arXiv subjects

L. Li

Publications and source records attributed to L. Li.

At least 19 recordsLinked to original sources

arXiv2026

TCAD + Allpi$\text{x}^2$ Simulation study of MALTA2, a Depleted Monolithic Active Pixel Sensor for future tracking

In this work, a hybrid simulation framework combining TCAD and Allpi$\text{x}^2$ is presented to investigate the sensor properties of MALTA2, a depleted monolithic active pixel sensor designed for future tracking. The study starts from 3D modeling and transient simulations in TCAD, with generic doping profiles and simple well structures. The resulting doping profiles and electric field are extracted and fed into Allpi$\text{x}^2$ for high-statistics Monte Carlo simulations in both DUT-only and full-telescope mode. Simulations reveal a strong dependence of sensor performance, specifically the detection efficiency and cluster size, on the doping concentration of the N-type blanket at the sensor surface. The doping concentration is then optimized by comparing simulations with measurement data. The active depth of the depleted region of the MALTA2 sensor is estimated in both simulations and measurements using a grazing angle method, in which the sensor is positioned at various inclinations relative to the beam, covering angles from 0 to 60 degrees. Excellent agreement on active depth is obtained with the optimal doping concentration, showing a deviation of 2\% from the measured value at a threshold of 450\,$\text{e}^-$. Consequently, the framework offers a generic toolkit for sensor studies without requiring proprietary information.

physics.ins-det↗

arXiv2026

The GRB joint scientific analysis pipeline of the ECLAIRs and GRM instruments on board SVOM

The study of the prompt high-energy emission of Gamma-Ray Bursts (GRBs) with SVOM relies on the observations performed by ECLAIRs (4-150 keV) and the Gamma-Ray Monitor (GRM, 0.015-5 MeV), the two wide field-of-view instruments on board the satellite. In this article, we introduce the eclgrm pipelines running at the French Science Center of SVOM, which combine the ECLAIRs and GRM data to generate scientific data products describing the GRB broad-band temporal and spectral properties. The architecture of the pipelines is presented, as well as their activation following each onboard trigger, and their workflow. The statistical data analysis methods employed by the pipelines are described, along with the scientific data products that are created in real time or from the full event data. We also present the eclgrm-ui user interface which allows the scientists on shift to monitor the automated data processings in the pipelines, and to optimize the analysis results interactively.

astro-ph.HE↗

arXiv2026

Measurement of coherent elastic neutrino nucleus scattering on germanium by COHERENT

The COHERENT collaboration reports the most precise measurement of the coherent elastic neutrino-nucleus scattering cross section to date. This measurement was performed with COHERENT's germanium detector array, Ge-Mini, at the Spallation Neutron Source at Oak Ridge National Laboratory. A cumulative exposure of $4.68\times10^{22}$ protons on target yielded a total number of observed counts of $124^{+14}_{-12}$ and a flux-averaged cross section of $1.00 \pm 0.10 \mathrm{(statistical)} \pm 0.10 \mathrm{(systematic)}$ relative to the standard-model expectation of $5.9\times10^{-39} \mathrm{cm}^2$. The well-understood energy and timing distributions of the neutrino source allow for independent measurements of muon- and electron-neutrino scattering rates. This information is used to improve constraints on non-standard neutrino interactions mediated by heavy particles.

hep-ex↗

arXiv2026

A dataset of medication images with instance segmentation masks for preventing adverse drug events

Medication errors and adverse drug events (ADEs) pose significant risks to patient safety, often arising from difficulties in reliably identifying pharmaceuticals in real-world settings. AI-based pill recognition models offer a promising solution, but the lack of comprehensive datasets hinders their development. Existing pill image datasets rarely capture real-world complexities such as overlapping pills, varied lighting, and occlusions. MEDISEG addresses this gap by providing instance segmentation annotations for 32 distinct pill types across 8262 images, encompassing diverse conditions from individual pill images to cluttered dosette boxes. We trained YOLOv8 and YOLOv9 on MEDISEG to demonstrate their usability, achieving mean average precision at IoU 0.5 of 99.5 percent on the 3-Pills subset and 80.1 percent on the 32-Pills subset. We further evaluate MEDISEG under a few-shot detection protocol, demonstrating that base training on MEDISEG significantly improves recognition of unseen pill classes in occluded multi-pill scenarios compared to existing datasets. These results highlight the dataset's ability not only to support robust supervised training but also to promote transferable representations under limited supervision, making it a valuable resource for developing and benchmarking AI-driven systems for medication safety.

