SLAC Large Detector Research Articles

First results with prototype ISIS devices for ILC vertex detector

The vertex detectors at the International Linear Collider (ILC) (there will be two of them, one for each of two general purpose detectors) will certainly be built with silicon pixel detectors, either monolithic or perhaps vertically integrated. However, beyond this general statement, there is a wide range of options supported by active R&D programmes all over the world. Pixel-based vertex detectors build on the experience at the SLAC large detector (SLD) operating at the SLAC linear collider (SLC), where a 307 Mpixel detector permitted the highest physics performance at LEP or SLC. For ILC, machine conditions demand much faster readout than at SLC, something like 20 time slices during the 1 ms bunch train. The approach of the image sensor with in-situ storage (ISIS) is unique in offering this capability while avoiding the undesirable requirement of ‘pulsed power’. First results from a prototype device that approaches the pixel size of 20 μm square, needed for physics, are reported. The dimensional challenge is met by using a 0.18 μm imaging CMOS process, instead of a conventional CCD process.

Direct Measurements ofAbandAcUsing Vertex and Kaon Charge Tags at the SLAC Detector

Exploiting the manipulation of the SLAC Linear Collider electron-beam polarization, we present precise direct measurements of the parity-violation parameters A(c) and A(b) in the Z-boson-c-quark and Z-boson-b-quark coupling. Quark-antiquark discrimination is accomplished via a unique algorithm that takes advantage of the precise SLAC Large Detector charge coupled device vertex detector, employing the net charge of displaced vertices as well as the charge of kaons that emanate from those vertices. From the 1996-1998 sample of 400 000 Z decays, produced with an average beam polarization of 73.4%, we find A(c)=0.673+/-0.029(stat)+/-0.023(syst) and A(b)=0.919+/-0.018(stat)+/-0.017(syst).

Precise measurement of the b-quark fragmentation function in Z0 boson decays

We have developed a new technique for inclusive reconstruction of the energy of B hadrons. The excellent efficiency and resolution of this technique allow us to make the most precise determination of the b-quark fragmentation function, using e(+)e(-)-->Z0 decays recorded in the SLAC Large Detector experiment. We compared our measurement with the predictions of a number of fragmentation models. We excluded several of these models and measured the average scaled energy of weakly decaying B hadrons to be <x(B)> = 0.714+/-0. 005(stat)+/-0.007(syst)+/-0.002 (model dependence).

Measurement of the left-right forward-backward asymmetry for charm quarks with D*+ and D+ mesons.

We present a direct measurement of {ital A}{sub {ital c}}=2{ital v}{sub {ital c}}{ital a}{sub {ital c}}/({ital v}{sup 2}{sub {ital c}}+{ital a}{sup 2}{sub {ital c}}) from the left-right forward-backward asymmetry of {ital D}{sup *}+ and {ital D}{sup +} mesons in {ital Z}{sup 0} events produced with the longitudinally polarized SLAC Linear Collider beam. These {ital Z}{sup 0}{r_arrow}{ital c} over bar events are tagged on the basis of event kinematics and decay topology from a sample of hadronic {ital Z}{sup 0} decays recorded by the SLAC Large Detector. We measure {ital A}{sup 0}{sub {ital c}} = 0.73 {plus_minus} 0.22(stat) {plus_minus} 0.10(syst). {copyright} {ital 1995} {ital The} {ital American} {ital Physical} {ital Society}.

First results from the SLD silicon calorimeters

The small-angle calorimeters of the SLAC Large Detector (SLD) were successfully operated during the recent SLAC Linear Collider (SLC) engineering run. The Luminosity Monitor and Small-Angle Tagger (LMSAT) covers the angular region region between 28 and 68 mrad from the beam axis, while the Medium-Angle Silicon Calorimeter (MASC) covers the 68-190-mrad region. Both are silicon-tungsten sampling calorimeters; the LMSAT employs 23 layers of 0.86 X/sub 0/ sampling, while the MASC has 10 layers of 1.74 X/sub 0/ sampling. The authors present results from the first run of the SLC with the SLD on beamline. The calorimeters and electronics performed reliably with no major problems during a 15-week period with no access. Bhabha events were easily identified, and the 36-68-mrad region of the LMSAT was found to be approximately=100% efficient and background-free, which made it possible to measure L to be 14.4+or-0.5 nb/sup -1/ for this run. >

Initial performance of the SLD Cherenkov ring imaging detector system

All of the major subsystems for the barrel Cerenkov Ring Imaging Detector (CRID) in the SLAC Large Detector (SLD) at Stanford Linear Accelerator Center (SLAC) have now been commissioned. The CRID participated in the SLD engineering run of June-August 1991. In a cosmic ray test at the end of the run, Cerenkov rings were observed for the first time. Initial data for the CRID, including Cerenkov rings, studies of minimum ionizing particles, and data from the fiber optics calibration system are presented. The SLD engineering run and the ensuing dedicated CRID test runs have demonstrated that the system behaves as expected. It has been possible to track particles using ionization in the drift boxes and to reconstruct single electron coordinates very well. The runs have also enabled debugging of this complex system. >