 16:00 Coffee break

16:00 → 17:00 Vertex detector upgrade at the LHC

Convener: Oskar Hartbrich (Oak Ridge National Lab)

16:00 The CMS Tracker Upgrade for Phase-2: Meeting the Challenges of the HL-LHC

The High-Luminosity Large Hadron Collider (HL-LHC) will significantly increase the instantaneous luminosity of proton-proton collisions, pushing the CMS experiment into a regime of extreme radiation levels, high particle multiplicities, and unprecedented data rates. To maintain and extend the physics performance of the CMS detector under these conditions, a complete replacement of the tracking system is underway as part of the Phase-2 Upgrade. This talk presents the design, goals, and status of the Phase-2 CMS Tracker Upgrade, which includes entirely new silicon pixel and strip detectors with enhanced radiation hardness, finer granularity, and extended pseudorapidity coverage. The upgraded tracker will also feature on-detector data reduction through the use of real-time trigger information—an essential capability for sustaining low trigger thresholds at the HL-LHC. Special emphasis is placed on innovations in sensor technology, powering and cooling strategies, and the mechanical integration of large-scale modular components. We discuss the R&D, prototyping, and production progress, along with results from recent beam tests and system integration campaigns. The talk will also highlight key challenges in quality assurance, large-scale assembly, and pre-installation testing, as well as the timeline toward installation and commissioning during Long Shutdown 3.

Speaker: Matteo Magherini (CERN)

Vertex_Magherini_25Aug.pdf

Vertex_Magherini_25Aug.pptx

16:30 Vertex and Tracking Detectors for Future Lepton Colliders

Several proposals for future high-energy lepton colliders are currently under study, including circular (FCC-ee, CEPC) and linear (CLIC, LCF) options. The physics goals and experimental conditions at these 'Higgs Factories' pose challenging demands on the performance of the detector systems. For the silicon-based vertex and tracking layers, a single-plane spatial resolution of a few microns is needed, combined with very thin sensors (<100 microns). Moreover, hit-time tagging with a few nanosecond resolution is required to reject beam-induced background events for some of the collider options. An even better track-timing precision well below 100 ps opens up the possibility of particle identification by time-of-flight measurements.
To address these stringent detector requirements, a broad R&D program on new silicon-sensor technologies is being pursued within various collaborative frameworks.
This contribution introduces the Lepton-Collider detector requirements and gives an overview of the R&D program for silicon-based vertex and tracking detectors.

Speaker: Dominik Dannheim (CERN)

Vertex_Tracking_Future_Lepton_Colliders_VERTEX2025_26Aug2025.pdf

19:00 → 21:00 Reception

Tuesday, 26 August

09:00 → 11:00 Monolithic Detector R&D for HEP experiments

Convener: Mathieu Benoit (ORNL)

09:00 Monolithic active pixel sensors based on the TPSCo 65 nm imaging CMOS technology: an overview of results and future challenges

Monolithic active pixel sensors (MAPS) are crucial for current and future High Energy Physics detectors, due to their minimal material budget, low power consumption and low cost per unit area. Following the successful deployment of the first detector based on MAPS at CERN (ALICE Inner Tracker System 2, ITS2) adopting the TowerJazz 180 nm imaging CMOS technology, the investigation of the TPSCo 65 nm imaging technology was started. This effort is done in the framework of the CERN EP R&D program, in synergy with the ALICE experiment, interested in developing a wafer-scale, stitched sensor for its ITS3 upgrade to replace the inner layers of the ITS2. The smaller feature size of this 65 nm technology is crucial to match the requirements of pixel pitch, time resolution, output data rate and radiation hardness of future HEP detectors. In addition, this technology allows the fabrication of wafer-scale sensors on larger wafers (300 mm instead of 200 mm for the 180 nm process) and reduce the material budget to less than 0.09% X$_0$, due to the inclusion of all power and data connections on chip.
This presentation will give an overview of this R&D program, highlighting the path from the design and characterization of test structures to qualify the technology for use in HEP, to the development of wafer-scale sensors. Efficient operation was demonstrated before and after irradiation (up to 10$^{15}$ 1 MeV neq/cm$^2$ at room temperature) for pixel pitches between 10 and 25 µm, and sensor timing resolution down to ~ 65 ps RMS was obtained for a 10 µm pitch. The H2M (Hybrid-to-Monolithic) ASIC implemented a hybrid pixel architecture in a monolithic sensor at 35 µm pitch and revealed some sensitivity to circuit layout for larger pixel pitches. Different approaches to stitching were investigated in the MOSS and MOST sensors, in preparation for the design of the MOSAIX, the wafer-scale stitched chip for the ITS3 upgrade based on 22.8 x 20.8 µm$^2$ pixels. This R&D activity has raised interest in this technology and helped gain experience to provide support and access to the TPSCo 65 nm process, fostering further developments in the field of monolithic CMOS sensors. The presentation will end with an outlook on the future challenges of this R&D in view of ALICE3, FCC-ee, and other applications.

Speaker: Giacomo Ripamonti (CERN)

Vertex2025_Ripamonti.pdf

Vertex2025_Ripamonti.pptx

09:30 Status and Performance of the MIMOSIS CMOS Sensor for the Micro-Vertex Detector of CBM Experiment

The Compressed Baryonic Matter (CBM) experiment is an upcoming fixed-target heavy-ion experiment designed to study the Quantum Chromodynamics (QCD) phase diagram at high net baryon densities and moderate temperatures. The Micro Vertex Detector (MVD) is located 5-10 cm downstream of the target and serves as the first detector in the setup. It is designed for precise tracking and vertex reconstruction in the high track density environment close to the interaction point, requiring a low material budget with each layer contributing only 0.3% to 0.5% of the radiation length (x/X₀).

All stations of the MVD will be equipped with CMOS Monolithic Active Pixel Sensors (MAPS), specifically the MIMOSIS sensor, featuring 1024 × 504 pixels with approximately 5 µs time resolution and about 5-6 µm spatial resolution. The MIMOSIS sensors are required to withstand a Total Ionizing Dose (TID) of about 5 MRad and Non-Ionizing Energy Loss (NIEL) fluences up to 7 x 10$^{13}$ n$_{eq}$/cm$^{2}$ per year of CBM operation. Various prototypes have been developed through a joint R&D effort by IPHC Strasbourg, Goethe University Frankfurt and GSI Darmstadt. These prototypes have undergone extensive laboratory testing before and after dedicated beam tests with minimum ionizing particles at several test facilities. Furthermore, comprehensive tests of radiation tolerance and robustness against heavy-ion impacts have been performed.

