Gian Mario Bilei

The design and construction of the silicon strip microvertex detector (SMD) of the L3 experiment at LEP are described. We present the sensors, readout electronics, data acquisition system, mechanical assembly and support, displacement monitoring systems and radiation monitoring system of the recently installed double-sided, double-layered SMD. This detector utilizes novel and sophisticated techniques for its readout.

We present a precise measurement of the left-right cross section asymmetry ($A_{LR}$) for $Z$ boson production by $\ee$ collisions. The measurement was performed at a center-of-mass energy of 91.26 GeV with the SLD detector at the SLAC Linear Collider (SLC). The luminosity-weighted average polarization of the SLC electron beam was (63.0$\pm$1.1)%. Using a sample of 49,392 $\z0$ decays, we measure $A_{LR}$ to be 0.1628$\pm$0.0071(stat.)$\pm$0.0028(syst.) which determines the effective weak mixing angle to be $\swein=0.2292\pm0.0009({\rm stat.})\pm0.0004({\rm syst.})$.}

In this work we propose a new combined TCAD radiation damage modelling scheme, featuring both bulk and surface radiation damage effects, for the analysis of silicon detectors aimed at the High Luminosity LHC. In particular, a surface damage model has been developed by introducing the relevant parameters (N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OX</sub> , N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IT</sub> ) extracted from experimental measurements carried out on p-type substrate test structures after gamma irradiations at doses in the range 10-500 Mrad(Si). An extended bulk model, by considering impact ionization and deep-level cross-sections variation, was included as well. The model has been validated through the comparison of the simulation findings with experimental measurements carried out at very high fluences (2 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">16</sup> 1 MeV equivalent n/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) thus fostering the application of this TCAD approach for the design and optimization of the new generation of silicon detectors to be used in future HEP experiments.

The formation of the η′ in the reaction e+e−→e+e−η′→e+e−π+π−γ has been measured by the L3 detector at a centre-of-mass energy of 91GeV. The radiative width of the η′ has been found to be Γγγ=4.17±0.10(stat.)±0.27(sys.)keV. The Q2 dependence of the η′ formation cross section has been measured for Q2≤10GeV2 and the η′ electromagnetic transition form factor has been determined. The form factor can be parametrised by a pole form with Λ=0.900±0.046(stat.)±0.022(sys.)GeV. It is also consistent with recent non-perturbative QCD calculations.

The strong coupling αs(M2Z) has been measured using hadronic decays of Z0 bosons collected by the SLD experiment at SLAC. The data were compared with QCD predictions both at fixed order O(α2s) and including resummed analytic formulas based on the next-to-leading logarithm approximation. In this comprehensive analysis we studied event shapes, jet rates, particle correlations, and angular energy flow, and checked the consistency between αs(M2Z) values extracted from these different measures. Combining all results we obtain αs(M2Z)= 0.1200±0.0025 (expt) ±0.0078 (theor), where the dominant uncertainty is from uncalculated higher order contributions.Received 19 September 1994DOI:https://doi.org/10.1103/PhysRevD.51.962©1995 American Physical Society

We analyse e+e−→ττγ events using 100pb−1 of data collected by the L3 experiment during the 1991-1995 LEP runs at the Z pole. From the energy of the photons and their isolation from the tau decay products, we determine the anomalous magnetic and electric dipole moments of the tau to be, respectively: aτ=0.004±0.027±0.023;dτ=(0.0±1.5±1.3)×10−16e·cm.This is a direct measurement of these τ form factors at q2=0.

We have searched for anomalous Z → γγγ events with the L3 detector at LEP. No significant deviations from the expected QED e+e− → γγγ events are observed. The branching ratio upper limit for a compoite Z decaying directly into three photons is found to be 1.0 × 10−5 at 95% C.L. The branching ratio upper limits for the process Z → γX, X → γγ are in the range of 0.4 to 1.3 × 10−5, depending on the mass and width of the scalar particle X. In the context of a model with magnetic monopoles coupling to the Z, we find BR(Z → γγγ) < 0.8 × 10−5 at 95% C.L.; this results in a lower mass limit of 510 GeV for a magnetic monopole.

We report on a study of energetic, isolated photons in a sample of ∼ 320 000 Z0 hadronic decays. Energetic isolated photons probe the short-distance structure of QCD. We compare our data with the prediction of several QCD-based calculations. A search for new processes with one or two photons in the hadronic final state is also presented. No evidence for physics beyond the standard model is found.

The Compact Muon Solenoid (CMS) is one of the experiments at the Large Hadron Collider (LHC) under construction at CERN. Its inner tracking system consist of the world largest Silicon Strip Tracker (SST). In total it implements 24,244 silicon sensors covering an area of 206m2. To construct a large system of this size and ensure its functionality for the full lifetime of 10 years under LHC condition, the CMS collaboration developed an elaborate design and a detailed quality assurance program. This paper describes the strategy and shows first results on sensor qualification.

Pixel detectors at HL-LHC experiments or other future experiments are facing new challenges, especially in terms of unprecedented levels of radiation and particle flux. This paper describes the progress made by the CHIPIX65 project of INFN for the development of a new generation readout ASIC using CMOS 65 nm technology.

In this work we propose the application of an enhanced radiation damage model based on the introduction of deep level traps / recombination centers suitable for device level numerical simulation of silicon detectors at very high fluences (e.g. 2.0x10E16 1 MeV equivalent neutrons/cm2). We present the comparison between simulation results and experimental data for p-type substrate structures in different operating conditions (temperature and biasing voltages) for fluences up to 2.2x10E16 neutrons/cm2. The good agreement between simulation findings and experimental measurements fosters the application of this modeling scheme to the optimization of the next silicon detectors to be used at HL-LHC.

This paper is a review of recent progress of RD53 Collaboration. Results obtained on the study of the radiation effects on 65 nm CMOS have matured enough to define first strategies to adopt in the design of analog and digital circuits. Critical building blocks and analog very front end chains have been designed, tested before and after 5–800 Mrad. Small prototypes of 64×64 pixels with complex digital architectures have been produced, and point to address the main issues of dealing with extremely high pixel rates, while operating at very small in-time thresholds in the analog front end. The collaboration is now proceeding at full speed towards the design of a large scale prototype, called RD53A, in 65 nm CMOS technology.

Future High Energy Physics experiments require sensors to operate at extreme fluences exceeding $1\times10^{17}$ 1 MeV n$_{eq}/$cm$^2$. Therefore, technologies used for the HL-LHC scenario will be no longer applicable and novel sensors and readout electronics must be devised. Within this framework, state-of-the-art Technology CAD tools can be proficiently used to account for the radiation-induced damage effects in semiconductor sensors, fostering design optimization and enabling predictive insight into the electrical behavior of novel solid-state detectors. Various numerical models addressing radiation damage effects have been developed and applied to the study of irradiated devices and will be illustrated in this work. Their applicability needs to be extended to extreme fluences accounting for the modeling of dopant removal, impact ionization, carriers’ mobility and lifetime, and trap dynamics.

We present a new measurement of the left-right cross section asymmetry $({A}_{\mathrm{LR}})$ for $Z$ boson production by ${e}^{+}{e}^{\ensuremath{-}}$ collisions. The measurement was performed at a center-of-mass energy of 91.28 GeV with the SLD detector at the SLAC Linear Collider (SLC). The luminosity-weighted average polarization of the SLC electron beam was $(77.23\ifmmode\pm\else\textpm\fi{}0.52)%$. Using a sample of 93 644 $Z$ decays, we measure the pole value of the asymmetry, ${A}_{\mathrm{LR}}^{0}$, to be $0.1512\ifmmode\pm\else\textpm\fi{}0.0042(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.0011(\mathrm{syst})$, which is equivalent to an effective weak mixing angle of $\mathrm{sin}{}^{2}{\ensuremath{\theta}}_{W}^{\mathrm{eff}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.23100\ifmmode\pm\else\textpm\fi{}0.00054(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.00014\left(\mathrm{syst}\right)$.

