LCWS 2004

      click here for a full report  

The process e+ e- -> 3 jets offers the opportunity to measure the strong coupling constant.  For an accurate determination, precise theoretical  calculations are necessary.  I will give an overview on the status of the next-to-next-to-leading order calculations.

More than 20 European laboratories have joined forces on a Design Study for the Linear Collider in the TeV range. In a bid submitted to the European Union the consortium tries to gain support to address some of the remaining high ranking issues identified in the report of the TRC. It is expected that these studies will be complemented by similar activies in Asia and in the Americas. The talk will give an overview of the topics tackled in this study.

One charge to the US LC Technology Options Study was to evaluate the projected availability of the warm and cold LC designs and indicate the effort required to meet specified goals. A Monte Carlo simulation was developed which estimated availability based on device counts, frequency of failure (MTTF) and time to repair (MTTR). The simulation included device accessibility, tunnel access and beam recovery times, and time for machine development studies. The study also considered the impact of 1 vs 2 tunnels, and the benefit of a conventional positron source for either design.

As part of the US LC Technology Options Study, a risk analysis was performed to identify aspects of the warm and cold designs where there was significant risk that the LC might fail to achieve its energy, luminosity or availability goals. The study identified 42 items and assigned each of these a rank for likelihood, severity, time of discovery and impact. This pointed to which sub-systems of each design pose the greatest risk.

GLCTA (Global Linear Collider Test Accelerator) is a facility to demonstrate that we are ready to build a linear collider with a warm technology.  It is a great and important step to realize the LC project.  We have built the GLCTA at KEK and just started a high-power test of an X-band accelerating structure. In the near future,we will accelerate an ultra low-emittance beam from the ATF. It should be a good and direct demonstration of the GLC accelerator complex.

C-band accelerator has succeeded in accelerating a beam at the injector of KEKB. In the early stage of the LC, C-band technology may be the best technology because of its simplicity and reliability. To reach 1TeV or higher energy, however, X-band technology is indispensable. We have studied to operate both C-band and X-band simultaneously in LC main linac.

I will report on the status and future prospects of the GLCTA and C+X option.

Fermilab is the only laboratory in the US Laboratory that is collaborating on both warm (NLC) and SRF (TESLA) linear collider technology R&D. Fermilab's contributions and plans to these accelerator hardware R&D will be discussed.  New initiatives in the accelerator physics, ground motion etc. at Fermilab will be presented. A proposal and scope of a next generation Linear Collider Engineering Test Facility will be discussed.

Including some updates and cross-references to relevant talks in SUSY session and by Lohmann, Drugakov and Hauptman

Includes a few slides contributed by Bambade, Mouton and Napoly for point B

Includes contributions from Aihara and comments on the extraction line design

Includes some summarizing comments on the different crossing-angle schemes

We present a study of the loop-level lepton number violating signal e-e-  --->  l- l-  (l = \mu, \tau) in models with heavy Majorana neutrinos and of the reactions  e- e-  ---> l- e- (l = \mu, \tau)
in the supersymmetric extension of the standard model with slepton mixing.

Some of the physics motivations for e-e-
collisions are reviewed.

Studies of CCD-based vertex detector for a linear collider are presented. In 2003 physical year, our work was focused on the aspects of radiation tolerance for the high energy electrons and charge diffusion time for faster readout operation. This talk gives an overviwe of our current results and future plans.

The LCFI collaboration is conducting a comprehensive research and development programme towards a silicon pixel-based vertex detector for the future LC.  The latest results in the development and prototyping of column parallel CCDs, their associated readout electronics and ultra-low mass ladders will be discussed, along with future plans.

Very high granularity, very modest material budget, fast read-out and radiation hard sensors are required for construction of the Vertex Detector, providing the measurement precision asked by the physics programme at the Future e+e- Linear Collider (FLC). Various versions of MAPS detectors, searching for optimum operation under given experimental conditions, are being developed within the IReS-LEPSI collaboration in Strasbourg. The detectors are produced in the form of VLSI chips using standard CMOS processes. The active volume is a thin, moderately doped silicon layer, operated undepleted. The key is the use of an n-well-to-substrate diode to collect, mostly through thermal diffusion, the charge (electrons) generated in the active volume underneath the readout electronics.

We are developing CMOS monolithic active pixel sensors for the vertex detector for the future Linear Collider. We have produced two working test structures designed in 0.25 CMOS which feature four different types of pixels: standard 3MOS, 4MOS allowing correlated double sampling, charge amplifier pixels and a Flexible APS. The FAPS has a 10 deep pipeline on each pixel specifically designed for the linear collider. A program to test our devices is well underway. We will report results of a radiation test including measurements and simulations. Also results of a source test will be presented.

