• Volume 69, Issue 6

December 2007,   pages  953-1258

• Meeting to discuss laser cavity design for photon linear collider - Daresbury, UK, 10 January 2006

The outcome of the meeting to discuss the proposed design for a laser cavity for the photon linear collider is presented.

• Ultimate parameters of the photon collider at the international linear collider

At linear colliders, the $e^{+} e^{-}$ luminosity is limited by beam-collision effects, which determine the required emittances of beams in damping rings (DRs). In $\gamma \gamma$ collisions at the photon collider, these effects are absent, and so smaller emittances are desirable. In the present damping ring designs, nominal DR parameters correspond to those required for $e^{+} e^{-}$ collisions. In this note, I would like to stress once again that as soon as we plan the photon collider mode of ILC operation, the damping ring emittances are dictated by the photon collider requirements - namely, they should be as small as possible. This can be achieved by adding more wigglers to the DRs; the incremental cost is easily justified by a considerable potential improvement of the $\gamma \gamma$ luminosity. No expert analysis exists as of now, but it seems realistic to obtain a factor five increase of the 𝛾 luminosity compared to the nominal' DR design.

• CMOS monolithic pixel sensors research and development at LBNL

This paper summarizes the recent progress in the design and characterization of CMOS pixel sensors at LBNL. Results of lab tests, beam tests and radiation hardness tests carried out at LBNL on a test structure with pixels of various sizes are reported. The first results of the characterization of back-thinned CMOS pixel sensors are also reported, and future plans and activities are discussed.

• Status on the development of front-end and readout electronics for large silicon trackers

Final results on a CMOS 0.18 𝜇m front-end chip for silicon strips readout are summarized and preliminary results on time measurement are discussed. The status of the next version in 0.13 𝜇m is briefly presented.

• Preliminary thoughts on the data acquisition for the next generation of silicon tracking systems

Preliminary thoughts about the data acquisition system to be developed for the next generation of large area silicon tracker are presented in this paper. This paper describes the set of data delivered by these tracking systems, and the various stages of processing and data flow transmission from the front-end chip sitting on the detector to the latest stage in the data processing. How to best profit from the status of the art technologies is a major goal.

• A beam test of prototype time projection chamber using micro-pattern gas detectors at KEK

We conducted a series of beam tests of prototype TPCs for the international linear collider (ILC) experiment, equipped with an MWPC, a MicroMEGAS, or GEMs as a readout device. The prototype operated successfully in a test beam at KEK under an axial magnetic field of up to 1 T. The analysis of data is now in progress and some of the preliminary results obtained with GEMs and MicroMEGAS are presented along with our interpretation. Also given is the extrapolation of the obtained spatial resolution to that of a large TPC expected as the central tracker of the ILC experiment.

• Studies on the drift properties and spatial resolution using a microMEGAS-equipped time projection chamber

R &amp; D studies on the performance as well as on the gas properties of the microMEGAS-based time projection chamber with standard readout were carried out in June 2005 using 4 GeV/c pion beam in a magnetic field from 0 to 1 T at the proton synchrotron beam line at KEK, Japan. Analysis of the electron drift velocity, diffusion constant and point resolution of padrow measurement for MicroMEGAS TPC filled with 95% argon and 5% isobutane gas are presented. The underlying physical mechanism which determines the optimal TPC performance are briefly discussed. Preliminary measurements of gas properties and spatial resolution in close agreement with the analytical calculation and MAGBOLTZ simulation are summarized and presented in this paper.

• Small visible energy scalar top iterative discriminant analysis

Light scalar top quarks with a small mass difference with respect to the neutralino mass are of particular cosmological interest. This study uses an iterative discriminant analysis method to optimize the expected selection efficiency at the international linear collider (ILC).

• Linear Collider Flavour Identification status report: Sensors for the International Linear Collider

The Linear Collider Flavour Identification (LCFI) collaboration is continuing the work to develop column-parallel CCDs (CPCCD) and CMOS readout chips to be used in the vertex detector at the international linear collider (ILC). The CPCCD achieves several orders of magnitude faster readout than conventional CCDs because every column is equipped with amplifier and ADC, enabling efficient data taking with low occupancy. Already two generations of CPCCDs and readout chips have been manufactured and the first chips have been fully tested. The second generation devices are now being evaluated. A new CCD-based device, the in-situ storage image sensor (ISIS) has also been developed. The ISIS offers numerous advantages in terms of relaxed readout, increased radiation hardness and great immunity to EMI. In this paper we present the results from the tests of the CPCCDs, readout chips and ISIS, as well as the plans for future developments.

