International Linear Collider Detector Research Articles

Higgs → ττ Branching Ratio Measurement at CEPC

The CEPC (Circular Electron Positron Collider) and ILC (International Linear Collider) detector design provides a high efficiency vertex and Arbor Particle Flow Algorithm[1] uses a new charged particle identification with efficiency higher than 98%. Taking these advantages, the Higgs decaying to ττ channels have been studied in full simulation samples, and the precision of the production cross section times the branching ratio have been improved to 1% level.

Preliminary conceptual design about the CEPC calorimeters

The Circular Electron Positron Collider (CEPC) as a Higgs factory was proposed in September 2013. The preliminary conceptual design report was completed in 2015.1 The CEPC detector design was using International Linear Collider Detector — ILD2 as an initial baseline. The CEPC calorimeters, including the high granularity electromagnetic calorimeter (ECAL) and the hadron calorimeter (HCAL), are designed for precise energy measurements of electrons, photons, taus and hadronic jets. The basic resolution requirements for the ECAL and HCAL are about 16%[Formula: see text][Formula: see text] (GeV) and 50%[Formula: see text][Formula: see text] (GeV), respectively. To fully exploit the physics potential of the Higgs, [Formula: see text], [Formula: see text] and related Standard Model processes, the jet energy resolution is required to reach 3%–4%, or 30%/[Formula: see text] (GeV) at energies below about 100 GeV. To achieve the required performance, a Particle Flow Algorithm (PFA) — oriented calorimetry system is being considered as the baseline design. The CEPC ECAL detector options include silicon–tungsten or scintillator–tungsten structures with analog readout, while the HCAL detector options have scintillator or gaseous detector as the active sensor and iron as the absorber. Some latest R&D studies about ECAL and HCAL within the CEPC working group is also presented.

BeamCal Instrumentation IC: Design, Implementation, and Test Results

The BeamCal detector, one of the calorimeters in the forward region of the International Linear Collider detector, will serve three purposes: ensure hermeticity of the detector for small polar angles, reduce the backscattering from pairs into the detector center, and provide a low-latency signal for beam diagnostics. The BeamCal specifications in terms of noise suppression, signal charge, pulse rate and occupancy pose unique challenges in the front-end and readout electronics design. The Bean - BeamCal Instrumentation IC - is a 32-channel front-end and readout IC that will address the BeamCal instrumentation requirements. By employing switched-capacitor filters and a slow reset-release technique, the Bean will process the signal charge at the International Linear Collider pulse rate. Each channel will have a 10-bit successive approximation analog-to-digital converter and digital memory for readout purposes. The Bean will also feature a fast feedback adder, capable of providing an 8-bit, low-latency output for beam diagnostic purposes. This work presents the design and characterization of the Bean prototype, a 3-channel IC that proves the principle of operation described.

Construction and performance of a silicon photomultiplier/extruded scintillator tail-catcher and muon-tracker

A prototype module for an International Linear Collider (ILC) detector was built, installed, and tested between 2006 and 2009 at CERN and Fermilab as part of the CALICE test beam program, in order to study the possibilities of extending energy sampling behind a hadronic calorimeter and to study the possibilities of providing muon tracking.The ``tail catcher/muon tracker'' (TCMT) is composed of 320 extruded scintillator strips (dimensions 1000 × 50 × 5 mm3) packaged in 16 one-meter square planes interleaved between steel plates. The scintillator strips were read out with wavelength shifting fibers and silicon photomultipliers. The planes were arranged with alternating horizontal and vertical strip orientations. Data were collected for muons and pions in the energy range 6 GeV to 80 GeV. Utilizing data taken in 2006, this paper describes the design and construction of the TCMT, performance characteristics, and a beam-based evaluation of the ability of the TCMT to improve hadronic energy resolution in a prototype ILC detector. For a typical configuration of an ILC detector with a coil situated outside a calorimeter system with a thickness of 5.5 nuclear interaction lengths, a TCMT would improve relative energy resolution by 6-16% for pions between 20 and 80 GeV.