A new generation of DEPFET (DEPleted Field Effect Transistor) active pixel sensors with 25 micrometer pixel size has been developed and produced to meet the requirements of the future e+e- linear collider physics program in point measurement resolution and multiple track separation. A silicon technology is presented which allows the production of large sensor arrays consisting of linear DEPFET pixel cells. The DEPFET concept combines detection and amplification in one single device. The signal charge is stored underneath a MOSFET channel and allows a row-wise read out with only one row being electrically active at a time. The envisaged pixel array offers therefore low noise and low power operation. We will present the operation principles and the results of the first prototype production.

Includes results from Barklow, Murayama and Abe

Coordinating with J. Hauptman's talk in the same session.

Continuing the previous talk and including results by Murayama and Graf on the electron ID algorithm

Coordinating with W. Lohmann's talk in the same session

Includes a few slides contributed by Bonvicini on his proposal

Includes analysis using pair profiles from the planned 7 mrad GLC crossing-angle (possibly also 20 mrad)

The monolithic active pixel detector realized in the Silicon on Insulator technology (SOI) is a novel solution of ionising radiation detectors, which allows integration of the particle detector and readout electronics in one entity by the utilization of the both silicon layers (support and device layers) of a wafer-bonded SOI substrate.  First test structures of the SOI detectors have been manufactured and preliminary characterized. The performed sensor tests with an infrared laser spot and radioactive sources proved the sensor sensitivity for the ionising radiation and validate the concept of the device. Following the positive results of the SOI detector test structures measurements the fully functional SOI detector, covering area of 2 cm x 2 cm have been designed. The resent results of the SOI detector measurements and the architecture the new SOI sensor will be presented.

We propose the Integrated Pixel Tracker (IPT), a device that is part of the vertex detector based on the MIMOSA CMOS pixel sensor. The IPT takes raw data from the pixel sensors, and applies real-time data reduction in two steps by means of hardware: cluster collection on a local level and track reconstruction on a global level.  Only the track features are stored on disk. We also discuss our progress on the demonstrator of the IPT, which is a sample system that presents the functionality of the IPT but not the performance, and we give an outlook.

A new generation of DEPFET active pixel sensors with 25 um pixel size is currently being developed to meet the requirements in the point measurement resolution and multiple track separation. To minimize the influence of the multiple scattering on the impact parameter resolution, the sensors have to be made as thin as possible. We will present a technology based on direct wafer bonding and deep anisotropic etching for the production of ultra thin fully depleted sensors with electrically active back side. PiN diodes with 50 um thickness have been produced in this way and the results show the feasibility of this approach. A module concept for thin DEPFET arrays with an integrated support frame outside of the sensitive area will be presented.

We will report on the silicon R&D activities in Korea for the future Linear Collider. The activities includes design, production and simulation of double-side silicon strip sensors. The charateristics of our first prototype sensors and the results of simulation will be presented.

Expected properties of a resistive structure of gallium arsenide doped by Chromium, GaAs:Cr, are discussed. Pad GaAs:Cr detectors of the size 10mm*10mm are presented as an output of new technologies developed in Tomsk. Results of the recent tests of radiation hardness of these detectors in hadron and gamma beams are reported. Further plans for direct comparison of GaAs:Cr detectors and Si detectors are shown and prospects are discussed for using GaAs:Cr as a material for pixel vertex and tracking detectors at small angles.

We present the progress of the hardware program on short-shaping time microstrip readout at UC Santa Cruz.

Latest results, within the SiLC R&D program, on the measurements achieved with a long ladder prototype with microstrips of length up to 2m24, on the design and simulation studies of a complete FE and readout electronics chain, on the CAD mechanical design of such a tracking system and related integration issues, on the thermo-mechanical studies are presented as well as the near future prospects.

Includes 1-2 slides contributed by Schreiber on DESY design updates

Includes some comments on the GLC extraction line design

Includes a few slides on similar work by Kurihara

We would like to list the relevant topics where work and collaboration could be enhanced by organizing informal inter-regional working groups. The discussion needs some preparation. Among the topics are for instance issues to do with having 2 IRs with comparable luminosity and energy, one of which with a crossing-angle large enough to make possible the option of a future gg-collider upgrade

The (e+e- -> t tbar H) process has been extensively studied to determine the accuracy on the top-Higgs Yukawa coupling achievable with the TESLA collider at 800 GeV, for Higgs masses ranging from 120 GeV/c2 to 200 GeV/c2.  The analysis of (H -> b bbar) and (H -> WW) channels has already shown  that an accuracy on the top-Higgs Yukawa coupling better than about 10 % was achievable for most of the Higgs masses below 200 GeV/c2.  Present work is going on in order to improve the precision on the coupling by including the Higgs decays into Z pairs. The analysis is also being extended to higgs bosons heavier than 200 GeV/c2.  First results of these extensions of the analysis will be presented.