In this contribution, we summarize the final results of the MIMOSIS prototype R&D phase and present the resulting design highlights for the final CBM MVD sensor.

Speaker: Ajit Kumar (Goethe-Universität Frankfurt(UFfm-IKP))

vertex25_ajit_final.pdf

10:00 An overview of the imaging layers of the Barrel Imaging Calorimeter for ePIC at the Electron Ion Collider

The Barrel Imaging Calorimeter (BIC) is a hybrid detector for the electron-Proton/Ion Collider (ePIC) experiment at the Electron-Ion Collider (EIC). The BIC is a high-performance lead-scintillating-fiber-based sampling calorimeter with layers of AstroPix sensors, an inexpensive, low-power HV-CMOS silicon sensor, for shower profiling. The detector design fulfills stringent ECAL requirements in the barrel region from the EIC yellow report. Some of the important requirements are 10$^4$ $\pi$ suppression at low momenta, decent energy resolution for photon energy reconstruction, fine granularity for good $\pi^0$-$\gamma$ separation up to 10 GeV, and measurement of low energy photons down to 100 MeV with range exceeding 10 GeV.
With this submission, an overview of the Barrel Imaging Calorimeter design will be presented with emphasis on the imaging layers and AstroPix sensors. The BIC, with a coverage of (-1.71 $< \eta <$ 1.31), consists of 48 trapezoidal sectors built of layers of scintillating fibers embedded in lead and six slots for imaging layers. Each imaging layer consists of several AstroPix staves subdivided into modules. The BIC will incorporate a total of about 140 m$^2$ of AstroPix sensors. The AstroPix sensor was inspired by ATLASPix3 and MuPix and is being designed using a 180 nm CMOS process for future gamma-ray astrophysics missions. The AstroPix sensors have the advantage of a fully monolithic structure, low manufacturing cost, low material budget , fast charge collection, and high radiation tolerance with low-power operation, large sensitive area, low noise, wide dynamic range, and good energy/spatial resolution. The presentation will also include a brief discussion on measured AstroPix performance.

Speaker: Manoj Jadhav (Argonne National Laboratory)

BIC_VERTEX_MJ_25Aug2025.pdf

10:30 Performance of the AstroPix Prototype Module for the Barrel Imaging Calorimeter at the ePIC Detector and in Space-Based Payloads

AstroPix is a high-voltage CMOS (HV-CMOS) monolithic silicon sensor originally developed to enable precision gamma-ray imaging and spectroscopy in the medium-energy regime (~100 keV–100 MeV) based on the experience from ATLASpix and MuPix. It features a 500 µm pixel pitch, on-pixel amplification and digitization, and low power consumption (~1.5 mW/cm²), making it scalable for large-area, multilayer telescope detector planes. The detectors have a designed dynamic range of 25 keV to 700 keV.

With these features, AstroPix meets the requirements of both the multilayer telescope detectors for space missions and the imaging layers of the Barrel Imaging Calorimeter (BIC) in the ePIC detector at the future Electron-Ion Collider (EIC). For the space-based payload, AstroPix is being integrated into sounding rocket and balloon payloads as more demonstrations of the utility of the devices. For BIC, AstroPix-based imaging layers interleaved within the lead/scintillating-fiber (Pb/SciFi) sampling calorimeter provide fine-grained shower imaging, enabling key performance features such as electron/pion or gamma/pion separation.

As part of the ongoing detector R&D efforts, we have been testing various AstroPix version 3 configurations: the single chip, a quad-chip assembly, a three-layer stack of quad chips, and a 9-chip PCB module that represents the smallest prototype unit of the imaging layer. This presentation will highlight recent performance test results from these AstroPix detector configurations.

Speaker: Bobae Kim (Argonne National Laboratory)

2025VERTEX_astropix_bb_.pdf

11:00 → 11:30 Coffee Break

11:30 → 12:30 LGAD Detector R&D

Convener: Oskar Hartbrich (Oak Ridge National Lab)

11:30 Performance of first full-size production of AC-LGADs for the ePIC detector

Low Gain Avalanche Detectors (LGADs) are characterized by a fast rise time (~500ps) and extremely good time resolution (down to 17ps), and potential for a very high repetition rate with ~1 ns full charge collection. For the application of this technology to near future experiments such as e+e- Higgs factories (FCC-ee), the ePIC detector at the Electron-Ion Collider, or smaller experiments (e.g., the PIONEER experiment), the intrinsic low granularity of LGADs and the large power consumption of readout chips for precise timing is problematic. AC-coupled LGADs, where the readout metal is AC-coupled through an insulating oxide layer, could solve both issues at the same time thanks to the 100% fill factor and charge-sharing capabilities. Charge sharing between electrodes allows a hit position resolution well below the pitch/sqrt(12) of standard segmented detectors. At the same time, it relaxes the channel density and power consumption requirement of readout chips. Extensive characterization of AC-LGAD devices from the first full size (up to 3x4 cm) production from HPK for ePIC will be shown in this contribution. Eight wafers of strip sensors were produced and tested with both laser TCT and probe station (IV/CV). We will also present the first results on AC-LGADs irradiated with 1 MeV reactor neutrons at JSI/Ljubljana to fluences on the order of 1e13 to 1e15 n/cm2.

