938 research outputs found

    Omega-3 Fatty Acid, Selenium, and Mercury Content of Aquaculture Products in Hawaii

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    The purpose of this study was to gather baseline data on the fatty acid profile and selenium and mercury concentration of aquaculture products in Hawaii

    Mass enhancements and band shifts in strongly hole overdoped Fe-based pnictide superconductors: KFe2_2As2_2 and CsFe2_2As2_2

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    The interplay of high and low-energy mass renormalizations with band-shifts reflected by the positions of van Hove singularities (VHS) in the normal state spectra of the highest hole-overdoped and strongly correlated AFe2_2As2_2 (A122) with A = K, Cs is discussed phenomenologically based on ARPES data and GGA band-structure calculations with full spin-orbit coupling. The big increase of the Sommerfeld coefficient γ\gamma from K122 to Cs122 is ascribed to an enhanced coupling to low-energy bosons in the vicinity of a quantum critical point to an unknown, yet incommensurate phase different from the commensurate Mott one. We find no sizeable increase in correlations for Cs122 in contrast to F. Eilers et al., PRL v. 116, 237003 (2016) [3]. The empirical (ARPES) VHS positions as compared with GGA-predictions point even to slightly weaker correlations in Cs122 in accord with low-TT magnetic susceptibility χ(T)\chi(T) data and a decreasing Wilson ratio χ(0)/γ\propto \chi(0)/\gamma.Comment: 8 pages, 7 figures, updated references, and a Note for arXiv-reader

    Meson Decay Constants from Isospin Mass Splittings in the Quark Model

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    Decay constants of DD and BB mesons are estimated within the framework of a heavy-quark approach using measured isospin mass splittings in the DD, DD^*, and BB states to isolate the electromagnetic hyperfine interaction between quarks. The values fD=(262±29)f_D = (262 \pm 29) MeV and fB=(160±17)f_B = (160 \pm 17) MeV are obtained. Only experimental errors are given; possible theoretical ambiguities, and suggestions for reducing them, are noted.Comment: 7 pages, LaTeX, EFI-92-3

    Born Effective Charges and Infrared Response of LiBC

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    Calculations of the zone center optical mode frequencies (including LO-TO splitting), Born effective charges Zαα^*_{\alpha\alpha} for each atom, dielectric constants ϵ0\epsilon_{0} and ϵ\epsilon_{\infty}, and the dielectric response in the infrared, using density functional linear response theory, are reported. Calculated Raman modes are in excellent agreement with experimental values (170 cm1^{-1} and 1170 cm1^{-1}), while it will require better experimental data to clarify the infrared active mode frequencies. The Born effective charges Zαα^*_{\alpha \alpha} (i) have surprisingly different values for B and C, and (ii) show considerable anisotropy. Relationships between the effective charges and LO-TO splitting are discussed, and the predicted reflectivity in the range 0 -- 1400 cm1^{-1} is presented. These results hold possible implications for Li removal in LiBC, and C substition for B in MgB2_2.Comment: 6 pages, 3 figure

    Theoretical overview of atomic parity violation. Recent developments and challenges

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    Recent advances in interpreting the most accurate to-date measurement of atomic parity violation in Cs are reviewed. The inferred nuclear weak charge, Q_W = - 72.65(28)_expt (36)_theor, agrees with the prediction of the standard model at 1 sigma level. Further improved interpretation is limited by an accuracy of solving basic correlation problem of atomic structure. We report on our progress in solving this problem within the relativistic coupled-cluster formalism. We include single-, double- and triple- electronic excitations in the coupled-cluster expansion. Numerical results for energies, electric-dipole matrix elements, and hyperfine-structure constants of Cs are presented.Comment: PAVI'06 proceedings + EJPA; refs + SM Qw fixe

