arXiv subjects

I. L. Solovtsov

Publications and source records attributed to I. L. Solovtsov.

23 records · Page 2Linked to original sources

arXiv1997

Non-perturbative Expansion, Renormalons, and $τ$ Decay

We analyze inclusive $τ$ decay using a modified version of the $a$ expansion, a non-perturbative technique in which the effective coupling is analytic in the infrared region. The modification involves renormalization group improvement of the integrand in a spectral representation for the D-function prior to implementing the $a$ expansion. The advantage of this approach is that it enables us to monitor the structure of the induced power corrections and to ensure that these are consistent with the operator product expansion. Numerically the method agrees well with experiment: the comparison is made with the physical quantity $R_Z$ using $R_τ$ as input.

hep-ph↗

arXiv1997

Analytic Model for the QCD Running Coupling with Universal $\barα_s(0)$ Value

We discuss the new model expression $\barα_{an}(Q^2)$ recently obtained for the QCD running coupling with a regular ghost-free behavior in the "low $Q^2$" region. Being deduced from the standard "asymptotic-freedom" expression by imposing the $Q^2$-analyticity -- without any adjustable parameters -- it obeys nice features: (i) The universal limiting value $\barα_{an}(0)=4π/β_0 \simeq 1.4$ expressed only via group symmetry factors and independent of experimental estimates on the running coupling $\barα_s(Q^2)$ (of QCD scale parameter $Λ$). This value turns out to be stable with respect to higher order corrections; (ii) Stability of IR behavior with respect to higher-loop effects; (iii) Coherence between the experimental $\barα_{an}(M_τ^2)$ value and integral information on IR $\barα_s(Q^2)$ behavior as extracted from jet physics data.

hep-ph↗

arXiv1996

Analytic perturbation theory in QCD and Schwinger's connection between the beta-function and the spectral density

We argue that a technique called analytic perturbation theory leads to a well-defined method for analytically continuing the running coupling constant from the spacelike to the timelike region, which allows us to give a self-consistent definition of the running coupling constant for timelike momentum. The corresponding $β$-function is proportional to the spectral density, which confirms a hypothesis due to Schwinger.

hep-ph↗

arXiv1996

A New Approach to QCD Sum Rules and Inclusive $τ$ Decay

We show that renormalization group improvement, making use of analyticity and the structure of the operator product expansion, combined with a non-perturbative expansion method allows one to describe quarkonium states via QCD sum rules without the need for explicit power corrections. This technique also allows an accurate determination of parameters related to the inclusive decay of the $τ$ lepton.

hep-ph↗

arXiv1996

Analytic QCD running coupling with finite IR behaviour and universal ${\bar α}_s(0)$ value

As is known from QED, a possible solution to the ghost-pole trouble can be obtained by imposing the $Q^2$-analyticity imperative. Here, the pole is compensated by the $α$ non-analytic contribution that results in finite coupling renormalization. We apply this idea to QCD and arrive at the $Q^2$ analytic $\barα_s(Q)$. This solution corresponds to perturbation expansion, obeys AF and, due to non-perturbative contribution, has a regular IR behaviour. It does not contain any adjustable parameter and has a finite IR limit $\barα_s(0)$ which depends only on group symmetry factors. In the one-loop approximation it is equal to $4π/β_0 \simeq 1.40\,$ and turns out to be surprisingly stable with respect to higher order corrections. On the other hand, the IR behaviour of our new analytic solution agrees with recent global low energy experimental estimates of $\barα_s(Q^2)$.

hep-ph↗