126266001
Measurement of the isolated direct photon cross section with conversions in $p \bar{p}$ collisions at $\sqrt{s}$ = 1.8-TeV
123009611
A search for weakly interacting dark matter with the LUX experiment
Cosmological and astrophysical measurements indicate that our galaxy is filled with a new type of matter previously unknown to physics. This "dark matter" apparently has no electromagnetic or strong interactions, but an interaction of the strength of the weak nuclear force is strongly suggested by the data. The LUX collaboration is attempting to detect the faint signature of weakly interacting dark matter as it passes through the earth. The experiment searches for recoiling atomic nuclei in a target consisting of 350 kg of liquefied xenon. LUX is the largest experiment of its type ever attempted, and it is expected to improve upon current experimental sensitivities by two orders of magnitude. The experiment is being assembled at the Sanford Underground Science and Engineering Laboratory (SUSEL) in Lead, South Dakota, USA, and first data is expected in 2011. We report on the status of LUX and the prospects for future large-scale dark matter searches with liquid xenon.
10985334
Searching for Double Beta Decay with the Enriched Xenon Observatory
The Enriched Xenon Observatory (EXO) Collaboration is building a series of experiments to search for the neutrinoless double beta decay of 136Xe. The first experiment, known as EXO‐200, will utilize 200 kg of xenon enriched to 80% in the isotope of interest, making it the largest double beta decay experiment to date by one order of magnitude. This experiment is rapidly being constructed, and will begin data taking in 2007. The EXO collaboration is also developing a technique to identify on an event‐by‐event basis the daughter barium ion of the double beta decay. If successful, this method would eliminate all conventional radioactive backgrounds to the decay, resulting in an ideal experiment. We summarize here the current status of EXO‐200 construction and the barium tag R&D program.
111274459
Microgap multiwire chambers
The multiwire proportional counter (MWPC) is well established device for capturing x-ray images at synchrotron sources such as at the synchrotron radiation source (SRS) at Daresbury. The latest generation of synchrotrons can deliver much more intense x-ray fluxes than the SRS which itself produces xray fluxes well beyond the capabilities of current photon counting detectors. There is an imminent demand for 2-D photon counting detectors which can cope with rates >10 5 photons/mm 2 /sec locally and readout systems with an unbuffered throughput of >10 7 events per second. This must be achieved with a high dynamic range and a good efficiency. The detector development group at the SRS have developed the wire microgap detector to address these problems. A new readout system has been designed using a highly parallel approach. Each detector channel in the detector is separately instrumented, and the data is accumulated using fast, state-of-the-art electronics systems. A prototype of the system has been constructed and tested with the 2 dimensional wire microgap detector. We report the results of the use of a wire microgap linear detector on the SRS and the first results from the 2D wire microgap detector system.
119247141
Are falling planets spinning up their host stars
We investigate the effects of tidal interactions on the planetary orbits and stellar spin rates of the WASP-18 and WASP-19 planetary systems using a forward integration scheme. By fitting the resulting evolutionary tracks to the observed eccentricity, semimajor axis and stellar rotation rate, and to the stellar age derived from isochronal fitting, we are able to place constraints on the stellar and planetary reduced tidal quality factors, Q ' s and Q ' p . We find that for WASP-18, log(Q ' s ) = 8.21 +0.90 ―0.52 and log(Q ' p ) = 7.77 +1.54 ―1.25 , implying a system age of 0.579 +0.305 ―0.250 Gyr. For WASP-19 we obtain values of log(Q ' s ) = 6.47 +2.19 ―0.95 and log(Q ' p ) = 6.75 +1.86 ―1.77 , suggesting a system age of 1.60 +2.84 ―0.79 Gyr and a remaining lifetime of 0.0067 +1.1073 ―0.0061 Gyr. We investigate a range of evolutionary histories consistent with these results and the observed parameters for both systems, and find that the majority imply that the stars have been spun up through tidal interactions as the planets spiral towards their Roche limits. We examine a variety of evidence for WASP-19 A's age, both for the value above and for a younger age consistent with gyrochronology, and conclude that the older estimate is more likely to be correct. This suggests that WASP-19 b might be in the final stages of the spiral-in process, although we are unable to rule out the possibility that it has a substantial remaining lifetime.
8809403
Use of a wave reverberation technique to infer the density compression of shocked liquid deuterium to 75 GPa.
A novel approach was developed to probe density compression of liquid deuterium (L-D2) along the principal Hugoniot. Relative transit times of shock waves reverberating within the sample are shown to be sensitive to the compression due to the first shock. This technique has proven to be more sensitive than the conventional method of inferring density from the shock and mass velocity, at least in this high-pressure regime. Results in the range of 22-75 GPa indicate an approximately fourfold density compression, and provide data to differentiate between proposed theories for hydrogen and its isotopes.
119843682
The selection and performance of diamond radiators used in coherent bremsstrahlung experiments
The bremsstrahlung emitted as a result of scattering electrons in thin diamond crystals provides a useful source of high energy photons for use in photonuclear experiments, since the coherent bremsstrahlung produced is linearly polarized. Techniques for selecting the most favorable diamonds have been investigated. These are optical polaroid analysis, X-ray topography and rocking curve measurements. The diamonds are characterized with a view to determining their performance as radiators, and bremsstrahlung spectra from a diamond radiator used at the Mainz MAMI-B facility are presented. The changes caused by high energy electrons to the crystal properties of the diamond and to the resulting coherent bremsstrahlung spectra are discussed.
117134508
Experimental Study of Background Induced in High Energy Gamma Ray Telescopes that use a Coded Aperture Mask