Stanford Linear Collider Research Articles

The Liquid Argon Calorimeter system for the SLC Large Detector

The physical packaging and the logical organization of the liquid argon calorimeter (LAC) electronics system for the Stanford Linear Collider Large Detector (SLD) at SLAC are described. This system processes signals from approximately 44000 calorimeter towers and is unusual in that most electronic functions are packed within the detector itself as opposed to an external electronics support rack. The signal path from the towers in the liquid argon through the vacuum to the outside of the detector is explained. The organization of the control logic, analog electronics, power regulation, analog-to-digital conversion circuits, and fiber-optic drivers mounted directly on the detector is described. Redundancy considerations for the electronics and cooling issues are discussed. >

A cryogenic monitor system for the liquid argon calorimeter in the SLD detector

The authors describe the monitoring electronics system design for the liquid argon calorimeter (LAC) portion of the SLD (Stanford Linear Collider Large Detector). This system measures temperatures and liquid levels inside the LAC cryostat and transfers the results over a fiber-optic serial link to an external monitoring computer. System requirements, unique design constraints, and detailed analog, digital, and software designs are presented. Fault tolerance and the requirement for a single design to work in several different operating environments are discussed. >

A status report on the SLD data acquisition system

The basic design of the SLD (Stanford Linear Collider Large Detector) data acquisition system and its present status are reviewed. Aspects of the design that take particular advantage of the relatively low e/sup +/e/sup -/ cross section and the low beam crossing rate of a linear collider are explained. The design of the SLD electronics has taken significant advantage of the unique rate characteristic of an e/sup +/e/sup -/ linear collider. This has involved a significant increase in the amount of electronics built into and onto the detector, which has involved the development of custom VLSI (very large scale integration) and many hybrid packages. Most of the data from the detector electronics are heavily time-multiplexed and carried on optical fibers leading to a minimal cable plant. Particular attention is given to the subsystem designs, including the vertex detector, the tracking system, the Cerenkov ring imaging detector, and the liquid-argon and warm-ion calorimeters.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Performance of the electronics for the liquid argon calorimeter system of the SLC large detector

Results of performance tests on electronics for the liquid argon calorimeter (LAC) for the SLD (Stanford Linear Collider Large Detector) experiment are presented. The behavior of a subunit called a tophat, which processes 720 detector signals is described. The electronics consists of charge-sensitive preamplifiers, analog memories, A/D (analog/digital) converters, and associated control and readout circuitry. An internal charge-injection system is used to calibrate the overall response of the devices. Linearity is better than 1% for 0-28-pC charge at the input of the amplifiers. Noise (expressed as equivalent input charge) is less than 3000 electrons at a shaping time of 4 mu s, with a slope of 2600 e/sup -//nF. Crosstalk to adjacent channels is less than 0.5%. The power consumption at a duty cycle of 13% is 61 W.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A high resolution wire scanner for micron-size profile measurements at the SLC

Fine conductive fibers have been used to measure transverse beam dimensions of a few microns at the Stanford Linear Collider (SLC). The beam profile is obtained by scanning a fiber across the beam in steps as small as 1 μm, and recording the secondary emission signal at each step, using a charge sensitive amplifier. We first outline the mechanical construction and the analogue electronics of the wire scanner. We then describe its performance in test beams and in actual operation. The article closes with a brief discussion of performance limitations of such a beam profile monitor.

Measurement of electron beam polarization at the SLC

The polarimeters needed to monitor and measure electron beam polarization at the Stanford Linear Collider are discussed. Two types of polarimeters, are to be used. The first is based on the spin dependent elastic scattering of photons from high energy electrons. The second utilizes the spin dependence of elastic electron-electron scattering. The plans of the SLC polarization group to measure and monitor electron beam polarization are discussed. A brief discussion of the physics and the demands it imposes on beam polarization measurements is presented. The Compton polarimeter and the essential characteristics of two Moeller polarimeters are presented. (LEW)

The slac linear collider - a status report

This report presents progress made at the Stanford Linear Collider (SLC). Design goals of the various components are compared to measurements made on the equipment. 8 figs., 2 tabs. (JDH)

Invisible decays of Higgs bosons in supersymmetric models.