• Monolithic CMOS pixel detector for international linear collider vertex detection

A monolithic CMS pixel detector is under development for an ILC experiment. This chronopixel array provides a time stamp resolution of one bunch crossing, a critical feature for background suppression. The status of this effort is summarized.

• Preliminary results from India-based Neutrino Observatory detector R &amp; D programme

We are currently developing and studying the performance of glass RPC prototypes, under the INO detector R &amp; D programme. While we were successful in building and characterising a large number of chambers using local glass, these have met with severe aging problems after a few months of continuous operation. We have then built a couple of RPCs using a Japanese glass. We report in this paper on our long term stability tests of these RPCs. We also present some of our recent results on tracking of cosmic ray muons in a stack of glass RPCs.

• An electromagnetic calorimeter for the silicon detector concept

A silicon–tungsten calorimeter for silicon detector (SiD) at the International Linear Collider is under development. Recent progress is summarized.

• CALICE scintillator hadron calorimeter prototype commissioning and calibration

First experience with construction and positron beam tests of a scintillator tile hadron calorimeter are discussed.

• The 4th concept detector

The 4th concept detector consists of four detector subsystems, a small-pixel vertex detector, a high-resolution TPC, a new multiple-readout fiber calorimeter and a new dual-solenoid iron-free muon system. We discuss the design of a comprehensive facility that measures and identifies all partons of the standard model, including hadronic $W \rightarrow jj$ and $Z \rightarrow jj$ decays, with high precision and high e±ciency. We emphasis here the calorimeter and muon systems.

• Muon identification and pion rejection in the 4th concept

We describe a completely new way to reconstruct and identify muons with high efficiency and very high pion rejection in the 4th concept detector. The dual-solenoid magnetic field allows the reconstruction and precision momentum measurement of muons down to a few GeV (just the energy loss in the $10-\lambda_{\text{int}}$ calorimeter and the coil) and the dual-readout calorimeter provides a new, unique and powerful separation of muons from pions. We use test beam data for the calorimeter and calculations for the magnetic fields

• Systematic studies of small scintillators for new sampling calorimeter

A new sampling calorimeter using very thin scintillators and the multi-pixel photon counter (MPPC) has been proposed to produce better position resolution for the international linear collider (ILC) experiment. As part of this R &amp; D study, small plastic scintillators of different sizes, thickness and wrapping reflectors are systematically studied. The scintillation light due to beta rays from a collimated 90Sr source are collected from the scintillator by wavelength-shifting (WLS) fiber and converted into electrical signals at the PMT.

The wrapped scintillator that gives the best light yield is determined by comparing the measured pulse height of each $10 \times 40 \times 2$ mm strip scintillator covered with 3M reflective mirror film, teflon, white paint, black tape, gold, aluminum and white paint+teflon. The pulse height dependence on position, length and thickness of the 3M reflective mirror film and teflon wrapped scintillators are measured.

Results show that the 3M radiant mirror film-wrapped scintillator has the greatest light yield with an average of 9.2 photoelectrons. It is observed that light yield slightly increases with scintillator length, but increases to about 100% when WLS fiber diameter is increased from 1.0 mm to 1.6 mm. The position dependence measurement along the strip scintillator showed the uniformity of light transmission from the sensor to the PMT. A dip across the strip is observed which is 40% of the maximum pulse height. The block type scintillator pulse height, on the other hand, is found to be almost proportional to scintillator thickness.

• Software studies of GLD calorimeter

The baseline design of the GLD calorimeter is scintillator-strip arrays interleaved with absorber plates. We present preliminary performance studies of the hit clustering with this calorimeter using a simulator. Also, simulation results of a digital' calorimeter, which is an option of the GLD calorimeter, are presented.

• CALICE silicon-tungsten electromagnetic calorimeter

A highly granular electromagnetic calorimeter prototype based on tungsten absorber and sampling units equipped with silicon pads as sensitive devices for signal collection is under construction. The full prototype will have in total 30 layers and be read out by about 10000 Si cells of $1 \times 1$ cm2. A first module consisting of 14 layers and depth of $7.2 X_{0}$ at normal incidence, having in total 3024 channels of 1 cm2, was tested recently with $e^{-}$ beam. We describe the prototype and discuss some preliminary testbeam results on its performance with respect to position resolution, response inhomogeneity and transverse containment.

