arXiv subjects

Shikma Bressler

Publications and source records attributed to Shikma Bressler.

At least 19 recordsLinked to original sources

arXiv2026

Signal formation and induction-gap optimization in a THGEM coupled to a resistive plate anode

A Thick Gaseous Electron Multiplier (THGEM) detector coupled to a resistive plate anode was investigated for the first time, using an Ar:CO$_2$ (93:7) gas mixture. The resistive anode concept enabled stable operation with induction gaps significantly smaller than those typically employed in THGEM detectors, opening the possibility of improving signal formation and timing performance. The effect of the induction gap on the detector current- and charge-signal characteristics was systematically investigated. An optimal induction gap of 0.2 mm was identified based on several key signal parameters. Subsequently, detailed studies were carried out for this optimal configuration under different electric-field settings. The detector achieved a highest peak amplitude of $\sim$56 $μ$A with a rise time of $\sim$5 ns at $Δ\text{V}_{\text{THGEM}}$=1900 V, $Δ\text{V}_{\text{induction}}$=100 V, and a drift field of 1 kV/cm when irradiated with 5.9 keV X-rays. Under the same operating conditions, a time resolution of $\sim$6.0 ns was measured detecting cosmic muons. This study establishes a new THGEM detector configuration and provides guidance for its potential application in particle-detection systems, such as muon spectrometers and sampling elements of digital hadronic calorimeters.

physics.ins-det↗

arXiv2025

Physics Briefing Book: Input for the 2026 update of the European Strategy for Particle Physics

The European Strategy for Particle Physics (ESPP) reflects the vision and presents concrete plans of the European particle physics community for advancing human knowledge in fundamental physics. The ESPP is updated every five-to-six years through a community-driven process. It commences with the submission of specific proposals and other input from the community at large, outlining projects envisioned for the near-, mid-, and long-term future. All submitted contributions are evaluated by the Physics Preparatory Group (PPG), and a preliminary analysis is presented at a Symposium meant to foster a broad community discussion on the scientific value and feasibility of the various ideas proposed. The outcomes of the analysis and the deliberations at the Symposium are synthesized in the current Briefing Book, which provides an important input in the deliberations of the Strategy recommendations by the European Strategy Group (ESG).

hep-ex↗

arXiv2025

Automatizing the search for mass resonances using BumpNet

Physics Beyond the Standard Model (BSM) has yet to be observed at the Large Hadron Collider (LHC), motivating the development of model-agnostic, machine learning-based strategies to probe more regions of the phase space. As many final states have not yet been examined for mass resonances, an accelerated approach to bump-hunting is desirable. BumpNet is a neural network trained to map smoothly falling invariant-mass histogram data to statistical significance values. It provides a unique, automatized approach to mass resonance searches with the capacity to scan hundreds of final states reliably and efficiently.

hep-ph↗

arXiv2025

Point Cloud Deep Learning Methods for Particle Shower Reconstruction in the DHCAL

Precision measurement of hadronic final states presents complex experimental challenges. The study explores the concept of a gaseous Digital Hadronic Calorimeter (DHCAL) and discusses the potential benefits of employing Graph Neural Network (GNN) methods for future collider experiments. In particular, we use GNN to describe calorimeter clusters as point clouds or a collection of data points representing a three-dimensional object in space. Combined with Graph Attention Transformers (GATs) and DeepSets algorithms, this results in an improvement over existing baseline techniques for particle identification and energy resolution. We discuss the challenges encountered in implementing GNN methods for energy measurement in digital calorimeters, e.g., the large variety of hadronic shower shapes and the hyper-parameter optimization. We also discuss the dependency of the measured performance on the angle of the incoming particle and on the detector granularity. Finally, we highlight potential future directions and applications of these techniques.

