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S. Wu

Publications and source records attributed to S. Wu.

36 records · Page 2Linked to original sources
arXiv2016

Design, Construction and Commissioning of the Digital Hadron Calorimeter - DHCAL

A novel hadron calorimeter is being developed for future lepton colliding beam detectors. The calorimeter is optimized for the application of Particle Flow Algorithms (PFAs) to the measurement of hadronic jets and features a very finely segmented readout with 1 x 1 cm2 cells. The active media of the calorimeter are Resistive Plate Chambers (RPCs) with a digital, i.e. one-bit, readout. To first order the energy of incident particles in this calorimeter is reconstructed as being proportional to the number of pads with a signal over a given threshold. A large-scale prototype calorimeter with approximately 500,000 readout channels has been built and underwent extensive testing in the Fermilab and CERN test beams. This paper reports on the design, construction, and commissioning of this prototype calorimeter.

physics.ins-det↗
arXiv2015

Testing for Efficacy in Single-Subject Trials with Intervention Analysis

Single subject or n-of-1 research designs have been widely used to evaluate treatment interventions. Many statistical procedures such as split-middle trend lines, regression trend line, Shewart-chart trend line, binomial tests, randomization tests and Tryon C-statistics have been used to analyze single-subject data, but they fail to control Type I error due to serially-dependent time-series observations. The interrupted time series analysis maintains Type I error but assumes that the intervention effect to be a linear trend change from baseline. In this paper, we consider an improved intervention analysis model (Box and Tiao, 1975) for dynamic characteristics of an intervention effect in a short series of single-subject data. The maximum likelihood estimates are derived and a hypothesis testing procedure is proposed. The method is illustrated with a real clinical trial on constraint induced language therapy for aphasia patients.

stat.AP↗
arXiv2015

Status of ArDM-1t: First observations from operation with a full ton-scale liquid argon target

ArDM-1t is the first operating ton-scale liquid argon detector for direct search of Dark Matter particles. Developed at CERN as Recognized Experiment RE18, the experiment has been approved in 2010 to be installed in the Spanish underground site LSC (Laboratorio Subterraneo de Canfranc). Under the label of LSC EXP-08-2010 the ArDM detector underwent an intensive period of technical completion and safety approval until the recent filling of the target vessel with almost 2 ton of liquid argon. This report describes the experimental achievements during commissioning of ArDM and the transition into a stage of first physics data taking in single phase operational mode. We present preliminary observations from this run. A first indication for the background discrimination power of LAr detectors at the ton-scale is shown. We present an outlook for completing the detector with the electric drift field and upgrade of the scintillation light readout system with novel detector modules based on SiPMs in order to improve the light yield.

physics.ins-det↗
arXiv2014

Performance study of the effective gain of the double phase liquid Argon LEM Time Projection Chamber

The Large Electron Multipliers (LEMs) are key components of double phase liquid argon TPCs. The drifting charges after being extracted from the liquid are amplified in the LEM positioned half a centimeter above the liquid in pure argon vapor at 87 K. The LEM is characterised by the size of its dielectric rim around the holes, the thickness of the LEM insulator, the diameter of the holes as well as their geometrical layout. The impact of those design parameters on the amplification were checked by testing seven different LEMs with an active area of 10$\times$10 cm$^2$ in a double phase liquid argon TPC of 21 cm drift. We studied their response in terms of maximal reachable gain and impact on the collected charge uniformity as well as the long term stability of the gain. We show that we could reach maximal gains of around 150 which corresponds to a signal-to-noise ratio ($S/N$) of about 800 for a minimal ionising particle (MIP) signal on 3 mm readout strips. We could also conclude that the dielectric surfaces in the vicinity of the LEM holes charge up with different time constants that depend on their design parameters. Our results demonstrate that the LAr LEM TPC is a robust concept that is well-understood and well-suited for operation in ultra-pure cryogenic environments and that can match the goals of future large-scale liquid argon detectors.