Speaker: Simone Mazza (University of California, Santa Cruz)

130825_AC_LGADs_Vertex2025.pdf

12:00 Performance Evaluation of the Timing Resolution of an AC-LGADs Bonded to a Si-Ge BJT ASICs

Reconstructing particle tracks in future high-luminosity collider experiments is expected to be challenging due to the huge pile-up tracks. 4D tracking by the inner tracking detectors with both spatial and timing resolution will provide reliable track reconstruction.
Capacitive Coupled Low Gain Avalanche Diodes (AC-LGADs) developed by KEK, Tsukuba group with Hamamatsu Photonics K.K. have an excellent timing resolution(~20ps) with 20um active thickness as well as a 100um×100um pitch pixelated electrodes to achieve O(10um) spatial resolution. To read out the pixelated AC-LGAD sensors without degrading timing performance low noise and low power consumption ASIC is required.
In this study, as a possible candidate of AC-LGADs read out ASIC, a silicon-germanium (Si-Ge) based ASIC, featuring low power consumption, low noise, and high-speed operation has been tested. In this presentation, a performance evaluation of the timing resolution of Si-Ge ASIC bonded to the AC-LGAD sensors by wirebonds and flip-chip evaluated by using a 3 GeV electron beam at KEK, Japan.

Speaker: Issei Horikoshi (University of Tsukuba)

horikoshi_AC-LGAD_Si-GeASIC_vertex2025_horikoshi.pdf

12:30 → 14:00 Lunch

14:00 → 15:30 Front-end electronics for LHC Upgrade

Convener: Stefan Spanier

14:00 Progress with precise on-pixel time stamping and event selection with Timepix4 and LA-Picopix

Hybrid pixel detector readout continues to permit maximum flexibility when addressing the need for precise time tagging in high-rate environments as the detector topology and readout circuitry can be optimised independently for maximum performance. By setting the detection threshold well above the noise floor, noise hit free readout is possible and this, in turn, allows for trigger-free data-driven operation strongly widening the scope of operation both in the high energy physics environment and elsewhere. The Timepix4 ASIC can provide on-pixel time stamping to within a bin of 200ps while the LA-Picopix aims for a bin size of 40-50ps. However, as the Timepix4 device demonstrates, data-driven readout can lead to challenges with off-chip bandwidth. The LA-Picopix ASIC contains new features which can help by rejecting large clusters which can dominate readout bandwidth needlessly in some cases. This contribution will describe the Timepix4 architecture and show a few examples of applications both within and beyond HEP. It will also describe the status of the LA-Picopix design. Recent progress in reducing the cost of flip chip and Through Silicon Via processing will also be described.

Speaker: Dr Michael Campbell (CERN)

MCampbell_Vertex2025.pptx

14:30 ALICE ITS3 MOSAIX stitched wafer-scale sensor – Implementation challenges and solutions

MOSAIX is a full-scale full-size monolithic CMOS pixel sensor prototype developed for the ALICE Inner Tracking System 3 (ITS3), which will replace the three innermost layers of the ALICE tracker during the LHC Long Shutdown 3 (LS3). With over 26 cm in length and 2 cm in width, it contains 12 repeated sensor units (RSU) containing each 12 pixel matrix tiles of 22.8 x 20.8 µm2 pixels. Power supply and data lines of each RSU are connected by stitching to the the power pins on the left and right end cap and to the readout processor in the Left End Cap, respectively. MOSAIX is designed to operate with air cooling only, and redefines the limits of monolithic CMOS pixel detectors - spanning an entire wafer while maintaining over 99% pixel detection efficiency and a fake hit rate of 10-6 hits/pixel/event. Thinned to 50 µm and integrated with carbon foam only, it presents a material budget of 0.09% X0 per layer. Developing an ASIC this size introduces challenges that go beyond traditional ASIC design. Wafer production failures, no longer confined to individual dies must be addressed by design across the entire stitched wafer. The architecture addresses this by implementing the sensor as a distributed system, where repeated processing units are integrated into a continuous structure and maintained through localized control and fault isolation. With all power and data IO connections constrained to the short edges, the system must sustain over 30 Gb/s of throughput while remaining below 40 mW/cm². This presentation will show how architecture, yield resilience, and power distribution management converge in MOSAIX, illustrating the design principles behind one of the most ambitious wafer-scale detectors built to date.

Speaker: Jelena Lalic (MIT)

MOSAIX_Vertex2025_JelenaLalic.pdf

15:00 Front-End Chip R&D for HL-LHC era Pixel detectors - latest results and lessons learned

ITkPix and CROC are the culmination of more than 10 years of Front-End Chip R&D to produce a Pixel detector readout chip to operate within the extreme environment of the ATLAS and CMS Pixel detectors during the HL-LHC era. Now that the Pixel detectors have entered their production phase we can look back to identify what worked well, which challenges were the hardest to overcome, and what can we learn for the next generation of Pixel detectors at future colliders. This talk with show some of the most recent bench measurements to emulate conditions the chips will see during detector operation, mass production and test data from more than 65,000 chips, and better understanding their integration in modules and larger systems. Detectors at future colliders will face new or more extreme challenges, some beyond simple design optimization and requiring novel approaches to be overcome. Reflecting over the past 10 years this talk will identify multiple strategies for future Pixel detectors to operate with higher performance, reliability, or streamline their R&D.

Speaker: Timon Heim (Lawrence Berkeley National Lab)

2025_08_26-itkpix_vertex-theim.pdf

15:30 → 16:00 Coffee: Coffee Break

16:00 → 17:00 Front-end electronics for LHC Upgrade

Convener: Stefan Spanier

16:00 Pixel Core Column Issue in the ATLAS Inner Tracker modules

Pixel modules for the ATLAS ITk Pixel detector upgrade are currently undergoing production and qualification testing. During pre-production electrical testing, a recurring front-end chip communication issue was observed that could be bypassed by selectively disabling pixel core columns within the affected chips. The issue, designated as the "core column issue," has been documented across a large number of both ITKPix v1.1 and v2 modules. Since disabling a core column significantly reduces the number of operation pixels in a module, the prevalence of this failure could substantially impact ITk tracking performance.

The erratic behavior of the core column has lead to difficulties in diagnosing its underlying cause. However, recent progress in visual inspection, combined with statistical analysis of production database records, points towards possible causes of the issue. This contribution highlights the discovery of, attempts to mitigate, production testing strategies, and current hypotheses of the core column issue.