• Understanding the performance of CMS calorimeter

The performance of the CMS hadron calorimeter is studied using test beam facilities at CERN. Two wedges of brass-scintillator calorimeter are exposed to negative and positive beams with momenta between 3 and 300 GeV/c. Light produced in the scintillators are collected using wavelength shifting fibres and read out using hybrid photo-diodes. Each of the wedges has 17 layers of scintillators. In one of these wedges signal from all 17 layers are grouped together while in the other each layer is read out separately. The response, energy resolution, longitudinal and lateral shower profiles are measured.

• Evolution of the dual-readout calorimeter

Measuring the energy of hadronic jets with high precision is essential at present and future colliders, in particular at ILC. The 4th concept design is built upon calorimetry criteria that result in the DREAM prototype, read-out via two different types of longitudinal fibers, scintillator and quartz respectively, and therefore capable of determining for each shower the corresponding electromagnetic fraction, thus eliminating the strong effect of fluctuations in this fraction on the overall energy resolution. In this respect, 4th is orthogonal to the other three concepts, which rely on particle flow analysis (PFA). The DREAM test-beam results hold promises for excellent performances, coupled with relatively simple construction and moderate costs, making such a solution an interesting alternative to the PFA paradigm. The next foreseen steps are to extend the dual-readout principle to homogeneous calorimeters (with the potential of achieving even better performances) and to tackle another source of fluctuation in hadronic showers, originating from binding energy losses in nuclear break-up (measuring neutrons of few MeV energy).

• Development of MPPC

For fine segmented scintillator calorimeter, we need semiconductor-based photon sensor. Progress for MPPC which is developed in Japan is presented. One of the results which is relevant to photon detection efficiency indicates promising future of MPPC. However, further development is required for the dynamic range and operating voltage value.

• Silicon detector technology development in India for the participation in international experiments

A specific research and development program has been carried out by BARC in India to develop the technology for large area silicon strip detectors for application in nuclear and high energy physics experiments. These strip detectors will be used as pre-shower detector in the CMS experiment at LHC, CERN for $\pi^{0}/\lambda$ rejection. The fabrication technology to produce silicon strip detectors with very good uniformity over a large area of $\sim 40$ cm2, low leakage currents of the order of 10 nA/cm2 per strip and high breakdown voltage of $&gt;500$ V has been developed by BARC. The production of detectors is already under way to deliver 1000 detector modules for the CMS and 90% production is completed. In this paper, research and development work carried out to develop the detector fabrication technology is briefly described. The performance of the silicon strip detectors produced in India is presented. The present status of the detector technology is discussed.

• Software for the international linear collider: Simulation and reconstruction frameworks

Software plays an increasingly important role already in the early stages of a large project like the ILC. In international collaboration a data format for the ILC detector and physics studies has been developed. Building upon this software frameworks are made available which ease the event reconstruction and analysis.

• Investigations into properties of charge traps created in CCDs by neutron and electron irradiation

Our group has been investigating the effects related to radiation damage of CCDs since 1998. In a series of measurements in 2003 we found the puzzling effect of very slow filling of charge traps created by radiation damage of the silicon device. In 2005 we intended to study this phenomenon in detail. However, while in 2003 we could see all the traps created by neutron irradiation in 1998-1997 unchanged, such traps unexpectedly almost completely disappeared in 2005. We explain this as an effect of annealing induced by electron irradiation, as in 2003 we irradiated with electrons the same device irradiated with neutrons in 1997-1998. Results of the 2005 measurements are presented.

• Calorimeter energy calibration using the energy conservation law

A new calorimeter energy calibration method was developed for the proposed ILC detectors. The method uses the center-of-mass energy of the accelerator as the reference. It has been shown that using the energy conservation law it is possible to make ECAL and HCAL cross calibration to reach a good energy resolution for the simple calorimeter energy sum.

• Particle flow calorimetry at the international linear collider

One of the most important requirements for a detector at the ILC is good jet energy resolution. It is widely believed that the particle flow approach to calorimetry is the key to achieving the goal of $0.3/\sqrt{E(GeV)}$. This paper describes the current performance of the PandoraPFA particle flow algorithm. For 45 GeV jets in the Tesla TDR detector concept, the ILC jet energy resolution goal is reached. At higher energies the jet energy resolution becomes worse and can be described by the empirical expression: $\sigma_{E}/E \approx 0.265/\sqrt{E(GeV)} + 1.2 times 10^{-4} E(GeV)$.

