arXiv subjects

O. V. Tarasov

Publications and source records attributed to O. V. Tarasov.

39 records · Page 3Linked to original sources

arXiv1993

The $α_s^3$ Corrections to the Effective Neutral Current and to the Z Decay Rate in the Heavy Top Quark Limit

We find the effective neutral current in the heavy top quark limit up to and including the terms of order $α_s^3$. The result is then employed to compute the correction of the same order to the axial part of the Z decay rate into hadrons ($\G^h_Z$) induced by the top-bottom quark mass splitting. The calculations confirm the prediction made in a previous work of K.G.Ch. and J.H.Kühn (Phys. Lett. B 308 (1993) 127), namely, the effect of the singlet corrections of order $α^3_s$ to the axial part of the $\G^h_Z$ should not exceed 25\% - 30\% (depending on the values chosen for $α_s(M_Z)$ and $m_t$) of the magnitude of the leading (singlet) $α_s^2$ term.

hep-ph↗

arXiv1993

Two-loop two-point functions with masses: asymptotic expansions and Taylor series, in any dimension

In all mass cases needed for quark and gluon self-energies, the two-loop master diagram is expanded at large and small $q^2$, in $d$ dimensions, using identities derived from integration by parts. Expansions are given, in terms of hypergeometric series, for all gluon diagrams and for all but one of the quark diagrams; expansions of the latter are obtained from differential equations. Padé approximants to truncations of the expansions are shown to be of great utility. As an application, we obtain the two-loop photon self-energy, for all $d$, and achieve highly accelerated convergence of its expansions in powers of $q^2/m^2$ or $m^2/q^2$, for $d=4$.

hep-ph↗

arXiv1992

Analytical on-shell QED results: 3-loop vacuum polarization, 4-loop beta-function and the muon anomaly

We present the results of analytical calculations of the 3-loop contributions to the asymptotic photon vacuum polarization function, in the on shell scheme, and of the 4-loop contributions to the on shell QED beta-function. These are used to evaluate various 4-loop and 5-loop contributions to the muon anomaly. Our analytical contributions to (g-2)_μdiffer significantly from previous numerical results. A very recent numerical re-evaluation of 4-loop muon-anomaly contributions has yielded results much closer to ours.

hep-ph↗