Article

# B→K 1 ℓ + ℓ − decays in a family non-universal Z′ model

European Physical Journal C (Impact Factor: 5.08). 07/2011; 71(10). DOI: 10.1140/epjc/s10052-011-1775-2

Source: arXiv

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**ABSTRACT:**Within the QCD factorization formalism, we study the possible impacts of the nonuniversal $Z^\prime$ model, which provides a flavor-changing neutral current at the tree level, on rare decays $B \to K_0^*\pi$. Under two different scenarios (S1 and S2) for identifying the scalar meson $K_0^*(1430)$, the branching ratios, CP asymmetries, and isospin asymmetries are calculated in both the standard model (SM) and the family nonuniversal $Z^\prime$ model. We find that the branching ratios and CP asymmetries are sensitive to weak annihilation. In the SM, with $\rho_A=1$ and $\phi_A\in[-30^\circ, 30^\circ]$, the branching ratios of S1 (S2) are smaller (larger) than the experimental data. Adding the contribution of the $Z^\prime$ boson in two different cases (Case-I and Case-II), for S1, the branching ratios are still far away from experiment. For S2, in Case-II, the branching ratios become smaller and can accommodate the data; in Case-I, although the center values are enhanced, they can also explain the data with large uncertainties. Similar conclusions are also reached for CP asymmetries. Our results indicate that S2 is more favored than S1, even after considering new physics effects. Moreover, if there exists a nonuniversal $Z^\prime$ boson, Case-II is preferred. All results can be tested in the LHC-b experiment and forthcoming super-B factory. - [Show abstract] [Hide abstract]

**ABSTRACT:**Motivated by the very recent measurements performed at the LHCb and the Tevatron of the $ B_s^0 - \overline B_s^0 $ mixing, in this paper we revisit it in a family non-universal Z′ model, to check if a simultaneous explanation for all the mixing observables, especially for the like-sign dimuon charge asymmetry observed by the D0 collaboration, could be made in such a specific model. In the first scenario where the Z′ boson contributes only to the off-diagonal element $ M_{{{12}}}^s $ , it is found that, once the combined constraints from ΔM s , ϕ s and ΔΓs are imposed, the model could not explain the measured flavour-specific CP asymmetry $ a_{{fs}}^s $ , at least within its 1σ ranges. In the second scenario where the NP contributes also to the absorptive part $ \Gamma_{{{12}}}^s $ via tree-level Z′-induced b → $ c\overline c s $ operators, we find that, with the constraints from ΔM s , ϕ s and the indirect CP asymmetry in $ {{\overline B }_d} $ → J/ψK S taken into account, the present measured 1σ experimental ranges for $ a_{{fs}}^s $ could not be reproduced too. Thus, such a specific Z′ model with our specific assumptions could not simultaneously reconcile all the present data on $ B_s^0 - \overline B_s^0 $ mixing. Future improved measurements from the LHCb and the proposed superB experiments, especially of the flavour-specific CP asymmetries, are expected to shed light on the issue. - [Show abstract] [Hide abstract]

**ABSTRACT:**In this work, within the QCD factorization approach, we investigate the branching fractions and CP asymmetries of decays $B \to K_0^*(1430)\rho$ and $B \to K_0^*(1430)\phi$ under two different scenarios both in the standard model and the family nonuniversal $Z^\prime$ model. We find that the annihilation terms play crucial roles in these decays and lead to the main uncertainties. For decays $B^- \to \bar K_0^{*-} (1430)\rho^0 (\omega)$, the new $Z^\prime$ boson could change branching fractions remarkably. However, for other decays, its contribution might be clouded by large uncertainties from annihilations. Unfortunately, neither the standard model nor $Z^\prime$ model can reproduce all experimental data under one certain scenario. We also noted that the CP asymmetries of $B^-\to \bar K_0^{*-}(1430) \rho^0 (\omega)$ could be used to identify the$K_0^*(1430)$ meson and search for the new physics contribution.