physics.ins-det↗
arXiv2014

New Physics Search with Precision Experiments: Theory Input

The best way to search for new physics is by using a diverse set of probes - not just experiments at the energy and the cosmic frontiers, but also the low-energy measurements relying on high precision and high luminosity. One example of such ultra-precision experiments is the MOLLER experiment planned at JLab, which will measure the parity-violating electron-electron scattering asymmetry and allow a determination of the weak mixing angle with a factor of five improvement in precision over its predecessor, E-158. At this precision, any inconsistency with the Standard Model should signal new physics. The paper will explore how new physics particles enter at the next-to-leading order one-loop level. For MOLLER we analyze the effects of dark Z'-boson on the total calculated asymmetry, and show how this new physics interaction carriers may influence the analysis of the future experimental results.

hep-ph↗
arXiv2014

Evidence of electric breakdown induced by bubbles in liquid argon

We report on the results of a high voltage test in liquid argon in order to measure its dielectric rigidity. Under stable conditions and below the boiling point, liquid argon was found to sustain a uniform electric field of 100 kV/cm, applied in a region of 20 cm$^2$ area across 1 cm thick gap. When the liquid is boiling, breakdowns may occur at electric fields as low as 40 kV/cm. This test is one of the R&D efforts towards the Giant Liquid Argon Charge Imaging ExpeRiment (GLACIER) as proposed Liquid Argon Time Projection Chamber (LAr TPC) for the LBNO observatory for neutrino physics, astrophysics and nucleon decay searches.

physics.ins-det↗
arXiv2013

Long-term operation of a double phase LAr LEM Time Projection Chamber with a simplified anode and extraction-grid design

We report on the successful operation of a double phase Liquid Argon Large Electron Multiplier Time Projection Chamber (LAr LEM-TPC) equipped with two dimensional projective anodes with dimensions 10$\times$10 cm$^2$, and with a maximum drift length of 21 cm. The anodes were manufactured for the first time from a single multilayer printed circuit board (PCB). Various layouts of the readout views have been tested and optimised. In addition, the ionisation charge was efficiently extracted from the liquid to the gas phase with a single grid instead of two previously. We studied the response and the gain of the detector to cosmic muon tracks. To study long-term stability over several weeks, we continuously operated the chamber at fixed electric field settings. We reproducibly observe that after an initial decrease with a characteristic time of $τ\approx 1.6$ days, the observed gain is stable. In 46 days of operation, a total of 14.6 million triggers have been collected at a stable effective gain of $G_\infty\sim 15$ corresponding to a signal-to-noise ratio $(S/N)\gtrsim 60$ for minimum ionising tracks. During the full period, eight discharges across the LEM were observed. A maximum effective gain of 90 was also observed, corresponding to a signal-to-noise ratio $(S/N)\gtrsim 400$ for minimum ionising tracks, or $S/N\approx10$ for an energy deposition of 15 keV on a single readout channel.

physics.ins-det↗
arXiv2013

ArDM: first results from underground commissioning

The Argon Dark Matter experiment is a ton-scale double phase argon Time Projection Chamber designed for direct Dark Matter searches. It combines the detection of scintillation light together with the ionisation charge in order to discriminate the background (electron recoils) from the WIMP signals (nuclear recoils). After a successful operation on surface at CERN, the detector was recently installed in the underground Laboratorio Subterráneo de Canfranc, and the commissioning phase is ongoing. We describe the status of the installation and present first results from data collected underground with the detector filled with gas argon at room temperature.

physics.ins-det↗
arXiv2013

Status of the ArDM Experiment: First results from gaseous argon operation in deep underground environment

The Argon Dark Matter (ArDM-1t) experiment is a ton-scale liquid argon (LAr) double-phase time projection chamber designed for direct Dark Matter searches. Such a device allows to explore the low energy frontier in LAr. After successful operation on surface at CERN, the detector has been deployed underground and is presently commissioned at the Canfranc Underground Laboratory (LSC). In this paper, we describe the status of the installation and present first results on data collected in gas phase.

