Single Event Sensitivity Research Articles

Particle identification using plastic scintillators in the COMET Phase-I experiment

The COMET (COherent Muon to Electron Transition) Phase-I experiment aims to search for muon to electron conversion with a single event sensitivity of O (10−15). In COMET, a Cylindrical Trigger Hodoscope (CTH), consisting of segmented plastic scintillators, provides a primary trigger signal and timing measurement while suppressing backgrounds under the high rate environment. This paper studies the particle identification capability of CTH to suppress one of the serious backgrounds induced by cosmic-rays. We demonstrated that a background suppression factor greater than 10 is achievable with a signal efficiency higher than 90%.

High efficiency muon registration system based on scintillator strips

Experiments such as mu2e (FNAL, USA) and COMET (KEK, Japan) seek the direct muon-to-electron conversion to study Charged Lepton Flavor Violation processes. A highly efficient (up to 99.99% efficiency) cosmic muon detection system is needed to achieve a single-event sensitivity below 10−17. In this article, the possibility of attaining such efficiency in the short and long term is discussed for modules based on 7-mm- or 10-mm-thick and 40-mm-wide plastic scintillation strips with a single 1.2 mm WLS fiber glued into the groove along the strip and using MPPC/SiPM for light detection.A Simplified Light Yield Distribution (SLYD) method to estimate the efficiency of the module is proposed, and the simulation results obtained with GEANT 4 for a system based on a 4-by-4 array of 7x40x3000 mm strips are compared with the experimental data. It is found that for the systems requiring efficiency of 99.99% and higher, it is important to improve the light yield as much as possible and to achieve the smallest possible gap between neighbor scintillation volumes is important.

Search for the lepton flavor violating decay μ + → e + e - e + with the Mu3e experiment at PSI

Mu3e is an experiment under construction at the Paul Scherrer Institute (Switzerland) aiming to find or exclude the charged lepton flavor violating decay μ + → e + e - e + at branching fractions above 10-16. A first running phase using an existing beamline targets a single event sensitivity of 2 · 10-15, while the ultimate sensitivity is reached in a second phase with a new high intensity muon beamline. Achieving such sensitivity requires a high muon rate along with a detector of large kinematic acceptance able to reconstruct the low momenta of the decay positrons and electrons with minimal material budget. The Mu3e experiment is mounted with ultra thin tracking detectors based on high-voltage monolithic active pixel sensors, combined with scintillating fibers and tiles for precise timing. This paper presents an overview of the experimental requirements, the technical design, and the construction readiness of Mu3e.

Probing the Single-Event Sensitivity of a COTS 3D-Integrated Imager With Alpha Particle Irradiation

Probing the Single-Event Sensitivity of a COTS 3D-Integrated Imager With Alpha Particle Irradiation

Reduction of charged kaon background in the KOTO experiment

The KOTO experiment at J-PARC searches for the rare kaon decay . In the analysis of the data collected from 2016 to 2018, the largest background was caused by decays of K ±. To detect K ± in the beam line, we developed an in-beam charged particle detector in 2020. After installing it in the KOTO detector system, we collected physics data in 2021. Using a control sample of K ± events, we estimated the inefficiency to be , which reduces the K ± background by a factor of 13. The number of K ± background events was suppressed to be at the single event sensitivity of 7.9 × 10−10.

Status of the COMET experiment

The COMET (COherent Muon to Electron Transition) experiment, currently being built in Tokai, Japan, will search for the coherent neutrinoless transition of muons to electrons in the coulomb field of atomic nuclei. The process is highly suppressed in the Standard Model and therefore provides a promising channel to probe new physics. The experiment will be carried out in a staged approach. Phase-I of COMET aims to search for the process with a single event sensitivity of 𝒪(10−15). Additionally, precise measurements of muon beam dynamics and detector prototyping for Phase-II will be conducted. Utilizing a much higher intensity proton beam, a more complex and longer muon/electron transport system, and gained experience from Phase-I, an improvement of at least four orders of magnitude over the current best branching ratio limit up to 𝒪(10−17) is envisioned for Phase-II. This article will give a status report for Phase-I of COMET.

