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[en] Two methods for determining |V_u_s| employing inclusive hadronic ττ decay data are discussed. The first is the conventional flavor-breaking sum rule determination whose usual implementation produces results ~3σ low compared to three-family unitary expectations. The second is a novel approach combining experimental strange hadronic ττ distributions with lattice light-strange current–current two-point function data. In preliminary explorations of the latter show the method promises |V_u_s| determinations are competitive with those from K_ℓ_3 and Γ[π_μ_2]/Γ[π_μ_2]. For the former, systematic issues in the conventional implementation are investigated. Unphysical dependences of |V_u_s| on the choice of sum rule weight, w, and upper limit, s_0, of the weighted experimental spectral integrals are observed, the source of these problems identified and a new implementation which overcomes these problems developed. The lattice results are shown to provide a tool for quantitatively assessing truncation uncertainties for the slowly converging D=2 OPE series. Our results for |V_u_s| from this new implementation are shown to be free of unphysical w- and s0-dependences, and ~0.0020 higher than those produced by the conventional implementation. With preliminary new Kπ branching fraction results as input, we find |V_u_s| in excellent agreement with that obtained from K_ℓ_3, and compatible within errors with expectations from three-family unitarity.
[en] In this study, we present the current status and prospects of the dark sector physics search program of the SeaQuest/E1067 fixed target dimuon experiment at Fermilab Main Injector. There has been tremendous excitement and progress in searching for new physics in the dark sector in recent years. Dark sector refers to a collection of currently unknown particles that do not directly couple with the Standard Model (SM) strong and electroweak (EW) interactions but assumed to carry gravitational force, thus could be candidates of the missing Dark Matter (DM). Such particles may interact with the SM particles through “portal” interactions. Two of the simple possibilities are being investigated in our initial search: (1) dark photon and (2) dark Higgs. They could be within immediate reach of current or near future experimental search. We show there is a unique opportunity today at Fermilab to directly search for these particles in a highly motivated but uncharted parameter space in high-energy proton–nucleus collisions in the beam-dump mode using the 120 GeV proton beam from the Main Injector. Our current search window covers the mass range 0.2–10 GeV/c2, and in the near future, by adding an electromagnetic calorimeter (EMCal) to the spectrometer, we can further explore the lower mass region down to about ~1 MeV/c2 through the di-electron channel. If dark photons (and/or dark Higgs) were observed, they would revolutionize our understanding of the fundamental structures and interactions of our universe.
[en] We review the present understanding of neutrino masses and mixings, discussing what are the unknowns in the three family oscillation scenario. Despite the anticipated success coming from the planned long baseline neutrino experiments in unraveling the leptonic mixing sector, there are two important unknowns which may remain obscure: the mixing angle θ13 and the CP-phase δ. The measurement of these two parameters has led us to consider the combination of superbeams and neutrino factories as the key to unveil the neutrino oscillation picture
[en] Here we present a determination of the strong coupling constant from lattice QCD using the moments of pseudo-scalar charmonium correlators calculated using highly improved staggerered quark action. We obtain a value α_s(μ = mc) = 0.3397(56), which is the lowest energy determination of the strong coupling constant so far.
[en] We review the attempts to construct black hole/string solutions in asymptotically plane wave spacetimes. First, we demonstrate that geometries admitting a covariantly constant null Killing vector cannot admit event horizons, which implies that pp-waves can't describe black holes. However, relaxing the symmetry requirements allows us to generate solutions which do possess regular event horizons while retaining the requisite asymptotic properties. In particular, we present two solution generating techniques and use them to construct asymptotically plane wave black string/brane geometries
[en] In this paper, the authors study the ground state of a particle moving on an even-dimensional Riemannian manifold (M,gμν under the action of a nondegenerate magnetic field Bμ,ν in the hypothesis that the metric and the symplectic two-form provided by B, define a conformal Kahler structure on M. On a Riemannian surface the Hamiltonian always has a degenerate ground state and in the compact case its degeneration is equal to the volume of the surface in h units minus one half of the Euler-Poincare characteristic
[en] In this paper, the authors derive the current algebra of principal chiral models with a Wess-Zumino term. At the critical coupling where the model becomes conformally invariant (Wess-Zumino-Novikov-Witten theory), this algebra reduces to two commuting Kac-Moody algebras, while in the limit where the coupling constant is taken to zero (ordinary chiral model), we recover the current algebra of that model. In this way, the latter is explicitly realized as a deformation of the former, with the coupling constant as the deformation parameter
[en] The nuclei 131I and 133I have been populated in multi-nucleon transfer reactions between 136Xe ions and various targets, and their structure investigated by time-correlated γ-ray coincidence spectroscopy and the measurement of γ-ray angular correlations. A 19/2- isomer at 1918 keV, with a half-life of 24(1) µs, has been identified in 131I, as well as nanosecond isomers with Jπ = 23/2+ in both isotopes. A T1/2 = 25(3) ns isomer at 4308 keV in 131I is suggested to have Jπ = (31/2-, 33/2-) and is primarily attributed to the coupling of an odd proton in the d5/2 or g7/2 orbit with the (π2)0+( νh11/2-3d3/2-1)15- configuration in 130Te, responsible for the 15- isomer in that nucleus. The observed level properties are compared with predictions of a shell-model calculation. (author)
[en] Interaction cross sections (σI) for Ne isotopes from the stability line to the vicinity of neutron-drip line have been measured using the RIBF facility at RIKEN. Measurements have been performed for 20-32Ne on C target at energies around 240 MeV/nucleon. A large enhancement of σI beyond the systematics of stable nuclei have been observed for neutron-rich Ne isotopes. The possible halo structures with lower orbital angular momentum for 29,31Ne are discussed by the preliminary analysis. (author)
[en] Recent experiments on positronium annihilation have confirmed QED calculations at high orders of alpha and tested discrete fundamental symmetries. These measurements search for rare modes of annihilation which are distinguished from backgrounds by their specific decay signatures. New developments in beyond Standard Model theory provide motivation for new measurements of such decays. A brief history of searches for rare annihilation modes of Ps is given. Recent experimental and theoretical developments are reviewed. Experiments currently being planned are discussed