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The B -> X_s l+ l- decay rate is known at the next-to-next-to-leading order in QCD. It is proportional to alpha_em (mu)^2 and has a +- 4% scale uncertainty before including the O(alpha_em log(M_W^2/m_b^2)) electromagnetic corrections. We evaluate these corrections and confirm the earlier findings of Bobeth et al. >. Furthermore, we complete the calculation of logarithmically enhanced electromagnetic effects by including also QED corrections to the matrix elements of four-fermion operators. Such corrections contain a collinear logarithm log(m_b^2/m_l^2) that survives integration over the low dilepton invariant mass region 1 GeV^2 < q^2 < 6 GeV^2 and enhances the integrated decay rate in this domain. For the low-q^2 integrated branching ratio in the muonic case, we find B (B -> X_s mu^+mu^-) = (1.59 +- 0.11) 10^(-6), where the error includes the parametric and perturbative uncertainties only. For B (B -> X_s e^+e^-), in the current BaBar and Belle setups, the logarithm of the lepton mass gets replaced by angular cut parameters and the integrated branching ratio for the electrons is expected to be close to that for the muons.
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The effects of non-local interactions in rare B decays, $Bsll$, are investigated. We show the correlation between the branching ratio and the forward-backward asymmetry via two coefficients of the non-local interactions. This will certainly help us find any deviations from the standard model through the non-local interactions.
The most general model-independent analysis of the rare $B$ decay, $Bsll$, is presented. There are ten independent local four-Fermi interactions which may contribute to this process. The branching ratio, the forward-backward asymmetry, and the double differential rate are written as functions of the Wilson coefficients of the ten operators. We also study the correlation between the branching ratio and the forward-backward asymmetry by changing each coefficient. This procedure tells us which types of operator contribute to the process, and it will be very useful to pin down new physics systematically, once we have the experimental data with high statistics and the deviation from the Standard Model is found.
We calculate O(alpha_s) two-loop virtual corrections to the differential decay width dGamma(B --> X_s l^+ l^-)/ds, where s is the invariant mass squared of the lepton pair. We also include those contributions from gluon bremsstrahlung which are needed to cancel infrared and collinear singularities present in the virtual corrections. Our calculation is restricted to the range 0.05 < s/m_b^2 < 0.25 where the effects from resonances are small. The new contributions drastically reduce the renormalization scale dependence of existing results for dGamma(B --> X_s l^+ l^-)/ds. For the corresponding branching ratio (restricted to the above s-range) the renormalization scale uncertainty gets reduced from +/- 13% to +/- 6.5%.
We investigate logarithmically enhanced electromagnetic corrections of all angular observables in inclusive B -> X_s l^+ l^-. We present analytical results, which are supplemented by a dedicated Monte Carlo study on the treatment of collinear photons in order to determine the size of the electromagnetic logarithms. We then give the Standard Model predictions of all observables, considering all available NNLO QCD, NLO QED and power corrections, and investigate their sensitivity to New Physics. Since the structure of the double differential decay rate is modified in the presence of QED corrections, we also propose new observables which vanish if only QCD corrections are taken into account. Moreover, we study the experimental sensitivity to these new observables at Belle II.
We present results from a search for the flavor-changing neutral current decays $Bto Kell^+ell^-$ and $Bto K^*ell^+ell^-$, where $ell^+ell^-$ is either an $e^+e^-$ or $mu^+mu^-$ pair. The data sample comprises $22.7times 10^6$ $Upsilon(4S)to Bbar B$ decays collected with the BABAR detector at the PEP-II $B$ Factory. We obtain the 90% C.L. upper limits ${mathcal B}(Bto Kell^+ell^-)< 0.50times 10^{-6}$ and ${mathcal B}(Bto K^*ell^+ell^-)<2.9times 10^{-6}$, close to Standard Model predictions for these branching fractions. We have also obtained limits on the lepton-family-violating decays $Bto Ke^{pm}mu^{mp}$ and $Bto K^{*}e^{pm}mu^{mp}$.
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