We have searched for lepton flavour violation in Z boson decays into lepton pairs using all data collected with the L3 detector during the 1990, 1991 and 1992 runs on an event sample corresponding to 1 500 000 Z's produced. At the 95% confidence level the upper limits on the branching ratio for Z→eμ is 0.6×10−5 and for Z→μτ this is 1.9×10−5.

The envisaged upgrade of the Large Hadron Collider (LHC) at CERN towards the Super-LHC (SLHC) with a 10 times increased luminosity of 1035 cm−2 s−1 will present severe challenges for the tracking detectors of the SLHC experiments. Unprecedented high radiation levels and track densities and a reduced bunch crossing time in the order of 10 ns as well as the need for cost effective detectors have called for an intensive R&D program. The CERN RD50 collaboration "Development of Radiation Hard Semiconductor Devices for Very High Luminosity Colliders" is working on the development of semiconductor sensors matching the requirements of the SLHC. Sensors based on defect engineered silicon like Czochralski, epitaxial and oxygen enriched silicon have been developed. With 3D, Semi-3D and thin detectors new detector concepts have been evaluated and a study on the use of standard and oxygen enriched p-type silicon detectors revealed a promising approach for radiation tolerant cost effective devices. These and other most recent advancements of the RD50 collaboration are presented.

In current particle physics experiments, silicon strip detectors are widely used as part of the inner tracking layers. A foreseeable large-scale application for such detectors consists of the luminosity upgrade of the Large Hadron Collider (LHC), the super-LHC or sLHC, where silicon detectors with extreme radiation hardness are required. The mission statement of the CERN RD50 Collaboration is the development of radiation-hard semiconductor devices for very high luminosity colliders. As a consequence, the aim of the R&D programme presented in this article is to develop silicon particle detectors able to operate at sLHC conditions. Research has progressed in different areas, such as defect characterisation, defect engineering and full detector systems. Recent results from these areas will be presented. This includes in particular an improved understanding of the macroscopic changes of the effective doping concentration based on identification of the individual microscopic defects, results from irradiation with a mix of different particle types as expected for the sLHC, and the observation of charge multiplication effects in heavily irradiated detectors at very high bias voltages.

Abstract The recently developed Low-Gain Avalanche Diode (LGAD) technology has gained growing interest within the high-energy physics (HEP) community, thanks to its capability of internal signal amplification that improves the particle detection. Since the next generation of HEP experiments will require tracking detectors able to efficiently operate in environments where expected fluences will exceed 1 × 10 17 1 MeV n eq /cm 2 , the design of radiation-resistant particle detectors becomes of utmost importance. To this purpose, Technology Computer-Aided Design (TCAD) simulations are a relevant part of the current detector R&amp;D, not only to support the sensor design and optimization, but also for a better understanding and modelling of radiation damage. In this contribution, the recent advances in the TCAD modelling of non-irradiated and irradiated LGAD sensors are presented, whose validation relies on the agreement between the simulated and experimental data — in terms of current-voltage (I-V), capacitance-voltage (C-V), and gain-voltage (G-V) characteristics, coming from devices manufactured by Hamamatsu Photonics (HPK), and accounting for different irradiation levels and temperatures.

In this paper, the issue of numerical modeling of radiation-damaged silicon devices is discussed, with reference to radiation detectors employed in high-energy physics experiments. Since the actual physical picture is far too complex to be accounted for at a first-principle (i.e., defect kinetics) level and not yet fully understood, a hierarchical approach has been followed looking for a suitable approximation of macroscopic changes of the electrical behavior of silicon device induced by radiation damage. In particular, a three deep-level trapping mechanism is accounted for by means of Shockley-Read-Hall theory, whereas the shallow-level sensitivity on the radiation is considered by means of a donor-removal model.

In this paper we discuss some design, implementation and test issues, with respect to the development of the RAPS01 chip in the framework of the Radiation Active Pixel Sensors (RAPS) INFN project. The project aimed at verifying feasibility of smart, high-resolution pixel arrays with a fully standard, submicron CMOS technology for particle detection purposes. Layout optimization of the pixel, including sensitive element and local read and amplification circuits has been carried out. Different basic pixel schemes and read-out options have been proposed and devised. Chip fabrication has been completed and test phase is now under way: to this purpose a suitable test environment has been devised and test strategies have been planned.

The very high radiation fluences expected at the high-luminosity large hadron collider (LHC) impose new challenges in terms of design of radiation resistant silicon detectors. The choice to use p-type substrates to improve the charge collection efficiency involves an optimization of the strip isolation to interrupt the inversion layer between the n± implants, limiting the breakdown voltage. To this purpose, TCAD modeling and simulation schemes, already developed and validated at typical LHC fluences have to be adapted to take into account effects usually neglected at lower fluences. To better understand in a comprehensive framework, the complex and articulated phenomena related to bulk and surface radiation damage, measurements on test structures and sensors, as well as TCAD simulations related to bulk, surface and interface effects, have been carried out. In particular, we have studied the properties of the SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> layer and of the Si-SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> interface, using MOS capacitors and gate-controlled diodes (gated diodes) manufactured by different vendors on a high-resistivity p-type silicon before and after irradiation with X-rays in the range from 50 krad to 10 Mrad. In this paper, we present the results of the experimental characterizations as well as the simulation findings, in order to analyze the effects of the interface traps on the strip isolation. This analysis helps us to validate the model and to identify the most sensitive technological and design parameters to be optimized for the design of advanced 2-D and 3-D silicon radiation detectors.

In this work we present the development and the application of a new TCAD modelling scheme to simulate the effects of radiation damage on silicon radiation detectors at the very high fluence levels expected at High Luminosity LHC (up to 2 × 1016 1MeV n/cm2). In particular, we propose a combined approach for the analysis of the surface effects (oxide charge build-up and interface trap states introduction) as well as bulk effects (deep level traps and/or recombination centers introduction). Experimental measurements have been carried out aiming at: i) extraction from simple test structures of relevant parameters to be included within the TCAD model and ii) validation of the new modelling scheme through comparison with measurements of different test structures (e.g. different technologies) before and after irradiation. The good agreements between experimental measurements and simulation findings foster the suitability of the TCAD modelling approach as a predictive tool for investigating the radiation detector behavior at different fluences and operating conditions. This would allow the design and optimization of innovative 3D and planar silicon detectors for future HL-LHC High Energy Physics experiments.

New measurements at a centre-of-mass energy s≃183 GeV of the hadronic photon structure function Fγ2(x) in the Q2 interval, 9 GeV2 ≤Q2≤30 GeV2, are presented. The data, collected in 1997 with the L3 detector, correspond to an integrated luminosity of 51.9 pb−1. Combining with the data taken at a centre-of-mass energy of 91 GeV, the evolution of Fγ2 with Q2 is measured in the Q2 range from 1.2 GeV2 to 30 GeV2. Fγ2 shows a linear growth with lnQ2; the value of the slope α−1dFγ2(Q2)/dlnQ2 is measured in two x bins from 0.01 to 0.2 and is somewhat higher than predicted.

Interstrip and backplane capacitances on silicon microstrip detectors with p+ strip on n substrate of 320μm thickness were measured for pitches between 60 and 240μm and width over pitch ratios between 0.13 and 0.5. Parametrisations of capacitance w.r.t. pitch and width were compared with data. The detectors were measured before and after being irradiated to a fluence of 4×1014protons/cm2 of 24GeV/c momentum. The effect of the crystal orientation of the silicon has been found to have a relevant influence on the surface radiation damage, favouring the choice of a 〈100〉 substrate. Working at high bias (up to 500 V in CMS) might be critical for the stability of detector, for a small width over pitch ratio. The influence of having a metal strip larger than the p+ implant has been studied and found to enhance the stability.

We have measured the distributions of the jet energies in ${e}^{+}$${e}^{\ensuremath{-}}$\ensuremath{\rightarrow}qq\ifmmode\bar\else\textasciimacron\fi{}g events, and of the three orientation angles of the event plane, using hadronic ${Z}^{0}$ decays collected in the SLD experiment at SLAC. We find that the data are well described by perturbative QCD incorporating vector gluons. We have also studied models of scalar and tensor gluon production and find them to be incompatible with our data.

