High-transverse-momentum leptons fromBmesons: Their characteristics and uses

A method for identifying bottom-quark production in $e^{+}{e}^{-}$ annihilation reactions at energies above threshold (but below the top-quark threshold) is proposed. The main ingredient of this method is the high-$k_{\perp }$ lepton resulting from bottom-quark decays, where $k_{\perp }$ is the transverse momentum with respect to the jet axis. The kinematic nature of this method makes it insensitive to many uncertainties, such as jet-axis misidentification, primordial transverse momentum of the heavy mesons, gluonic corrections, etc., as verified by means of a detailed Monte Carlo calculation. The characteristics of the spectra enable one to determine the quark jet (vs the antiquark jet) direction, and the $b$-quark fragmentation function. We recommend and justify the use of thrust in our analysis. We discuss several applications, especially the discrimination of quark fragmentation functions.