• Event reconstruction with MarlinReco at the International Linear Collider

After an overview of the modular analysis and reconstruction framework Marlin an introduction on the functionality of the Marlin-based reconstruction package MarlinReco is given. This package includes a full set of modules for event reconstruction based on the particle flow approach. The status of the software is reviewed and recent results using this software package for event reconstruction are presented.

• 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.

• New final doublets and power densities for the international linear collider small crossing angle layout

In this paper we use current and proposed final doublet magnet technologies to reoptimise the interaction region of the international linear collider and reduce the power losses. The result is a set of three new final doublet layouts with improved beam transport properties. The effect of localised power deposition and it's reduction using tungsten liners are considered.

• The impact of BeamCal performance at different international linear collider beam parameters and crossing angles on $\tilde{\tau}$ searches

The ILC accelerator parameters and detector concepts are still under discussion in the world-wide community. As will be shown, the performance of the BeamCal, the calorimeter in the very forward area of the ILC detector, is very sensitive to the beam parameter and crossing angle choices. We propose here BeamCal designs for small (0 or 2 mrad) and large (20 mrad) crossing angles and report about the veto performance study done. As an illustration, the influence of several proposed beam parameter sets and crossing angles on the signal-to-background ratio in the stau search is estimated for a particular realization of the supersymmetric model.

• The interaction region of the large detector concept

The recently optimised interaction region of the LDC detector is presented in this paper together with the requirements for the planned detector hall.

• International linear collider simulations using BDSIM

Power loss simulations for the 2, 14, and 20 mrad extraction line designs using the BDSIM toolkit are presented. A preliminary study on the backgrounds from the beam losses along the extraction line in the case of 20 mrad with high luminosity parameters is also given.

• The stabilisation of final focus system

The StaFF (stabilisation of final focus) system will use interferometers to monitor the relative positions and orientations of several key components in the beam-delivery and interaction region. Monitoring the relative positions of the ILC final focus quadrupole magnets will be the most demanding application, where mutual and beam-relative stability will have a direct impact on machine luminosity. Established, laser-based frequency scanning interferometry (FSI) and fixed-frequency interferometry (FFI) offer positional resolution at length scales of the laser wavelength (1500 nm to 1560 nm) and a thousandth of the wavelength, respectively. As part of the ATF at KEK, StaFF will use interferometers to measure lines of a geodetic network to record relative motion between two beam position monitors. Interferometers are being designed and tested in Oxford prior to deployment at the ATF.

• Study of charged and neutral minimal supersymmetric standard model Higgs boson decays and measurement of tan 𝛽 at the compact linear collider

The minimal supersymmetric extension of the standard model (MSSM) predicts the existence of new charged and neutral Higgs bosons. The pair creation of these new particles at the multi-TeV $e^{+} e^{-}$ compact linear collider (CLIC), followed by decays into standard model particles, were simulated along with the corresponding background. High-energy beam-beam effects such as ISR, beamstrahlung and hadronic background were included. We have investigated the possibility of using the ratio between the number of events found in various decay channels to determine the MSSM parameter tan 𝛽 and we have derived the corresponding statistical error from the uncertainties on the measured cross-sections and Higgs boson masses.

• A laser-wire system for the International Linear Collider

A new laser-wire has been installed in the extraction line of the ATF at KEK. It aims at demonstrating that laser-wires can be used to measure micrometre scale beam size. In parallel, studies have been made to specify a laser suitable for the ILC laser-wires.

• Fast and precise luminosity measurement at the international linear collider

The detectors of the ILC will feature a calorimeter system in the very forward region. The system comprises mainly two electromagnetic calorimeters: LumiCal, which is dedicated to the measurement of the absolute luminosity with highest precision and BeamCal, which uses the energy deposition from beamstrahlung pairs for a fast luminosity measure and the determination of beam parameters. The FCAL system is designed as a universal system fitting all detector concepts. It was implemented and simulated as a subsystem of the large detector concept [1]. The studies are carried out within the FCAL collaboration.

