154 research outputs found
Prospects for Probing Triple Gauge-boson Couplings at the LHC
In these proceedings I explore one aspect of gauge-boson physics at the LHC -
Triple Gauge-boson Couplings (TGCs) in and Wgamma production. Methods for
extracting confidence limits on anomalous TGCs are assessed, while accounting
for the effects of higher order QCD corrections and contributions from other
theoretical and detector related systematics. Detector response has been
parametrised according to the ATLAS detector's specifications. A strategy for
reporting the anomalous coupling limits is introduced which removes the
ambiguities of form factors by reporting the limits as a function of a cutoff
operating on the diboson system invariant mass. Techniques for measuring the
energy dependence of anomalous couplings are demonstrated.Comment: 12 pages, invited talk at Hadron Collider Physics 2004, East Lansing,
Michiga
Digital Frequency Domain Multiplexer for mm-Wavelength Telescopes
An FPGA based digital signal processing (DSP) system for biasing and reading
out multiplexed bolometric detectors for mm-wavelength telescopes is presented.
This readout system is being deployed for balloon-borne and ground based
cosmology experiments with the primary goal of measuring the signature of
inflation with the Cosmic Microwave Background Radiation. The system consists
of analog superconducting electronics running at 250mK and 4K, coupled to
digital room temperature backend electronics described here. The digital
electronics perform the real time functionality with DSP algorithms implemented
in firmware. A soft embedded processor provides all of the slow housekeeping
control and communications. Each board in the system synthesizes
multi-frequency combs of 8 to 32 carriers in the MHz band to bias the
detectors. After the carriers have been modulated with the sky-signal by the
detectors, the same boards digitize the comb directly. The carriers are mixed
down to base-band and low pass filtered. The signal bandwidth of 0.050 Hz - 100
Hz places extreme requirements on stability and requires powerful filtering
techniques to recover the sky-signal from the MHz carriers.Comment: 6 pages, 6 figures, Submitted May 2007 to IEEE Transactions on
Nuclear Science (TNS
Tuning of Kilopixel Transition Edge Sensor Bolometer Arrays with a Digital Frequency Multiplexed Readout System
A digital frequency multiplexing (DfMUX) system has been developed and used
to tune large arrays of transition edge sensor (TES) bolometers read out with
SQUID arrays for mm-wavelength cosmology telescopes. The DfMUX system
multiplexes the input bias voltages and output currents for several bolometers
on a single set of cryogenic wires. Multiplexing reduces the heat load on the
camera's sub-Kelvin cryogenic detector stage. In this paper we describe the
algorithms and software used to set up and optimize the operation of the
bolometric camera. The algorithms are implemented on soft processors embedded
within FPGA devices operating on each backend readout board. The result is a
fully parallelized implementation for which the setup time is independent of
the array size.Comment: 5 pages, 4 figure
Effect of the stellar spin history on the tidal evolution of close-in planets
We investigate how the evolution of the stellar spin rate affects, and is
affected by, planets in close orbits, via star-planet tidal interactions. To do
this, we used a standard equilibrium tidal model to compute the orbital
evolution of single planets orbiting both Sun-like stars and 0.1 M\odot
M-dwarfs. We tested two stellar spin evolution profiles, one with fast initial
rotation (P=1.2 day) and one with slow initial rotation (P=8 day). We tested
the effect of varying the stellar and planetary dissipation and the planet's
mass and initial orbital radius. Conclusions: Tidal evolution allows to
differentiate the early behaviors of extremely close-in planets orbiting either
a rapidly rotating star or a slowly rotating star. The early spin-up of the
star allows the close-in planets around fast rotators to survive the early
evolution. For planets around M-dwarfs, surviving the early evolution means
surviving on Gyr timescales whereas for Sun-like stars the spin-down brings
about late mergers of Jupiter planets. In light of this study, we can say that
differentiating between one spin evolution from another given the present
position of planets can be very tricky. Unless we can observe some markers of
former evolution it is nearly impossible to distinguish the two very different
spin profiles, let alone intermediate spin profiles. Though some conclusions
can still be drawn from statistical distributions of planets around fully
convective M-dwarfs. However, if the tidal evolution brings about a merger late
in its history it can also entail a noticeable acceleration of the star in late
ages, so that it is possible to have old stars that spin rapidly. This raises
the question of better constraining the age of stars
The psychosocial impact of microtia and ear reconstruction: A national data-linkage study
Introduction: Children with visible facial differences are believed to be at increased risk of negative psychosocial behaviours which may manifest as affective disorders. The aim of this study was to determine whether a diagnosis of microtia, and the associated surgical intervention, is associated with psychosocial implications including impaired educational attainment and a diagnosis of an affective disorder.Methods: A retrospective case-control study was conducted using data linkage to identify patients in Wales with a diagnosis of microtia. Matched controls were sought on the basis of age, gender and socioeconomic deprivation status to yield a total sample size of 709. incidence was calculated using annual and geographic birth rates. Surgical operation codes were used to classify patients into those that had no surgery, autologous reconstruction or prosthetic reconstruction. Educational attainment at 11 years of age, plus a diagnosis of depression or anxiety were used as markers of adverse psychosocial outcomes and the relative risk was attained using logistic regression analyses.Results: There were no significant associations between a diagnosis of microtia and an increased risk of adverse educational attainment or a risk of an affective disorder diagnosis. Male gender and higher deprivation scores were significantly associated with poorer educational attainment, irrespective of a diagnosis of microtia. Surgical intervention of any nature was also not associated with any increased risk of adverse educational or psychosocial outcomes in microtia patients.Discussion: Microtia patients in Wales do not appear to be at greater risk of developing affective disorders or impaired academic performance as a result of their diagnosis or associated surgical intervention. Whilst reassuring, the need for appropriate support mechanisms to maintain positive psychosocial wellbeing and academic achievement in this patient cohort is reinforced
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