Eur. Phys. J. C (2016) 76: 173
https://doi.org/10.1140/epjc/s10052-016-4017-9

Regular Article - Theoretical Physics

Hadron energy spectrum in polarized top-quark decays considering the effects of hadron and bottom quark masses

¹ Faculty of Physics, Yazd University, P.O. Box 89195-741, Yazd, Iran
² School of Particles and Accelerators, Institute for Research in Fundamental Sciences (IPM), P.O.Box 19395-5531, Tehran, Iran

^* e-mail: moosavi@ipm.ir
^** e-mail: mmoosavi@yazd.ac.ir

Received: 6 January 2016
Accepted: 14 March 2016
Published online: 29 March 2016

Abstract

We present the analytical expressions for the next-to-leading order corrections to the partial decay width , followed by , for nonzero b-quark mass () in the fixed-flavor-number scheme (FFNs). To make the predictions for the energy distribution of outgoing hadrons , as a function of the normalized -energy fraction , we apply the general-mass variable-flavor-number scheme (GM-VFNs) in a specific helicity coordinate system where the polarization of top quark is evaluated relative to the b-quark momentum. We also study the effects of gluon fragmentation and finite hadron mass on the hadron energy spectrum so that hadron masses are responsible for the low- threshold. In order to describe both the b-quark and the gluon hadronizations in top decays we apply realistic and nonperturbative fragmentation functions extracted through a global fit to the annihilation data from CERN LEP1 and SLAC SLC by relying on their universality and scaling violations.