cs.CV↗

arXiv2026

Evaluating Few-Shot Pill Recognition Under Visual Domain Shift

Adverse drug events are a significant source of preventable harm, which has led to the development of automated pill recognition systems to enhance medication safety. Real-world deployment of these systems is hindered by visually complex conditions, including cluttered scenes, overlapping pills, reflections, and diverse acquisition environments. This study investigates few-shot pill recognition from a deployment-oriented perspective, prioritizing generalization under realistic cross-dataset domain shifts over architectural innovation. A two-stage object detection framework is employed, involving base training followed by few-shot fine-tuning. Models are adapted to novel pill classes using one, five, or ten labeled examples per class and are evaluated on a separate deployment dataset featuring multi-object, cluttered scenes. The evaluation focuses on classification-centric and error-based metrics to address heterogeneous annotation strategies. Findings indicate that semantic pill recognition adapts rapidly with few-shot supervision, with classification performance reaching saturation even with a single labeled example. However, stress testing under overlapping and occluded conditions demonstrates a marked decline in localization and recall, despite robust semantic classification. Models trained on visually realistic, multi-pill data consistently exhibit greater robustness in low-shot scenarios, underscoring the importance of training data realism and the diagnostic utility of few-shot fine-tuning for deployment readiness.

cs.CV↗

arXiv2026

Charge collection parameterization of MALTA2, a depleted monolithic active pixel sensor

A fast simulation method is presented for a depleted monolithic active pixel sensor, which uses a data driven parameterization of the charge collection and propagation. This approach provides an efficient alternative to TCAD simulations, particularly for sensors whose proprietary process details - such as doping profiles or implant geometries - are unavailable. Data was obtained with a MALTA2 sensor fabricated in a 180 nm CMOS imaging technology on 30 {\mu}m epitaxial silicon using the MALTA beam telescope at CERN SPS. The model reproduces the measured inpixel efficiency with high accuracy and enables a realistic yet computationally lightweight analog pixel simulation. This method will be further employed in optimizing the digital sensor design for applications in high-rate particle tracking and high-granularity calorimetry.

physics.ins-det↗

arXiv2026

The COHERENT Experiment: 2026 Update

The COHERENT experiment measures neutrino-induced recoils from coherent elastic neutrino-nucleus scattering (CEvNS) with multiple nuclear targets at the Spallation Neutron Source (SNS) at the Oak Ridge National Laboratory (ORNL), USA. Several successful CEvNS measurements have been achieved in recent years with tens-of-kg detector masses, with a CsI scintillating crystal, a liquid argon single-phase detector, and high-purity germanium spectrometers. For the next phase, COHERENT aims at high-statistics detection of CEvNS events for precision tests of the standard model of particle physics, and to probe new physics beyond-the-standard model. Percent-level precision can be achieved by lowering thresholds, reducing backgrounds, and by scaling up the detector masses. It goes hand in hand with benchmarking the neutrino flux from the SNS. Further detectors will measure CEvNS in additional nuclei, including lighter target nuclei such as sodium and neon, to continue to test the expected neutron-number-squared dependence of the cross section. COHERENT can furthermore study charged-current and neutral-current inelastic neutrino-nucleus cross sections on various nuclei at neutrino energies below $\sim$50 MeV. Many of these cross sections have never been measured before, but are critical input for the interpretation of core-collapse supernova detection in large-scale neutrino experiments such as DUNE, Super-K, Hyper-K, and HALO.

hep-ex↗

arXiv2025

Beam-test evaluation of pre-production Low Gain Avalanche Detectors for the ATLAS High Granularity Timing Detector

The High Granularity Timing Detector (HGTD) will be installed in the ATLAS experiment as part of the Phase-II upgrade for the High Luminosity-Large Hadron Collider (HL-LHC). It will mitigate pile-up effects in the forward region, and measure per bunch luminosity. The design of HGTD is based on Low Gain Avalanche Detector (LGAD) sensors. This paper presents the results of beam-test campaigns conducted at CERN and DESY in 2023 and 2024 on single LGADs from HGTD pre-production test structures, before and after neutron irradiation up to fluences of $2.5 \times 10^{15}~\mathrm{n_{eq}/cm^2}$. The tested LGADs can meet HGTD requirements in terms of charge collection, time resolution, and hit efficiency, even under HL-LHC end-of-life conditions, supporting their deployment in the final detector.

