We study model-independently the implications of nonstandard scalar and pseudoscalar interactions for the decays b→s␥, b→sg, b→sᐉ ϩ ᐉ Ϫ (ᐉϭe,) and B s → ϩ Ϫ . We find sizable renormalization effects from scalar and pseudoscalar four-quark operators in the radiative decays and at O(␣ s ) in hadronic b decays. Constraints on the Wilson coefficients of an extended operator basis are worked out. Further, the ratios R H ϭB(B→H ϩ Ϫ )/B(B→He ϩ e Ϫ ), for HϭK ( * ) ,X s , and their correlations with the B s → ϩ Ϫ decay are investigated. We show that the standard model prediction for these ratios defined with the same cut on the dilepton mass for electron and muon modes, R H ϭ1ϩO(m 2 /m b 2 ), has a much smaller theoretical uncertainty (Շ1%) than the one for the individual branching fractions. The present experimental limit R K р1.2 puts constraints on scalar and pseudoscalar couplings, which are similar to the ones from current data on B(B s → ϩ Ϫ ). We find that new physics corrections to R K* and R X s can reach 13% and 10%, respectively. 1 Our definition of O S, P is different from that of Refs. ͓2-4͔ ͑i.e., without the factor of m b ) in order for C S, P to be dimensionless. As a consequence, the scalar and pseudoscalar operators have a nonvanishing anomalous dimension.

We perform an analysis of the K * polarization states in the exclusive B meson decay B 0 → K * 0 (→ K − π + )l + l − (l = e, µ, τ ) in the low dilepton mass region, where the final vector meson has a large energy. Working in the transversity basis, we study various observables that involve the K * spin amplitudes A ⊥ , A , A 0 by exploiting the heavyto-light form factor relations in the heavy quark and large-E K * limit. We find that at leading order in 1/m b and α s the form-factor dependence of the asymmetries that involve transversely polarized K * completely drops out. At next-to-leading logarithmic order, including factorizable and non-factorizable corrections, the theoretical errors for the transverse asymmetries turn out to be small in the standard model (SM). Integrating over the lower part of the dimuon mass region, and varying the theoretical input parameters, the SM predicts A (1) T = 0.9986 ± 0.0002 and A(2) T = −0.043 ± 0.003. In addition, the longitudinal and transverse polarization fractions are found to be (69 ± 3)% and (31 ± 3)% respectively, so that Γ L /Γ T = 2.23 ± 0.31. Beyond the SM, we focus on new physics that mainly gives sizable contributions to the coefficients C eff(′) 7 of the electromagnetic dipole operators. Taking into account experimental data on rare B decays, we find large effects of new physics in the transverse asymmetries. Furthermore, we show that a measurement of longitudinal and transverse polarization fractions will provide complementary information on physics beyond the SM. PACS number(s): 13.20.He, 13.25.Hw

We develop an understanding of the anomalous metal state of the parent compounds of recently discovered iron-based superconductors starting from a strong-coupling viewpoint, including orbital degrees of freedom. On the basis of an intermediate-spin (S =1) state for the Fe2+ ions, we derive a Kugel-Khomskii spin-orbital Hamiltonian for the active t2g orbitals. It turns out to be a highly complex model with frustrated spin and orbital interactions. We compute its classical phase diagrams and provide an understanding for the stability of the various phases by investigating its spin-only and orbital-only limits. The experimentally observed spinstripe state is found to be stable over a wide regime of physical parameters and can be accompanied by three different types of orbital orders. Of these the orbital-ferro and orbital-stripe orders are particularly interesting since they break the in-plane lattice symmetry-a robust feature of the undoped compounds. We compute the magnetic excitation spectra for the effective spin Hamiltonian, observing a strong reduction in the ordered moment, and point out that the proposed orbital ordering pattern can be measured in resonant x-ray diffraction.

The effective Hamiltonian for the decay b → s l + l − predicts a characteristic polarization for the final state lepton, which can serve as an important test of the underlying theory. The lepton polarization has, in addition to a longitudinal component P L , two orthogonal components P T and P N , lying in and perpendicular to the decay plane which are proportional to m l /m b , and therefore significant for the τ + τ − channel.The normal polarization component P N is a T -odd effect connected with the nonhermiticity of the effective Hamiltonian, arising mainly from cc intermediate states. We calculate all three polarization components for the decay B → X s τ + τ − as a function of the lepton pair mass, and find average values P L τ = −0.37, P T τ = −0.63, P N τ = 0.03. By comparison, the µ − polarization is P L µ = −0.77, P T µ = P N µ ≈ 0.

We report on a calculation of Higgs-boson contributions to the decays B s → l + l − andB → Kl + l − (l = e, µ) which are governed by the effective Hamiltonian describing b → sl + l − . Compact formulae for the Wilson coefficients are provided in the context of the type-II two-Higgs-doublet model (2HDM) and supersymmetry (SUSY) with minimal flavour violation, focusing on the case of large tan β. We derive, in a model-independent way, constraints on Higgs-boson-mediated interactions, using present experimental results on rare B decays including b → sγ,B s → µ + µ − , andB → K ( * ) µ + µ − . In particular, we assess the impact of possible scalar and pseudoscalar interactions transcending the standard model (SM) on the branching ratio ofB s → µ + µ − and the forward-backward (FB) asymmetry of µ − inB → Kµ + µ − decay. The average FB asymmetry, which is unobservably small within the SM, and therefore a potentially valuable tool to search for new physics, is predicted to be no greater than 4% for a nominal branching ratio of about 6 × 10 −7 . Moreover, striking effects on the decay spectrum ofB → Kµ + µ − are already ruled out by experimental data on theB s → µ + µ − branching fraction. In addition, we study the constraints on the parameter space of the 2HDM and SUSY with minimal flavour violation. While the type-II 2HDM does not give any sizable contributions to the above decay modes, we find that SUSY contributions obeying the constraint on b → sγ can significantly affect the branching ratio ofB s → µ + µ − . We also comment on previous calculations *