Recent developments in the treatment of a system of heavy quarks close to their production threshold are discussed. Particular emphasis is put on the next-to-next-to-next-to-leading order corrections to the energy levels and the wave function and their effect on the cross section sigma(e+e-  ->  t tbar). Furthermore, the resummation of logarithmic corrections within the framework of potential NRQCD are considered.

Accelerator and detector DAQ interplay - Do we need joint MDI/DAQ sessions ?
Detector R&D and DAQ interplay - Do we need joint tracking/Calorimetry/DAQ sessions?
GND issues for the DAQ ?

A prototype TPC with GEM readout was operated in axial magnetic fields for the first time at TRIUMF and DESY in the summer of 2003. Results from an updated analysis of cosmic ray tracks recorded with this device will be shown. Plans for further tests with the prototype TPC will be presented.

One possible option for the main tracking device of a detector at a future Linear Collider is a large Time Projection Chamber (TPC).  To replace the traditional wire based gas amplification system of a TPC, so called Micro Pattern Gas Detectors (MPGDs) are considered a good choice. One example of such a MPGD is the Gas Electron Multiplier (GEM). At DESY a prototype TPC equipped with GEMs has been built and tested in cosmic muon runs in a superconducting 5 T magnet. The tracking performance of a GEM TPC in high magnetic fields will be reported and compared to results without B field.

In order to study whether a TPC in combination with a Micro Pattern Gas Amplification stage can meet the demands of future Linear Collider central tracking systems, a small cylindrical TPC Prototype was built in Karlsruhe and equipped with two GEMs and highly-integrated front-end electronics. The studies imply two beam tests at the Proton-Synchrotron (PS) at CERN as well as a test in a superconducting magnet with a magnetic field of up to 5T at DESY. Here the results concerning efficiency, diffusion and spatial resolution will be presented. In the hadronic beam single-row efficiencies of 99.3% for all different gas mixtures could be reached. The spatial resolution shows good agreement in all tests and reaches values of down to 60 microns.

The LC TPC prototype built and commissioned at MPI-Munich is equipped with wire gas amplification now and is foreseen to also be modified for the Gem and Micromegas (MPGD) technologies.  The chamber was transferred to Desy for testing with cosmics and lasers in the 5T magnet and with the readout electronics there.  It will then be shipped to KEK for continuation of this series of measurements with final testing in a beam in June.  MPGD planes are in preparation for this chamber.  Status and results from these activities will be presented at the LCWS2004 tracking session; collaborating institutes include Desy, IPN Orsay, KEK + members of the CDC group, and MPI-Munich.

We present first results on magnetic field tests of a Micromegas TPC using cosmic rays. The large-area TPC prototype (1024 channels, 50 cm drift and 50 cm diameter) has been in operation since July 2003 at Saclay. Results from data taken in November 2003 for both Ar-Isobutane and Ar-CF4 mixtures at various magnetic field settings will be shown.

An 'ideal' readout scheme of a TPC would consist of gas multiplication by either one or more GEM or Micromegas foils, followed by a charge collection device with a granularity  corresponding to the primary ionisation cluster spread (and assuming sufficiently low diffusion). A readout channel with granularity similar to the 'grid' size in GEM and Micromegas foils has been realised, as a first step, based on the existing MediPix2 chip. Hit-pixel data show the expected patterns from the conversion of Fe55 quanta in gas mixtures like Argon-Methane (95/5) and Argon-Isobutane (95/5). Measurements of detection of single electrons from minimum ionising particles are at present under way.

If a TPC will be used as central detector at a high energy linear collider the spatial resolution must be improved. Charge amplification with micro pattern gas detectors (MPGD), such as GEMs and Micromegas, will eliminate large systematic effects inherent in the conventional proportional wire cathode pad readout TPC. However, the transverse confinement of the spatial charge in a magnetic field will make it harder for the MPGD readout to achieve good spatial resolution unless the readout pad width is reduced. We have previously demonstrated that a resistive anode can be used to disperse the MPGD charge after amplification to achieve good resolution with wide pads for a point x-ray source. We present here our first results for tracking studies of cosmic-ray particles in a GEM-TPC with a resistive anode.

In the framework of our studies of a  GEM readout for a TPC at a Future Linear Collider we present studies on charge broadening effects and the shape of the cluster charge as a function of the magnetic field.  Results of measurements with a test chamber in fields up to 5 T will be shown. For further studies a TPC is being built which is designed to fit into the 5T magnet at DESY. Numerical simulations to optimize the design of the field cage have been performed. A status report on the construction of this TPC will be given.

A critical factor in the design of a TPC for a Linear Collider is the amount of ions drifting back into the sensitive volume. To reduce this ion feedback, multi-GEM-structures are used, which further improve the intrinsic ion feedback suppression of single GEM foils. To optimize the operational parameters of such a structure extensive simulations have been performed. The simulations have been verified by measurements with a small test chamber as well as a large TPC. In addition initial studies on the impact of the ion feedback on the spatial resolution will be presented.