physics.ins-det↗

arXiv2025

A Catalog of Galactic Atomic Hydrogen Position-Position-Velocity Filaments

We present a catalog of 3D Galactic HI filaments over 1/3 of the sky using Galactic Arecibo L-band Feed Array HI (GALFA-HI) data. The 3D filaments are defined to be linear HI features that are continuous in position-position-velocity (PPV) and are found with fil3d, an algorithm that expands on the 2D FilFinder. The catalog contains 3333 HI filaments between +/- 50 km/s at a range of Galactic positions. 1542 of the PPV filaments are identified as local at the distance of the wall of the Local Bubble, and 209 are likely at the disk-halo interface of our Galaxy. The catalog and properties of the PPV filaments are obtained after an unsharp mask (USM) is applied to the data. The widths of the filaments are consistently ~12' (0.34 pc at 100 pc), and constrained by the 4' resolution. The local filaments have median properties of N_HI = $6 \times 10^{18}$ cm$^{-2}$, M_HI = 0.17 M_sun, FWHM = 3.2 km/s, and length of 6.4 pc. The disk-halo population has similar column densities, but the median FWHM = 7.7 km/s, consistent with them being higher z-height, warmer structures. The L $\propto$ M$^{0.5}$ relationship found for the HI filaments and their bundling on the sky are consistent with a hierarchical structure, and is likely related to turbulence playing a role in their formation.

astro-ph.GA↗

arXiv2025

On the plaque topological stability of partially hyperbolic diffeomorphisms

We prove that every dynamically coherent plaque expansive partially hyperbolic diffeomorphism is topologically stable with respect to the central foliation (in short, {\em plaque topologically stable}). Next, we study partially hyperbolic diffeomorphisms that are both expansive and topologically stable with respect to a central foliation. We show that the center chain recurrent set for such diffeomorphisms belongs to the closure of the center periodic points.

math.DS↗

arXiv2025

Thermal Cycling Reliability of Hybrid Pixel Sensor Modules for The ATLAS High Granularity Timing Detector

The reliability of bump connection structures has become a critical aspect of future silicon detectors for particle physics. The High Granularity Timing Detector (HGTD) for the ATLAS experiment at the High-Luminosity Large Hadron Collider will require 8032 hybrid pixel sensor modules, composed of two Low Gain Avalanche Diode sensors bump-bonded to two readout ASICs and glued to a passive PCB. The detector will operate at low temperature (-30 degrees Celsius) to mitigate the impact of irradiation. The thermomechanical reliability of flip-chip bump connections in HGTD modules is a critical concern, particularly due to their characteristically lower bump density (pixel pitch dimensions of 1.3 mm by 1.3 mm). This paper elaborates on the challenges arising from this design characteristic. Finite element analysis and experimental testing were employed to investigate failure modes in the flip-chip bump structures under thermal cycling from -45 degrees Celsius to 40 degrees Celsius and to guide the module redesign. The optimized design demonstrates significantly enhanced robustness and is projected to fulfill the full lifetime requirements of the HGTD.

physics.ins-det↗

arXiv2025

The CMS Barrel Timing Layer: test beam confirmation of module timing performance

First of its kind, the barrel section of the MIP Timing Detector is a large area timing detector based on LYSO:Ce crystals and SiPMs which are required to operate in an unprecedentedly harsh radiation environment (up to an integrated fluence of $2\times10^{14}$ 1 MeV $n_{eq}/cm^2$). It is designed as a key element of the upgrade of the existing CMS detector to provide a time resolution for minimum ionizing particles in the range between 30-60 ps throughout the entire operation at the High Luminosity LHC. A thorough optimization of its components has led to the final detector module layout which exploits 25 $\rm \mu m$ cell size SiPMs and 3.75 mm thick crystals. This design achieved the target performance in a series of test beam campaigns. In this paper we present test beam results which demonstrate the desired performance of detector modules in terms of radiation tolerance, time resolution and response uniformity.

physics.ins-det↗

arXiv2025

Antiferromagnetic Chiral Bobber Formation and Topological Proximity Effect in MnBi2Te4

With topological materials being billed as the key to a new generation of nanoelectronics via either functional real-space topological structures (domain walls, skyrmions etc.) or via momentum-space topology (topological insulators), tailored and controllable topological properties are of paramount significance, since they lead to topologically protected states with negligible dissipation, enabling stable and non-volatile information processing. Here, we report on the evolution of topological magnetic textures in the proximity of other topological defects, i.e., antiferromagnetic domain walls in the topological insulator MnBi2Te4. The transition from the antiferromagnetic ground state to a canted antiferromagnetic state at finite magnetic fields is accompanied by the formation of chiral bobbers - bulk-terminated topological defects adjacent to the domain walls in this system, leading to a topological proximity effect.

cond-mat.mes-hall↗

arXiv2025

Study of MALTA2, a Depleted Monolithic Active Pixel Sensor, with grazing angles at CERN SPS 180 GeV/c hadron beam