Development of a TPC for an ILC Detector

Abstract The ILD concept, one of two proposed detector concepts for the planned International Linear Collider (ILC), foresees a Time Projection Chamber (TPC) as the main tracking detector. The LCTPC (Linear Collider TPC) collaboration pursues R&D to develop such a TPC based on the best state-of-the-art technology. After tests with smaller prototypes, the current efforts focus on studies using a large prototype with a diameter of 770 mm and a length of 610 mm. This prototype can accommodate seven read-out modules of a size comparable to the onesthatwouldbeusedinthe finalTPC.Several prototypesof modulesusing MicromegasorGEM structuresasgas amplification were constructedand tested. Besidesthe traditionalpad read-out,apixel read-out basedontheTimePix chipis studiedinthese testswithupto8TimePixchipsona board.The current statusand futureplansoftheR&Dare presented.

Electromagnetic response of a highly granular hadronic calorimeter

The CALICE collaboration is studying the design of high performance electromagnetic and hadronic calorimeters for future International Linear Collider detectors. For the hadronic calorimeter, one option is a highly granular sampling calorimeter with steel as absorber and scintillator layers as active material. High granularity is obtained by segmenting the scintillator into small tiles individually read out via silicon photo-multipliers (SiPM). A prototype has been built, consisting of thirty-eight sensitive layers, segmented into about eight thousand channels. In 2007 the prototype was exposed to positrons and hadrons using the CERN SPS beam, covering a wide range of beam energies and angles of incidence. The challenge of cell equalization and calibration of such a large number of channels is best validated using electromagnetic processes. The response of the prototype steel-scintillator calorimeter, including linearity and uniformity, to electrons is investigated and described.

Engineering prototype of the CALICE analog hadron calorimeter

A new prototype of a tile hadron calorimeter (AHCAL) for the International Linear Collider detector is currently developed within the CALICE collaboration. The aim is to improve the energy resolution by measuring details of the shower development and combining them with the data of the tracking chamber (particle flow). The prototype is based on scintillating tiles that are read out by novel Silicon-Photomultiplier (SiPM). This new prototype will take into account all design aspects that are demanded by the intended operation at the ILC It will contain about 2500 detector channels. This is the first calorimeter design which makes full use of the high integration potential of the novel photo-sensor technology.Main focus of this contribution is the mechanical and electrical integration of the front-end electronics into the calorimeter absorber structure, with the aim of maintaining high-density calorimeter. Integration aspects and scalability to an ILC detector are discussed. For the analog calorimeter the proposal of an integrated light-calibration system for calibration and gain monitoring are presented, addressing temperature and bias dependence of the SiPM gain.First results from the measurements with one prototype module at the DESY test beam are presented, which demonstrate the quality of the readout system, and of the light-calibration system.

The EUDET research infrastructure for detector R&D

EUDET is an initiative supported by the European Union to improve infrastructures for detector R&D, in particular for the International Linear Collider (ILC). The project is focused on providing support for larger scale prototype experiments as well as on facilitating collaborative efforts. It encompasses developments for vertex detectors, gaseous and silicon tracking, and highly granular electromagnetic and hadron calorimeters. In total 32 European institutes participate in the project. Twenty-seven other institutes in Europe and abroad are associated members and linked to the progress and later exploitation of the infrastructures. EUDET is closely linked to the international R&D collaborations for a future ILC detector. The R&D infrastructure program is described and some results of the R&D efforts are presented.

The forward region of the future ILC detector

In the very forward region of the future detector at the International Linear Collider (ILC) the following subsystems will be considered: a luminosity detector (LumiCal) for precise measurement of the Bhabha event rate; a beam calorimeter (BeamCal) and a beamstrahlung photon monitor (GamCal) for providing a fast feed-back in tuning the luminosity. BeamCal and GamCal will support also the determination of beam parameters. Both LumiCal and BeamCal will extend the angular coverage of the electromagnetic calorimeter at small polar angles. Detailed simulations are currently done to optimize the design of these detectors. Both LumiCal and BeamCal are planned as compact and highly segmented sandwich calorimeters. Tungsten disks of one X0 thickness are interspersed with sensor planes. For LumiCal, silicon pad sensors will be used. BeamCal will work in an extreme radiation environment, hence radiation hard sensors will be used. The sensors have to withstand a dose of up to several MGy per year. Several options for possible sensor materials have been investigated: polycrystalline and single crystal CVD diamond, as well as GaAs. Since the occupancy of LumiCal is relatively large and BeamCal must be readout after each bunch crossing, a fast readout electronics is necessary. The uncertainty of the luminosity measurement must be smaller than 10 − 3 for the running at high energy and about 10 − 4 in the GigaZ program focused to precision measurements of the Z boson. Systematic effects originating from hardware design as the accuracy of the sensor position, the calorimeter position and the dynamic range of the readout electronics, but also from physics processes have been studied. This work presents the current status of the research carried out to instrument this difficult region of the future ILC detector.

