875 research outputs found

    Predicative Ability of QCD Sum Rules for Decuplet Baryons

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    QCD sum rules for decuplet baryon two-point functions are investigated using a comprehensive Monte-Carlo based procedure. In this procedure, all uncertainties in the QCD input parameters are incorporated simultaneously, resulting in realistic estimates of the uncertainties in the extracted phenomenological parameters. Correlations between the QCD input parameters and the phenomenological parameters are studied by way of scatter plots. The predicted couplings are useful in evaluating matrix elements of decuplet baryons in the QCD sum rule approach. They are also used to check a cubic scaling law between baryon couplings and masses, as recently found by Dey and coworkers. The results show a significant reduction in the scaling constant and some possible deviations from the cubic law.Comment: 13 pages, RevTeX, 5 PS figures embedded with psfig.st

    B0 - anti-B0 mixing beyond factorization

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    We present a calculation of the B0 - anti-B0 mixing matrix element in the framework of QCD sum rules for three-point functions. We compute alpha_s corrections to a three-point function at the three-loop level in QCD perturbation theory, which allows one to extract the matrix element with next-to-leading order (NLO) accuracy. This calculation is imperative for a consistent evaluation of experimentally-measured mixing parameters since the coefficient functions of the effective Hamiltonian for B0 - anti-B0 mixing are known at NLO. We find that radiative corrections violate factorization at NLO; this violation is under full control and amounts to 10%.Comment: 4 pages, 3 figures, LaTeX2

    Critical Behavior of J/psi across the Phase Transition from QCD sum rules

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    We study behavior of J/psi in hot gluonic matter using QCD sum rules. Taking into account temperature dependences of the gluon condensates extracted from lattice thermodynamics for the pure SU(3) system, we find that the mass and width of J/psi exhibit rapid change across the critical temperature.Comment: 5 pages, 3 figures. Poster contribution for Quark Matter 2008. To be published in the proceeding

    Isospin Breaking in the Pion-Nucleon Coupling from QCD Sum Rules

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    We use QCD sum rules for the three point function of a pseudoscalar and two nucleonic currents in order to estimate the charge dependence of the pion nucleon coupling constant gNNπg_{NN\pi} coming from isospin violation in the strong interaction. The effect can be attributed primarily to the difference of the quark condensates and and . For the splitting (gppπ0gnnπ0)/gNNπ(g_{pp\pi_0} - g_{nn\pi_0}) / g_{NN\pi} we obtain an interval of 1.21021.2 * 10^{-2} to 3.71023.7 * 10^{-2}, the uncertainties coming mainly from the input parameters. The charged pion nucleon coupling is found to be the average of gppπ0g_{pp\pi_0} and gnnπ0g_{nn\pi_0}. Electromagnetic effects are not included.Comment: 18 pages (REVTeX) + 2 figures (as PostScript), to be published in PRC, replaced with final version: inclusion of pi-eta mixing and N -> N* transition

    The Psychobiology of Authentic and Simulated Dissociative Personality States:The Full Monty

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    The etiology of dissociative identity disorder (DID) remains a topic of debate. Proponents of the fantasy model and the trauma model of DID have both called for more empirical research. To this end, the current study presents new and extended data analyses of a previously published (H2O)-O-15 positron emission tomography imaging study. This study included 29 subjects: 11 patients with DID and 10 high- and 8 low-fantasy-prone DID-simulating mentally healthy control subjects. All subjects underwent an autobiographical memory script-driven (neutral and trauma related) imagery paradigm in 2 (simulated) dissociative personality states (neutral and trauma related). Psychobiological and psychophysiological data were obtained. Results of the new post-hoc tests on the psychophysiological responses support the trauma model. New results of the brain imaging data did not support the fantasy model. This study extends previously published results by offering important new supporting data for the trauma model of DID.</p