We point out that the dominant decay of the light scalar Higgs boson in a supersymmetric model may be into a pair of the lightest neutralinos (assumed to be the lightest supersymmetric particles), which would result in an invisible final state. Thus, in the search at the Stanford Linear Collider and the CERN collider LEP for a Higgs scalar produced in association with a real or virtual Z boson, it is important not to cut out events with significant missing energy recoiling against the Z.

High energy electron accelerator based synchrotron radiation sources

This paper discusses the possibility of using electron linear accelerators as picosecond synchrotron radiation sources. Calculations presented show that the Stanford Linear Collider could exceed the spectral brilliance of existing storage rings (although at a much lower total flux) while producing 3 ps long pulses at a repitition rate of 180 pulses per second. Higher performance sources might be feasible but would require major modifications of existing linear accelerators or the development of new facilities.

Construction and initial operation of a proportional wire detector for use in a Cerenkov ring imaging system

The final version of the multiwire single-electron detector for the Cerenkov ring imaging device of the Stanford Linear Collider Detector is described. Recent research-and-development efforts to define the design parameters are reported. These were concerned with computer simulations necessary for the detector design; wire aging and its solution; surface resistivity and voltage breakdown of G-10 in a TMAE environment; corona studies for various gases; wire breaking in the spark; measured mechanical characteristics of 7- mu m carbon wires; wire-stretching technique for 7- mu m carbon wires; and wire tension measuring for th final detector. The details of the geometry of the detector and experimental tests with the detector itself are discussed. >

Test stands for the central drift chamber front end hybrid in the Stanford Linear Collider Detector

The central drift chamber (CDC) of the SLAC Linear Collider Detector (SLD) uses 1280 front-end electronic hybrid modules. Each of these modules contains over 450 components and performs numerous functions. The four test stands for production and detailed circuit characterizations of these hybrids are described, as well as the performance of some of the important functions of the test systems. >

Radiative corrections to the Z0 resonance.

We review calculations of the radiative corrections to the ${Z}^{0}$ resonance, and we show that while the radiative corrections are quite large, they can be calculated and incorporated into the comparison with experiment so that there will be no significant theoretical uncertainties on the measurements of the ${Z}^{0}$ mass and width at the Stanford Linear Collider and the CERN collider LEP. We compare calculations based on matrix elements and structure-function methods, and discuss two Monte Carlo programs based on these calculations. We use the new calculations to refit the J/\ensuremath{\psi} resonance.

Design and fabrication of advanced hybrid circuits for high energy physics

Current design and fabrication techniques of hybrid devices as applied to the Stanford Linear Collider Large Detector (SLD) are discussed. Methods of developing layouts ranging from hand-cut templates to advanced designs utilizing CAD tools with special hybrid design software were applied. Physical and electrical design rules for good yield and performance are discussed. Fabrication and assembly of of a variety of SLD hybrids using different construction methods are described.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The hybridized front end electronics of the central drift chamber in the Stanford Linear Collider Detector

A description is given of the front-end electronics, which has been hybridized in order to accommodate high-packaging-density requirements. The hybrid package contains eight channels of amplifiers together with all the associated circuits for calibration, event recognition, and power-economy switching functions. A total of 1280 such hybrids are used. The amplifiers and associated circuits are described, and their performance is discussed. >

Leptoquark-boson signals at e+e- colliders.

We examine the production of scalar-leptoquark-boson (S) pairs in ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ annihilation along with indirect limits of leptoquark-boson properties from existing ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ data and that which can be obtained in the near future from the Stanford Linear Collider and the CERN collider LEP.

The performance of “Virtual Phase” CCDs as detectors of minimum-ionizing particles

The Texas Instruments “Virtual Phase” CCD has been the basis of an ambitious design for a precision vertex detector to be used at the Stanford Linear Collider. The performance of this chip shows promise for future use in electron linear colliders. Experimental results are reported in addition to description of the electronic readout and preliminary mechanical design.

Signatures of vector-boson compositeness in e+e---> micro+ micro- for the strongly coupled standard model.

We study the cross section and the forward-backward asymmetry of e/sup +/e/sup -/..--> mu../sup +/..mu../sup -/ in the strongly coupled standard model, at energies appropriate for the colliders TRISTAN at KEK, the Stanford Linear Collider, and LEP at CERN (60--180 GeV). Constraints from low-energy measurements are used to calculate the expected deviations from the standard-model results, arising as contributions of excited W and isoscalar vector bosons. The experimental observability, especially at the Z pole, of these deviations is discussed.