In this work we present a methodology to develop a surface and bulk TCAD radiation damage effects model which enables a predictive insight into the electrical behavior of novel solid-state detectors up to the particle fluences expected at the end of HL-LHC. To better understand, in a comprehensive framework, the complex and articulated phenomena related to the radiation damage mechanisms several TCAD simulations have been carried out and compared with measurements performed on test structures and sensors. Surface radiation damage effects have been deeply investigated on both p-type and n-type substrate test structures exposed to X-ray irradiation at doses in the range 0.05-100 Mrad(SiO2). The complete bulk and surface radiation damage model findings have been then compared with available measurements in terms of charge collection efficiency up to 2.0×1016 1 MeV equivalent neq/cm2.

Using an impact parameter tag to select an enriched sample of Z0→bb¯ events, and the net momentum-weighted track charge to identify the sign of the charge of the underlying b quark, we have measured the left-right forward-backward asymmetry for b quark production as a function of polar angle. Based on 1.8pb−1 of Z0 decay data produced with a mean electron beam polarization of Pe=63%, this yields a direct measurement of the extent of parity violation in the Zbb coupling of Ab=0.87±0.11(stat)±0.09(syst).Received 3 October 1994DOI:https://doi.org/10.1103/PhysRevLett.74.2890©1995 American Physical Society

Abstract In this paper we discuss an enhanced approach to the analysis of radiation-damaged silicon devices, with reference to numerical modelling implemented in a general-purpose device simulator. In particular, the emission and capture mechanism of deep levels are accounted for by means of Shockley–Read–Hall theory and shallow-level sensitivity to radiation is considered by means of a donor removal model. The effects produced by regions containing very high defect concentrations (referred to as “clusters”) are considered by calculating the direct charge exchange between two deep levels. The resulting analysis technique has been validated and calibrated by means of comparison with experimental measurements carried out on irradiated samples. The model is shown to provide comprehensive and accurate results for several radiation damage phenomena.

The application of a general-purpose device-simulator to the analysis of silicon microstrip radiation detector is described. Physical models include charge-collection dynamics, as well as radiation-induced deep-level recombination centers. Realistic description of multiple-strip devices can be accounted for. To allow for validation of the analysis tool, actual detectors have been measured, before and-after being irradiated with neutrons. Simulation predictions agree well with experiments. Limitations of the adopted model are discussed, with reference to simulation-based comparison with higher-order models.

In this paper, a computer-based analysis of AC-coupled silicon microstrip detectors is presented. The study aims at investigating the main geometrical parameters responsible for potentially critical effects, such as early micro-discharges and breakdown phenomena. The adoption of CAD tools allows for evaluating the actual field distribution within the device, and makes it possible to identify critical regions. The adoption of overhanging metal strips is shown to have a positive impact on the electric field distribution, reducing corner effects and thus minimizing breakdown risks.

The lifetimes of B 1 and B 0 mesons are measured using a sample of 150 000 hadronic Z 0 decays collected by the SLD experiment at the SLAC Linear Collider between 1993 and 1995.Two analyses are presented in which the decay length and charge of the B meson are reconstructed.The first method uses a novel topological vertexing technique while the second uses semi-inclusively reconstructed semileptonic decays.The topological analysis yields a sample of 6033 ( 3665) charged (neutral) vertices with good charge purity, whereas the semileptonic analysis yields a smaller sample of 634 ( 584) charged (neutral) decays with excellent charge purity.Combining the results from both analyses, we find t B 1 1.66 6 0.06͑stat͒ 6 0.05͑syst͒ ps, t B 0 1.64 6 0.08͑stat͒ 6 0.08͑syst͒ ps, and t B 1 ͞t B 0 1.01 6 0.07͑stat͒ 6 0.06͑syst͒.[S0031-9007(97)

Bhabha scattering with polarized electrons at the ${Z}^{0}$ resonance has been measured with the SLD experiment at the SLAC Linear Collider. The first measurement of the left-right asymmetry in Bhabha scattering is presented, yielding the effective weak mixing angle of ${sin}^{2}{\ensuremath{\theta}}_{W}^{\mathrm{eff}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.2245\ifmmode\pm\else\textpm\fi{}0.0049\ifmmode\pm\else\textpm\fi{}0.0010$. The effective electron couplings to the ${Z}^{0}$ are extracted from a combined analysis of polarized Bhabha scattering and the left-right asymmetry previously published: ${\ensuremath{\upsilon}}_{e}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}0.0414\ifmmode\pm\else\textpm\fi{}0.0020$ and ${a}_{e}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{-}0.4977\ifmmode\pm\else\textpm\fi{}0.0045$.

Abstract A large hadron calorimeter and muon tracking device using plastic streamer tubes has been constructed in the iron flux-return structure for the SLD detector at SLAC. Various studies of the operating characteristics of the streamer tubes of this system are presented. Emphasis is placed on the tracking capabilities of the device and on the optimization of the high voltage and readout electronics.

In this paper, we discuss some issues related to the design, implementation and test of a CMOS active pixel sensor chip (RAPS01), developed in the framework of RAPS (Radiation Active Pixel Sensors) INFN project. Two different basic pixel schemes have been proposed The first one is based on a standard Active Pixel Sensor (APS) architecture, while a second architecture, named Weak Inversion Pixel Sensor (WIPS) exploits a different circuitry which allows for "sparse" access mode and thus for speeding-up the read-out phase. Device simulation has been extensively used to estimate the photodiode response for different technologies (thus addressing selection of the silicon foundry). Chip fabrication has been completed and a preliminary test phase has been performed. A suitable test environment has been devised and test strategies have been planned Future work is also outlined, aimed at the fabrication of a second version of the chip, more effectively integrating smart circuitry.

The very high fluences (e.g. up to 2×1016 1 MeV neq/cm2) and total ionising doses (TID) of the order of 1 Grad, expected at the High Luminosity LHC (HL-LHC), impose new challenges for the design of effective, radiation resistant detectors. Ionising energy loss is the dominant effect for what concerns SiO2 and SiO2/Si interface radiation damage. In particular, surface damage can create a positive charge layer near the SiO2/Si interface and interface traps along the SiO2/Si interface, which strongly influence the breakdown voltage, the inter-electrode isolation and capacitance, and might also impact the charge collection properties of silicon sensors. To better understand in a comprehensive framework the complex and articulated phenomena related to surface damage at these very high doses, measurements on test structures have been carried out in this work (e.g. C–V and I–V). In particular, we have studied the properties of the SiO2 layer and of the SiO2/Si interface, using MOS capacitors, gated diodes (GD) and MOSFETs manufactured by FBK on high-resistivity n-type and p-type silicon, before and after irradiation with X-rays in the range from 50 krad(SiO2) to 20 Mrad(SiO2). Relevant parameters have been determined for all the tested devices, converging in the oxide charge density NOX, the surface generation velocity s0 and the integrated interface-trap density NIT dose-dependent values. These parameters have been extracted to both characterize the technology as a function of the dose and to be used in TCAD simulations for the surface damage effect modeling and the analysis and optimization of different classes of detectors for the next HEP experiments.

In this work we propose the application of a radiation damage model based on the introduction of deep level traps/recombination centers suitable for device level numerical simulation of radiation detectors at very high fluences (e.g. 1{\div}2 10^16 1-MeV equivalent neutrons per square centimeter) combined with a surface damage model developed by using experimental parameters extracted from measurements from gamma irradiated p-type dedicated test structures.