Mu2e Crystal Calorimeter Readout Electronics: Design and Characterisation

The Mu2e experiment at Fermi National Accelerator Laboratory will search for the charged-lepton flavour-violating neutrinoless conversion of negative muons into electrons in the Coulomb field of an Al nucleus. The conversion electron with a monoenergetic 104.967 MeV signature will be identified by a complementary measurement carried out by a high-resolution tracker and an electromagnetic calorimeter, improving by four orders of magnitude the current single-event sensitivity. The calorimeter—composed of 1348 pure CsI crystals arranged in two annular disks—has a high granularity, 10% energy resolution and 500 ps timing resolution for 100 MeV electrons. The readout, based on large-area UV-extended SiPMs, features a fully custom readout chain, from the analogue front-end electronics to the digitisation boards. The readout electronics design was validated for operation in vacuum and under magnetic fields. An extensive radiation hardness certification campaign certified the FEE design for doses up to 100 krad and 1012 n1MeVeq/cm2 and for single-event effects. A final vertical slice test on the final readout chain was carried out with cosmic rays on a large-scale calorimeter prototype.

The Mu2e Crystal Calorimeter: An Overview

The Mu2e experiment at Fermilab will search for the standard model-forbidden, charged lepton flavour-violating conversion of a negative muon into an electron in the field of an aluminium nucleus. The distinctive signal signature is represented by a mono-energetic electron with an energy near the muon’s rest mass. The experiment aims to improve the current single-event sensitivity by four orders of magnitude by means of a high-intensity pulsed muon beam and a high-precision tracking system. The electromagnetic calorimeter complements the tracker by providing high rejection power in muon to electron identification and a seed for track reconstruction while working in vacuum in presence of a 1 T axial magnetic field and in a harsh radiation environment. For 100 MeV electrons, the calorimeter should achieve: (a) a time resolution better than 0.5 ns, (b) an energy resolution <10%, and (c) a position resolution of 1 cm. The calorimeter design consists of two disks, each loaded with 674 undoped CsI crystals read out by two large-area arrays of UV-extended SiPMs and custom analogue and digital electronics. We describe here the status of construction for all calorimeter components and the performance measurements conducted on the large-sized prototype with electron beams and minimum ionizing particles at a cosmic ray test stand. A discussion of the calorimeter’s engineering aspects and the on-going assembly is also reported.

Quantitative Research on Generalized Linear Modeling of SEU and Test Programs Based on Small Sample Data

Complex integrated circuits (ICs) have complex functions and various working modes, which have many factors affecting the performance of a single event effect. The single event effect performance of complex ICs is highly program-dependent and the single event sensitivity of a typical operating mode is generally used to represent the single event performance of the circuits. Traditional evaluation methods fail to consider the cross effects of multiple factors and the comprehensive effects of each factor on the single event soft error cross section. In order to solve this problem, a new quantitative study method of single event error cross section based on a generalized linear model for different test programs is proposed. The laser test data is divided into two groups: a training set and a validation set. The former is used for model construction and parameter estimation based on five methods, such as the generalized linear model and Ensemble, while the latter is used for quantitative evaluation and validation of a single event soft error cross section of the model. In terms of percentage error, the minimum mean estimation error on the validation set is 13.93%. Therefore, it has a high accuracy to evaluate the single event soft error cross section of circuits under different testing programs based on the generalized linear model, which provides a new idea for the evaluation of a single event effect on complex ICs.

Sensitivity of lepton flavor violation process B+ → K+μ−τ+ in future experiments

The upcoming upgrades of Large Hadron Collider (LHC) to High Luminosity LHC (HL-LHC) and the proposed Future Circular Collider (FCC-hh) offer an opportunity of observing the Lepton Flavor Violating (LFV) process beyond the Standard Model. Monte Carlo simulation of generating and detecting an LFV process [Formula: see text] on CMS at LHC (Run-3), HL-LHC, and FCC-hh reference detector (FRD) is performed. This process is favored by the leptoquark models, particularly the three-site Pati–Salam model but disfavored by the gauged [Formula: see text] model, both of which are introduced to address the [Formula: see text] anomalies. We study possible backgrounds with similar final states and use Multi-Variable Analysis (MVA) to discriminate signal events from possible backgrounds. The MVA output is used to estimate Single Event Sensitivity (SES) of this process, yielding encouraging results on CMS at HL-LHC and FRD at FCC-hh with considerable SES values of about [Formula: see text] (CMS, LHC Run-3), [Formula: see text] (CMS, HL-LHC) and [Formula: see text] (FRD, FCC-hh), suggesting it’s promising to probe such process in the future high energy physics experiments and constrain the new physics models more rigorously.