Speakers: Charles Hultquist (Lawrence Berkeley National Lab. (US)), Lingxin Meng (Lancaster University, UK)

Hultquist_Core_Column_Vertex_2025 - .pdf

16:30 $^{60}\rm{Co}$ $\gamma$ Irradiation of a CMS CROC v2 to 1.6 Grad

We report on an irradiation of the production version of the read-out-chip for the CMS HL-LHC pixel detector (CROC v2) to 1.6 Grad with $^{60}\rm{Co}$ $\gamma$s at Sandia National Lab. The CROC was kept powered, configured, and as close to its nominal operating temperature (-20$^o$ C) as much as possible during the irradiation. Internal chip voltages, pixel response, and diagnostic ring oscillators were continuously measured. Detailed threshold optimization was performed twice a day when possible. The CROC was very performant at 1.6 Grad when an external event ended the irradiation and damaged the CROC. Where available, these results will be compared with those for similar ROCs fabricated in the TSMC 65 nm process using the RD53A, B, and C (this ROC) architectures, and irradiated to a few Grad using much-lower-energy x-ray sources.

Speaker: Dr Stephen R. Wagner (University of Colorado)

8_26_25_wagner_v3.pdf

Wednesday, 27 August

09:00 → 10:00 LGAD Detector R&D

Convener: Mathieu Benoit (ORNL)

09:00 Next-generation LGADs: A Measurement-Simulation Synergy to Quantify Donor Removal

The acceptor removal mechanism is well established as a limiting factor for the operational lifespan of standard n-in-p Low-Gain Avalanche Diodes (LGADs) and has been extensively studied. However, with the emergence of new LGAD designs, such as resistive LGADs and compensated LGADs, attention must now shift to understanding donor removal at high initial donor concentrations ($>10^{16}$ atoms/cm$^3$). This mechanism has a significant impact on the performance of these next-generation detectors, which aim to meet the requirements of future high-energy physics experiments. In resistive LGADs, the donor-doped resistive layer enables high spatial resolution (a few micrometres), even with larger pixel sizes, while in compensated LGADs, potential frontrunners for 4D tracking at fluences exceeding $10^{17}$ 1 MeV $\text{n}_{\text{eq}}/\text{cm}^2$, the gain implant is achieved through a precisely balanced compensation of acceptor and donor doping.

In this contribution, we present a methodology for evaluating donor removal by observing changes in sheet resistance resulting from irradiation using van der Pauw test structures. Typically, these structures consist of the layer under study implanted in a substrate with opposite doping to minimise parasitic effects. However, we demonstrate that valuable insights can also be gained when the substrate shares the same doping type, thanks to comparisons with simulations. Furthermore, we show that donor removal can also be assessed through capacitance measurements in compensated LGADs when compared with simulations. The first results will be presented, highlighting the correlation between resistance- and capacitance-based methods and their potential as donor removal characterisation tools for next-generation LGADs.

Speaker: Alessandro Fondacci (University and INFN of Perugia)

fondacci_VERTEX25_Static_FinalVersion.pdf

09:30 Detailed investigation of Acceptor Removal in LGAD

Tracking detectors in future high-energy and high-luminosity hadron colliders are required to correctly assign the tracks associated to the hard-scattering vertex among a huge number of pile-up vertices.

A detector with high spatial and timing resolution can remove pile-up tracks using the time information, enabling high-quality track reconstruction.

​​Capacitive Coupled Low Gain Avalanche Diodes (AC-LGAD) are semiconductor detectors that have high spatial resolution $\mathcal{O}(10)\ \mathrm{\mu m}$ and high timing resolution $\mathcal{O}(10)\ \mathrm{ps}$ .

However, LGAD does not have the radiation tolerance of $\mathcal{O}(10^{16})\ \mathrm{n_{eq}/cm^2}$ required for use as track detectors in future high-luminosity hadron accelerator experiments.

This is because, in addition to conventional semiconductor detectors, radiation damage in LGAD has a problem of acceptor removal, in which the p+ layer unique to LGAD, which is doped to provide a gain layer, no longer functional as an acceptor due to radiation damage.

The microscopic mechanism of acceptor removal is known to be that boron in the p+ layer, which has been inactivated by radiation damage, combines with oxygen in the sensor to generate $\rm{B_iO_i}$, which acts as a donor.

To understand and suppress acceptor removal, KEK and University of Tsukuba, in collaboration with Hamamatsu Photonics K.K. (HPK), have developed LGAD samples with various types of a gain layer as well as different wafer types. Especially to test the effect of oxygen concentration, radiation tolerance coefficients are compared among the samples with different oxygen concentration types and the Partially Activated Boron method which removes oxygen in the sensor by implanting more inactive boron than in normal samples.

We conduct proton irradiation experiments on these prototypes to evaluate their radiation tolerance by time resolution and IV measurements.

In this presentation, we will talk about the radiation tolerance measurement results for the prototype samples with various improvement and understanding of microscopic mechanism of acceptor removal then discuss possible further improvements.

Speaker: Yua Murayama (University of Tsukuba)

Detailed_investigation_of_Acceptor_Removal_in_LGAD_vertex2025.pdf

10:00 → 10:30 Coffee

10:30 → 12:00 Mechanical Design for HL-LHC and EIC

Convener: Stefan Spanier

10:30 Vertex and Tracking mechanics for EIC ePIC Detector

Speaker: Andy Jung (Purdue University)

11:00 Production and Quality Control of the ITk Pixel Outer Endcap Local Supports for the High-Luminosity upgrade of the ATLAS detector

The ATLAS experiment will be upgraded with a new Inner Tracker (ITk) detector for the High-Luminosity phase of the Large Hadron Collider. The ITk, a fully silicon-based detector, will replace the current Inner Detector, enhancing its tracking performance through increased acceptance and improved spatial and time resolution. The ITk will operate in a very harsh radiation environment, requiring an optimal cooling system to deliver effective performance and protect the components from damage. In the ITk pixel outer endcaps, the cooling is provided by bi-phase $\textrm{CO}_2$ that flows through the local supports, carbon-based structures that secure the pixel sensors in place.

The design and construction of these local supports present several challenges, which lead to an extensive R&D campaign over the past few years that included testing numerous prototypes. The local support assembly demands meticulous procedures and state-of-the-art technology to achieve the high level of precision necessary to meet the design specifications and prevent operational failures. A series of Quality Control tests, including metrology and infrared thermography measurements, have been implemented to assess the thermo-mechanical properties of the local supports and identify defective objects. This presentation will cover the techniques used, the major challenges encountered during the R&D phase, and the solutions developed. Additionally, highlights from the ongoing production campaign will also be shown.