Design and electronics commissioning of the physics prototype of a Si-W electromagnetic calorimeter for the International Linear Collider

The CALICE collaboration is studying the design of high performance electromagnetic and hadronic calorimeters for future International Linear Collider detectors. For the electromagnetic calorimeter, the current baseline choice is a high granularity sampling calorimeter with tungsten as absorber and silicon detectors as sensitive material. A ``physics prototype'' has been constructed, consisting of thirty sensitive layers. Each layer has an active area of 18 × 18 cm2 and a pad size of 1 × 1 cm2. The absorber thickness totals 24 radiation lengths. It has been exposed in 2006 and 2007 to electron and hadron beams at the DESY and CERN beam test facilities, using a wide range of beam energies and incidence angles. In this paper, the prototype and the data acquisition chain are described and a summary of the data taken in the 2006 beam tests is presented. The methods used to subtract the pedestals and calibrate the detector are detailed. The signal-over-noise ratio has been measured at 7.63±0.01. Some electronics features have been observed; these lead to coherent noise and crosstalk between pads, and also crosstalk between sensitive and passive areas. The performance achieved in terms of uniformity and stability is presented.

Estimation of radiation effects in the front-end electronics of an ILC electromagnetic calorimeter

The front-end electronics of the electromagnetic calorimeter of an International Linear Collider detector are situated in a radiation environment. This requires the effect of the radiation on the performance of the electronics, specifically FPGAs, to be examined. In this paper we study the flux, particle spectra and deposited doses at the front-end electronics of the electromagnetic calorimeter of a detector at the ILC. We also study the occupancy of the electromagnetic calorimeter. These estimates are compared with measurements, e.g. of the radiation damage of FPGAs, done elsewhere. The outcome of the study shows that the radiation doses and the annual flux is low enough to allow today's FPGAs to operate. The Single Event Upset rate, however, lies between 14 min and 12 h depending on the FPGA used and therefore needs to be considered in the design of the data acquisition system of the electromagnetic calorimeter. The occupancy is about 0.002 per bunch train not taking into account the effect of noise which depends on the choice of the detector.

Performance of GLD detector

Most of the important physics processes to be studied in the international linear collider (ILC) experiment have multi-jets in the final state. In order to achieve better jet energy resolution, the so-called particle flow algorithm (PFA) will be employed and there is a general consensus that PFA derives overall ILC detector design. Four detector concepts for the ILC experiment have been proposed so far in the world; the GLD detector that has a large inner calorimeter radius, which is considered to have an advantage for a PFA, is one of them. In this paper, general scheme and performance of the GLD-PFA will be presented.

Innovations in ILC detector design using a particle flow algorithm approach

The International Linear Collider (ILC) is a future e+e− collider that will produce particles with masses up to the design center-of-mass (CM) energy of 500 GeV. The ILC complements the Large Hadron Collider (LHC) which, although colliding protons at 14 TeV in the CM, will be luminosity-limited to particle production with masses up to ∼1–2 TeV. At the ILC, interesting cross-sections are small, but there are no backgrounds from underlying events, so masses should be able to be measured by hadronic decays to dijets (∼80% BR) as well as in leptonic decay modes. The precise measurement of jets will require major detector innovations, in particular to the calorimeter, which will be optimized to reconstruct final state particle 4-vectors—called the particle flow algorithm approach to jet reconstruction.

