Speaker
Description
The QCD-coupling is a necessary input in the computation of many observables, and the parametric error on input parameters can be a dominant source of uncertainty. The coupling can be extracted by comparing high order perturbative computations and lattice evaluated moments of mesonic two-point functions with heavy quarks, which provide a high energy scale for perturbation theory. The truncation of the perturbative series is an important systematic uncertainty.
We study this issue by measuring pseudo-scalar two-point functions in volumes of $L=2$ fm with twisted-mass Wilson fermions in the quenched approximation.
We use full twist, the non-perturbative clover term and lattice spacings down to $a=0.015$ fm to tame the sizable discretization effects. Our preliminary results indicate that higher order perturbative corrections lead to $\sim 10\%$ deviations of the extracted Lambda parameter from its asymptotic value when the quark mass is around $1.5\, m_\mathrm{charm}$.
