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This document collects a written summary of all contributions presented at the workshop $alpha_s$(2019): Precision measurements of the strong coupling held at ECT* (Trento) in Feb. 11--15, 2019. The workshop explored in depth the latest developments on the determination of the QCD coupling $alpha_s$ from the key categories where high precision measurements are available: (i) lattice QCD, (ii) hadronic $tau$ decays, (iii) deep-inelastic scattering and parton distribution functions, (iv) event shapes, jet cross sections, and other hadronic final-states in $e^+e^-$ collisions, (v) Z boson and W boson hadronic decays, and (vi) hadronic final states in p-p collisions. The status of the current theoretical and experimental uncertainties associated to each extraction method, and future perspectives were thoroughly reviewed. Novel $alpha_s$ determination approaches were discussed, as well as the combination method used to obtain a world-average value of the QCD coupling at the Z mass pole.
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This document provides a writeup of all contributions to the workshop on High precision measurements of $alpha_s$: From LHC to FCC-ee held at CERN, Oct. 12--13, 2015. The workshop explored in depth the latest developments on the determination of the QCD coupling $alpha_s$ from 15 methods where high precision measurements are (or will be) available. Those include low-energy observables: (i) lattice QCD, (ii) pion decay factor, (iii) quarkonia and (iv) $tau$ decays, (v) soft parton-to-hadron fragmentation functions, as well as high-energy observables: (vi) global fits of parton distribution functions, (vii) hard parton-to-hadron fragmentation functions, (viii) jets in $e^pm$p DIS and $gamma$-p photoproduction, (ix) photon structure function in $gamma$-$gamma$, (x) event shapes and (xi) jet cross sections in $e^+e^-$ collisions, (xii) W boson and (xiii) Z boson decays, and (xiv) jets and (xv) top-quark cross sections in proton-(anti)proton collisions. The current status of the theoretical and experimental uncertainties associated to each extraction method, the improvements expected from LHC data in the coming years, and future perspectives achievable in $e^+e^-$ collisions at the Future Circular Collider (FCC-ee) with $cal{O}$(1--100 ab$^{-1}$) integrated luminosities yielding 10$^{12}$ Z bosons and jets, and 10$^{8}$ W bosons and $tau$ leptons, are thoroughly reviewed. The current uncertainty of the (preliminary) 2015 strong coupling world-average value, $alpha_s(m_Z)$ = 0.1177 $pm$ 0.0013, is about 1%. Some participants believed this may be reduced by a factor of three in the near future by including novel high-precision observables, although this opinion was not universally shared. At the FCC-ee facility, a factor of ten reduction in the $alpha_s$ uncertainty should be possible, mostly thanks to the huge Z and W data samples available.
We study QCD radiation for the WH and WZ production processes at the LHC. We identify the regions sensitive to anomalous couplings, by considering jet observables, computed at NLO QCD with the use of the Monte Carlo program VBFNLO. Based on these observations, we propose the use of a dynamical jet veto. The dynamical jet veto avoids the problem of large logarithms depending on the veto scale, hence, providing more reliable predictions and simultaneously increasing the sensitivity to anomalous coupling searches, especially in the WZ production process.
We present a review of measurements of alpha_S. The individual measurements are discussed and intermediate averages for classes of related measurements are found. The final average is built using the intermediate values. Correlations are treated consistently. The ICHEP 2006 world average is alpha_S(M_Z) = 0.1175 +/- 0.0011 dominated by the recent result from lattice QCD.
These are the proceedings of the Workshop on Precision Measurements of alphas held at the Max-Planck-Institute for Physics, Munich, February 9-11, 2011. The workshop explored in depth the determination of alphas(mZ) in the MS-bar scheme from the key categories where high precision measurements are currently being made, including DIS and global PDF fits, tau-decays, electroweak precision observables and Z-decays, event-shapes, and lattice QCD. These proceedings contain a short summary contribution from the speakers, as well as the lists of authors, conveners, participants, and talks.
We present an update of results from the HPQCD collaboration on charm physics using the Highly Improved Staggered Quark action. This includes a precise determination of m_c using moments of current-current correlators combined with high-order continuum QCD perturbation theory. We also include an update on the determination of alpha_s from lattice QCD, preliminary results on the determination of m_b and a summary plot of the status of the gold-plated meson spectrum. There is an appendix on tackling systematic errors in fitting using the Bayesian approach.
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