Detectors for a linear collider

The International Linear Collider (ILC) is the next large project in high energy physics and currently being designed in a global effort. The main scientific goal is to complement the anticipated discoveries at the LHC by precision measurements at the TeV scale. This has challenging implications on the ILC detector design and performance requiring unprecedented precision in vertexing, tracking and calorimetry. Design studies on four detector concepts are ongoing which are complemented by international R&D programmes to develop detectors suitable for the conditions at the collider and matching the required performances. A survey will be given on the detector concepts and technologies under investigation together with the current status of the R&D programmes and future plans.

Tracking at the ILC: Why silicon tracking is best, and how it might be optimized

Basic scaling laws are used to compare the relative capabilities of gaseous and solid-state tracking. Conclusions are drawn in the context of physics processes expected to be at the focus of studies at the International Linear Collider (ILC). An efficient approach to the readout and deployment of microstrip tracking for an ILC detector is presented.

Determination of new electroweak parameters at the ILC – sensitivity to new physics

We present a study of the sensitivity of an International Linear Collider (ILC) to electroweak parameters in the absence of a light Higgs boson. In particular, we consider those parameters that have been inaccessible at previous colliders, quartic gauge couplings. Within a generic effective-field theory context we analyze all processes that contain quasi-elastic weak-boson scattering, using complete six-fermion matrix elements in unweighted event samples, fast simulation of the ILC detector, and a multidimensional parameter fit of the set of anomalous couplings. The analysis does not rely on simplifying assumptions such as custodial symmetry or approximations such as the equivalence theorem. We supplement this by a similar new study of triple weak-boson production, which is sensitive to the same set of anomalous couplings. Including the known results on triple gauge couplings and oblique corrections, we thus quantitatively determine the indirect sensitivity of the ILC to new physics in the electroweak symmetry-breaking sector, conveniently parameterized by real or fictitious resonances in each accessible spin/isospin channel.

Detecting metastable staus and gravitinos at the ILC

A study of various SUSY scenarios is presented in which the lightest supersymmetric particle is the gravitino \(\tilde{G}\) and the next-to-lightest supersymmetric particle is a scalar tau \(\tilde{\tau}\) with lifetimes ranging from seconds to years. Gravitinos are interesting dark matter candidates which can be produced in decays of heavier sparticles at the International Linear Collider (ILC), but remain undetected in direct searches of astrophysical experiments. We investigate the detection and measurement of metastable staus, which may be copiously produced at the ILC either directly or via cascade decays. A proper choice of the experimental conditions will allow one to collect large samples of \(\tilde{\tau}\)s coming to rest in the calorimeters of the ILC detector and to study the subsequent decays \(\tilde{\tau}\to\tau\tilde{G}\). Detailed simulations show that the properties of the stau and the gravitino, such as \(\tilde{\tau}\) mass and lifetime and \(\tilde{G}\) mass, can be accurately determined at a future ILC and may provide direct access to the gravitational coupling, respectively Planck scale.

Ion feedback suppression in time projection chambers

A controlled-voltage Gas Electron Multiplier (GEM) can be used to block the re-injection of positive ions in large volume Time Projection Chambers (TPC). With proper choice of geometry, gas filling and external fields, good electron transmission can be obtained at very low GEM voltages; pulsed ion gating is then much easier than with conventional wire grids, requiring hundreds of volts. Gating schemes suited for the TPC detector planned for the International Linear Collider detector are described. The possibility of GEM-based DC-operated ion filters, exploiting the difference in diffusion properties of ions and electrons, is also discussed.

A high-granularity scintillator calorimeter readout with silicon photomultipliers

We report on the design, construction and performance of a prototype for a high-granularity tile hadronic calorimeter for a future international linear collider detector. Scintillating tiles are read out via wavelength-shifting fibers that guide the scintillation light to a novel photodetector, the silicon photomultiplier. A prototype has been tested using a positron test beam at DESY. The results are compared with a reference prototype calorimeter equipped with multichannel vacuum photomultipliers. Detector calibration, noise, linearity and stability are discussed, and the energy response in a 1–6 GeV positron beam is compared with simulations. The present results demonstrate that the silicon photomultiplier is well-suited as photodetectors in calorimeters and thus has been selected for the construction of a 1 m 3 calorimeter prototype to operate in hadron beams.