Probing thess content of the η and η ′ mesons and considering mixing between these states as well as gluonic contributions, the form factors responsible for semileptonic D s → (η, η ′ )lν transitions are calculated via light cone QCD sum rules. Corresponding branching fractions and their ratio for different mixing angles are also obtained. Our results are in a good consistency with experimental data as well as predictions of other nonperturbative approaches.

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Using the factorization approach and considering the contributions of the currentcurrent, QCD penguin and electroweak penguin operators at the leading approximation, the decay amplitudes and decay widths of B q → D q (D * q )P and B q → D q (D * q )V transitions, where q = u, d, s and P and V are pseudoscalar and vector mesons, are calculated in terms of the transition form factors of the B q → D q and B q → D * q . Having computed those form factors in three-point QCD sum rules, the branching fraction for these decays are also evaluated. A comparison of our results with the predictions of the perturbative QCD as well as the existing experimental data is presented. *

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In this paper the polarized and unpolarized lepton pair forward-backward asymmetries and their averages inB →K 1 ð1270Þℓ þ ℓ − andB →K Ã ℓ þ ℓ − decays using model III of the two Higgs doublet model are investigated. The obtained results of both decay modes are compared to each other and to those of SM. In addition, by obtaining the minimum required number of events for detecting each asymmetry and comparing them with the number of produced BB pairs at the LHC or supposed to be produced at the Super-LHC, we present a comprehensive discussion regarding the polarized and unpolarized forwardbackward asymmetries ofB →K 1 ð1270Þℓ þ ℓ − andB →K Ã ℓ þ ℓ − decays. We discover that the study of these asymmetries and the corresponding averages inB →K 1 ð1270Þℓ þ ℓ − andB →K Ã ℓ þ ℓ − decays can provide good signals for probing new physics beyond the SM in the future B-physics experiments.

This study investigates the influence of the fourth generation quarks on the double lepton polarizations in the B → Kℓ + ℓ − decay. Taking |V t ′ s V t ′ b | ∼ {0.01 − 0.03} with phase about 100 • , which is consistent with the b → sℓ + ℓ − rate and the B s mixing parameter ∆m Bs , we have found out that the double lepton(µ, τ ) polarizations are quite sensitive to the existence of fourth generation. It can serve as an efficient tool to search for new physics effects, precisely, to indirect search for the fourth generation quarks(t ′ , b ′ ).