S. Kyre

First results from the LUX dark matter experiment at the Sanford Underground Research Facility

The Large Underground Xenon (LUX) experiment is a dual-phase xenon time-projection chamber operating at the Sanford Underground Research Facility (Lead, South Dakota). The LUX cryostat was filled for the first time in the underground laboratory in February 2013. We report results of the first WIMP search data set, taken during the period from April to August 2013, presenting the analysis of 85.3 live days of data with a fiducial volume of 118 kg. A profile-likelihood analysis technique shows our data to be consistent with the background-only hypothesis, allowing 90% confidence limits to be set on spin-independent WIMP-nucleon elastic scattering with a minimum upper limit on the cross section of 7.6 × 10(-46) cm(2) at a WIMP mass of 33 GeV/c(2). We find that the LUX data are in disagreement with low-mass WIMP signal interpretations of the results from several recent direct detection experiments.

The Large Underground Xenon (LUX) Experiment

The Large Underground Xenon (LUX) collaboration has designed and constructed a dual-phase xenon detector, in order to conduct a search for Weakly Interacting Massive Particles (WIMPs), a leading dark matter candidate. The goal of the LUX detector is to clearly detect (or exclude) WIMPS with a spin independent cross-section per nucleon of 2×10-46cm2, equivalent to ∼1event/100kg/month in the inner 100-kg fiducial volume (FV) of the 370-kg detector. The overall background goals are set to have <1 background events characterized as possible WIMPs in the FV in 300 days of running. This paper describes the design and construction of the LUX detector.

Performance, radiation damage, and future plans of the BABAR silicon vertex tracker

The BABAR silicon vertex tracker (SVT) has been in operation for four years at the PEP-II electron-positron storage ring. During this time the SVT modules have accumulated a radiation dose up to 2 Mrad. We study the degradation in the performance of the SVT due to this accumulated dose which is highly non uniform across the device and also within the individual silicon detectors. To extrapolate the performance of the device to the future we study separately the effect of the irradiation on silicon detectors, front end integrated circuits and on a complete detector module under controlled radiation conditions, using a /sup 60/Co source and a 0.9 GeV e/sup -/ beam. We compare the results to the data from the SVT. In particular we show the dependence of the charge collection efficiency on the radiation dose even when a small stripe of the module is irradiated up to space charge sign inversion. Since the modules that are located in the plane of the beams will suffer significant radiation damage, we will describe our plans for their replacement in 2005 and for the operation of the SVT through the lifetime of the BABAR experiment.

Status and future plans of the BABAR silicon vertex tracker

Abstract A brief summary of the design goals, description, and performance of the BABAR Silicon Vertex Tracker is given. Results from radiation hardness tests are discussed, which indicate satisfactory operation up to 5 Mrad of accumulated radiation. The local alignment procedure has made significant improvements recently, and four readout sections were recovered during the BABAR shutdown in 2002.

Studies of double-sided, double metal silicon strip detectors

Abstract We have studied double-sided, double-metal silicon microstrip detectors for the CLEO-II vertex detector. The double-layer structure permits the transverse strips to be connected via longitudinal readout traces to preamplifiers located at the end of the detectors. The detectors are manufactured by Hamamatsu Photonics. They are full size AC coupled detectors with polysilicon bias resistors on the n-side and punchthrough biasing on the p-side. We present measurements of detector static properties, including the extra capacitance due to the double layer structure, as well as measurements of signal and noise.

Lessons learned from BaBar silicon vertex tracker, limits, and future perspectives of the detector

The silicon vertex tracker (SVT) of the BaBar experiment at PEP-II is described. This is the crucial device for the measurement of the B meson decay vertices to extract charge-conjugation parity (CP) asymmetries. It consists of five layers of double-sided ac-coupled silicon strip detectors, read out by a full-custom integrated circuit, capable of simultaneous acquisition, digitization, and transmission of data. It represents the core of the BaBar tracking system, providing position measurements with a precision of 10 /spl mu/m (inner layers) and 30 /spl mu/m (outer layers). The relevant performances of the SVT are presented, and the experience acquired during the construction, installation, and the first five years of data-taking is described. Innovative solutions are highlighted, like the sophisticated alignment procedure, imposed by the design of the silicon tracker, integrated in the beamline elements and mechanically separated from the other parts of BaBar. The harshness of the background conditions in the interaction region required several studies on the radiation damage of the sensors and the front-end chips, whose results are presented. Over the next five years the luminosity is predicted to increase by a factor three, leading to radiation and occupancy levels significantly exceeding the detector design. Extrapolation of future radiation doses and occupancies is shown together with the expected detector performance and lifetime. Upgrade scenarios to deal with the increased luminosity and backgrounds are discussed.

New effects observed in the BaBar silicon vertex tracker: interpretation and estimate of their impact on the future performance of the detector

The silicon vertex tracker (SVT) of the BaBar experiment at PEP II is briefly described. It consists of five layers of double-sided AC-coupled silicon strip detectors, constituting the core of the BaBar tracking system. After six years of operation, some unexpected effects have appeared. In particular, a shift in the pedestal for the channels of the AToM readout chips that are most exposed to radiation has been observed. The behavior has been understood and reproduced in AToM chip irradiations with 1-GeV electrons at Elettra (Trieste) and the results of the studies are presented here. A second unexpected behavior has been detected, consisting of an anomalous increase in the bias leakage current for the modules in the outer layers. The effect is beam-related but not directly linked to radiation damage, as suggested by the fact that it is not present in the inner layers. The cause has been understood and the conclusions are presented here. The effect has been reproduced in a qualitative way in the laboratory. Over the next three years the luminosity is predicted to increase by a factor of three, leading to radiation and occupancy levels significantly exceeding the detector design. Estimates of future radiation doses and occupancies are shown together with the extrapolated detector performance and lifetime, in light of the new observations. Upgrade scenarios to deal with the increased luminosity and backgrounds are discussed.

Lessons learned from BaBar silicon vertex tracker, limits and future perspectives of the detector

The silicon vertex tracker (SVT) of the BaBar experiment at PEP-II is described. This is the crucial device for the measurement of the B meson decay vertices to extract CP-asymmetries. It consists of five layers of double-sided AC-coupled silicon strip detectors, read out by a full-custom integrated circuit, capable of simultaneous acquisition, digitization and transmission of data. It represents the core of the BaBar tracking system, providing position measurements with a precision of 10 /spl mu/m (inner layers) and 30/spl mu/m (outer layers). The relevant performances of the SVT are presented, and the experience acquired during the construction, installation and the first five years of data-taking is described. Innovative solutions are highlighted, like the sophisticated alignment procedure, imposed by the design of the silicon tracker, integrated in the beam-line elements and mechanically separated from the other parts of BaBar. The harshness of the background conditions in the interaction region required several studies on the radiation damage of the sensors and the front-end chips, whose results are presented. Over the next five years the luminosity is predicted to increase by a factor three, leading to radiation and occupancy levels significantly exceeding the detector design. Extrapolation of future radiation doses and occupancies is shown together with the expected detector performance and lifetime. Upgrade scenarios to deal with the increased luminosity and backgrounds are discussed.

Studies of double-sided, double-metal silicon microstrip detectors

Double-sided, double-layer silicon microstrip detectors for the CLEO-II vertex detector have been studied. The double-layer structure permits the transverse strips to be connected via longitudinal readout traces to preamplifiers located at the end of the detectors. The detectors are full-size AC coupled detectors with polysilicon bias resistors on the n-side and punch-through biasing on the p-side. The authors present measurements of detector static properties, including the extra capacitance due to the double-layer structure, as well as measurements of signal and noise.<<ETX>>