Abstract
We present our result for the strong coupling constant computed from the u-d vector Hadronic Vacuum Polarisation function. We use nf = 2 + 1 flavours of Domain Wall fermions at 3 lattice spacings, generated by the RBC-UKQCD collaboration. We identify several possible pitfalls in this method for determining the coupling and illustrate how to resolve them.
Highlights
IntroductionThe strong coupling constant of QCD αs is a fundamental input parameter of the Standard Model of particle physics and it is known to the lowest precision of almost all fundamental constants despite decades of effort measuring it
The strong coupling constant of QCD αs is a fundamental input parameter of the Standard Model of particle physics and it is known to the lowest precision of almost all fundamental constants despite decades of effort measuring it.αs is a purely perturbative quantity, and its precise measurement is of great importance for accurate perturbative calculations
In this work we have chosen to investigate a determination of the coupling from the lattice Hadronic Vacuum Polarisation (HVP) function as performed in [3, 4]
Summary
The strong coupling constant of QCD αs is a fundamental input parameter of the Standard Model of particle physics and it is known to the lowest precision of almost all fundamental constants despite decades of effort measuring it. Lattice QCD measurements of the coupling have dominated the world average in terms of statistical precision over the past twenty years with several complementary evaluations being performed, reviews of which can be found in [2]. In this work we have chosen to investigate a determination of the coupling from the lattice Hadronic Vacuum Polarisation (HVP) function as performed in [3, 4]. We find this measurement technique compelling as it has good theoretical motivations and seems like a natural competitor and perhaps even successor for τ-decay based analyses. We will improve upon previous determinations of the coupling using the HVP in the following ways: first by introducing several lattice spacings to investigate the cut-off dependence of the result, secondly by working at a scale that does not require fitting the arguably poorly-behaved D(2) series or higher-order condensates and by performing a multiple renormalisation scale analysis
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