, 2010:52
Date: 13 Apr 2010

BK* + , Kℓ + decays in a family non-universal Z′ model

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Motivated by the observed forward-backward asymmetry in BK* + decay, we perform a detailed analysis of this decay mode within a family non-universal Z′ model. With the related coupling \( Z' - \bar sb \) constrained by \( {B_s} - {\bar B_s} \) mixing, BπK and BX s μ + μ decays, we look for further constraint on the couplings Z′ − μ + μ from \( {A_{FB}}{\left( {B \to {K^*}{\mu^{+} }{\mu^{-} }} \right)_{0{\text{Ge}}{{\text{V}}^2} \leqslant {q^2} \leqslant 2{\text{Ge}}{{\text{V}}^2}}} \) and get numerically \( B_{\mu \mu }^{L,R} \sim \mathcal{O}\left( {{{10}^{ - 2}}} \right) \) . Moreover, we find that the relations \( B_{\mu \mu }^L < B_{\mu \mu }^R \) and \( B_{\mu \mu }^L + B_{\mu \mu }^R < 0 \) , with a small negative phase ϕ s L , are crucial to moderate the discrepancy for A FB (BK*μ + μ ) between the SM prediction and the experimental data. Numerically, comparing with the SM prediction, we find that \( {A_{FB}}{\left( {B \to {K^*}{\mu^{+} }{\mu^{-} }} \right)_{0{\text{Ge}}{{\text{V}}^2} \leqslant {q^2} \leqslant 2{\text{Ge}}{{\text{V}}^2}}} \) could be enhanced about 80% and 50% by Z′ contribution at most in scenarios S1 and S2, corresponding to the two fitted results of ϕ s by UTfit collaboration, respectively. However, the results are still about 1.5σ lower than the experimental measurement.

ArXiv ePrint: 1002.2758