hep-ph↗

arXiv2025

Signal Formation in THGEM-like Detectors

Numerical simulations were used to study signal formation in a Thick Gaseous Electron Multiplier (THGEM) and in THGEM -based Thick-WELL (THWELL) and Resistive-Plate WELL (RPWELL) detectors. The signal shapes were simulated in mixtures of Argon and Neon with $5\%$ Methane under irradiation with soft x-rays and muons. Anode-induced raw signals were convoluted with the response functions of charge-sensitive and current-sensitive pre-amplifiers. The simulation toolkit was validated by the good agreement reached between the simulated and measured response, with different pre-amplifiers. It indicates that our simulations framework provides valid insight into the inherent complex dynamical processes of the various detectors.

physics.ins-det↗

arXiv2025

Automatizing the search for mass resonances using BumpNet

The search for resonant mass bumps in invariant-mass distributions remains a cornerstone strategy for uncovering Beyond the Standard Model (BSM) physics at the Large Hadron Collider (LHC). Traditional methods often rely on predefined functional forms and exhaustive computational and human resources, limiting the scope of tested final states and selections. This work presents BumpNet, a machine learning-based approach leveraging advanced neural network architectures to generalize and enhance the Data-Directed Paradigm (DDP) for resonance searches. Trained on a diverse dataset of smoothly-falling analytical functions and realistic simulated data, BumpNet efficiently predicts statistical significance distributions across varying histogram configurations, including those derived from LHC-like conditions. The network's performance is validated against idealized likelihood ratio-based tests, showing minimal bias and strong sensitivity in detecting mass bumps across a range of scenarios. Additionally, BumpNet's application to realistic BSM scenarios highlights its capability to identify subtle signals while managing the look-elsewhere effect. These results underscore BumpNet's potential to expand the reach of resonance searches, paving the way for more comprehensive explorations of LHC data in future analyses.

physics.data-an↗

arXiv2024

Learning New Physics from Data -- a Symmetrized Approach

Thousands of person-years have been invested in searches for New Physics (NP), the majority of them motivated by theoretical considerations. Yet, no evidence of beyond the Standard Model (BSM) physics has been found. This suggests that model-agnostic searches might be an important key to explore NP, and help discover unexpected phenomena which can inspire future theoretical developments. A possible strategy for such searches is identifying asymmetries between data samples that are expected to be symmetric within the Standard Model (SM). We propose exploiting neural networks (NNs) to quickly fit and statistically test the differences between two samples. Our method is based on an earlier work, originally designed for inferring the deviations of an observed dataset from that of a much larger reference dataset. We present a symmetric formalism, generalizing the original one; avoiding fine-tuning of the NN parameters and any constraints on the relative sizes of the samples. Our formalism could be used to detect small symmetry violations, extending the discovery potential of current and future particle physics experiments.

hep-ex↗

arXiv2024

Discharge quenching mechanism and performance of RPWELL with tunable 3D printed resistive plates, charge evacuation in semiconductive glass RPWELL and discharge quenching for Cryogenic-RWELL over a wide range of resistivity

Resistive electrodes are used in gaseous detectors to quench electrical discharges. This helps to protect delicate electrodes and readout electronics and to improve the stability of the detector operation. An RPWELL is a THGEM-based WELL detector with a resistive plate coupled to a conductive anode. Till now, the choice of the resistive plate was limited to a few materials, like LRS Glass and Semitron. These materials have fixed resistivities and, sometimes, thickness and area limitations. This restricts the potential usage of the detector to a rather small range of applications, as well as the possibility of studying in depth the physics processes governing the discharge quenching mechanism. In our present study, we used a new plastic material doped with carbon nanotubes to produce resistive plates with a commercial 3D printer. This method has the flexibility to produce samples of different thicknesses and different resistivity values. We describe here the sample production and characterize the RPWELL performance with different resistive plates. In particular we show the dependence of discharge quenching on the thickness and resistivity of the plate. The dynamics of the charge carriers in the material is proposed as an explanation for the long gain recovery time after a discharge.

physics.ins-det↗

arXiv2023

The Thick Gas Electron Multiplier and its derivatives: physics, technologies and applications

The Thick Gas Electron Multiplier (THGEM) is a robust high-gain gas-avalanche electron multiplier - a building block of a variety of radiation detectors. It can be manufactured economically by standard printed-circuit drilling and etching technology. We present a detailed review of the THGEM and its derivatives. We focus on the physics phenomena that govern their operation and performances under different operation conditions. Technological aspects associated with the production of these detectors and their current and potential applications are discussed.