We present direct measurements of the ${Z}^{0}$-lepton coupling asymmetry parameters ${A}_{e}$, ${A}_{\ensuremath{\mu}}$, and ${A}_{\ensuremath{\tau}}$, based on a data sample of 12 063 leptonic ${Z}^{0}$ decays collected by the SLD detector. The $Z$ bosons are produced in collisions of beams of polarized ${e}^{\ensuremath{-}}$ with unpolarized ${e}^{+}$ at the SLAC Linear Collider. The couplings are extracted from the measurement of the left-right and forward-backward asymmetries for each lepton species. The results are ${A}_{e}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.152\ifmmode\pm\else\textpm\fi{}0.012(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.001(\mathrm{syst})$, ${A}_{\ensuremath{\mu}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.102\ifmmode\pm\else\textpm\fi{}0.034\ifmmode\pm\else\textpm\fi{}0.002$, and ${A}_{\ensuremath{\tau}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.195\ifmmode\pm\else\textpm\fi{}0.034\ifmmode\pm\else\textpm\fi{}0.003$.

The iron flux-return structure for the SLC Large Detector (SLD) has been instrumented with plastic streamer tubes covering an area of about 4500 m2, to provide muon identification plus energy measurement of hadron showers. A description is given of the production techniques used to construct this large detector system, with an emphasis on the methods by which high reliability and a small number of defects in the completed assembly were ensured.

Radiation damage effects at High Luminosity LHC (HL-LHC) fluences greater than 2.2×1016n∕cm2 1 MeV equivalent and total ionizing doses (TID) greater than 1 Grad will impose very stringent constraints in terms of radiation resistance of solid-state detectors. To cope with this design challenge, TCAD tools can be used to study different technology and design options, in order to optimize the performance of silicon detectors in terms of inter-electrode isolation and charge collection properties. A comprehensive modeling approach based on combined bulk and surface damage effects accounting for a limited number of measurable parameters needs therefore to be developed and validated over different technology options. In this work, we mainly focus on the effects of surface damage on detectors fabricated on p-type substrates by different providers. Actually, starting from standard test structure measurements (i.e. MOS capacitors, gated diodes), the integrated interface trap state density (NIT) and the oxide charge (QOX) can be extracted for different vendors and used as input parameter to the simulation tools. Test structures under study include MOS capacitors, gated-diodes, fabricated both at Hamamatsu Photonics (Japan) and at Infineon (Austria). Using High-Frequency (HF) and Quasi-Static (QS) C–V characteristics and current–voltage (I–V) measurements, the effective oxide charge density (NEFF), the surface generation velocity (s0) and the interface trap density (DIT) have been determined and compared for the two technologies before and after irradiation with X-rays with doses ranging from 0.05 to 20 Mrad(SiO2). A detailed simulation analysis on MOS capacitor capacitances and gated diode currents has been carried out, varying the previously mentioned parameters, with the aim to evaluate the effects of oxide charge density and interface trap density increase with the dose. The separate effects of different types of interface trap states have been considered as well, by varying one by one the total density of donor- and acceptor-type trap states, respectively. The effects of different trap energy distributions and capture cross sections have been evaluated within Synopsys Sentaurus TCAD device simulator by means of steady-state, AC and transient analyses. The good agreement obtained for both vendors would support the use of the model as a predictive tool to optimize the design and the operation of novel solid-state detectors in the HL-LHC scenario.

Device simulation allows for accurate analysis of device behavior, accounting for several physical details that cannot easily be taken into account within compact, equivalent-circuit models. This is especially true for some issues typical of the design of silicon radiation detectors, where silicon properties are exploited in a non-conventional way and radiation damage raises severe reliability concerns. In this paper, a couple of significant applications of device simulation to the investigation and design of advanced solid-state radiation sensors are presented. More specifically, (i) radiation damage influence on detectors operating at cryogenic temperatures is successfully modeled and (ii) features of an innovative scheme for CMOS active pixel sensors are analyzed by means of mixed-mode simulation tools. From these examples, the usefulness and potentiality of advanced simulation techniques in the perspective of radiation detectors can be appreciated.

An active pixel sensor has been developed using standard CMOS technology, UMC 0.18μm with no epitaxial layer, with pixel size 4.4×4.4μm, in the framework of the INFN RAPS project. In this work we will report on the results obtained using several types of ionizing radiation sources (laser, X-ray tubes, β and γ) to test extensively the device. Some of the main results obtained are: a signal/noise value for minimum ionizing particles of about 20, a very good linearity of the response, a good spatial confinement of the signal (cluster size of the order of few pixels).

The numerical simulation of a silicon microstrip detector is discussed. Physical models for the bulk radiation damage have been taken into account, based on a generalized Shockley–Read–Hall expression of the recombination rate. The actual shape of depletion layer, depending on the radiation fluence, has been investigated. The build-up of a dual depletion layer, as reported in some literature works, has been described and interpreted.

We report the results of two beam tests performed in July and September 1995 at CERN using silicon microstrip detectors of various types: single sided, double sided with small angle stereo strips, double sided with orthogonal strips, double sided with pads. For the read-out electronics use was made of Preshape32, Premux128 and VA1 chips. The signal to noise ratio and the resolution of the detectors was studied for different incident angles of the incoming particles and for different values of the detector bias voltage. The goal of these tests was to check and improve the performances of the prototypes for the CMS Central Detector.

Radiation damage effects at High Luminosity LHC (HL-LHC) expected fluences and total ionizing doses (TID) will impose very stringent constraints in terms of radiation resistance of silicon detectors. In this work, we address the effects of surface damage on detectors fabricated on p-type substrates by two different foundries. Starting from standard test structure measurements, the interface trap state density and the oxide charge can be extracted for each specific foundry before and after irradiation with X-rays with doses ranging from 0.05 to 100 Mrad(SiO2). These parameters are then used as inputs to the Technology-CAD simulation tools, aiming at evaluating the effects of oxide charge density and interface trap density variation with the dose on MOS capacitor capacitances and interstrip resistances. The good agreement between simulation results and measurements would support the use of the model as a predictive tool to optimize the design and the operation of novel silicon detectors in the HL-LHC scenario.

We report on a study of single W boson production in a data sample collected by the L3 detector at centre-of-mass energies from 130 to 183 GeV. The signal consists of large missing energy final states with a single energetic lepton or two hadronic jets. The measured cross sections at five different centre-of-mass energies are consistent with the Standard Model expectations. The following limits on the anomalous WWγ gauge couplings are derived at 95% CL: −0.46<Δκγ<0.57 and −0.86<λγ<0.75.

A study of twelve distinct decay channels of the ηc has been performed with the L3 detector at LEP, for an integrated luminosity of 30 pb−1. Summing all channels, 28 candidate events have been identified, with an estimated background of 11 events. The two-photon radiative width is evaluated to be Γγγ(ηc) = 8.0 ± 2.3 ± 2.4 keV.

A search for the decays Bd,s0 → γγ in 2.95 million hadronic Z decays has been performed using the L3 detector at LEP. No candidates are found in the signal region and upper limits have been set on the branching ratios: Br(Bd0→γ)<3.9×10−5 and Br(Bs0 → γγ) < 14.8 × 10−5 at 90% CL. These are the first limits set on these exclusive rare decays.

In this paper, we discuss some issues related to the design, implementation, and test of a CMOS active pixel sensor chip (RAPS01), developed in the framework of the radiation active pixel sensors (RAPS) INFN project. Two different basic pixel schemes have been proposed. The first one is based on a standard active pixel sensor (APS) architecture, while a second architecture, named weak inversion pixel sensor (WIPS) exploits a different circuitry which allows for "sparse" access mode and thus for speeding-up the readout phase. Chip fabrication has been completed and a preliminary test phase has been performed. A suitable test environment has been devised and test strategies have been planned. Preliminary test results, featuring a static and dynamic characterization of the basic sensitive elements are outlined. Future works are also outlined, aimed at the optimization of a second version of the chip, more effectively integrating smart circuitry.

In this work, the application of numerical device simulation to the analysis of high resistivity silicon microstrip detectors is illustrated. The analysis of DC, AC and transient responses of a single-sided, DC-coupled detector has been carried out, providing results in good agreement with experimental data. In particular, transient-mode simulation has been exploited to investigate the collection of charges generated by ionizing particles. To this purpose, an additional generation term has been incorporated into the transport equations; the motion of impact-generated carriers under the combined action of ohmic and diffusive forces is hence accounted for. Application to radiation tolerance studies is also introduced.