Speaker: Dr Matteo D'Uffizi (University of Manchester)

2025_08_Vertex_conference_mduffizi.pdf

11:30 Mechanical Design and Integration of the CMS Phase-2 Tracker

The mechanical design of the CMS Phase-2 tracker addresses the stringent requirements of the HL-LHC environment, including stability under high radiation and thermal loads, minimal material budget, and precise alignment over large detector volumes. This talk details the engineering challenges and solutions behind the mechanical architecture of both the Inner Tracker (IT) and Outer Tracker (OT). Key topics include support structures, thermal management systems, carbon-fiber components, and the modularity enabling efficient assembly and maintenance. We present the integration strategy from substructures to full tracker systems, along with results from mechanical tests, thermal cycling, and alignment validation. The current status of assembly campaigns and the roadmap toward full detector integration are also discussed.

Speaker: Pierre Rose (CERN)

2025-08-27 - Vertex25- Pierre Rose.pptx

12:00 → 18:00 Excursions

18:00 → 21:00 Conference dinner

Thursday, 28 August

08:30 → 09:30 Interconnect technology for future detector upgrades

Convener: Mathieu Benoit (ORNL)

08:30 Novel interconnections for detector modules

Reliable, cost-effective and scalable interconnects are essential for next-generation detectors. Within the CERN EP-R&D programme and the DRD3 and AIDAinnova collaborations, the University of Geneva and CERN (together with other research partners) have built a semiconductor assembly platform targeted to single-die processing. The platform unifies several bumping and bonding techniques, focusing on maskless bumping (ENIG or Au studs) combined with adhesive bonding (Anisotropic Conductive Adhesives (ACA) or Non Conductive Paste (ACP)).

The developed ENIG plating line, performed at a single-die level, delivers uniform plating with variations below 1 µm from pad to pad. For pixel detector hybridization, pixel connection yields above 95% in multiple detector demonstrators, ranging from 0.1 to >2+ cm² bonding area and pixel pitch from 25 to 1500 µm, have been achieved. One of the advantages of the developed bonding line is its customization capability, depending on the application needs. In particular, the processing can be performed at low temperatures, which has enabled successful hybridization of highly irradiated pixel sensors without unwanted annealing.

Beyond pixel hybridization, we have successfully integrated the RDL/TSV connections from the Timepix4 chip with a carrier chip-board (with successful tests up to 10 Gbps of data transmission), as well as the IO pads of large-area monolithic active pixel sensors into lightweight flexible circuits, replacing wire-bonding and enabling 4-side buttable assemblies.

With the combined interconnection platform, we have managed to shorten prototyping turnaround from months to weeks and cut material costs significantly. These results provide a flexible, high-yield pathway for the next collider vertex-detector R&D programmes and other advanced imaging applications.

This contribution introduces the developed bumping and interconnect processes and presents examples of recent achievements.

Speaker: Mateus Vicente (UNIGE/CERN)

VERTEX_MVicente_Aug-2025.pdf

09:00 28 nm front end ASIC and 12” LGADs for 3D integration

The 3DIntSenS Collaboration—a joint effort between SLAC, Fermilab, and LLNL—is developing enabling technologies for next-generation radiation imaging detectors that combine ultra-fine spatial resolution (»10 μm) with precision timing (<20 ps), while maintaining low power <1 W/cm2 and high data throughput. The approach leverages 3D integration between advanced CMOS readout ASICs and finely pixelated LGAD sensors to achieve the performance and scalability required for large-area, high-rate applications.

High-granularity, precision-timing detectors are essential for scientific advances in HEP, NP, BES, and FES, but widespread adoption is limited by the cost and complexity of 3D integration. To close this gap, the collaboration is developing LGAD sensors compatible with 12-inch commercial CMOS processes, enabling cost-effective integration with high-performance ASICs under development.

We present the design and results from a 28 nm CMOS ASIC prototype, including a low-jitter front end, and in-pixel TDC demonstrating sub-10 ps timing resolution. We also report on the co-design and characterization of reticle-scale LGAD sensors with 50 μm and 100 μm pixels and introduce the next 10k-pixel ASIC designed for full 3D integration. These advances represent a critical step toward scalable, high-resolution radiation imaging systems for future scientific instrumentation.

Speaker: Troy England (Fermilab)

09:30 → 10:30 Module construction, testing and commissioning for the HL-LHC

Convener: Oskar Hartbrich (Oak Ridge National Lab)

09:30 Sensor and Module Development for the CMS Phase-2 Tracker Upgrade

The CMS Phase-2 tracker upgrade relies on a new generation of silicon sensors and modules designed to perform reliably under the extreme conditions of the HL-LHC. This talk provides an overview of the R&D, prototyping, and pre-production phases for both pixel and strip detector modules. We discuss sensor technology choices, front-end hybrid development, and innovations in powering and readout architectures. Emphasis is placed on performance validation through laboratory testing and beam campaigns, as well as the scaling up to industrialized production and the strategies adopted for quality assurance and integration into larger structures. The progress and lessons learned during module construction and early integration are presented, with a focus on meeting the demanding requirements for data rates, radiation hardness, material budget, and long-term reliability.

Speaker: Dimitra Andreou (CERN)

Andreou_Vertex2025_final.pdf

10:00 Readout implementation and testing procedures to characterise the pixel detector modules of the CMS inner tracker for the high luminosity upgrade of LHC

The LHC will be upgraded to the High Luminosity LHC in the coming years, aiming to reach an instantaneous luminosity of up to 7.5x$10^{34}$ cm$^{-2}$ s$^{-1}$. The CMS Tracker detectors will be replaced and significantly upgraded to cope with the increased radiation fluence while ensuring excellent performance. In particular, a new hybrid pixel detector chip was developed for the Inner Tracker detector (CROC). The chip is capable of coping with extreme hit rates up to 3 GHz/cm$^2$ (~12 GHz per chip), together with a trigger rate of 1 MHz, featuring an efficient readout of up to 5.12 Gbits/s. The chip exhibits radiation tolerance of up to 1 Grad and an induced single-event upset rate of up to 100 upsets per second. The new Inner Tracker will have six times smaller area pixels covering a surface close to 5 m$^2$, thus resulting in approximately two billion pixels over about 3900 modules. The individual detector modules will need to be characterised and calibrated before being mounted on the final detector structure. To this extent, a dedicated data acquisition system (DAQ), based on minimal hardware featuring a custom FPGA board, was developed. A description of the DAQ, the testing procedures, and experience with the CROC is presented in this document.