    Octet Baryons at Finite Temperature: QCD Sum Rules vs. Chiral Symmetry

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    Correlators of the octet baryons in the hot pion gas are studied in the framework of the QCD sum rule. The condensates appearing in the OPE side of the correlators become T-dependent through the interaction with thermal pions. We present an explicit demonstration that the O(T2)O(T^2)-dependence of the condensates is completely compensated by the change of the pole residue and the π+BB\pi + B \rightarrow B' scattering effect in the spectral functions. Therefore the baryon masses are constant to this order, although uˉuTuˉu0(1T2/8fπ2)\langle\bar{u}u\rangle_T\simeq\langle\bar{u}u\rangle_0(1-T^2/8f_\pi^2), which is consistent with the chiral symmetry constraint by Leutwyler and Smilga.Comment: 19 pages, MSUNSCL-870, LaTex files, 2 figs. consisting of simple Feynmann diagrams not included, Phys.Rev.D in pres

    Light-Quark Mesons and Four-Quark Condensates at Finite Temperature

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    We propose an analog of the familiar gap equation for the case of four-quark condensates at finite temperature. The condensates of interest correspond to scalar, vector, psudoscalar, axial vector, and tensor Dirac structures. Working with correlators at zero chemical potential without factorization, we arrive at coupled equations for these four-quark condensates and the masses of certain light-quark mesons. We study the temperature dependence of the four-quark condensates and masses; in one of our models, factorization of the four-quark condensates is shown to be increasingly violated as the temperature is increased toward TcT_c. The 2++^{++} tensor mesons a2_2(1320)-f2_2(1270) are identified as especially sensitive probes of the four-quark condensates.Comment: Latex file, 6 Fig

    QCD sum rules for the pseudoscalar decay constants - To constrain the strange quark mass

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    We study the higher order corrections of quark masses to the Gell-Mann-Oakes-Renner (GOR) relation by constructing QCD sum rules exclusively for pseudoscalar mesons from the axial-vector correlation function, id4x eipxi \int d^4x~ e^{ip\cdot x} . To project out the pseudoscalar meson contributions, we apply pμpν/p2-p^\mu p^\nu/p^2 to this correlation function and construct sum rules for the decay constants of pseudoscalar mesons, fπ,fkf_\pi, f_k and fη8f_{\eta_8}. The OPE is proportional to quark masses due to PCAC. To leading order in quark mass, each sum rule reproduces the corresponding GOR relation. For kaon and η8\eta_8, the deviation from the GOR relation due to higher orders in quark mass is found to be substantial. But the deviation gives better agreements with the phenomenology. Our sum rule provides a sensitive relation between fKf_K and msm_s, which stringently constrain the value for msm_s. To reproduce the experimental value for fKf_K, msm_s is found to be 186 MeV at 1 GeV scale. The fη8f_{\eta_8} sum rule also supports this finding.Comment: 14 pages including 3 figures. slightly revised. Accepted for publication in Physical Review

    On the asymptotic O(ααS){\cal O}(\alpha \alpha_S) behavior of the electroweak gauge bosons vacuum polarization functions for arbitrary quark masses

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    We derive the QCD corrections to the electroweak gauge bosons vacuum polarization functions at high and zero--momentum transfer in the case of arbitrary internal quark masses. We then discuss in this general case (i) the connection between the O(ααS)O(\alpha \alpha_S) calculations of the vector bosons self--energies using dimensional regularization and the one performed via a dispersive approach and (ii) the QCD corrections to the ρ\rho parameter for a heavy quark isodoublet.Comment: 14 pages + 2 figures (not included: available by mail from A. Djouadi), Preprint UdeM-LPN-TH-93-156 and NYU-TH-93/05/0

    Contribution of higher meson resonances to the electromagnetic π\pi-meson mass difference

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    Modifications of the DGMLY relation for calculation of electromagnetic π\pi-meson mass difference based on the Chiral Symmetry Restoration phenomenon at high energies as well as the Operator Product Expansion of quark densities for vector (ρ\rho) and axial-vector (a1a_1) meson fields difference are proposed. In the calculations higher meson resonances in vector and axial-vector channels are taken into account. It is shown that the inclusion of the first ρ\rho and a1a_1 radial excitations improves the results for electromagnetic π\pi-meson mass difference as compared with the previous ones. Estimations on the electromagnetic ρ\rho and a1a_1-meson decay constants and the constant L10L_{10} of effective chiral Lagrangian are obtained from the generalized Weinberg sum rules.Comment: Latex2e, 10 pages, submitted to Yad. Phy
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