We present evidence for leading particle production in hadronic decays of the ${Z}^{0}$ boson to light-flavor jets. A polarized electron beam was used to tag quark and antiquark jets, and a vertex detector was employed to reject heavy-flavor events. Charged hadrons were identified with a Cherenkov ring imaging detector. In the quark jets, more high-momentum $p$, $\ensuremath{\Lambda}$, ${K}^{\ensuremath{-}}$, and ${\overline{K}}^{*0}$ were observed than their antiparticles, and vice versa for antiquark jets, providing direct evidence that the higher-momentum particles in jets are more likely to carry the primary quark or antiquark from the ${Z}^{0}$ decay, and that $s\overline{s}$ production is suppressed in fragmentation.

Low-resistivity materials have been proposed for the fabrication of radiation-hard solid-state particle detectors. A complete analysis of low-resistivity detector performance, including the estimate of charge collection efficiency, has been carried out by using a numerical device simulator, and compared with results expected from conventional, high-resistivity devices. By exploiting the features of the CAD environment, characterization of devices over a wide range of fluences and applied biases has been possible, avoiding the actual fabrication of prototypes, as well as lengthy and expensive testing procedures. Encouraging results have been obtained: low-resistivity devices appear to provide some definite advantages in terms of long-term performance optimization.

RD53A is a large scale 65 nm CMOS pixel demonstrator chip that has been developed by the RD53 collaboration for very high rate (3 GHz/cm 2 ) and very high radiation levels (500 Mrad, possibly 1 Grad) for ATLAS and CMS phase 2 upgrades.It features serial powering operation and design variations in the analog and digital pixel matrix for different testing purposes.The design and verification of RD53A are described together with an outline of the plans to develop final pixel chips for the two experiments.

The very high radiation fluences expected at the High Luminosity LHC (HL-LHC) impose new challenges in terms of design of effective silicon radiation detectors. To this purpose, TCAD modeling and simulation schemes, already developed and validated at typical LHC fluences, have to be adapted to take into account new effects usually neglected at lower fluences. To better understand in a comprehensive framework these complex and articulated phenomena, measurements on test structures and sensors, as well as TCAD simulations related to surface and interface effects, have been carried out. In particular, we have studied the properties of the SiO2 layer and of the Si-SiO2 interface, using MOS capacitors and gate-controlled diodes (gated diodes) manufactured on high-resistivity p-type silicon before and after irradiation with X-ray in the range from 50 krad to 10 Mrad. In this work we present the results of the experimental characterizations as well as the simulation findings, in order to validate the model and to identify the most sensitive technological and design parameters to be optimized for the design of advanced 2D and 3D silicon radiation detectors.

We report on a detailed study of the energy and particle flow in the event plane of three-jet events (qqg) and radiative two-jet events (qqγ) in hadronic Z decays recorded with the L3 detector. We find a significant decrease in particle and energy density in the angular region between quark and antiquark jets for qqg events as compared with qqγ events. Several QCD model predictions are compared with the observed effect.

Abstract The changes of the electrical properties induced by hadron irradiation on silicon detectors have been studied by using the device level simulator HFIELDS. The model of the radiation damage assumes the introduction of radiation-induced acceptor and donor “deep-levels”. The electric field profile and the space charge region extension have been calculated for differently irradiated structures. The simulation has been carried out at different biases in order to study the evolution of the space charge region of irradiated detectors as a function of the applied voltages, below and above the full depletion. The time-dependent current responses and the charge collection properties of the structure illuminated by a red LED light have been calculated. The use of the red light results in a shallow (quasi-surface) generation of e–h pairs in silicon, which has been properly taken into account by the simulation. The results of the simulations have been compared to experimental measurements carried out at CERN on samples irradiated with 24 GeV/c protons. The comparison results in a satisfactory agreement, and supports the physical interpretation of experimental data.

Silicon particle detectors in the next generation of experiments at the CERN Large Hadron Collider will be exposed to a very challenging radiation environment. The principal obstacle to long-term operation arises from changes in detector doping concentration (N/sub eff/), which lead to an increase in the bias required to deplete the detector and hence achieve efficient charge collection. We have previously presented a model of interdefect charge exchange between closely spaced centers in the dense terminal clusters formed by hadron irradiation. This manifestly non-Shockley-Read-Hall (SRH) mechanism leads to a marked increase in carrier generation rate and negative space charge over the SRH prediction. There is currently much interest in the subject of cryogenic detector operation as a means of improving radiation hardness. Our motivation, however, is primarily to investigate our model further by testing its predictions over a range of temperatures. We present measurements of spectra from /sup 241/Am alpha particles and 1064-nm laser pulses as a function of bias between 120 and 290 K. Values of N/sub eff/ and substrate type are extracted from the spectra and compared with the model. The model is implemented in both a commercial finite-element device simulator (ISE-TCAD) and a purpose-built simulation of interdefect charge exchange. Deviations from the model are explored and comments made as to possible future directions for investigation of this difficult problem.

This paper aims at exploring and validating the adoption of standard fabrication processes for the realization of CMOS active pixel sensors, for particle detection purposes. The goal is to implement a single-chip, complete radiation sensor system, including on a CMOS integrated circuit the sensitive devices, read-out and signal processing circuits. A prototype chip (RAPS01) based on these principles has been already fabricated, and a chip characterization has been carried out; in particular, the evaluation of the sensitivity of the sensor response on the actual operating conditions was estimated, as well as the response uniformity. Optimization and tailoring of the sensor structures for High Energy Physics applications are being evaluated in the design of the next generation chip (RAPS02). Basic features of the new chip includes digitally configurable readout and multi-mode access (i.e., either sparse of line-scan readout).

Cloud computing is perceived as the next wave of ICT, and many real experiences are on the commercial scene. However this kind of architecture has open legal issues which makes it an endeavor for Public Administrations, despite its potential impact on the efficiency, effectiveness and transparency of administrative initiatives. In the present paper we present the experience made in the deployment of a Cloud solution in the Regione Marche Local Public Administration, which represents one of the pilot experiences at Nationallevel.

The two-photon collision reaction e+e− → e+e−l+l− has been studied at 2≈91GeV using the L3 detector at LEP for l = e, μ, τ. We have analysed untagged configurations where the two photons are quasi-real. Good agreement is found between our measurements and the O(α4) QED expectation.

We have studied the four-fermion processes ee → eeee, eeμμ, eeττ, μμμμ, μμττ, eeqq and μμqq with the L3 detector at LEP. For an integrated luminosity of 36 pb−, corresponding to 960 000 hadronic Z decays, we find a total of 67 candidate events. The rate and kinematical distributions are found to be consistent with first order Monte Carlo calculations based on the Standard Model. No significant structure is seen in the dilepton invariant or recoil mass spectra.

A measurement of the lifetime of the τ lepton has been made using a sample of 1671 Z0→τ+τ− decays collected by the SLD detector at the SLC. The measurement benefits from the small and stable collision region at the SLC and the precision pixel vertex detector of the SLD. Three analysis techniques have been used: decay length, impact parameter, and impact parameter difference methods. The combined result is ττ=297±9 (stat)±5(syst) fs.Received 7 June 1995DOI:https://doi.org/10.1103/PhysRevD.52.4828©1995 American Physical Society

Abstract The gas mixtures presently used in plastic limited streamer tubes (“Iarocci tubes” or LSTs) have a high hydrocarbon content and are very flammable when mixed with air, posing a potential safety hazard in modern large underground experiments. The SLD Warm Iron Calorimeter group has therefore made an extensive investigation of nonflammable ternary mixtures based on CO 2 . Ar and various hydrocarbons. We present here brief results of this research. In particular, we describe a detailed study of a nonflammable gas mixture (2.5% Ar: 9.5% iC 4 H 10 : 88% CO 2 ) which indicates that this mixture has properties comparable to those of the two commonly used gases (25% Ar: 75% iC 4 H 10 and 21% Ar: 37% nC 5 H 12 : 42% CO 2 ) and could successfully replace these mixtures in LST-based tracking devices and hadron calorimeters.