physics.ins-det↗

arXiv2023

Diamond-like carbon coatings for cryogenic operation of particle detectors

Characterization of diamond-like carbon (DLC) coatings at cryogenic temperatures (down to 77 K) is presented, covering the electrical resistivity range of practical interest to gaseous and liquid particle instrumentation: 10^-1-10^5 Mohm/sq. The good behaviour observed in terms of linearity, surface uniformity and stability with time and transported charge add to other well-known characteristics like low chemical reactivity and tolerance to radiation. The observed temperature dependence and stability of electrical properties with transported charge is consistent with a conductivity mechanism based on 2-dimensional variable-range electron hopping, as expected for the surface conductivity of thin films made from amorphous carbon. First results from a resistive-protected WELL detector ('RWELL') built with DLC and operated close to the liquid-vapor coexistence point of argon (87.5 K at 1 bar) are presented.

physics.ins-det↗

arXiv2022

Test-Beam and Simulation Studies Towards RPWELL-based DHCAL

Digital Hadronic Calorimeters (DHCAL) were suggested for future Colliders as part of the particle-flow concept. Though studied mainly with Resistive Plate Chambers (RPC), studies focusing on Micro-Pattern Gaseous Detector (MPGD)-based sampling elements have shown the potential advantages; they can be operated with environmental friendly gases and reach similar detection efficiency at lower average pad-multiplicity. We summarize here the experimental test-beam results of a small-size DHCAL prototype, incorporating six Micromegas (MM) and two Resistive-Plate WELL (RPWELL) sampling elements, interlaced with steel-absorber plates. It was investigated with 2-6 GeV pion beam at the CERN/PS beam facility. The data permitted validating a GEANT4 simulation framework of a DHCAL, and evaluating the expected pion energy resolution of a full-scale RPWELL-based calorimeter. The pion energy resolution of $\fracσ{E[GeV]}=\frac{50.8\%}{\sqrt{E[GeV]}} \oplus 10.3\%$ derived expected with the RPWELL concept is competitive to that of glass RPC and MM sampling techniques.

physics.ins-det↗

arXiv2022

Electrical breakdown in Thick-GEM based WELL detectors

The occurrence of electrical discharges in gas detectors restricts their dynamic range and degrades their performance. Among the different methods developed to mitigate discharge effects, the use of resistive materials in the detector assembly was found to be very effective. In this work, we present the results of a comparative study of electrical discharges in Thick-GEM-based WELL-type detectors - with and without resistive elements. We present a new method to measure discharges in the resistive-detector configurations; it allows demonstrating, for the first time, the occurrence of discharges also in the Resistive-Plate WELL detector configuration. It also provides direct evidence for the Raether limit.

physics.ins-det↗

arXiv2022

$b\to cτ\barν_{e,μ}$ contributions to $R(D^{(*)})$

The $R(D^{(*)})$ puzzle stands for a $\sim3σ$ violation of lepton flavor universality between the decay rates of $B\to D^{(*)}τν$ and $B\to D^{(*)}\ellν$, where $\ell=e,μ$. If it is accounted for by new physics, there is no reason in general that the relevant neutrinos are, respectively, $ν_τ$ and $ν_\ell$. We study whether the $τ$ related rate could be enhanced by significant contributions to $B\to D^{(*)}τν_\ell$ from a class of operators in the Standard Model Effective Field Theory (SMEFT). We find the upper bounds from forbidden or rare meson decays imply that the contributions from the lepton flavor violating processes account for no more than about $4\%$ of the required shift. Yet, no fine-tuned flavor alignment is required for the new physics. Searching for the related high-$p_T$ process $pp\toτ^\pmμ^\mp$ can at present put a lower bound on the scale of the lepton flavor violating new physics that is a factor of $2.2$ weaker than the bound from meson decays. An exception to our conclusion arises from a specific combination of scalar and tensor SMEFT operators.