Renormalization-group-improved Yennie-Frautschi-Suura theory.

We use the renormalization group to improve the ultraviolet aspect of the program of Yennie, Frautschi, and Suura for the cancellation and exponentiation of infrared divergences in Abelian gauge theories. Possible applications to high-precision ${Z}_{0}$ physics at the Stanford Linear Collider and CERN LEP are considered.

Light scalar top quark at e+e- colliders.

We examine the production and decay of a supersymmetric scalar top t${\ifmmode \tilde{}\else \~{}\fi{}}_{1}$ at ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ colliders such as TRISTAN at KEK, the Stanford Linear Collider, and LEP at CERN, based on supersymmetric models with soft breaking. Existing bounds for supersymmetric particles imply that t${\ifmmode \tilde{}\else \~{}\fi{}}_{1}$ in the energy range of these colliders would be lighter than other scalar quarks and than the top quark. We make a careful study of available t${\ifmmode \tilde{}\else \~{}\fi{}}_{1}$ decay modes in this scenario. The flavor-changing decay t${\ifmmode \tilde{}\else \~{}\fi{}}_{1}$\ensuremath{\rightarrow}c\ensuremath{\gamma}\ifmmode \tilde{}\else \~{}\fi{} is found to proceed through the misalignment of the scalar-quark and quark mixing matrices. If the three-body decay t${\ifmmode \tilde{}\else \~{}\fi{}}_{1}$\ensuremath{\rightarrow}${\mathrm{bl}}^{+}$\ensuremath{\nu}\ifmmode \tilde{}\else \~{}\fi{} is kinematically accessible it dominates the two-body decay. The decay t${\ifmmode \tilde{}\else \~{}\fi{}}_{1}$\ensuremath{\rightarrow}b\ensuremath{\nu}l${\ifmmode \tilde{}\else \~{}\fi{}}^{+}$ is even larger due to different chirality structure, but is likely to suffer from a large phase-space suppression. Four-body decays are negligible. The t${\ifmmode \tilde{}\else \~{}\fi{}}_{1}$ pair production cross section including the \ensuremath{\gamma} and Z contribution and the left-right mixing is presented.

Longitudinal-e--beam-polarization asymmetry in e+e--->hadrons.

We introduce and analyze the longitudinal-polarization asymmetry of the process ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$\ensuremath{\rightarrow}hadrons with longitudinally polarized electron beams on and near the ${Z}^{0}$ resonance. We show that, in spite of the intrinsic strong-interaction presence in the final state, the vast majority of the diagrams which contribute to one electroweak loop are free of strong-interaction effects. Further, on ${Z}^{0}$ resonance the asymmetry is independent of the final states, giving a commensurate increase in statistics. We show that for these reasons the total theoretical strong-interaction uncertainty on ${Z}^{0}$ resonance is \ensuremath{\Delta}${A}_{\mathrm{LR}}^{{e}^{+}{e}^{\mathrm{\ensuremath{-}}}\ensuremath{\rightarrow}\mathrm{hadrons}\ensuremath{\lesssim}0.004}$, allowing a measurement of ${A}_{\mathrm{LR}}$ to \ifmmode\pm\else\textpm\fi{}0.015 (which can be interpreted as a measurement of ${\mathrm{sin}}^{2}$${\mathrm{\ensuremath{\theta}}}_{\mathrm{W}}$ to \ifmmode\pm\else\textpm\fi{}0.002) with only \ensuremath{\sim}5\ifmmode\times\else\texttimes\fi{}${10}^{4}$ ${Z}^{0}$'s. Further, a measurement of ${A}_{\mathrm{LR}}$ to \ifmmode\pm\else\textpm\fi{}0.008, or ${\mathrm{sin}}^{2}$${\mathrm{\ensuremath{\theta}}}_{\mathrm{W}}$ to \ifmmode\pm\else\textpm\fi{}0.001, can be done with \ensuremath{\sim}${10}^{6}$ ${Z}^{0}$'s. This rather peculiar property of the asymmetry could allow Stanford Linear Collider and CERN LEP experiments to test the standard Glashow-Salam-Weinberg (GSW) theory and possible new physics beyond GSW early in the lifetime of these accelerators.