physics.ins-det↗
arXiv2010

Tunneling into d-wave superconductors: Effects of interface spin-orbit coupling

Tunneling conductance of a clean normal metal/d-wave superconductor junction is studied by using the extended Blonder-Tinkham-Klapwijk formalism. We show that the conductance is significantly affected by the interface spin-orbit coupling of the Rashba type, which is inevitably present due to the asymmetry of the junction.

cond-mat.supr-con↗
arXiv2010

Effects of interface spin-orbit coupling on tunneling between normal metal and chiral p-wave superconductor

We study the tunneling conductance of a clean normal metal/chiral p-wave superconductor junction using the extended Blonder-Tinkham-Klapwijk formalism. It is shown that the spin-orbit coupling of the Rashba type that is present near the interface causes the subgap conductance peaks associated with the Andreev surface bound states to shift to a nonzero bias. We also investigate the effect of the Fermi wavevector mismatch between the normal metal and the superconductor.

cond-mat.supr-con↗
arXiv2009

Tunneling conductance of ferromagnet/noncentrosymmetric superconductor junctions

Based on the extended Blonder-Tinkham-Klapwijk formalism, the tunneling conductance characteristics of a planar junction between a ferromagnet and a noncentrosymmetric superconductor are studied. The effects of the Rashba spin-orbit coupling (RSOC), the exchange energy, and the Fermi wave-vector mismatch (FWM) on the conductance are all taken into account. In the absence of the FWM, it is found that far away from the gap edge the conductance is suppressed by the RSOC, while around the gap edge it is almost independent of RSOC. The interplay of the RSOC and the exchange energy causes an enhancement of the subgap conductance, which is more pronounced when the RSOC is small. When the FWM is introduced, it is shown that the conductance is monotonically enhanced as the FWM parameter decreases.

cond-mat.supr-con↗
arXiv2008

Demonstration of perfect coherence preservation for matter-waves perturbed by a delta-kicked rotor

We demonstrate perfect coherence preservation in an atom interferometer perturbed by kicks from off-resonant standing wave pulses. Under most conditions, the decoherence induced by the pulses reduces the signal; however, the coherence is perfectly preserved when the kicking period is equal to the rational fraction of the inverse atomic recoil frequency, independent of the number or the randomness of the strength of the applied kicks. The width narrowing of coherence revival as a function of increasing kick number and strength provides a new accurate measurement of the recoil frequency.

physics.atom-ph↗
arXiv2008

Calibration of a digital hadron calorimeter with muons

The calibration procedure of a finely granulated digital hadron calorimeter with Resistive Plate Chambers as active elements is described. Results obtained with a stack of nine layers exposed to muons from the Fermilab test beam are presented.

physics.ins-det↗
arXiv2007

At-Speed Logic BIST for IP Cores

This paper describes a flexible logic BIST scheme that features high fault coverage achieved by fault-simulation guided test point insertion, real at-speed test capability for multi-clock designs without clock frequency manipulation, and easy physical implementation due to the use of a low-speed SE signal. Application results of this scheme to two widely used IP cores are also reported.

cs.AR↗
arXiv1996

Measurement of the Far Infrared Magneto-Conductivity Tensor of Superconducting YBa$_2$Cu$_3$O$_{7-δ}$ Thin Films

We report measurements of the far infrared transmission of superconducting YBa$_2$Cu$_3$O$_{7-δ}$ thin films from 5 cm$^{-1}$ to 200 cm$^{-1}$ in fields up to 14$T$. A Kramers-Kronig analysis of the magneto-transmission spectrum yields the magneto-conductivity tensor. The result shows that the magneto-conductivity of YBa$_2$Cu$_3$O$_{7-δ}$ is dominated by three terms: a London term, a low frequency Lorentzian ($ω_1\approx $ 3 cm$% ^{-1}$) of width $Γ_1=$ 10 cm$^{-1}$ and a finite frequency Lorentzian of width $Γ_2=$ 17 cm$^{-1}$ at $ω_2=$ 24 cm$^{-1}$ in the hole cyclotron resonance active mode of circular polarization.\\

cond-mat↗