Single Event Effect Analysis of SiGe Low Noise Amplifier

This paper analyzes the single event transient (SET) response of low noise amplifier (LNA) designed using SiGe heterojunction bipolar transistors (HBT). To verify the radiation tolerance of the proposed LNA, a total of four cascode configurations were designed. Comprehensive mixed-mode simulations were performed to evaluate the SET susceptibility of considered LNA cascode configurations, and we have analyzed how the strike parameters affect their output response. In this fact the strike position, linear energy transfer (LET), and track radius, were varied, and the resulting transients were compared for the different LNA configurations. Through this study, the potential capability of the inverse mode SiGe heterojunction bipolar transistor (HBT) in LNA radiation tolerance was confirmed for various strike operating conditions. It has been demonstrated that the single event sensitivity was reduced for LNA employing inverse mode SiGe HBT for strike device. The strike influence on the different LNA configurations response depends on strike LET, where a reduced SET variation is observed for high LET.

Searching for the Muon Decay to Three Electrons with the Mu3e Experiment

Mu3e is a dedicated experiment designed to find or exclude the charged lepton flavor violating μ→ eee decay at branching fractions above 10−16. The search is pursued in two operational phases: Phase I uses an existing beamline at the Paul Scherrer Institute (PSI), targeting a single event sensitivity of 2·10−15, while the ultimate sensitivity is reached in Phase II using a high intensity muon beamline under study at PSI. As the μ→ eee decay is heavily suppressed in the Standard Model of particle physics, the observation of such a signal would be an unambiguous indication of the existence of new physics. Achieving the desired sensitivity requires a high rate of muons (108 stopped muons per second) along with a detector with large kinematic acceptance and efficiency, able to reconstruct the low momentum of the decay electrons and positrons. To achieve this goal, the Mu3e experiment is mounted with an ultra thin tracking detector based on monolithic active pixel sensors for excellent momentum and vertex resolution, combined with scintillating fibers and tiles for precise timing measurements.

The Mu3e experiment

The experiment aims for a single event sensitivity of 2\cdot 10^{-15}2⋅10−15 on the charged lepton flavour violating \mu^+\rightarrow e^+ e^+ e^-μ+→e+e+e− decay. The experimental apparatus, a light-weight tracker based on custom High-Voltage Monolithic Active Pixel Sensors placed in a 1 T magnetic field is currently under construction at the Paul Scherrer Institute, where it will fully use the intense 10^88\mu^+μ+/s beam available. A final sensitivity of 1 \cdot 10^{-16}1⋅10−16 is envisioned for a phase II experiment, driving the development of a new high-intensity continuous muon source which will deliver >10^99\mu^+μ+/s to the experiment.

Technical design of the phase I Mu3e experiment

The Mu3e experiment aims to find or exclude the lepton flavour violating decay μ→eee at branching fractions above 10−16. A first phase of the experiment using an existing beamline at the Paul Scherrer Institute (PSI) is designed to reach a single event sensitivity of 2⋅10−15. We present an overview of all aspects of the technical design and expected performance of the phase I Mu3e detector. The high rate of up to 108 muon decays per second and the low momenta of the decay electrons and positrons pose a unique set of challenges, which we tackle using an ultra thin tracking detector based on high-voltage monolithic active pixel sensors combined with scintillating fibres and tiles for precise timing measurements.

Measurement of the very rare K+\u2192 {pi}^{+}nu overline{nu} decay

The NA62 experiment reports the branching ratio measurement mathrm{BR}left({K}^{+}to {pi}^{+}nu overline{nu}right)=left({10.6}_{-3.4}^{+4.0}left|{}_{mathrm{stat}}right.pm {0.9}_{mathrm{syst}}right)times {10}^{-11} at 68% CL, based on the observation of 20 signal candidates with an expected background of 7.0 events from the total data sample collected at the CERN SPS during 2016–2018. This provides evidence for the very rare K+→ {pi}^{+}nu overline{nu} decay, observed with a significance of 3.4σ. The experiment achieves a single event sensitivity of (0.839 ± 0.054) × 10−11, corresponding to 10.0 events assuming the Standard Model branching ratio of (8.4 ± 1.0) × 10−11. This measurement is also used to set limits on BR(K+→ π+X), where X is a scalar or pseudo-scalar particle. Details are given of the analysis of the 2018 data sample, which corresponds to about 80% of the total data sample.

