David d'Enterria, Peter Zeiler Skands

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The strong coupling αs is one of the fundamental parameters of the Standard Model (SM), setting the scale of the strength of the strong interaction theoretically described by Quantum Chromodynamics (QCD). Its measured (2014) value amounts to αs(m2Z) = 0.1185 ± 0.0006 at the reference Z pole mass scale. Given its current δαs(m2Z)/αs(m2Z) ≈ 0.5% uncertainty—orders of magnitude larger than that of the gravitational (δG/G ≈ 10−5), Fermi (δGF/GF ≈ 10−8), and QED (δα/α ≈ 10−10)couplings—the strong coupling is the least precisely known of all fundamental constants in nature.Improving our knowledge of αs is a prerequisite to reduce the theoretical uncertainties in the calculations of all high-precision perturbative QCD (pQCD) processes whose cross sections or decayrates depend on higher-order powers of αs, as is the case for virtually all those measured at the LHC. In the Higgs sector, in particular, the uncertainty on αs is currently the second major contributor(after the bottom mass) to the parametric uncertainties of its dominant H → bb partial decay.The same applies for the extraction of the charm Yukawa coupling via future H → cc¯ measurements
Original languageEnglish
Title of host publicationHigh-Precision αs Measurements from LHC to FCC-ee
EditorsDavid d'Enterria, Peter Skands
Place of PublicationGeneva Switzerland
Number of pages2
Publication statusPublished - 16 Dec 2015
EventHigh-Precision αs Measurements from LHC to FCC-ee - CERN, Geneva, Switzerland
Duration: 12 Oct 201513 Oct 2015


ConferenceHigh-Precision αs Measurements from LHC to FCC-ee
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