In practice the asymmetry, which is defined based on the angular distribution of the final states in scattering or decay processes, can be utilized to scrutinize underlying dynamics in and/or beyond the standard model (BSM). As one of the possible BSM physics which might be discovered early at the LHC, extra neutral gauge bosons Z ′ s are theoretical well motivated. Once Z ′ s are discovered at the LHC, it is crucial to discriminate different Z ′ s in various BSM. In principle such task can be accomplished by measuring the angular distribution of the final states which are produced via Z ′ -mediated processes. In the real data analysis, asymmetry is always adopted. In literature several asymmetries have been proposed at the LHC. Based on these works, we stepped further on to study how to optimize the asymmetries in the left-right model and the sequential standard model, as the examples of BSM. In this paper, we examined four kinds of asymmetries, namely rapidity-dependent forward-backward asymmetry, one-side forward-backward asymmetry, central charge asymmetry and edge charge asymmetry (see text for details), with ℓ + ℓ − (ℓ = e, µ), bb and tt as the final states. In the calculations with bb and tt final states, the QCD-induced higher order contributions to the asymmetric cross section were also included. For each kind of final states, we estimated the four kinds of asymmetries and especially the optimal cut usually associated with the definition of the asymmetry. Our numerical results indicated that the capacity to discriminate Z ′ models can be improved by imposing the optimal cuts.

Varying the Standard Model (SM) fermion Yukawa couplings universally by a generic positive scale factor (F Y u ), we study the phenomenological fit to the current available experimental results for the Higgs boson search at hadron colliders. We point out that the Higgs production cross section and its decay branching ratio to γγ can be varied oppositely by F Y u to make their product almost invariant. Thus, our scenario and the SM Higgs are indistinguishable in the inclusive H → γγ channel. The current measurements on direct Yukawa coupling strength in the H → bb/τ τ channel are not precise enough to fix the scale factor F Y u . The most promising is the vector-boson-fusion channel in which the CMS has already observed possible suppression effect on the Yukawa couplings. Further more, the global χ 2 fit of the experimental data can get the optimal value by introducing a suppression factor F Y u ∼ 1/2 on the SM Yukawa couplings.