Related papers: Alpha_s from hadronic tau decay data
The hadronic vacuum-polarization contribution to the muon anomalous magnetic moment a_{mu}(hadr) and to the value of the eleectromagnetic coupling constant at q^2 = M^2_z are determined more precisely in connection with a new more exact…
I review recent estimates of the non-perturbative hadronic vacuum polarization contributions. Since these at present can only be evaluated in terms of experimental data of limited precision, the related uncertainties pose a serious…
We perform a NLO QCD analysis of the combined SLAC-BCDMS-NMC-E665-H1-ZEUS data on inclusive deep inelastic cross section. Particular attention was paid to the extraction of strong coupling constant $\alpha_s$ and high twist (HT)…
Upper and lower bounds are established on the Lambda_b -> Lambda_c semileptonic decay form factors by utilizing inclusive heavy-quark-effective-theory sum rules. These bounds are calculated to leading order in Lambda_QCD/m_Q and alpha_s.…
Correlations between the QCD coupling \alpha_s, the gluon condensate < \alpha_s G^2 >, and the c,b-quark running masses m_c,b in the MS-scheme are explicitly studied (for the first time) from the (axial-)vector and (pseudo)scalar charmonium…
Using the recent four-loop calculations of the QCD beta-function and the three-loop matching coefficients we study the induced error in $\alpha_s(m_Z)$ obtained from $\alpha_s(m_tau)$ due to the evolution procedure. We show that, when…
We update our previous work on an analysis of the electroweak data by including new and partly preliminary data available up to the 1996 summer conferences. The new results on the Z partial decay widths into b and c hadrons now offer a…
Hadronic $\tau$ decays provide a clean laboratory for the precise study of quantum chromodynamics (QCD). Observables based on the spectral functions of hadronic $\tau$ decays can be related to QCD quark-level calculations to determine…
I discuss the standard SVZ-expansion of the QCD two-point correlators in terms of the QCD vacuum condensates and beyond it due to a new unflavoured 1/Q^2-term (tachyonic gluon mass squared \lambda^2) which modelizes the effects of…
We evaluate the effect of a virtual top quark on the coefficient of $\alpha_{s}^{2}$ in the decay rates $\Gamma(Z \rightarrow {\rm hadrons})$ and $\Gamma(Z \rightarrow b\overline{b} )$. We treat the dependence on the top quark mass exactly…
We revisit QCD sum rules for the decay constants of heavy-light mesons. In the sum rules for the vector mesons B^*_(s) and D^*_(s) we improve the accuracy of OPE, taking into account the O(alpha_s^2) terms in the perturbative part and…
A QCD model with an infinite number of vector mesons suggested by one of the authors is used to derive the value of the correction $\delta\alpha_{hadr}$ for $\alpha(m_{Z}^{2})$ due to the strong interactions. The result is…
The leading hadronic effects in electroweak theory derive from vacuum polarization which are non-perturbative hadronic contributions to the running of the gauge couplings, the electromagnetic alpha_{em}(s) and the SU(2)_L coupling…
The strong coupling alpha_s is a fundamental parameter of the Standard Model. In comparison to parameters like alpha_em and M_Z it is relatively poorly known. However the precision of alpha_s measurements has improved dramatically in recent…
Experimental data on the total cross section of $e^+ e^-$ annihilation into hadrons are confronted with QCD and the operator product expansion using finite energy sum rules. Specifically, the power corrections in the operator product…
The prediction of the strong coupling assuming (supersymmetric) coupling constant unification is reexamined. We find, using the new electroweak data, $\alpha_{s}(M_{Z}) \approx 0.129 \pm 0.010$. The implications of the large $\alpha_{s}$…
Exclusive non-leptonic two-body decays are discussed on the basis of a generalized factorization approach which also includes non-factorizeable contributions. Numerous decay processes can be described satisfactorily. The success of the…
We estimate the QCD coupling constant from a lattice calculation of the bottomonium spectrum. The second order perturbative expansion of the plaquette expectation value is employed to determine alpha_S at a scale set by the 2S-1S and 1P-1S…
We present a new estimate of the hadronic contribution to the shift in the fine structure constant at LEP and TESLA energies and calculate the effective fine structure constant. Substantial progress in a precise determination of this…
Various moments of the hadronic spectral functions have been employed in the determination of the strong coupling alpha_s from tau decays. In this work we study the behaviour of their perturbative series under different assumptions for the…