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Register a new userThe Effects of Non-Local Interactions in Rare B Decays, B -> X_s l^+l^-
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S. Fukae Hiroshiman University
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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.
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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.
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.
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 $Bto K^{*}e^{pm}mu^{mp}$.
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%.
In the SUSY SO(10) GUT context, we study the exclusive processes $B to K^{(*)} l^+l^-(l=mu,tau)$. Using the Wilson coefficients of relevant operators including the new operators $Q_{1,2}^{(prime)}$ which are induced by neutral Higgs boson (NHB) penguins, we evaluate some possible observables associated with these processes like, the invariant mass spectrum (IMS), lepton pair forward backward asymmetry (FBA), lepton polarization asymmetries etc. In this model the contributions from Wilson coefficients $C_{Q_{1,2}}^prime$, among new contributions, are dominant. Our results show that the NHB effects are sensitive to the FBA, $dL/dhat{s}$, and $dT/dhat{s}$ of $B to K^{(*)} tau^+ tau^-$ decay, which are expected to be measured in B factories, and the average of the normal polarization $dN/dhat{s}$ can reach several percent for $B to K mu^+ mu^-$ and it is 0.05 or so for $Bto K tau^+tau^-$, which could be measured in the future super B factories and provide a useful information to probe new physics and discriminate different models.
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