Averages of b-hadron, c-hadron, and tau-lepton Properties
The Heavy Flavor Averaging Group, D. Asner, Sw. Banerjee, R. Bernhard, S. Blyth, A. Bozek, C. Bozzi, D. G. Cassel, G. Cavoto, G. Cibinetto, J. Coleman, W. Dungel, T. J. Gershon, L. Gibbons, B. Golob, R. Harr, K. Hayasaka, H. Hayashii, C. -J. Lin, D. Lopes Pegna, R. Louvot, A. Lusiani, V. Luth, B. Meadows, S. Nishida, D. Pedrini, M. Purohit, M. Rama, M. Roney, O. Schneider, C. Schwanda, A. J. Schwartz, B. Shwartz, J. G. Smith, R. Tesarek, D. Tonelli, K. Trabelsi, P. Urquijo, R. Van Kooten
TL;DR
HFAG aggregates world-average properties for b-hadron, c-hadron, and tau properties using results available through 2009 (with 2010 updates), applying input rescalings to a common basis and explicit correlation handling. The tau section reports a mass average, branching-fraction averages and a global fit, tests of charged-current lepton universality, determinations of |V_us|, and searches for lepton-flavor violation, all derived from a large corpus of measurements. The results show lepton universality in tau decays is consistent with the SM at the permille-to-percent level, while several tau-derived extractions of |V_us| lie about 3–4 sigma below CKM unitarity. The methodological framework of global fits and correlation handling enhances precision in tau physics and provides critical inputs for tests of the SM and CKM structure.
Abstract
This article reports world averages for measurements of b-hadron, c-hadron, and tau-lepton properties obtained by the Heavy Flavor Averaging Group (HFAG) using results available at least through the end of 2009. Some of the world averages presented use data available through the spring of 2010. 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, and parameters of semileptonic decays.