ep - p h / 94 02 23 0 v 1 4 F eb 1 99 4 τ Decay and the QCD infrared fixed point
نویسنده
چکیده
We apply the optimization procedure based on the Principle of Minimal Sensitivity to the third-order calculation of Rτ . Since the effective couplant remains finite, freezing to a value αs/π = 0.26 at low energies, we can actually evaluate the defining integral of Rτ and compare the optimized perturbation theory result to that of the optimized result obtained after the integral has been evaluated using contour techniques. The good agreement shows that the optimization procedure is consistent and suggests that the infrared fixed point is meaningful.
منابع مشابه
ar X iv : h ep - t h / 99 02 02 7 v 1 3 F eb 1 99 9 INFRARED REGION OF QCD AND CONFINEMENT
Gauge field configurations appropriate for the infrared region of QCD is proposed. Using the usual QCD action, confinement is realized as in the London theory of Meissner effect.
متن کاملep - p h / 98 02 27 4 v 1 9 F eb 1 99 8 QCD Field Strength Correlator at the One - Loop Order
The leading perturbative contributions into the two-point gauge-invariant correlator T rgF µν (x)U(x, 0)U(0, y)gF ρσ (y)U(y, 0)U(0, x) are calculated at the one-loop order. It is shown, that nonlocal condensate T rα s F µν F µν is nonzero at this order. The relation with the renormalization properties of Wilson loops is briefly discussed.
متن کاملar X iv : h ep - p h / 99 02 21 7 v 1 1 F eb 1 99 9 Padé - Improved Extraction of α s ( M τ
The perturbative series used to extract α s (M τ) from the τ hadronic width exhibits slow convergence. Asymptotic Padé-approximant and Padé summation techniques provide an estimate of these unknown higher-order effects, leading to values for α s (M τ) that are about 10% smaller than current estimates. Such a reduction improves the agreement of α s (M τ) with the QCD evolution of the strong coup...
متن کاملar X iv : h ep - p h / 94 09 23 7 v 1 6 S ep 1 99 4 OITS - 549 A LIGHT Z ′ BOSON ∗
A model of a light Z ′ boson based on gauged L µ − L τ U (1) symmetry is constructed. The Z ′ boson mass is constrained to be in the range of 0.8 to 1 GeV from Z and Z ′ mass relation, g-2 of muon, and tau decays. The two body decay τ → µZ ′ is possible. This will provide a striking signature to test the model.
متن کاملep - p h / 97 02 24 5 v 1 4 F eb 1 99 7 The Static Potential in QCD – a full Two - Loop Calculation ∗
A full analytic calculation of the two-loop diagrams contributing to the static potential in QCD is presented in detail. Using a renormalization group improvement, the “three-loop” potential in momentum space is thus derived and the third coefficient of the β-function for the V -scheme is given. The Fourier transformation to position space is then performed, and the result is briefly discussed.
متن کامل