Bernd A. Kniehl, Gustav Kramer, Seyed M. Moosavi Nejad
We study the scaled-energy (x_B) distribution of bottom-flavored hadrons (B) inclusively produced in top-quark decays at next-to-leading order (NLO) in the general-mass variable-flavor-number scheme endowed with realistic, nonperturbative fragmentation functions that are obtained through a global fit to e^+e^- data from CERN LEP1 and SLAC SLC exploiting their universality and scaling violations. Specifically, we study the effects of gluon fragmentation and finite bottom-quark and B-hadron masses. We find the NLO corrections to be significant. Gluon fragmentation leads to an appreciable reduction in the partial decay width at low values of x_B. Hadron masses are responsible for the low-x_B threshold, while the bottom-quark mass is of minor importance. Neglecting the latter, we also study the doubly differential distribution d^2Gamma/[dx_B dcos(theta)] of the partial width of the decay t -> b W^+ -> B l^+ nu_l + X, where theta is the decay angle of the charged lepton in the W-boson rest frame.
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http://arxiv.org/abs/1205.2528
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