Abstract A comparison between silicon microstrip detectors with the same geometry built on 〈1 0 0〉 and 〈1 1 1〉 substrates have been carried out. Three sets of structures— 〈1 0 0〉 low resistivity, 〈1 1 1〉 low resistivity and 〈1 1 1〉 high resistivity—have been electrically characterized. Leakage current, depletion voltage, interstrip capacitance and resistance have been measured before and after neutron irradiation. The samples have been irradiated at five different fluences, up to ≃1.5×10 14 n / cm 2 . The measurements show that the leakage current does not depend, at a given fluence, on crystal orientation and on silicon resistivity. At high irradiation fluences the interstrip resistance decreases for all structures to few tens MΩ . The low resistivity substrates, after type inversion, have a lower depletion voltage than the high resistivity ones. The interstrip capacitance is much less sensitive to radiation effects in 〈1 0 0〉 than in 〈1 1 1〉 structures. We conclude that 〈1 0 0〉 low resistivity sensors show, after irradiation, better performances with respect to standard 〈1 1 1〉 high resistivity devices.

Abstract The suitability of standard CMOS technology for particle detection has been investigated through extensive experimental characterization. Different sensor layout and read-out schemes have been devised and implemented, as well as different test strategies. In particular, CMOS technology suitability for radiation detection purposes has been already demonstrated. In this work, we focus on the performance of Active Pixel Sensors (APS) fabricated in a standard CMOS technology (0.18 μm, twin-tub, featuring no epitaxial layer). Noise effects, time response and cross-talk of the proposed structures have been carefully evaluated. The sensitivity to a Minimum Ionizing Particle stimulus has been eventually extrapolated, with the aim of evaluating potential applications of CMOS APS sensors for High Energy Physics experiments.

A Real-Time demonstrator based on the ATCA Pulsar-IIB custom board and on the Pattern Recognition Mezzanine (PRM) board has been developed as a flexible platform to test and characterize low-latency algorithms for track reconstruction and L1 Trigger generation in future High Energy Physics experiments.The demonstrator has been extensively used to test and characterize the Track-Trigger algorithms and architecture based on the use of the Associative Memory ASICs and of the PRM cards.The flexibility of the demonstrator makes it suitable to explore other solutions fully based on a high-performance FPGA device.

In this work we address the effects of surface radiation damage on detectors fabricated on high-resistivity p-type FZ ⟨ 100⟩ substrates by Hamamatsu Photonics (HPK) and by Infineon Technologies (IFX). Test structures underwent a wide set of measurements before and after X-ray irradiation with doses from 0.05 to 100 Mrad (SiO2) in order to extract the integrated interface trap density (NIT) and the oxide charge (QOX) peculiar to different vendors, processes and technology options. These parameters can be then used as inputs to TCAD simulation tools. On the basis of the new experimental evidences at these high doses, the TCAD numerical model has been updated considering two main bands of defects, one acceptor and one donor, extended to the whole silicon bandgap and simulating the net effect of the radiation-induced acceptor-like and donor-like defects. The comparison between simulation findings and measured macroscopic electric behaviour, e.g. in terms of C–V curves of MOS capacitors has been used as cross-check for model validation purposes. By means of the same modelling scheme it is possible to reproduce the I–V curves of gated-diodes and the interstrip resistance as a function of the dose from 0.05 to 100 Mrad (SiO2) for the range of technology and design options investigated. The good agreement between simulations and measurements would support the use of this TCAD surface radiation damage model as a predictive tool to optimize the design and the operations of the new generation of silicon detectors for the future High Energy Physics experiments.

This work discusses the design and the main results relevant to the characterization of analog front-end processors in view of their operation in the pixel detector readout chips of ATLAS and CMS at the High-Luminosity LHC.The front-end channels presented in this paper are part of RD53A, a large scale demonstrator designed in a 65 nm CMOS technology by the RD53 collaboration.The collaboration is now developing the full-sized readout chips for the actual experiments.Some details on the improvements implemented in the analog front-ends are provided in the paper.

The increment of luminosity at HL-LHC will require the introduction of tracker information at Level-1 trigger system for the experiments in order to maintain an acceptable trigger rate for selecting interesting events despite the one order of increased magnitude in the minimum bias interactions. In order to extract the track information in the required latency (∼ 5–10 μ s depending on the experiment), a dedicated hardware processor needs to be used. We here propose a prototype system (Pattern Recognition Mezzanine) as core of pattern recognition and track fitting for HL-LHC experiments, combining the power of both Associative Memory custom ASIC and modern Field Programmable Gate Array (FPGA) devices.

A prototype hadron calorimeter, of similar design to the Warm Iron Calorimeter (WIC) planned for the SLD experiment, has been built and its performance has been studied in a test beam. The WIC is an iron sampling calorimeter whose active elements are plastic streamer tubes similar to those used for the Mont-Blanc proton decay experiment. The construction and operation of the tubes will be briefly described together with their use in an iron calorimeter - muon tracker. Efficiency, resolution and linearity have been measured in a hadron/muon beam up to 11 GeV. The measured values correspond to the SLD design goals.

An upgrade of the L3 central tracking system, a silicon muvertex detector (SMD), is described. The detector consists of two layers of silicon, each equipped for rφ and z readout with resolution ≈ 6 μm and ≈ 20 μm respectively. The SMD will provide full azimuthal coverage over the polar angular range 22°≤θ≤158°. The total thickness is ≈0.9% of one radiation length.

Two modules of the L3 Silicon Microvertex Detector (SMD) have been tested on beam. The active area of the modules consists of double sided silicon microstrip detectors; the implantation pitch is 25 μm and 50 μm in the junction and ohmic side, respectively. The detectors are read out by a VLSI radiation hard amplifier (SVX-H). The position resolution, with a readout pitch of 50 μm and 200 μm for the two sides, is determined to be 7.0 μm and 14.3 μm. A signal to noise ratio ⩾ 16 and a detection efficiency ⩾ 99% are measured for both sides.

The front-end digital electronics and the Fastbus readout and data reduction module for limited streamer tube strips of the SLD warm iron calorimeter and muon tracker are described. A special high-sensitivity front-end hybrid has been developed to read strip information from limited streamer tubes working well below the limited streamer voltages. An MC68020-based Fastbus module to perform fast readout, zero suppression, cluster searching and apparatus monitoring has also been designed, built and tested.

We present the beam test results of single-sided silicon microstrip detectors, with different substrate resistivities. The effects of radiation damage are studied for a detector irradiated to a fluence of 2.4×1014n/cm2. The detectors are read out with the APV6 chip, which is compatible with the 40MHz LHC clock. The performance of different detectors and readout modes are studied in terms of signal-to-noise ratio and efficiency.

The effect of particle irradiation on high-resistivity silicon detectors has been extensively studied with the goal of engineering devices able to survive the very challenging radiation environment at the CERN Large Hadron Collider (LHC). The main aspect under investigation has been the changes observed in detector effective doping concentration (N/sub eff/). We have previously proposed a mechanism to explain the evolution of N/sub eff/, whereby charge is exchanged directly between closely-spaced defect centres in the dense terminal clusters formed by hadron irradiation. This model has been implemented in both a commercial finite-element device simulator (ISE-TCAD) and a purpose-built simulation of interdefect charge exchange. To control the risk of breakdown due to the high leakage currents foreseen during ten years of LHC operation, silicon detectors will be operated below room temperature (around -10/spl deg/C). This, and more general current interest in the field of cryogenic operation, has led us to investigate the behavior of our model over a wide range of temperatures. We present charge collection spectra from 1064 nm laser pulses as a function of detector bias between temperatures of 115 K and 290 K, using devices irradiated with 23 GeV protons in the range 10/sup 13/-4/spl times/10/sup 14/ protons/spl middot/cm/sup -2/. These data allow a deeper investigation of the influence of defect capture cross sections on N/sub eff/. The model prediction for the reversion to n-type of heavily-irradiated detectors at low temperature is investigated and deviations from the model are explored.