    Framework for Identification of Neutral B Mesons

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    We introduce a method for the study of CP-violating asymmetries in tagged states of neutral BB mesons with arbitrary coherence properties. A set of time-dependent measurements is identified which completely specifies the density matrix of the initial state in a two-component space with basis vectors B0B^0 and B0\overline B^0, and permits a determination of phases in the Cabibbo-Kobayashi-Maskawa matrix. For a given tagging configuration, the measurement of decays both to flavor eigenstates and to CP eigenstates provides the necessary information.Comment: Submitted to Phys. Rev. Letters. 8 pages, LaTeX, Technion-PH-93-31 / EFI 93-3

    QCD sum rules study of the meson Z^+(4430)

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    We use QCD sum rules to study the recently observed meson Z+(4430)Z^+(4430), considered as a DD1D^*D_1 molecule with JP=0J^{P}=0^{-}. We consider the contributions of condensates up to dimension eight and work at leading order in αs\alpha_s. We get m_Z=(4.40\pm0.10) \GeV in a very good agreement with the experimental value. We also make predictions for the analogous mesons ZsZ_{s} and ZbbZ_{bb} considered as DsD1D_s^*D_1 and BB1B^*B_1 molecules respectively. For ZsZ_{s} we predict mZs=(4.70±0.06)GeVm_{Z_{s}}= (4.70\pm 0.06) {\rm GeV}, which is above the DsD1D_s^*D_1 threshold, indicating that it is probably a very broad state and, therefore, difficult to be experimentally seen. For ZbbZ_{bb} we predict mZbb=(10.74±0.12)GeVm_{Z_{bb}}= (10.74\pm 0.12) {\rm GeV}, in agreement with quark model predictions.Comment: 2 new figures included. version accepted for publication in Phys. Lett.

    Identification of Neutral B Mesons Using Correlated Hadrons

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    The identification of the flavor of a neutral BB meson can make use of hadrons produced nearby in phase space. Examples include the decay of ``BB^{**}'' resonances or the production of hadrons as a result of the fragmentation process. Some aspects of this method are discussed, including time-dependent effects in neutral BB decays to flavor states, to eigenstates of CP and to other states, and the effects of possible coherence between B0B^0 and B0\overline{B}^0 in the initial state. We study the behavior of the leading hadrons in bb-quark jets and the expected properties of BB^{**} resonances. These are extrapolated from the corresponding DD^{**} resonances, of whose properties we suggest further studies.Comment: To be submitted to Phys. Rev. D. 26 pages, LaTeX, figures not included (available upon request). Technion-PH-93-32 / EFI 93-4

    Photoemission and x-ray absorption study of MgC_(1-x)Ni_3

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    We investigated electronic structure of MgC_(1-x)Ni_3 with photoemission and x-ray absorption spectroscopy. Both results show that overall band structure is in reasonable agreement with band structure calculations including the existence of von Hove singularity (vHs)near E_F. However, we find that the sharp vHs peak theoretically predicted near the E_F is substantially suppressed. As for the Ni core level and absorption spectrum, there exist the satellites of Ni 2p which have a little larger energy separation and reduced intensity compared to the case of Ni-metal. These facts indicate that correlation effects among Ni 3d electrons may be important to understand various physical properties.Comment: 12 pages, 4 figure

    Model of the Quark Mixing Matrix

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    The structure of the Cabibbo-Kobayashi-Maskawa (CKM) matrix is analyzed from the standpoint of a composite model. A model is constructed with three families of quarks, by taking tensor products of sufficient numbers of spin-1/2 representations and imagining the dominant terms in the mass matrix to arise from spin-spin interactions. Generic results then obtained include the familiar relation Vus=(md/ms)1/2(mu/mc)1/2|V_{us}| = (m_d/m_s)^{1/2} - (m_u/m_c)^{1/2}, and a less frequently seen relation Vcb=2[(ms/mb)(mc/mt)]|V_{cb}| = \sqrt{2} [(m_s/m_b) - (m_c/m_t)]. The magnitudes of VubV_{ub} and VtdV_{td} come out naturally to be of the right order. The phase in the CKM matrix can be put in by hand, but its origin remains obscure.Comment: Presented by Mihir P. Worah at DPF 92 Meeting, Fermilab, November, 1992. 3 pages, LaTeX fil
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