Shear wave sensors for viscoelastic properties

AbstractElectromechanical resonators are sensitive to the properties of the surrounding medium due to interaction forces onto the surface caused by motions in the medium. In the present contribution, fully metallic Lorentz force resonators exhibiting in-plane oscillation are used to excite shear waves to measure the linear viscoelastic storage and loss-moduli at specific frequencies in the kHz range of complex fluids (e.g. aqueous polymeric solutions). Reflected shear waves in a well defined gap are employed to extend the measurement range as well as the capability to measure at multiple frequencies. Numerical methods and reduced order models are employed to solve for the velocity field and interaction forces to determine the required quantities from the measured frequency response

Quality Control Process for EQ-5D-5L Valuation Studies

Background: The values of the five-level EuroQol five-dimensional questionnaire (EQ-5D-5L) are elicited using composite time trade-off and discrete choice experiments. Unfortunately, data quality issues and interviewer effects were observed in the first few EQ-5D-5L valuation studies. To prevent these issues from occurring in later studies, the EuroQol Group established a cyclic quality control (QC) process. Objectives: To describe this QC process and show its impact on data quality. Methods: A newly developed QC tool provided information about protocol compliance, interviewer effects, and mean values by health state severity. In a cyclic process, this information is initially used to evaluate whether new interviewers meet minimal quality requirements and later to provide feedback about how their performance may be improved. To investigate the impact of this cyclic process, we compared the quality of the data in Dutch and Spanish valuation studies that did not have this QC process with that in the follow-up studies in the same countries that used the QC process. Data quality was measured using protocol violations, variability between interviewers, the proportion of inconsistent responders, and clustering of composite time trade-off values. Results: In Spain, protocol violations were reduced from 87% in the valuation study to 5% in the follow-up study and in the Netherlands from 20% to 8%. In both countries, interviewers performed more homogeneously in the follow-up studies. The number of inconsistent respondents was reduced by 23.2% in Spain and 23.6% in the Netherlands. Values were less clustered in the follow-up studies. Conclusions: The implementation of a strict QC process in EQ-5D-5L valuation studies increases interviewer protocol compliance and promotes data quality

Spin Glass Behavior in RuSr2Gd1.5Ce0.5Cu2O10

The dynamics of the magnetic properties of polycrystalline RuSr2Gd1.5Ce0.5Cu2O10 (Ru-1222) have been studied by ac susceptibility and dc magnetization measurements, including relaxation and ageing studies. Ru-1222 is a reported magneto-superconductor with Ru spins magnetic ordering at temperatures near 100 K and superconductivity in Cu-O2 planes below Tc ~ 40 K. The exact nature of Ru spins magnetic ordering is still debated and no conclusion has been reached yet. In this work, a frequency-dependent cusp was observed in ac susceptibility vs. T measurements, which is interpreted as a spin glass transition. The change in the cusp position with frequency follows the Vogel-Fulcher law, which is commonly accepted to describe a spin glass with magnetically interacting clusters. Such interpretation is supported by themoremanaent magnetization (TRM) measurements at T = 60 K. TRM relaxations are well described by a stretched exponential relation, and present significant ageing effects.Comment: 4 pages, 6 figures, submitted to Phys. Rev.

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC

Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the anti-kt algorithm with values for the distance parameter that determines the nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp. Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. Rcp varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters

Measurement of the inclusive isolated prompt photon cross-section in pp collisions at sqrt(s)= 7 TeV using 35 pb-1 of ATLAS data

A measurement of the differential cross-section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy sqrt(s) = 7 TeV is presented. The measurement covers the pseudorapidity ranges |eta|<1.37 and 1.52<=|eta|<2.37 in the transverse energy range 45<=E_T<400GeV. The results are based on an integrated luminosity of 35 pb-1, collected with the ATLAS detector at the LHC. The yields of the signal photons are measured using a data-driven technique, based on the observed distribution of the hadronic energy in a narrow cone around the photon candidate and the photon selection criteria. The results are compared with next-to-leading order perturbative QCD calculations and found to be in good agreement over four orders of magnitude in cross-section.Comment: 7 pages plus author list (18 pages total), 2 figures, 4 tables, final version published in Physics Letters

Measurement of the production cross section of prompt j/psi mesons in association with a W (+/-) boson in pp collisions root s=7 TeV with the ATLAS detector

The process pp → W±J/ψ provides a powerful probe of the production mechanism of charmonium in hadronic collisions, and is also sensitive to multiple parton interactions in the colliding protons. Using the 2011 ATLAS dataset of 4.5 fb-1 of p s = 7TeV pp collisions at the LHC, the first observation is made of the production of W± + prompt J/ events in hadronic collisions, using W± → μ and J/ψ → μ+μ-. A yield of 27.4±7.5 -6.5 W± + prompt J/ψ events is observed, with a statistical significance of 5.1. The production rate as a ratio to the inclusive W± boson production rate is measured, and the double parton scattering contribution to the cross section is estimated. Copyright CERN, for the benefit of the ATLAS Collaboration