The SLD detector at the Stanford Linear Accelerator Center is a general purpose device for studying e{sup +}{epsilon}{sup {minus}} interaction at the Z{sup 0}. The SLD calorimeter system consists of two parts: a lead Liquid Argon Calorimeter (LAC) with both electromagnetic (22 radiation lengths) and hadronic sections (2.8 absorption lengths) housed inside the coil, and the Warm Ion limited streamer tubes Calorimeter (WIC) outside the coil which uses as radiator the iron of the flux return for the magnetic field. The WIC completes the measurement of the hadronic shower energy ({approximately}85% on average is contained in the LAC) and it provides identification and tracking for muons over 99% of the solid angle. In this note we report on the construction, test and commissioning of such a large system.

In this work we present a surface radiation damage effects model based on the introduction of amphoteric, uniform energy band distributed deep-level defects. The main characteristic parameters of the surface damage, e.g. the equivalent oxide charge and interface trap densities, have been extracted from experimental measurements carried out on test structures manufactured by the three foundries: HPK, FBK and Infineon. The surface damage model has been coupled with a bulk damage model based on multiple, single-level defects with tunable capture-cross sections. The model is able to reproduce the measurements carried out on irradiated test structures in terms of C–V curves, interstrip resistance as well as charge collection of segmented detectors.

The Phase 2 upgrades of silicon pixel detectors at HL-LHC experiments feature extreme require- ments, such as: 50x50 μm pixels, high rate (3 GHz/cm2), unprecedented radiation levels (1 Grad), high readout speed and serial powering. As a consequence a new readout chip is required. In this framework the RD53 collaboration submitted RD53A, a large scale chip demonstrator de- signed in 65 nm CMOS technology, integrating a matrix of 400×192 pixels. It features design variations in the analog and digital pixel matrix for testing purposes. An overview of the building blocks will be given together with test results on single chips.

The RD53A large scale pixel demonstrator chip has been developed in 65 nm CMOS technology by the RD53 collaboration, in order to face the unprecedented design requirements of the pixel 2 phase upgrades of the CMS and ATLAS experiments at CERN. This prototype chip is designed to demonstrate that a set of challenging specifications can be met, such as: high granularity (small pixels of 50×50 or 25× 100 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) and large pixel chip size (~2×2 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ), high hit rate (3 GHz/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ), high readout speed, very high radiation levels (500 Mrad - 1 Grad) and operation with serial powering. Furthermore, coping with the long latency of the trigger signal (~12.5 μs), used to select only events of interest in order to achieve sustainable output data rates, requires increased buffering resources in the limited pixel area. The RD53A chip has been fabricated in an engineer run. It integrates a matrix of 400×192 pixels and features various design variations in the analog and digital pixel matrix for testing purposes. This paper presents an overview of the chip architecture and of the methodologies used for efficient design of large complex mixed signal chips for harsh radiation environments. Experimental results obtained from the characterization of the RD53A chip are reported to demonstrate that design objectives have been achieved. Moreover, design improvements and new features being developed in the RD53B framework for final ATLAS and CMS production chips are discussed.

The increase of luminosity at HL-LHC will require the introduction of tracker information at Level-1 trigger system for the experiments to maintain an acceptable trigger rate to select interesting events despite the one order of magnitude increase in the minimum bias interactions. To extract in the required latency the track information a dedicated hardware has to be used. We present the tests of a prototype system (Pattern Recognition Mezzanine) as core of pattern recognition and track fitting for HL-LHC ATLAS and CMS experiments, combining the power of both Associative Memory custom ASIC and modern Field Programmable Gate Array (FPGA) devices.

The increase of the luminosity in the High Luminosity upgrade of the CERN Large Hadron Collider (HL-LHC) will require the use of Tracker information in the evaluation of the Level-1 trigger in order to keep the trigger rate acceptable (i.e.: <; 1MHz). A custom real-time system will be needed to extract the track information within the latency constraints (<;10usec). We developed the prototype of the building block of this system, the Pattern Recognition Mezzanine (PRM) that combines the power of both Associative Memory custom ASICs and modern FPGA devices. The architecture and the functionalities of the PRM are described here.

We report test beam results on the overall system performance of two modules of the L3 Silicon Microvertex Detector exposed to a 50 GeV pion beam. Each module consists of two AC coupled double-sided silicon strip detectors equipped with VLSI readout electronics. The associated data acquisition system comprises an 8 bit FADC, an optical data transmission circuit, a specialized data reduction processor and a synchronization module. A spatial resolution of 7.5 mu;m and 14 mu;m for the two coordinates and a detection efficiency in excess of 99% are measured.

The new technologies used in the construction of the L3 Silicon Microvertex Detector (SMD) at LEP are presented. The SMD consists of two cylindrical layers of double sided silicon sensors to provide very precise measurements of both rφ and z coordinates. In order to minimize the amount of material in the central region, a Kapton fanout has been developed to bring the signals of the z strips (transverse coordinate) to the end of the mechanical structure. To get rid of the leakage currents a new capacitor chip, with diode protection against overvoltages, has been designed and used. In addition, a solution based on optodecoupling has been adopted to read the silicon n-side strips operating at the bias voltage.

A study has been made of the properties of the SGS D779-based readout electronics for limited streamer tubes, both with pulses from a pulse generator and with strip pulses from the actual chambers to be used in the SLD detector. To accommodate the special requirements of the SLD detector, a hybrid circuit has been developed and tested that is capable of operating with pulses from the strips of tubes operated below the limited-streamer-node voltages.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A system allowing for deep investigation of charge collection properties of active pixel particle detectors fabricated in standard 0.18 mum CMOS bulk technology (i.e. without epitaxial layer) has been devised and implemented. The system includes an advanced laser test bench featuring fast laser pulser (68 ps, 80 MHz) and different laser heads (UV 407 nm, VIS 783 nm, IR 1060 nm), as well as integrated movement and acquisition capabilities. In particular, the sub-micron focusing and positioning capabilities of the whole system enable efficient, fast and versatile sensor characterization. Extensive test have been carried out, with the aim of evaluating the sensitivity, the spatial resolution and the efficiency of APS CMOS sensors with different wavelength laser stimuli. The test system provides advanced capabilities for deep understanding of silicon particle detectors to be used in high energy physics experiments and/or medical imaging systems.

The SVX is a charge preamplifier with a sample and hold stage and sparse readout capability developed at the Lawrence Berkeley Laboratory. The SVX radiation hard version has been used by the SMD collaboration to build the L3 Silicon Microvertex Detector where double-sided AC coupled silicon sensors are read out. The SVX-H test procedure in the SMD detector assembly phase will be described as well as the obtained results.

The SLD detector consists of five major subsystems, each with associated front-end electronics and an integrated FASTBUS control and data acquisition system. This paper highlights the choices among electronic technologies that have been developed for the SLD detector electronics. The common control, calibration, and data acquisition architectures are described. The functions of selected SLD integrated circuits, standard cells, gate arrays, and hybrids are summarized, and the integration of these functions into the common data acquisition path is described. Particular attention is directed to four areas of electronic technology developed for the SLD detector: (1) the preamplifier hybrid designs are compared and their performance and implementation examined; (2) the application of full custom CMOS digital circuits in SLD is compared to gate array and EPLD (electrically programmable logic device) implementations; (3) the fiber optic signal transmission techniques in SLD are examined and the data rates and link topology are presented; and (4) finally, the packaging, power consumption, and cooling requirements for system functions resident inside the detector structure are explored. The rationale for the implementation choices in the SLD electronics is presented so that others might benefit from our experience.

A brief description is given of the SLD calorimeter system, with emphasis on the iron calorimeter/muon identifier. Design choices and expected performance are summarized.

