A set of 35 photomultiplier tubes (ETL D730/9829Q), intended for use in the ZEPLIN III Dark Matter detector, was tested from room temperature down to −100°C, with the aim of confirming their ...suitability for detecting xenon scintillation light at
175
nm
while immersed in the cryogenic liquid. A general improvement of both gain and quantum efficiency at the xenon scintillation wavelength was observed with cooling, the best combined effect being 40%, while little change was noted in the timing properties and dark current. Saturation of response due to accumulation of charge in the resistive bialkali photocathodes was seen at an average photocurrent of
10
8
photoelectrons/s
for the device with best quantum efficiency, whereas an order of magnitude higher current was required to saturate the least sensitive one. Variations in photocathode thickness from tube to tube could account for this behaviour, as well as the fact that the quantum efficiency improves the most for devices with poorest efficiency at room temperature.
We present a possible design of future large-scale dark matter detector using liquid xenon. A low energy threshold is achieved by using a large CsI-coated internal photocathode for primary light ...collection. A focusing field, in the active volume and an electron focusing structure at the liquid surface, are used to transport free-electrons to the luminescence field. A 3D reconstruction of the events can be achieved by timing and location of the luminescent signal. A liquid xenon Compton veto and self-shield are integrated in the compact design. This detector could be used to probe most of the SUSY predicted dark matter. ZEPLIN IV can be initially tested at Boulby and then be moved to the USA to operate at a US deep underground science and engineering laboratory.
We study WW and WZ production with lvqq (l = e, mu) final states using data collected by the D0 detector at the Fermilab Tevatron Collider corresponding to 4.3 fb(-1) of integrated luminosity from p ...(p) over bar collisions at root s = 1.96 TeV. Assuming the ratio between the production cross sections sigma(WW) and sigma(WZ) as predicted by the standard model, we measure the total WV (V = W, Z) cross section to be sigma(WV) = 19.6(-3.0)(+3.2) pb and reject the background-only hypothesis at a level of 7.9 standard deviations. We also use b-jet discrimination to separate the WZ component from the dominant WW component. Simultaneously fitting WW and WZ contributions, we measure sigma(WW) = 15.9(-3.2)(+3.7) pb and sigma(WZ) = 3.3(-3.3)(+4.1) pb, which is consistent with the standard model predictions.
The design and performance of the Fermilab E781 (SELEX) Hardware Scattering Trigger (HST) are described. This trigger functioned by distinguishing beam scattering at small angles (
>150
μ
rad) from ...non-interacting beam. Six
50
μ
m pitch silicon planes grouped in three (
x,
y) stations, two before and one after the target, were used as the particle detectors. The triggering system involved 1920 channels of readout providing data to the Fast Encoding and Readout System (FERS) with programmable trigger logic processor. The overall system was tested successfully at Fermilab during the 1996-1997 fixed target run. The encoding time of the readout part of the FERS device was 30
ns and the processor decision time was 55
ns. The HST provided an output signal 250
ns after beam traversal of the target.
We report on the calibration and performance of a large lead liquid-argon electromagnetic calorimeter used by experiment E706 at Fermilab. The reconstructed π
0 mass was used to calibrate the energy ...response of the calorimeter. The systematic uncertainty in the linearity and uniformity of the mean-energy response of the calorimeter after calibration was found to be less than ±0.5% for the sample of data analyzed. Detector characteristics, including sampling fluctuations and position resolution, are discussed.
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