27,581 research outputs found

    Tau Electroweak Couplings

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    We review world-average measurements of the tau lepton electroweak couplings, in both decay (including Michel parameters) and in production (Z0τ+τZ^0\to \tau^+\tau^- and W^-\to\tau^-\nubar_\tau). We review the searches for anomalous weak and EM dipole couplings. Finally, we present the status of several other tau lepton studies: searches for lepton flavor violating decays, neutrino oscillations, and tau neutrino mass limits.Comment: 12 pages, 16 figures; talk presented at Heavy Flavours 8, Southampton, UK, 199

    Probing gravitational wave polarizations with signals from compact binary coalescences

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    In this technical note, we study the possibility of using networks of ground-based detectors to directly measure gravitational-wave polarizations using signals from compact binary coalescences. We present a simple data analysis method to partially achieve this, assuming presence of a strong signal well-captured by a GR template.Comment: Technical not

    On the Kottwitz conjecture for local Shimura varieties

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    Kottwitz’s conjecture describes the contribution of a supercuspidal represention to the cohomology of a local Shimura variety in terms of the local Langlands correspondence. Using a Lefschetz-Verdier fixedpoint formula, we prove a weakened generalized version of Kottwitz’s conjecture. The weakening comes from ignoring the action of the Weil group and only considering the actions of the groups G and Jb up to non-elliptic representations. The generalization is that we allow arbitrary connected reductive groups G and non-minuscule coweights µ

    Experimental Limits on Weak Annihilation Contributions to b → ulv Decays

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    We present the first experimental limits on high-q^2 contributions to charmless semileptonic B decays of the form expected from the weak annihilation (WA) decay mechanism. Such contributions could bias determinations of |V_(ub)| from inclusive measurements of B→X_ulν. Using a wide range of models based on available theoretical input we set a limit of Γ_(WA)/Γ_(b→u) <7.4% (90% confidence level) on the WA fraction, and assess the impact on previous inclusive determinations of |V_(ub)|

    Demonstration of ultra-high-Q small mode volume toroid microcavities on a chip

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    Optical microcavities confine light spatially and temporally and find application in a wide range of fundamental and applied studies. In many areas, the microcavity figure of merit is not only determined by photon lifetime (or the equivalent quality-factor, Q), but also by simultaneous achievement of small mode volume V . Here we demonstrate ultra-high Q-factor small mode volume toroid microcavities on-a-chip, which exhibit a Q/V factor of more than 106(λ/n)310^{6}(\lambda/n)^{-3}. These values are the highest reported to date for any chip-based microcavity. A corresponding Purcell factor in excess of 200 000 and a cavity finesse of 2.8×1062.8\times10^{6} is achieved, demonstrating that toroid microcavities are promising candidates for studies of the Purcell effect, cavity QED or biochemical sensingComment: 4 pages, 3 figures, Submitted to Applied Physics Letter

    Measurement of turbulent correlations in a coaxial flow of dissimilar fluids

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    Axial turbulence measurements in coaxial flow of dissimilar gase

    Trapping radioactive ^{82}Rb in an optical dipole trap and evidence of spontaneous spin polarization

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    Optical trapping of selected species of radioactive atoms has great potential in precision measurements for testing fundamental physics such as EDM, PNC and parity violating beta-decay asymmetry correlation coefficients. We report trapping of 10^4 radioactive ^{82}Rb atoms (t_{1/2}=75 s) with a trap lifetime of ~55 seconds in an optical dipole trap. Transfer efficiency from the magneto-optical trap was ~14%. We further report the evidence of spontaneous spin polarization of the atoms in optical dipole trap loading. This advancement is an important step towards a new generation of precision J-beta correlations measurements with polarized ^{82}Rb atoms.Comment: 4 pages, 4 figure

    Geometric quantization of Hamiltonian actions of Lie algebroids and Lie groupoids

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    We construct Hermitian representations of Lie algebroids and associated unitary representations of Lie groupoids by a geometric quantization procedure. For this purpose we introduce a new notion of Hamiltonian Lie algebroid actions. The first step of our procedure consists of the construction of a prequantization line bundle. Next, we discuss a version of K\"{a}hler quantization suitable for this setting. We proceed by defining a Marsden-Weinstein quotient for our setting and prove a ``quantization commutes with reduction'' theorem. We explain how our geometric quantization procedure relates to a possible orbit method for Lie groupoids. Our theory encompasses the geometric quantization of symplectic manifolds, Hamiltonian Lie algebra actions, actions of families of Lie groups, foliations, as well as some general constructions from differential geometry.Comment: 40 pages, corrected version 11-01-200
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