MALTA2 is a Depleted Monolithic Active Pixel Sensor designed to meet the challenging requirements of future collider experiments, in particularly extreme radiation tolerance and high hit rate. The sensor is fabricated in a modified Tower 180 nm CMOS imaging technology to mitigate performance degradation caused by 100 MRad of Total Ionising Dose and greater than 10^{15} 1 MeV n_{eq}/cm^2 of Non-Ionising Energy Loss. MALTA2 samples have been tested during the CERN SPS test beam campaign in 2023-2024, before and after irradiation at a fluence of 1 $\times$ 10^{15} 1 MeV n_{eq}/cm^2. The sensors were positioned at various inclinations relative to the beam, covering grazing angles from 0 to 60 degrees. This contribution presents measurements of detection efficiency and cluster size as functions of these angles, along with an estimation of the active depth of the depleted region based on the test beam results.

hep-ex↗

arXiv2025

Timing characterization of MALTA and MALTA2 pixel detectors using Micro X-ray source

The MALTA monolithic active pixel detector is developed to address some of the challenges anticipated in future high-energy physics detectors. As part of its characterization, we conducted timing studies necessary to provide a figure of merit for this family of monolithic pixel detectors. MALTA has a metal layer in front-end electronics, and the conventional laser technique is not suitable for timing studies due to the reflection of the laser from the metallic surface. X-rays have been employed as a more effective alternative for penetration through these layers. The triggered X-ray set-up is designed to study timing measurements of monolithic detectors. The timing response of the X-ray set-up is characterized using an LGAD. The timing response of the MALTA and MALTA2 pixel detectors is studied, and the best response time of MALTA2 pixel detectors is measured at about 2.6 ns.

physics.ins-det↗

arXiv2024

Determining Absolute Neutrino Mass using Quantum Technologies

Next generation tritium decay experiments to determine the absolute neutrino mass require high-precision measurements of $\beta$-decay electron energies close to the kinematic end point. To achieve this, the development of high phase-space density sources of atomic tritium is required, along with the implementation of methods to control the motion of these atoms to allow extended observation times. A promising approach to efficiently and accurately measure the kinetic energies of individual $\beta$-decay electrons generated in these dilute atomic gases, is to determine the frequency of the cyclotron radiation they emit in a precisely characterised magnetic field. This cyclotron radiation emission spectroscopy technique can benefit from recent developments in quantum technologies. Absolute static-field magnetometry and electrometry, which is essential for the precise determination of the electron kinetic energies from the frequency of their emitted cyclotron radiation, can be performed using atoms in superpositions of circular Rydberg states. Quantum-limited microwave amplifiers will allow precise cyclotron frequency measurements to be made with maximal signal-to-noise ratios and minimal observation times. Exploiting the opportunities offered by quantum technologies in these key areas, represents the core activity of the Quantum Technologies for Neutrino Mass project. Its goal is to develop a new experimental apparatus that can enable a determination of the absolute neutrino mass with a sensitivity on the order of 10~meV/$c^2$.

hep-ex↗

arXiv2024

Finite-time stability of nonlinear conformable fractional-order delayed impulsive systems: Impulsive control and perturbation perspectives

This paper investigates the finite-time stability (FTS) of nonlinear conformable fractional-order delayed impulsive systems (CFODISs). Using the conformable fractional-order (CFO) derivative framework, we derive a novel FTS result by extending the existing works on continuous integer-order (IO) systems. This result highlights that the settling time of continuous CFO systems depends on the system order and plays a crucial role in discussing FTS scenarios subject to delayed impulses. We establish Lyapunov-based FTS criteria for CFODISs, considering both impulsive control and impulsive perturbation. Additionally, we estimate the settling time for both cases, revealing distinct forms compared to the IO case. We apply the theoretical results to delayed impulsive conformable fractional-order memristive neural networks (CFOMNNs) under an elaborately designed controller. We present several simulations to illustrate the validity and applicability of our results.

math.DS↗

arXiv2024

The MUSE Beamline Calorimeter

The MUon Scattering Experiment (MUSE) was motivated by the proton radius puzzle arising from the discrepancy between muonic hydrogen spectroscopy and electron-proton measurements. The MUSE physics goals also include testing lepton universality, precisely measuring two-photon exchange contribution, and testing radiative corrections. MUSE addresses these physics goals through simultaneous measurement of high precision cross sections for electron-proton and muon-proton scattering using a mixed-species beam. The experiment will run at both positive and negative beam polarities. Measuring precise cross sections requires understanding both the incident beam energy and the radiative corrections. For this purpose, a lead-glass calorimeter was installed at the end of the beam line in the MUSE detector system. In this article we discuss the detector specifications, calibration and performance. We demonstrate that the detector performance is well reproduced by simulation, and meets experimental requirements.

physics.ins-det↗