Measurements of the Angular Distributions in the Decays $B\to K^{(*)}{\mu }^{+}{\mu }^{-}$ at CDF

We report an indirect search for nonstandard model physics using the flavor-changing neutral current decays $B\to K^{(*)}{\mu }^{+}{\mu }^{-}$. We reconstruct the decays and measure their angular distributions, as a function of $q^2=M_{\mu \mu }^2{c}^2$, where $M_{\mu \mu }$ is the dimuon mass, in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ using a data sample corresponding to an integrated luminosity of $6.8{\mathrm{fb}}^{-1}$. The transverse polarization asymmetry $A_T^{(2)}$ and the time-reversal-odd charge-and-parity asymmetry $A_{\mathrm{im}}$ are measured for the first time, together with the $K^{*}$ longitudinal polarization fraction $F_L$ and the muon forward-backward asymmetry $A_{\mathrm{FB}}$ for the decays $B^0\to K^{*0}{\mu }^{+}{\mu }^{-}$ and $B^{+}\to K^{*+}{\mu }^{+}{\mu }^{-}$. The $B\to K^{*}{\mu }^{+}{\mu }^{-}$ forward-backward asymmetry in the most sensitive kinematic regime, $1\le q^2<6{\mathrm{GeV}}^2/c^2$, is measured to be $A_{\mathrm{FB}}={0.29}_{-0.23}^{+0.20}(\mathrm{stat})\pm 0.07(\mathrm{syst})$, the most precise result to date. No deviations from the standard model predictions are observed.

Figure 1

Invariant mass of $B^0\to K^{*0}{\mu }^{+}{\mu }^{-}$ (left) and $B^{+}\to K^{*+}{\mu }^{+}{\mu }^{-}$ (right), with fit results overlaid.

Figure 2

Measurements of forward-backward asymmetry $A_{\mathrm{FB}}$ in the decay (a) $B^0\to K^{*0}{\mu }^{+}{\mu }^{-}$ and (b) $B^{+}\to K^{+}{\mu }^{+}{\mu }^{-}$ as a function of dimuon mass squared $q^2$. Points are the fit results from the data. The solid curves are the SM expectation [24]. The dotted curve is the $C_7=-C_7^{\mathrm{SM}}$ expectation suggested by some BSM models. Hatched regions are excluded resonant (charmonium) decay regions.

Figure 3

Measurements of (a) longitudinal $K^{*}$ polarization fraction $F_L$, (b) forward-backward asymmetry $A_{\mathrm{FB}}$, (c) transverse polarization asymmetry $A_T^{(2)}$, and (d) $T$-odd $CP$ asymmetry $A_{\mathrm{im}}$ in the combined decay mode $B\to K^{*}{\mu }^{+}{\mu }^{-}$.