Speaker: Mauro Dinardo (Università degli Studi di Milano - Bicocca)

2025_08_25 Dinardo.pdf

10:30 → 11:00 Coffee break

11:00 → 12:00 Module construction, testing and commissioning for the HL-LHC

Convener: Oskar Hartbrich (Oak Ridge National Lab)

11:00 Electrical QC Testing of Pixel Modules in the ATLAS Inner Tracker Upgrade for the HL-LHC

The upgrade Inner Tracker (ITk) for the ATLAS detector in the HL-LHC era is in its production phase. About 10000 hybrid pixel modules will be produced for the pixel detector in this all-silicon tracker. The electrical performance of these modules during quality control (QC) is assessed on the 3D and planar sensors, the RD53 frontend chip and on the module as a whole.

A pixel module consists of 3 or 4 frontend chips. The interplay between the chips is derived from first principle and is evaluated during QC on the testbench. In addition to the typical leakage current measurement and chip calibration and tuning, our QC also tests the novel features of this chip that allow to minimise the radiation length of the detector.
These features include the shunt-LDO (SLDO) circuit which enables powering of multiple modules in a serial chain and on-detector data aggregation.

The assembly and testing of these modules are performed at about 25 sites worldwide, thus it is of utmost importance to ensure the consistency and uniformity of the testing procedures. For this purpose, we have developed a modular testing suite based on python. It is easily installed and automates tasks like interacting with the production database, conducting tests with pre-defined procedures, interpreting the measurements and the creation of a test report. One major challenge is the requirement to be conform to different testing environments and work flows depending on testing site, requiring overall flexibility while still ensuring uniform evaluation of all modules.

Speaker: Lingxin Meng (Lancaster University, UK)

20250828_Vertex_ITkPixelModuleEQC_lmeng.pdf

11:30 Recent testbeam studies of ATLAS ITk pixel modules

The High-Luminosity Large Hadron Collider (HL-LHC) will deliver instantaneous luminosities up to five times higher than those of the current LHC, reaching an unprecedented $7.5 \times 10^{34} cm^{−2}s^{−1}$. This significant increase in luminosity — resulting in an average pileup of over 200 interactions per bunch crossing — will pose serious challenges to existing detector systems. To maintain tracking performance under these conditions, the ATLAS Inner Detector (ID) will be replaced by an all-silicon Inner Tracker (ITk), providing coverage up to $|\eta| < 4$ and designed to withstand fluences up to $1.9×10^{16} n_{eq}/cm^2$. The ITk will consist of five pixel layers and four strip layers in the barrel region. The innermost pixel layer will use triplet modules based on 3D silicon sensors, offering enhanced radiation hardness. The second layer will feature quad modules with 100 $\mu m$ planar sensors, while the outer two layers will use quad modules with 150 $\mu m$ planar sensors.
Testbeam activities are essential for characterizing the performance of ITk modules under the extreme conditions expected at the HL-LHC. In this talk, we will present results from the most recent testbeam campaigns conducted in 2024 and 2025 at the North Experimental Area at CERN. These measurements were carried out using a 120  GeV/c pion beam from the H6 beamline and a high-resolution Mimosa telescope for precise track reconstruction. A variety of module geometries were tested, including single-chip cards (SCC), quad, and triplet configurations, with particular focus on the performance of irradiated sensors. These results provide critical input for the final design validation and quality assurance processes ahead of large-scale production.
Among the tested modules was a 3D sensor from SINTEF featuring a new passivation method, irradiated to a fluence of $1.7×10^{16 } n_{eq}/cm^2$, which achieved an efficiency of 96%. Two planar sensors from FBK, irradiated to $0.5×10^{16} n_{eq}/cm^2$, demonstrated efficiencies of approximately 99%. Other notable modules tested include an HPK quad module, a Micron SCC, and an FBK SCC, all equipped with an ITkPixV2, and two linear triplet modules—one produced by FBK and the other by SINTEF.

Speaker: Matias Mantinan (University of Chicago)

Vertex2025_Aug_28_testbeam.pdf

12:00 → 13:30 Lunch

13:30 → 15:00 Time-Of-Flight detectors

Convener: Mathieu Benoit (ORNL)

13:30 Precision timing in CMS at the HL-LHC: current progress on validation and production

During the High Luminosity phase of LHC, up to 200 proton-proton collisions per bunch crossing will bring severe challenges for event reconstruction. To mitigate pileup effects, an extended upgrade program of the CMS experiment is expected. Among which, a new timing layer, the MIP Timing Detector (MTD), will be integrated between the tracker and the calorimeters. With a time resolution of 30-60 ps, the MTD will enable 4D vertexing, bringing significant improvements in track-to-vertex association and object identification. The MTD is composed of two subsystems based on different technologies: the Barrel Timing Layer (BTL) consists of LYSO:Ce scintillating crystals readout by SiPMs, and the Endcap Timing Layer (ETL) is made of Low-Gain Avalanche Diodes. The BTL is currently under production, while ETL sensor prototyping and validation are ongoing. Recent system tests have confirmed the performance of the full acquisition chain. This talk will provide an overview of the MTD design, along with the physics motivation, and the current status of BTL construction and ETL development.

