This article reports world averages of measurements of b-hadron, c-hadron, and τ -lepton properties obtained by the Heavy Flavor Averaging Group using results available through summer 2016. 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, CP violation parameters, parameters of semileptonic decays, and Cabbibo-Kobayashi-Maskawa matrix elements. 10 Summary 11 Acknowledgments References 3.2.5 B + c lifetime Early measurements of the B + c meson lifetime, from CDF [132, 133] and D0 [134], use the semileptonic decay mode B + c → J/ψ + ν and are based on a simultaneous fit to the mass and lifetime using the vertex formed with the leptons from the decay of the J/ψ and the third lepton. Correction factors to estimate the boost due to the missing neutrino are used. Correlated systematic errors include the impact of the uncertainty of the B + c p T spectrum on the correction factors, the level of feed-down from ψ(2S) decays, Monte Carlo modeling of the decay model varying from phase space to the ISGW model, and mass variations. With more statistics, CDF2 was able to perform the first B + c lifetime based on fully reconstructed B + c → J/ψπ + decays [135], which does not suffer from a missing neutrino. Recent measurements from LHCb, both with B + c → J/ψ µ + ν [136] and B + c → J/ψ π + [137] decays, achieve the highest level of precision. All the measurements are summarized in Table 11 and the world average, dominated by the LHCb measurements, is determined to be τ (B + c ) = 0.507 ± 0.009 ps . (46) 3.2.6 Λ 0 b and b-baryon lifetimes The first measurements of b-baryon lifetimes, performed at LEP, originate from two classes of partially reconstructed decays. In the first class, decays with an exclusively reconstructed Λ + c baryon and a lepton of opposite charge are used. These products are more likely to occur in Measurements of B −c decays to charmed hadrons are summarized in Sections 6.5.1 to 6.5.2. Since the absolute cross-section for B − c meson production in any production environment is currently not known, it is not possible to determine absolute branching fractions. Instead, results are presented either as ratios of branching fractions of different B − c decays, or are normalised to the branching fraction of the decay of a lighter B meson (usually B − ). In the latter case the measured quantity is the absolute or relative B − c branching fraction multiplied by the ratio of cross-sections (or, equivalently, production fractions) of the B − c and the lighter B meson. It should be noted that the ratio of cross-sections for different b hadron species can depend on production environment, and on the fiducial region accessed by each experiment. While this has been studied for certain b hadron species (see Sec. 3.1), there is currently little published data that would allow to investigate the effect for B − c mesons. Therefore, ...