H.W. Kendall

Measurement of the ratio of the proton form factors, GE/GM, at high momentum transfers and the question of scaling☆

Abstract Electron-proton elastic scattering cross sections have been measured at the Stanford Linear Accelerator Center at four-momentum transfers squared (q2) of 1.0, 1.5, 2.0, 2.5and 3.75 (GeV/c)2. The angular distributions at q2 = 2.5 and 3.75 (GeV/c)2are sufficient to provide values of the ratio GE/GMindependent of the results from other laboratories. Our results are compatible with scaling, GE(q2) = GM(q2)/μ, within the experimental errors.

The iron calorimeter and muon identifier for SLD

Abstract The iron flux-return structure for the SLC Large Detector (SLD) has been instrumented with plastic streamer tubes covering an area of about 4500 m 2 , 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.

The limited streamer tubes of the SLD

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.

The ratio of deep-inelastic e-n to e-p cross sections in the threshold region☆

We report measurements of the ratio of the deep-inelastic electron-neutron to electron-proton differential cross sections in the threshold (ω<3) region. The ratio was found to scale and to decrease monotically with decreasing ω. No violation of the quark model lower bound of 0.25 was observed in the ratio.

The SLD VXD3 detector and its initial performance

The SLD collaboration completed construction of a new CCD vertex detector (VXD3) in January 1996 and started data taking in April 1996 with the new system. VXD3 is an upgrade of the original CCD vertex detector, VXD2, which had successfully operated in SLD for three years. VXD3 consists of 96 large area CCDs, each having 3.2 million 20 microns x20 microns pixels. By reducing the detector material and lengthening the lever arm, VXD3 is expected to improve secondary vertex resolution by about a factor of two compared with VXD2. The new three layered structure enables stand alone tracking without any ambiguity and its extended size along the beam direction improves the polar angle coverage to COS THETA {lt}0.85. An overview of this detector system and its initial performance are described.

A nonflammable gas mixture for plastic limited streamer tubes

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.

Hadron showers in a low-density fine-grained flash chamber calorimeter

Abstract Hadronic showers at six incident particle energies from 33.8 to 415.4 GeV have been studied using the low-density fine-grained flash chamber calorimeter of the Lab C neutrino detector at Fermilab. Transverse distributions of unprecedented fine granularity have been obtained for a range of depths in the shower. Longitudinal energy distributions have been compared with those from iron-scintillator detectors. Some differences are observed which may be attributable to the different relative sensitivity of the two detector types to electromagnetic and hadronic shower components. Both longitudinal and transverse distributions have been parametrized. Fluctuations in energy deposition have been studied. The relative size of the fluctuations is largest near the starting vertex and in the tail of the shower, and falls slowly with increasing beam energy. Correlations between energy deposition in neighboring parts of the shower are observed, and anticorrelation is seen between energy deposition in the peak and in the tail of the shower. Containment lengths and widths have also been measured and parametrized.

Tests of a muon chamber prototype based on limited streamer drift tubes

Abstract The design and performance of a large scale (1 × 4 m 2 ) muon drift chamber prototype for the GEM Detector are presented. The cosmic ray tests showed a spatial resolution of 80 μm by drift time measurements and resolution of 10 cm along the wires by time difference technique. The possibility of an accurate timing trigger from the chamber was tested on experimental data.

Performance of the new vertex detector at SLD

During the past year, the SLD collaboration completed the construction and began the operation of a new vertex detector (VXD3) employing 307 million pixels. This detector, based on 96 CCDs of 13 cm/sup 2/ area each, is an upgrade of the original vertex detector of SLD (VXD2), made possible by advances in the technology of CCD detectors. Its improved impact parameter resolution, larger solid angle coverage and virtually error-free track linking will enhance the SLD measurement of the polarization-enhanced forward-backward asymmetry for b and c-quarks, increase the precision of the measurement of the b-fraction in hadronic Z decays, and open the possibility to observe B/sub s//sup 0/-mixing. Full separation of primary, secondary and tertiary vertices is accessible. A description of the mechanics and electronics of VXD3 are presented along with results from the first data.

The SLD calorimeter system

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.