Speaker: Murtaza Safdari (Fermilab)

GSlides

Vertex2025_CMSMTD.pdf

14:00 The ATLAS High-Granularity Timing Detector for the HL-LHC : project status and results

The increase of the particle flux (pile-up) at the HL-LHC with instantaneous luminosities up to L ≃ $7.5 × 10^{34} cm^{−2}s^{−1}$ will have a severe impact on the ATLAS detector reconstruction and trigger performance. The end-cap and forward region where the liquid Argon calorimeter has coarser granularity and the inner tracker has poorer momentum resolution will be particularly affected. A High Granularity Timing Detector (HGTD) will be installed in front of the LAr endcap calorimeters for pile-up mitigation and luminosity measurement. The HGTD is a novel detector introduced to augment the new all-silicon Inner Tracker in the pseudo-rapidity range from 2.4 to 4.0, adding the capability to measure charged-particle trajectories in time as well as space. Two silicon-sensor double-sided layers will provide precision timing information for minimum-ionising particles with a resolution as good as 30 ps per track in order to assign each particle to the correct vertex. Readout cells have a size of 1.3 mm × 1.3 mm, leading to a highly granular detector with ~3.7 million channels. Low Gain Avalanche Detectors (LGAD) technology has been chosen as it provides enough gain to reach the large signal over noise ratio needed. The requirements and overall specifications of the HGTD will be presented as well as the technical design and the project status. The R&D effort carried out to study the sensors, the readout ASIC, and the other components, supported by laboratory and test beam results, will also be presented.

Speaker: Dominik Dannheim (CERN)

ATLAS-HGTD-overview-VERTEX-2025-28Aug2025.pdf

14:30 AC-LGAD Timing Detector at EIC

The Electron-Ion Collider (EIC), currently under development at Brookhaven National Laboratory, will provide unprecedented opportunities to study the internal structure of nucleons and nuclei. To exploit the full potential of the EIC physics program, excellent particle identification (PID) capabilities are required across a wide kinematic range. The ePIC experiment, the primary detector at the EIC, employs a novel Time-of-Flight (TOF) system based on AC-coupled Low Gain Avalanche Detectors (AC-LGADs) to provide precise timing and position measurements for charged particles.

This contribution presents the design, development, and performance of the AC-LGAD TOF detectors for both mid-rapidity (BTOF) and forward (FTOF) regions of ePIC. The AC-LGAD sensors are optimized for large-area coverage with fine segmentation and are capable of achieving a time resolution better than 30 ps and position resolution on the order of 20–30 μm. We discuss the detector layout, sensor characterization, readout electronics development, and the integration challenges within the compact ePIC environment.

The AC-LGAD TOF system represents one of the first large-scale deployments of AC-LGAD technology in a collider environment, and offers a path toward ultra-fast, low-material tracking and timing layers in future high-energy experiments.

Speaker: Satoshi Yano (Hiroshima University)

0828_syano_VETRTEX2025.pptx

15:00 → 15:30 Coffee Break

15:30 → 17:30 Edge data processing using AI/ML

Convener: Stefan Spanier

15:30 Spiking Neural Networks for HEP Data processing at the edge

Speaker: Catherine Schuman (University of Tennessee)

16:00 Status of the smartpixels project

The smartpixels project is a coordinated effort to co-design pixel ASICs, design tools, ML algorithms, and sensors for on-detector data reduction, motivated by the technical challenges of current and future colliders. The drive to greater precision requires smaller pixel pitch, which together with higher event rates arising from pileup and/or beam-induced background generates petabytes of data per second. Readout chips must be power-efficient, radiation-hard, and capable of real-time data processing. The smartpixels team has developed algorithms for selecting the signatures of high-momentum tracks and coarse particle-trajectory reconstruction, and explored how the performance changes with pixel sensor geometry, orientation, and irradiation. Further, we have leveraged and extended the open-source hls4ml tool to support neural network architectures meeting the strict latency and area constraints. To target our TSMC 28nm ASIC implementations, we have integrated the flow with Catapult HLS, allowing seamless synthesis of these designs into RTL for backend integration, and our first custom pixel ASICs have been produced and are undergoing testing. I will present the status of ongoing work, including efforts in testing ASICs, producing a new ASIC with a trajectory-reconstruction algorithm, and improving the realism of the detector simulation though including noise, charge thresholds, and other effects.

Speaker: corrinne mills (UIC)

smartpix_Vertex_cmills_aug25.pptx

16:30 Real-Time Track Reconstruction with FPGAs for MUonE

Event selection is central to high-intensity particle physics experiments to allow DAQ systems to manage the corresponding data rates. This is true for the MUonE experiment, which will be composed of 40 tracking stations and targets to reconstruct elastic scatters of muons on atomic electrons. Since the signal process and some backgrounds can be distinguished using track information alone, online track reconstruction can result in lower data rates with higher purity. Online track-fitting and vertexing for event selection will be implemented directly on FPGAs, using High-Level Synthesis to convert C++ code into an HDL description. This presentation will focus on results from a test beam at the M2 beamline at CERN in 2023, subsequent improvements to the algorithm, and plans for a 2025 test beam in the same location. In 2023, the standalone reconstruction of tracks from high-rate muons was performed, and the algorithm showed good agreement with offline reconstruction. Development after the test beam yielded significant timing and resource use improvements, namely those which allowed allow for single track fit results to be calculated above 50 MHz. This was achieved through pipelining the algorithm and implementing custom linear algebra functions which include basic assumptions on the fits. These results demonstrate the feasibility of FPGA-based online reconstruction for event selection for the MUonE experiment. In the 2025 test beam, a more general reconstruction algorithm will be demonstrated. This includes reconstructing events with higher occupancy, and implementations of candidate track selection and vertexing. Expected milestones and planned improvements to the more general algorithm will also be described. Finally, it will be shown that this algorithm and the assumptions made to improve performance can be generalized to applications beyond MUonE.

