The status of GEO 600

The GEO 600 laser interferometer with 600m armlength is part of a worldwide network of gravitational wave detectors. GEO 600 is unique in having advanced multiple pendulum suspensions with a monolithic last stage and in employing a signal recycled optical design. This paper describes the recent commissioning of the interferometer and its operation in signal recycled mode

First measurement of direct f0(980)f_0(980) photoproduction on the proton

We report on the results of the first measurement of exclusive $f_0(980)$ meson photoproduction on protons for $E_\gamma=3.0 - 3.8$ GeV and $-t = 0.4-1.0$ GeV$^2$. Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. The resonance was detected via its decay in the $\pi^+ \pi^-$ channel by performing a partial wave analysis of the reaction $\gamma p \to p \pi^+ \pi^-$. Clear evidence of the $f_0(980)$ meson was found in the interference between $P$ and $S$ waves at $M_{\pi^+ \pi^-}\sim 1$ GeV. The $S$-wave differential cross section integrated in the mass range of the $f_0(980)$ was found to be a factor of 50 smaller than the cross section for the $\rho$ meson. This is the first time the $f_0(980)$ meson has been measured in a photoproduction experiment

A measurement of the tau mass and the first CPT test with tau leptons

We measure the mass of the tau lepton to be 1775.1+-1.6(stat)+-1.0(syst.) MeV using tau pairs from Z0 decays. To test CPT invariance we compare the masses of the positively and negatively charged tau leptons. The relative mass difference is found to be smaller than 3.0 10^-3 at the 90% confidence level.Comment: 10 pages, 4 figures, Submitted to Phys. Letts.

Molecular velocity auto-correlation of simple liquids observed by NMR MGSE method

The velocity auto-correlation spectra of simple liquids obtained by the NMR method of modulated gradient spin echo show features in the low frequency range up to a few kHz, which can be explained reasonably well by a $t^{-3/2}$ long time tail decay only for non-polar liquid toluene, while the spectra of polar liquids, such as ethanol, water and glycerol, are more congruent with the model of diffusion of particles temporarily trapped in potential wells created by their neighbors. As the method provides the spectrum averaged over ensemble of particle trajectories, the initial non-exponential decay of spin echoes is attributed to a spatial heterogeneity of molecular motion in a bulk of liquid, reflected in distribution of the echo decays for short trajectories. While at longer time intervals, and thus with longer trajectories, heterogeneity is averaged out, giving rise to a spectrum which is explained as a combination of molecular self-diffusion and eddy diffusion within the vortexes of hydrodynamic fluctuations.Comment: 8 pages, 6 figur

A Measurement of the Product Branching Ratio f(b->Lambda_b).BR(Lambda_b->Lambda X) in Z0 Decays

The product branching ratio, f(b->Lambda_b).BR(Lambda_b->Lambda X), where Lambda_b denotes any weakly-decaying b-baryon, has been measured using the OPAL detector at LEP. Lambda_b are selected by the presence of energetic Lambda particles in bottom events tagged by the presence of displaced secondary vertices. A fit to the momenta of the Lambda particles separates signal from B meson and fragmentation backgrounds. The measured product branching ratio is f(b->Lambda_b).BR(Lambda_b->Lambda X) = (2.67+-0.38(stat)+0.67-0.60(sys))% Combined with a previous OPAL measurement, one obtains f(b->Lambda_b).BR(Lambda_b->Lambda X) = (3.50+-0.32(stat)+-0.35(sys))%.Comment: 16 pages, LaTeX, 3 eps figs included, submitted to the European Physical Journal

WW Production Cross Section and W Branching Fractions in e+e- Collisions at 189 GeV

From a data sample of 183 pb^-1 recorded at a center-of-mass energy of roots = 189 GeV with the OPAL detector at LEP, 3068 W-pair candidate events are selected. Assuming Standard Model W boson decay branching fractions, the W-pair production cross section is measured to be sigmaWW = 16.30 +- 0.34(stat.) +- 0.18(syst.) pb. When combined with previous OPAL measurements, the W boson branching fraction to hadrons is determined to be 68.32 +- 0.61(stat.) +- 0.28(syst.) % assuming lepton universality. These results are consistent with Standard Model expectations.Comment: 22 pages, 5 figures, submitted to Phys. Lett.

Determination of density and surface tension in ethanol and HFA 134a mixtures

Recent publications of a transient aerodynamic atomization model have highlighted saturated vapor pressure, density, viscosity and surface tension as key properties governing pressurized metered dose inhaler (pMDI) droplet size1, 2, 3. Pharmaceutical pMDI formulations widely use mixtures of propellant and excipients, such as ethanol, but mixing rules for the aforementioned properties are not available in the literature. Hence, composition-dependent surface tension and density were experimentally determined for ethanol-HFA 134a mixtures. The expressions presented of density and surface tension are advantageous to understanding transient flows inside the actuator and atomization of pMDI formulations containing ethanol as a co-solvent 2

Determination of viscosity in ethanol and HFA 134a mixtures

Knowledge of formulation liquid properties is beneficial when modelling internal transient flows of pMDI HFA 134a and ethanol binary mixtures during atomization1, 2. Non-linear expressions are available that correlate saturated vapor pressure, density and surface tension to HFA 134a-ethanol composition3, 4 2. In this study, experimentally determined dynamic viscosity is presented for ethanol-HFA 134a mixtures at 20.4 ± 1.2°C

Dissolution kinetics of crushed concrete waste: Effect of pH on leaching behaviour

Large volumes of concrete wastes are produced during building demolition that potentially can be reused as a secondary material. Reuse of crushed cementitious construction wastes as a fill material can result in leaching of reactive cement phases. The short-term dissolution kinetics of crushed concrete waste (CCW) from a UK nuclear site were studied in leaching tests using deionised water, acidic and alkaline leachants. The pseudo-steady state leaching rates for major and trace element constituents were determined as a function of leachate pH. At alkaline pH (>10), Ca and Si leaching rates were similar (2–6.5 x 10-11 mol m−2 s−1) producing leachates with Ca/Si ratios (1.1 ± 0.4) suggesting congruent leaching of the calcium silicate hydrate phases in the CCW (pre-leached Ca/Si = 0.9 ± 0.3). Below pH 10, the Ca/Si ratio in the leachate increased with decreasing pH because Ca leaching rates increased without much variation in the Si leaching rate. In this pH range leaching processes were dominated by initial rapid calcium carbonate dissolution and incongruent dissolution of calcium silicate hydrate phases, which produced Ca-depleted solids with overall higher rates of mass loss than in alkali-leached solids. The leaching rates of Mg, Fe and Mn were pH-dependent (with higher leaching rates at low pH) and solubility-controlled whilst the leaching rates of Cr, V, Pb, As, K and Zn were mostly pH independent. Trace element leaching rates were generally low relative to Ca or below detection between pH 3–13. This information can be used to help predict CCW leaching behaviour when disposed in scenarios where meteoric or groundwater flow through the waste is expected

Measurement of the B0 Lifetime and Oscillation Frequency using B0->D*+l-v decays

The lifetime and oscillation frequency of the B0 meson has been measured using B0->D*+l-v decays recorded on the Z0 peak with the OPAL detector at LEP. The D*+ -> D0pi+ decays were reconstructed using an inclusive technique and the production flavour of the B0 mesons was determined using a combination of tags from the rest of the event. The results t_B0 = 1.541 +- 0.028 +- 0.023 ps, Dm_d = 0.497 +- 0.024 +- 0.025 ps-1 were obtained, where in each case the first error is statistical and the second systematic.Comment: 17 pages, 4 figures, submitted to Phys. Lett.