The unique advantage of He-based mixtures is that the ion mobilities in He are almost by an order of magnitude higher than that in Ar. Accordingly, using the He-based mixtures could help to solve the problem of ion accumulation in the TPC volume. On the other hand, the unique advantage of GEMs is that they can operate at high gains in pure noble gases, in particular in He and its mixtures with other non-ageing gases, such as N2, Kr, Ne, etc. In this paper, we study the performance of triple-GEM detectors in pure He and its mixtures with N2 and Kr, in the range of 1-10 atm. Ion backdrift, ion feedback and photon feedback effects are observed. Ion mobilities in He and He/N2 are estimated: namely, the drift times of ions between the GEMs are measured analysing ion backdrift- and ion feedback-induced signals.

In the past 10 years, we have been developing a mini-jet cell type cylindrical drift chamber as a central tracker for a warm cavity future linear collider. This talk will summarize our activities including developments made since the Jeju meeting.

The large size of TESLA's damping rings is dictated by the performance of the kicker, which must eject every nth bunch while leaving adjacent bunches undisturbed. The speed with which the kicker fields can stabilize, then turn off, determines the minimum space between damping ring bunches, and therefore the minimum cirumference of the damping ring.

Novel schemes which might permit a considerable reduction in damping ring circumference will be described.

I will present the results of the FONT and FEATHER experiments on hardware prototyping and beam tests of the intra-train feedback system components.

A super strong magnet, which utilizes permanent magnet material and saturated iron, is considered as a candidate for the final focus quadrupole in a linear collider beamline. This modified Halbach magnet configuration can have a higher magnetic field gradient than a normal permanent magnet quadrupole (PMQ) or electromagnet. There are some issues to be solved if a PMQ is to be used as a final focus quadrupole: the variation of its strength with temperature and the need for the field strength to be deliberately changed. One can use special temperature compensation material to improve the temperature dependence with just a small decrease in field gradient compared to a magnet without temperature compensation. The required field variability can be obtained by slicing the magnet into pieces along the beamline direction and rotating these slices. The realization of the temperature compensation technique in a prototype magnet and a design with rotating slices will be discussed.

I am working on the simulation of CCD output (signals from individual pixels), which should  be included in the full detector simulation in the JAS. This can give the ideas about limits and optimization of the CCD based vertex detector in the spatial resolution, tracks separation, readout speed and so on. It also allows better understanding of the impact of vertex detector parameters on physics reach of LC detector. Details of the model of CCD operation and it's implementation in the software will be given. I will also present examples of results obtained with this code.

At the US LC workshop held at SLAC in January 2004, it became clear that the SLC experience with beam-related pickup could have important consequences for the vertex detector at the future LC.  There are major differences for the warm and cold machine, and for different detector technologies.  We review the current thinking in the light of these discussions, and consider pointers to architectures which would be tolerant of the levels of pickup likely to be encountered.

We have studied pattern recognition in a variant of the proposed SD detector where the outer 5 layers (r=20-125 cm) have axial-only strips. The purpose of these studies is to determine if this detector, combined with a fully 3D (CCD) inner tracker, is sufficient for the reconstruction of tracks in the dense core of jets. Using standard algorithms, track finding efficiencies are presented for various track pT as a function of the distance from the jet center, and failure modes are discussed. The change in response due to detector inefficiencies and event backgrounds (pair BG, other beam BGs, and BGs from overlapping 2-photon reactions) are also investigated, as is the gain from crude tiling in the longitudinal direction.

The concept of a large volume detector with continuous 3d tracking and granular calorimeters contained in a solenoidal magnetic field offers many desirable features for the linear collider. The design optimisation aims at reviewing its detailed design, assessing its physics performances for benchmark processes and identifing detector requirements to be supported by dedicated R&D activity. The activity ongoing within the American Linear Collider Physics Group is presented with some preliminary results and study perspectives discussed in detail.

Linear collider detector designs considered in the North American study include two technologies for the central tracking system: a TPC and an all-silicon tracker. These designs must be evaluated in terms of track reconstruction efficiency and resolution. Performance in these quantities determines the ability to successfully analyze complex events. In particular, superior tracking performance is required for energy flow analyses. This study concentrates on the track reconstruction efficiency of a TPC central tracking device. Current results in reconstruction efficiency as a function of TPC pad size will be presented.

The influence of varying the vertex detector design on searches for scalar top quarks at the Linear Collider have been studied. The benchmark reaction depends on the c-quark tagging capabilities of the detector design. The influence of the material thickness of the detector layers, and the number of sensitive layers has been considered.

(following Monday's afternoon talks)