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D0 and CDF collaborations at the Fermilab Tevatron have searched for non-standard-model single top-quark production and set upper limits on the anomalous top quark flavor-changing neutral current (FCNC) couplings κ g tc /Λ and κ g tu /Λ using the measurement of total cross section calculated at the next-to-leading order (NLO) in QCD. In this Letter, we report on the effect of anomalous FCNC couplings to various decay branching ratios of the top quark, calculated at the NLO. This result is not only mandatory for a consistent treatment of both the top quark production and decay via FCNC couplings by D0 and CDF at the Tevatron but is also important for the study of ATLAS and CMS sensitivity to these anomalous couplings at the CERN LHC. We find that the NLO corrections to the partial decay widths of the three decay channels t → q + g, t → q + γ and t → q + Z are at the order of 10% in magnitude and modify their branching ratios by about 20%, 0.4% and 2%, respectively, as compared to their leading order predictions. The top quark FCNC processes t → q + V (V = g, γ, Z) have tiny branching ratios in the standard model (SM) and are probably unmeasurable at the CERN Large Hadron Collider (LHC) and future colliders. On the other hand, any positive signal of these rare decay events would definitely imply some new physics beyond the SM. As the LHC will produce abundant top quark events (about 10 8 per year), even in the initial low luminosity run (∼ 10 fb −1 /year) 8 × 10 6 top quark pairs and 3 × 10 6 single top quark will be produced yearly, one may anticipate to discover first hint of new physics by observing anomalous couplings in the top quark sector.Recently, from their measurements of the total cross sections both D0 . These results show that studying top quark FCNC couplings will provide a good probe to new physics beyond the SM. Although there are many discussions in the literature on rare decay processes involving model-independent top quark FCNC couplings [6,7,8,9,10,11,12], most of them were based on LO calculations. However, especially for t → q + g, due to the large uncertainties from the renormalization scale dependence in its LO prediction through the strong coupling constant α s , it is necessary to improve the theoretical prediction to NLO in order to match the expected experimental accuracy at the LHC.In this Letter, we present the analytic results of the NLO QCD corrections to the partial decay widths and decay branching ratios of top quark via anomalous FCNC couplings for the three processes t → q + g, t → q + γ and t → q + Z, which are the most commonly studied decay channels by the experimentalists at the Tevatron and the LHC. New physics effects involved in top quark FCNC processes can be incorporated in a model-independent way into an effective Lagrangian which includes the dimension-5 operators as listed below [10]where Λ is the new physics scale, θ W is the Weinberg angle, and T a are the Gell-Mann matrices. κ V tq with V = g, γ and Z are normalized to be real and positive, while f V tq and h V tq...

In this paper detailed calculations of the complete O(α s ) corrections to top quark decay widths Γ(t → q + V ) are presented (V = g, γ, Z). Besides describing in detail the calculations in our previous paper (arXiv:0810.3889), we also include the mixing effects of the Flavor-Changing NeutralCurrent (FCNC) operators for t → q + γ and t → q + Z, which were not considered in our previous paper. The results for t → q + g are the same as in our previous paper. But the mixing effects can either be large or small, and increase or decrease the branching ratios for t → q + γ and t → q + Z,

At the large transverse momentum region, the production of heavy-heavy bound-states such as charmonium, bottomonium, andbc mesons in high energy e + e − and hadronic collisions is dominated by parton fragmentation. We calculate the heavy quark fragmentation functions into the D-wave quarkonium andbc mesons to leading order in the strong coupling constant and in the non-relativistic expansion. In thebc meson case, one set of its D-wave states is expected to lie below the open flavor threshold. The total fragmentation probability for ab antiquark to split into the D-wavebc mesons is about * Internet address:

At hadron colliders the dominant production mechanism of (bc) mesons with large transverse momentum is due to parton fragmentation. We compute the rates and transverse momentum spectra for production of S-wave and P-wave (bc) mesons at the Tevatron via the direct fragmentation of the bottom antiquark as well as the AltarelliParisi induced gluon fragmentation. Since all the radially and orbitally excited (bc) mesons below the BD flavor threshold will cascade into the pseudoscalar ground state B c through electromagnetic and/or hadronic transitions, they all contribute to the inclusive production of B c . The contributions of the excited S-wave and P-wave states to the inclusive production of B c are 58 and 23%, respectively, and hence significant.