Charm-Quark Production in Deep-Inelastic Neutrino Scattering at Next-to-Next-to-Leading Order in QCD.

We present a fully differential next-to-next-to-leading order calculation of charm-quark production in charged-current deep-inelastic scattering, with full charm-quark mass dependence. The next-to-next-to-leading order corrections in perturbative quantum chromodynamics are found to be comparable in size to the next-to-leading order corrections in certain kinematic regions. We compare our predictions with data on dimuon production in (anti)neutrino scattering from a heavy nucleus. Our results can be used to improve the extraction of the parton distribution function of a strange quark in the nucleon.

Transverse-momentum resummation for top-quark pairs at hadron colliders.

We develop a framework for a systematic resummation of the transverse momentum distribution of top-quark pairs produced at hadron colliders based on effective field theory. Compared to Drell-Yan and Higgs production, a novel soft function matrix is required to account for the soft gluon emissions from the final states. We calculate this soft function at the next-to-leading order, and perform the resummation at the next-to-next-to-leading logarithmic accuracy. We compare our results with parton shower programs and with the experimental data at the Tevatron and the LHC. We also discuss the implications for the top quark charge asymmetry.

Top-quark decay at next-to-next-to-leading order in QCD.

We present the complete calculation of the top-quark decay width at next-to-next-to-leading order in QCD, including next-to-leading electroweak corrections as well as finite bottom quark mass and W boson width effects. In particular, we also show the first results of the fully differential decay rates for the top-quark semileptonic decay t → W(+)(l(+)ν)b at next-to-next-to-leading order in QCD. Our method is based on the understanding of the invariant mass distribution of the final-state jet in the singular limit from effective field theory. Our result can be used to study arbitrary infrared-safe observables of top-quark decay with the highest perturbative accuracy.

Searching for anomalous top quark production at the early LHC.

We present a detailed study of the anomalous top quark production with subsequent decay at the LHC induced by model-independent flavor-changing neutral-current couplings, incorporating the complete next-to-leading order QCD effects. Our results show that, taking into account the current limits from the Tevatron, the LHC with √s=7 TeV may discover the anomalous coupling at 5σ level for a very low integrated luminosity of 61 pb⁻¹. The discovery potentials for the anomalous couplings at the LHC are examined in detail. We also discuss the possibility of using the charge ratio to distinguish the tug and tcg couplings.

Top quark forward-backward asymmetry and same-sign top quark pairs.

The top quark forward-backward asymmetry measured at the Tevatron collider shows a large deviation from standard model expectations. Among possible interpretations, a nonuniversal Z' model is of particular interest as it naturally predicts a top quark in the forward region of large rapidity. To reproduce the size of the asymmetry, the couplings of the Z' to standard model quarks must be large, inevitably leading to copious production of same-sign top quark pairs at the energies of the Large Hadron Collider (LHC). We explore the discovery potential for tt and ttj production in early LHC experiments at 7-8 TeV and conclude that if no tt signal is observed with 1 fb⁻¹ of integrated luminosity, then a nonuniversal Z' alone cannot explain the Tevatron forward-backward asymmetry.

Next-to-leading QCD effect on the quark compositeness search at the LHC.

We present the exact next-to-leading order (NLO) QCD corrections to the dijet production induced by the quark contact interactions at the CERN Large Hadron Collider. We show that, as compared to the exact calculation, the scaled NLO QCD prediction adopted by the ATLAS Collaboration has overestimated the new physics effect on some direct observables by more than 30% and renders a higher limit on the quark compositeness scale. The destructive contribution from the exact NLO correction will also lower the compositeness scale limit set by the CMS Collaboration.

Next-to-leading-order QCD corrections to the top-quark decay via model-independent flavor-changing neutral-current couplings.

D0 and CDF collaborations at the Fermilab Tevatron have searched for nonstandard-model single top-quark production and have set upper limits on the anomalous top-quark flavor-changing neutral-current (FCNC) couplings kappatcg/Lambda and kappatug/Lambda using the measurement of the 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.

[Identification of differential expression ESTs in pig muscle tissue by DHPLC].

The differential expression ESTs in muscle tissue of Large Yorkshire pig and Lantang pig, one of the local pig breeds in Guangdong province, were identified with DHPLC system and graphic analysis software LabWork4.0, and both methods verified the true differential display bands. The results showed that DHPLC can quickly and accurately detect differential expression mRNA profiles of different tissues, and can be widely used to study mRNA expression, differential expression of different animal tissues under variant environments.