Averages of b-hadron, c-hadron, and $$\tau $$-lepton properties as of 2018

Abstract This paper reports world averages of measurements of b -hadron, c -hadron, and $$\tau $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>τ</mml:mi> </mml:math> -lepton properties obtained by the Heavy Flavour Averaging Group using results available through September 2018. In rare cases, significant results obtained several months later are also used. For the averaging, common input parameters used in the various analyses are adjusted (rescaled) to common values, and known correlations are taken into account. The averages include branching fractions, lifetimes, neutral meson mixing parameters, $$C\!P$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>C</mml:mi> <mml:mspace/> <mml:mi>P</mml:mi> </mml:mrow> </mml:math> violation parameters, parameters of semileptonic decays, and Cabibbo–Kobayashi–Maskawa matrix elements.