The suitability of standard CMOS technology featuring no epitaxial layer for particle detection has been investigated through extensive experimental characterization. Different pixel layout and read-out schemes have been devised and implemented, as well as different test strategies. In this work test results are reported concerning the response of the detector to IR laser, beta-particles and X-rays stimuli, thus confirming the suitability of the proposed approach for high energy physics applications.

A practical, yet physically grounded, TCAD modeling approach to study the radiation damage effects on silicon detectors exposed to the very high fluences expected at High Luminosity LHC (greater than 2.2×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">16</sup> 1MeV n <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eq</sub> /cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) is presented in this work. The modeling strategy is based on combined bulk and surface damage effects accounting for a limited number of measurable parameters. Starting from standard test structure measurements (i.e. MOS capacitors, gated diodes and MOSFETs), the most relevant parameters able to describe the complex phenomena related to the damage effects at these very high fluences have been extracted and therefore fed as input to the simulation tools. In particular the properties of the SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> layer and of the SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Si interface have been deeply investigated on high-resistivity n-type and p-type silicon test structures, before and after irradiation with X-rays in the range from 50 krad(SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) to 20 Mrad(SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ). Thus the extrapolated dose-dependent parameters (e.g. interface trap density and oxide charge density) have been straight included in the TCAD modeling scheme. The adopted numerical approach has been validated by means of the comparison between simulation results and experimental data. To this purpose, steady-state and small signal analysis have been selected as reference analyses to assess the model suitability along with the charge collection efficiency. Different technology and design options/detector geometries can be therefore evaluated, from conventional planar pixelated (strip/pixel) detectors to active-edges or 3D (columnar electrodes) detectors, as well different principle of operation such as charge multiplication in Low Gain Avalanche Detector. This would support technology independence of the model and its use as a predictive tool for the design and the optimization of new classes of silicon sensors for the next generation High-Energy Physics experiments.

A FASTBUS module has been designed for the acquisition and preliminary elaboration of digital data coming from limited streamer-tube strip readout electronics. The module is based on the Motorola MC68020 microprocessor and will perform fast readout with zero suppression, cluster searching, and apparatus monitoring on calorimeter cathode strip data. A description is given of the readout system architecture, the front-end processor, and the FASTBUS interface.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Abstract In this paper, the application of technology CAD methodologies to design and optimization of silicon microstrip detectors is described. More specifically, extensive use of both process and device simulation has been made, in order to predict the performance of DC- and AC-coupled detectors being fabricated at CSEM SA, Neuchâtel, Switzerland, in the framework of a CERN R&D collaboration. Such devices, intended to be part of the CMS-project Si-Tracker, have also been extensively tested at INFN laboratories in Perugia, Italy. Satisfactory agreement between measured and simulated data has been found. This validates the proposed approach, which allows for fast and inexpensive characterization of “virtual” devices.

The gas mixtures generally used until now in limited streamer tube detectors (Ar+C4H10 or Ar+CO2+C5H12) are very flammable when leaked into air. The safety issues are therefore very relevant for large-volume underground experiments. We have found a set of completely safe (i.e. nonflammable) ternary mixtures of the kind Ar + hydrocarbon + CO2 containing less than ∼ 5% of Ar and less than ∼ 10% of hydrocarbon. We tested C4H10, C5H12 and C6H14 as quenching agents. The main characteristics of the various mixtures have been measured: singles (untriggered) counting rate versus high voltage and with different dead times, and average charge. The stability of these mixtures is good, and their spurious streamer activity is compared with the standard binary or ternary mixture. We studied in particular the combination Ar(2.5%) + C4H10(9.5%) + CO2(88%). All the data suggest that this or a similar gas mixture can successfully replace standard flammable mixtures both in tracking devices and hadron calorimeters.

We present the first study of rapidity gaps in e+e- annihilations using Z0 decays collected by the SLD experiment at SLAC. Our measured rapidity gap spectra fall exponentially with increasing gap size over five decades, and we observe no anomalous class of events containing large gaps. This supports the interpretation of the large-gap events measured in pp and ep collisions in terms of exchange of color-singlet objects. The presence of heavy flavors or additional jets does not affect these conclusions.

We present a comparison of the strong couplings of light (u, d, and s), c, and b quarks determined from multijet rates in flavor-tagged samples of hadronic Z0 decays recorded with the SLC Large Detector at the SLAC Linear Collider. Flavor separation on the basis of lifetime and decay multiplicity differences among hadrons containing light, c, and b quarks was made using the SLD precision tracking system. We find αudssαalls=0.987±0.027(stat)±0.022(syst)±0.022(theory), αcsαalls=1.012±0.104±0.102±0.096, and αbsαalls=1.026±0.041±0.041±0.030.Received 16 December 1994DOI:https://doi.org/10.1103/PhysRevD.53.R2271©1996 American Physical Society

In this paper, numerical analysis techniques are applied to the study of microstrip silicon detectors exploited in the field of high-energy physics. At high luminosity required by future experiments, radiation hardness of such device becomes a critical issue. The adoption of relatively low-resistivity substrates has been suggested as a key to face such a problem: simulations have been carried out to verify this assumption. Comparisons have been made in terms of depletion voltage, as well as of charge-collection efficiency, by exploiting some of the features of a customized simulation environment. Estimated, long-term radiation hardness of low-resistivity detectors favorably compares with high-resistivity ones.

The adoption of overhanging-metal contacts have been suggested as an effective mean to limit breakdown risks in heavy-damaged, high-voltage biased microstrip detectors. In this summary, the influence of such overhangs on device noise parameters is analyzed, with particular reference to the interstrip capacitance. Data have been collected on a set of detectors featuring variable overhang extensions and different width/pitch ratios, and numerical simulation has been exploited to provide physical interpretation of the experimental findings. In particular, the non-trivial dependence of interstrip capacitance over geometrical parameters is discussed. By looking at leakage currents and charge-collection as well, it is shown that limited-extension overhangs still have highly beneficial effects on the breakdown properties, while having no practical drawbacks on the detector performance.

The complex physical phenomena related to surface radiation damage effects in solid-state silicon particle detectors can be competently addressed by means of Technology-CAD tools. For modeling purposes, surface damage effects can be mainly characterized by two parameters: the oxide charge density and the interface trap states density. Sensitivity analyses to these two main parameters have been performed, fostering the application of the numerical TCAD model as a tool to investigate the trapping/de-trapping mechanisms behind silicon radiation damaging, thus encouraging the experimental measurements understanding from a microscopic point of view. A physically-based technology-independent numerical modeling scheme for the surface radiation damage effects simulation has been developed, within the TCAD environment.

The tracker system of the compact muon solenoid (CMS) experiment, will employ approximately 40000 analog fiber-optic data and control links. The optical readout system is responsible for converting and transmitting the electrical signals coming out from the front-end to the outside counting room. Concerning the inner part of the Tracker, about 3600 analog optohybrid circuits are involved in this tasks. These circuits have been designed and successfully produced in Italy under the responsibility of INFN Perugia CMS group, completing the volume production phase by February 2005. Environmental features, reliability, and performances of the analog optohybrid circuits have been extensively tested and qualified. This paper reviews the most relevant steps of the manufacturing and quality assurance process: from prototypes to mass-production for the final use in the CMS data acquisition system.

The suitability of standard CMOS technology - featuring no epitaxial layer - for the fabrication of particle detection sensor has been already demonstrated [1,2]. Different sensitive element layouts and read-out schemes have been devised and implemented, depending on the potential applications [3,4]. Manufacturing process peculiarities, however, may significantly affect their behaviour, and the correlation between detector performance and geometrical features/circuit topology is not necessarily straightforward. In this work we present the design and preliminary characterization of an array of APS-like CMOS sensors conceived for direct soft X-rays detection applications, as well as for MIP ionizing particles detection. Circuits include a 64 k pixel array of detectors with reconfigurable read-out electronics capable of both continuous and externally-triggered behaviour. To evaluate technology-related aspects, some smaller (1 k) arrays were included exploiting different geometrical features. A few test structures were also included, aimed at comparing performance both at the pixel and the transistor level.