We study inclusive production of doubly heavy baryon at a collider and at hadron colliders through fragmentation. We study the production by factorizing nonpertubative- and perturbative effects. In our approach the production can be thought as a two-step process: A pair of heavy quarks can be produced perturbatively and then the pair is transformed into the baryon. The transformation is nonperturbative. Since a heavy quark moves with a small velocity in the baryon in its rest frame, we can use NRQCD to describe the transformation and perform a systematic expansion in the small velocity. At the leading order we find that the baryon can be formed from two states of the heavy-quark pair, one state is with the pair in 3S1 state and in color -3, another is with the pair in 1S0 state and in color 6. Two matrix elements are defined for the transformation from the two states, their perturbative coefficients in the contribution to the cross-section at a collider and to the function of heavy quark fragmentation are calculated. Our approach is different than previous approaches where only the pair in 3S1 state and in color -3 is taken into account. Numerical results for e+e− colliders at the two B-factories and for hadronic colliders LHC and Tevatron are given.

We present results for the differential distributions of jets from non-leptonic decays of polarized top quarks within the Standard Model, including QCD radiative corrections. Our work extends existing results which are only available for semileptonic top quark decays at the parton level. For t(↑) → b-jet +2 light jets we compute in particular the QCD-corrected top-spin analysing power of the b-quark jet and the least energetic light jet. The dependence of the results on the choice of the jet recombination scheme is found to be small. In addition we compute the spin analysing power of the thrust axis. Our results constitute a so far missing ingredient to analyse top quark production and subsequent non-leptonic decay at next-to-leading order in as, keeping the full information on the top quark polarization.

We have computed the cross section for tt production by gluon-gluon fusion at next-toleading order (NLO) in the QCD coupling, keeping the full dependence on the tt spins. Furthermore we have determined to the same order the spin dependent cross sections for the processes g+q(q)→tt+q(q). Together with our previous results [1] for q+q→tt(g) these results allow for predictions, at NLO QCD, of the hadronic production of tt pairs in a general spin configuration. As an application we have determined the degree of correlation of the t and t spins at NLO, using various spin quantisation axes.