• The stimulated Breit-Wheeler process as a source of background $e^{+} e^{-}$ pairs at the international linear collider

Passage of beamstrahlung photons through the bunch fields at the interaction point of the ILC determines background pair production. The number of background pairs per bunch crossing due to the Breit-Wheeler, Bethe-Heitler and Landau-Lifshitz processes is well-known. However, the Breit-Wheeler process also takes place in and is modified by the bunch fields. A full QED calculation of this stimulated Breit-Wheeler process reveals cross-section resonances due to the virtual particle reaching the mass shell. The one-loop electron self-energy in the bunch field is also calculated and included as a radiative correction. The bunch field is considered to be a constant crossed electromagnetic field with associated bunch field photons. Resonance is found to occur whenever the energy of contributed bunch field photons is equal to the beamstrahlung photon energy. The stimulated Breit-Wheeler cross-section exceeds the ordinary Breit-Wheeler cross-section by several orders of magnitude and a significantly different pair background may result.

• The E166 experiment: Development of an undulator-based polarized positron source for the international linear collider

A longitudinal polarized positron beam is foreseen for the international linear collider (ILC). A proof-of-principle experiment has been performed in the final focus test beam at SLAC to demonstrate the production of polarized positrons for implementation at the ILC. The E166 experiment uses a 1 m long helical undulator in a 46.6 GeV electron beam to produce a few MeV photons with a high degree of circular polarization. These photons are then converted in a thin target to generate longitudinally polarized $e^{+}$ and $e^{-}$. The positron polarization is measured using a Compton transmission polarimeter. The data analysis has shown asymmetries in the expected vicinity of $3.4$% and $\sim 1$% for photons and positrons respectively and the expected positron longitudinal polarization is covering a range from $50$% to 90%.

• Study on low-energy positron polarimetry

A polarised positron source has been proposed for the design of the international linear collider (ILC). In order to optimise the positron beam, a measurement of its degree of polarisation close to the positron creation point is desired. In this contribution, methods for determining the positron polarisation at low energies are reviewed. A newly developed polarisation extension to GEANT4 will provide the basis for further polarimeter investigations.

• The lay-out of the photon collider at the international linear collider

One of the interaction regions at the linear colliders should be compatible both with $e^{+} e^{-}$ and $\gamma \gamma$, $\gamma e$ modes of operation. In this paper, the differences in requirements and possible design solutions are discussed.

• Detector issues for a photon collider

The photon collider is an option at the ILC. In this note detector issues are discussed that are relevant for the change from the $e^{+} e^{-}$ mode of the ILC to the $\gamma \gamma$ mode.

• Data acquisition in the EUDET project

The goal of the EUDET project is the development and construction of infrastructure to permit detector R &amp; D for the international linear collider (ILC) with larger scale prototypes. It encompasses major detector components: the vertex detector, the tracker and the calorimeters. We describe here the status and plans of the project with emphasis on issues related to data acquisition for future test beam experiments.

• Very forward calorimeters readout and machine interface

The paper describes the requirements for the readout electronics and DAQ for the instrumentation of the forward region of the future detector at the international linear collider. The preliminary design is discussed.

• Detector and trigger challenge for supersymmetrical dark matter scenarios at the international linear collider

Two supersymmetrical (SUSY) dark matter scenarios are discussed to illustrate how challenging it is to detect and trigger these events out of standard model background events at a future international linear collider (ILC).

• New developments of the R &amp; D silicon tracking for linear collider on silicon trackers

The status of the R &amp; D activity achieved so far within the SiLC (silicon tracking for the linear collider) collaboration is reported here. It includes the following items: present status of the collaboration, new developments on sensors, on mechanics (new directions for module construction, large support structure, cooling, and alignment and integration issues), new lab test bench results on electronics and sensors. The perspectives over a period of four years are presented with a detailed test beam schedule and the roadmap including the construction of new mechanical prototypes equipped with front end and readout chips in deep sub-micron CMOS technology are discussed. Combined tests with other sub-detectors are finally addressed. This test beam program is inserted in the framework of the EUDET European project.

• Physics issues on triggering

The detectors at the ILC are planned to run without hardware trigger. The physics constraints for a pure software trigger are discussed.

• Test-beam programs for devices to measure luminosity and energy and optimize the luminosity

An overview is given on the test-beam programs to perform detector and system studies for luminosity and energy measurements and beam diagnostics for luminosity optimization.

• Closing remarks

This talk will consist of a set of personal remarks giving my impressions of the International Workshop on Linear Colliders (LCWS06) and a theorist’s perspective.

• List of participants

• Subject Index of Volume 69

• Author Index of Volume 69

• Contents - Volume 69

• # Pramana – Journal of Physics

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• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019