Speaker: Michael McGinnis (Northwestern University)

25.8.28_Vertex_McGinnis.pdf

17:00 Real-time luminosity and beam spot analysis with FPGA-reconstructed hits from the LHCb vertex detector

The upgraded LHCb experiment is pioneering the landscape of real-time data-processing techniques using an heterogeneous computing infrastructure, composed of both GPUs and FPGAs, aimed at boosting the performance of the HLT1 reconstruction. Amongst the novelties in the reconstruction infrastructure made for the Run 3, the introduction of a real-time hit-finding FPGA-based architecture on the silicon pixel vertex detector (VELO) stands out. For the first time at any LHC experiment, the bi-dimensional clusters of active pixels on the VELO are reconstructed before event-building, directly on the detector readout boards, at the full interaction rate of ~30MHz. In addition to saving HLT1 computing resources and reducing the DAQ bandwidth, the availability of well reconstructed particle hits at the readout level opens up the possibility of further processing in order to reconstruct even more complex quantities. Specifically, measuring hit rates at several positions on the detector sensors yields a novel method to analyse and monitor the geometrical properties of the luminous region in real time. To pursue such idea, a set of programmable counters has been implemented in firmware. This set of counters uses minimal FPGA resources and it provides real-time measurements of instantaneous luminosity and beam spot position, shape and inclination. This is achieved via linearised computations based on principal component analysis (PCA), that are performed during data taking on the LHCb slow control software. This method differs substantially from the usual techniques relying on track and vertex reconstruction, that are prone to misalignment biases and depend on the HLT running conditions. The implementation of such a beamspot reconstruction algorithm has the potential to crucially reduce the time needed to perform vertex reconstruction at LHCb. In this contribution, we describe the implementation of such a system for real-time beam spot measurement, and report the results obtained with proton-proton and lead-lead data collected in 2024 and 2025.

Speakers: Elena Graverini (Università di Pisa - INFN Pisa - EPFL), Giulio Cordova (Scuola Normale Superiore - INFN Pisa)

Talk_VERTEX25.pdf

Friday, 29 August

09:00 → 10:30 Quantum detectors for particle tracking, TES

Convener: Stefan Spanier

09:00 Tracking & timing performance of SNSPDs under 160 GeV SPS pion beams

Quantum sensing techniques offer significant advantages in the low-energy detection regime and show strong potential for sub-picosecond timing applications. In the context of the Future Circular Collider (FCC), expanding the excellent single-photon resolution demonstrated by Superconducting Nanowire Single-Photon Detectors (SNSPDs) to charged particles, would open the door to applications such as precision luminometry, potentially achieving precision levels in the order 10−4 %. We thereafter plan to assess SNSPD efficiency, spatial/temporal resolution, and energy response with charged particles, laying foundation for future SNSPD-based detectors in collider experiments.
In this presentation, we report on applications of SNSPDs devices based on materials with various compositions and superconducting energy gaps tested with laboratory 90Sr beta sources and 160 GeV pion beams at the CERN SPS. The devices are studied in terms of their detection efficiency, timing, and spatial response within a EUDET-type MIMOSA-26 beam telescope, offering 5 µm tracking resolution. A pair of HPK LGADs providing 30 ps timing reference, combined with a CROC pixelated ROI trigger and a high-bandwidth (>3 GHz) data acquisition system, are employed. Synchronization with the SPS spill structure is achieved through dedicated electronics.
We compare the response of different materials to charged particles, investigating variations in geometrical characteristics such as nanowire width. Detector efficiency and preliminary insights into their potential for tracking and luminometers applications are discussed.

Speaker: Dr Evangelos Gkougkousis (ETH Zurich)

VERTEX25.pdf

09:30 Diamond detector for nuclear safety and national security

Speaker: Prof. Eric Lukosi (UTK)

10:00 High Energy Particle Detection with Large Area Superconducting Microwire Array

Superconducting Nanowire Single Photon Detectors (SNSPDs) are a leading detector technology for single-photon detection with diverse applications, due to their ultra-low energy threshold of below 0.04~eV, low dark counts of 10^-5~Hz, and pico-second level time resolution. Recent advancement in the fabrication of large area superconducting microwire single photon detectors (SMSPDs) make them an ideal photo sensor to detect single photons in dark matter detection experiments and a potential innovative detector technology for future accelerator-based experiments.
In this talk, we present the first detailed study of an 8-channel $2\times2$~mm$^{2}$ WSi SMSPD array exposed to 120~GeV proton beam and 8~GeV electron and pion beam at the Fermilab Test Beam Facility. The SMSPD detection efficiency was measured for the first time for protons, electrons, and pions, enabled by the use of a silicon tracking telescope that provided precise spatial resolution of 30~\um for 120~GeV protons and 130~\um for 8~GeV electrons and pions. Time resolution of 1.15~ns was measured for the first time for SMSPD with proton, electron, and pions, enabled by the use of an MCP-PMT which provided a ps-level reference time stamp.
We will also present our future plan to measure the SNSPD hit detection efficiency and beam-induced background more precisely by improving the SNSPD characterization system, to simulate the interactions between charged particles and SNSPD to refine the current physics models, and finally to optimize the SNSPD sensors for high energy particle detection.

Speaker: Cristian Pena (Fermilab)

CPena_SNSPD_Vertex.pdf

10:30 → 11:00 Coffee Break

11:00 → 12:00 Challenges for the next generation detectors

Convener: Oskar Hartbrich (Oak Ridge National Lab)

11:00 Challenges for Vertex Detectors at Linear Colliders

Vertex detectors at future linear e+e- colliders face unique challenges driven by the need for exceptional spatial resolution (~3 µm) and minimal material budget (<0.15% X₀ per layer) to enable precision flavor tagging. Unlike hadron colliders, radiation levels and background occupancies are modest, but tight constraints on power consumption, cooling, and integration remain critical due to the push for low-mass, high-granularity designs. This contribution reviews the detector requirements, discusses ongoing R&D on advanced pixel technologies, and outlines the design strategies being developed to meet the specific needs of e+e- collider experiments.

Speaker: Caterina Vernieri (SLAC)

LC-Vertex2025-2.pdf

11:30 EIC vertex and tracking detector

The Electron-Ion Collider facility at Brookhaven National Laboratory will enable a rich science programme with its high luminosity, high energy collisions of electrons with protons and ions. ePIC is the first detector being developed for this new facility. It is to be ready for data taking in the early 2030s. The ePIC detector will utilise an innermost, high resolution Silicon Vertex Tracker, able to precisely measure primary and secondary vertices as well as particle momentum with wide acceptance. This presentation will give an overview of the ePIC Silicon Vertex Tracker geometry, projected performance, development and design of ultra-thin detector layers with large area coverage.

Speaker: Dr James Glover (University of Birmingham (UK))

EIC_VERTEX2025_ JJG_rev5.pdf

12:00 → 12:30 Closeout

Convener: Mathieu Benoit (ORNL)

12:00 Closeout

Speaker: Mathieu Benoit (ORNL)

closeout.pdf