V. Elias

QCD sum-rule consistency of lowest-lying qq scalar resonances

Abstract We investigate lowest-lying scalar meson properties predicted from QCD Laplace sum rules based upon isovector and isoscalar non-strange q q currents. The hadronic content of these sum rules incorporates deviations from the narrow resonance approximation anticipated from physical resonance widths. The field theoretical content of these sum rules incorporates purely perturbative QCD contributions to three-loop order, the direct single-instanton contribution in the instanton liquid model, and leading contributions from QCD-vacuum condensates. In the isovector channel, the results we obtain are compatible with a0(1450) being the lowest-lying q q resonance, and are indicative of a non -q q interpretation for a0(980). In the isoscalar channel, the results we obtain are compatible with the lowest lying q q resonance being f0(980) or a state somewhat lighter than f0(980) whose width is less than half of its mass. A linear sigma-model interpretation of the lowest-lying resonances coupling, when compared to the coupling predicted by sum rules, is indicative of a renormalization-group invariant light-quark mass between 4 and 6 MeV.

Closed form summation of RG accessible logarithmic contributions to semileptonic B decays and other perturbative processes

For any perturbative series that is known to

Radiative Electroweak Symmetry Breaking Revisited

k

Massless scalar field theory in a quantized spacetime

-subleading orders of perturbation theory, we utilise the process-appropriate renormalization-group (RG) equation in order to obtain all-orders summation of series terms proportional to

VVA triangle graph ambiguities in four and N dimensions

\alpha^n \log^{n-k}(\mu^2)

Padé-Summation Approach to QCD β-Function Infrared Properties

with

Padé-improvement of CP-odd Higgs decay rate into two gluons

k = {0,1,2,3}

Asymptotic Padé-approximant predictions for renormalization-group functions of massive φ4 scalar field theory

, corresponding to the summation to all orders of the leading and subsequent-three-subleading logarithmic contributions to the full perturbative series. These methods are applied to the perturbative series for semileptonic

Gauge Independence of Subleading Contributions to the Operator Product Pole Mass

b

Optimal renormalization group improvement of the perturbative series for the e+ e- annihilation cross-section

-decays in both MS-bar and pole-mass schemes, and they result in RG-summed series for the decay rates which exhibit greatly reduced sensitivity to the renormalization scale