hep-ph↗

arXiv2022

Data-Directed Search for New Physics based on Symmetries of the SM

We propose exploiting symmetries (exact or approximate) of the Standard Model (SM) to search for physics Beyond the Standard Model (BSM) using the data-directed paradigm (DDP). Symmetries are very powerful because they provide two samples that can be compared without requiring simulation. Focusing on the data, exclusive selections which exhibit significant asymmetry can be identified efficiently and marked for further study. Using a simple and generic test statistic which compares two matrices already provides good sensitivity, only slightly worse than that of the profile likelihood ratio test statistic which relies on the exact knowledge of the signal shape. This can be exploited for rapidly scanning large portions of the measured data, in an attempt to identify regions of interest. Weakly supervised Neural Networks could be used for this purpose as well.

hep-ph↗

arXiv2022

A Data-Directed Paradigm for BSM searches: the bump-hunting example

We propose a data-directed paradigm (DDP) to search for new physics. Focusing on the data without using simulations, exclusive selections which exhibit significant deviations from known properties of the standard model can be identified efficiently and marked for further study. Different properties can be exploited with the DDP. Here, the paradigm is demonstrated by combining the promising potential of neural networks (NN) with the common bump-hunting approach. Using the NN, the resource-consuming tasks of background and systematic uncertainty estimation are avoided, allowing rapid testing of many final states with only a minor degradation in the sensitivity to bumps relative to standard analysis methods.

hep-ex↗

arXiv2021

Single Electron Spectra in RPWELL-based detectors

Single-electron avalanche distributions in gaseous multipliers affect their efficient detection and that of single UV-photons. In this work, we investigated the shape of single-photo-electron spectra in single- and double-stage Resistive Plate WELL (RPWELL) detector configurations, operated in $\mathrm{Ne/CH_{4}}$ and $\mathrm{Ar/CH_{4}}$. Discharge-free operation was reached over a broad dynamic range, with charge gains of \numrange[range-phrase = -]{e4}{e6}. Compared to the usual exponential ones, the observed Polya-like charge spectra pave the way towards higher single-electrons detection efficiencies. The latter were evaluated here, using experimental data combined with numerical simulations. The effects of the gas mixtures, electric field configuration and detector geometry on the Polya spectra and their related "$θ$" parameter are presented.

physics.ins-det↗

arXiv2019

First demonstration of a bubble-assisted Liquid Hole Multiplier operation in liquid argon

We demonstrate, for the time, the operation of a bubble-assisted Liquid Hole Multiplier (LHM) in liquid argon. The LHM, sensitive to both radiation-induced ionization electrons and primary scintillation photons, consists of a perforated electrode immersed in the noble liquid, with a stable gas-bubble trapped underneath. Electrons deposited in the liquid or scintillation-induced photoelectrons emitted from a photocathode on the electrode's surface, are collected into the holes; after crossing the liquid-gas interface, they induce electroluminescence within the bubble. After having validated in previous works the LHM concept in liquid xenon, we provide here first preliminary results on its operation in liquid argon. We demonstrate the bubble containment under a Thick Gas Electron Multiplier (THGEM) electrode and provide detector response to alpha particles, recorded with a SiPM - under electroluminescence and with modest gas multiplication; the imaging capability is also demonstrated.

physics.ins-det↗

arXiv2017

On the localization properties of an RPWELL gas-avalanche detector

A study of the localization properties of a single-element Resistive Plate WELL (RPWELL) detector is presented. The detector comprises of a single-sided THick Gaseous Electron Multiplier (THGEM) coupled to a segmented readout anode through a doped silicate-glass plate of 10$^{10}$ $Ω\cdot$cm bulk resistivity. Operated in ambient Ne/(5$\%$CH$_4$) gas, the detector has been investigated with 150 GeV muons at CERN-SPS. Signals induced through the resistive plate on anode readout strips were recorded with APV25/SRS electronics. The experimental results are compared with that of Monte Carlo simulations. The effects of various physics phenomena on the position resolution are discussed. The measured position resolution in the present configuration is 0.28 mm RMS - compatible with the holes-pattern of the multiplier. Possible ways for improving the detector position resolution are suggested.

physics.ins-det↗