Study of the K_{L}→π^{0}νν[over ¯] Decay at the J-PARC KOTO Experiment.

The rare decay K_{L}→π^{0}νν[over ¯] was studied with the dataset taken at the J-PARC KOTO experiment in 2016, 2017, and 2018. With a single event sensitivity of (7.20±0.05_{stat}±0.66_{syst})×10^{-10}, three candidate events were observed in the signal region. After unveiling them, contaminations from K^{±} and scattered K_{L} decays were studied, and the total number of background events was estimated to be 1.22±0.26. We conclude that the number of observed events is statistically consistent with the background expectation. For this dataset, we set an upper limit of 4.9×10^{-9} on the branching fraction of K_{L}→π^{0}νν[over ¯] at the 90%confidence level.

An investigation of the very rare {K}^{+}to {pi}^{+}nu overline{nu} decay

The NA62 experiment reports an investigation of the {K}^{+}to {pi}^{+}nu overline{nu} mode from a sample of K+ decays collected in 2017 at the CERN SPS. The experiment has achieved a single event sensitivity of (0.389 ± 0.024) × 10−10, corresponding to 2.2 events assuming the Standard Model branching ratio of (8.4 ± 1.0) × 10−11. Two signal candidates are observed with an expected background of 1.5 events. Combined with the result of a similar analysis conducted by NA62 on a smaller data set recorded in 2016, the collaboration now reports an upper limit of 1.78 × 10−10 for the {K}^{+}to {pi}^{+}nu overline{nu} branching ratio at 90% CL. This, together with the corresponding 68% CL measurement of ( {0.48}_{-0.48}^{+0.72} ) × 10−10, are currently the most precise results worldwide, and are able to constrain some New Physics models that predict large enhancements still allowed by previous measurements.

First search for KL→π0γ

We report the first search for the $K_L \to \pi^0 \gamma$ decay, which is forbidden by Lorentz invariance, using the data from 2016 to 2018 at the J-PARC KOTO experiment. With a single event sensitivity of $(7.1\pm 0.3_{\rm stat.} \pm 1.6_{\rm syst.})\times 10^{-8}$, no candidate event was observed in the signal region. The upper limit on the branching fraction was set to be $1.7\times 10^{-7}$ at the 90\% confidence level.

Search for at CERN

The decay , with a very precisely predicted branching ratio of less than 10−10, is one of the best candidates to reveal indirect effects of new physics at the highest mass scales. The NA62 experiment at CERN SPS is designed to measure the branching ratio of the with a decay-in-flight technique, novel for this channel. NA62 took data in 2016, 2017 and 2018. Statistics collected in 2016 allows NA62 to reach the Standard Model sensitivity for , entering the domain of 10−10 single event sensitivity and showing the proof of principle of the experiment. The analysis data is reviewed and the preliminary result from the 2016 data set presented.

Influence of fin width on single event-upset characteristics of FinFET SRAM

In this paper, the influence of fin width on single event-upset (SEU) characteristics of 14 nm bulk and SOI FinFET 6 T SRAM is investigated by 3D TCAD mixed-mode simulation. Simulation results show that the threshold linear energy transfer (LETth) of SOI FinFET SRAM is larger than bulk FinFET SRAM. Moreover, the LETth of bulk and SOI FinFET SRAM increases with fin width scaling, and LETth of SOI FinFET SRAM increases more rapidly than bulk FinFET counterpart. The results indicate that bulk and SOI FinFET SRAM would be more immune to SEU response as fin width scales down, especially for SOI FinFET SRAM. Furthermore, the effect of fin width on critical charge and collected charge are explored to explain the fin width dependence of LETth in FinFET SRAM. Both critical charge and collected charge decrease with fin width reducing. However, the collected charge decreases much faster, which becomes the dominant factor for single event sensitivity of FinFET SRAM with fin width scaling.