LEPTON (HADRON) FORWARD-BACKWARD ASYMMETRY IN ${{\mathit B}}$ $\rightarrow$ ${{\mathit K}^{(*)}}{{\mathit \ell}^{+}}{{\mathit \ell}^{-}}$ (${{\mathit B}}$ $\rightarrow$ ${{\mathit K}}$ $/$ ${{\mathit \pi}}{{\mathit h}^{+}}{{\mathit h}^{-}}$) DECAY

The forward-backward angular asymmetry of the lepton pair in ${{\mathit B}}$ $\rightarrow$ ${{\mathit K}^{(*)}}{{\mathit \ell}^{+}}{{\mathit \ell}^{-}}$ (${{\mathit B}}$ $\rightarrow$ ${{\mathit K}}$ $/$ ${{\mathit \pi}}{{\mathit h}^{+}}{{\mathit h}^{-}}$) decay is defined as
A$_{FB}$(s) = ${ N(cos\theta >0) − N(cos\theta <0)\over N(cos\theta >0) + N(cos\theta <0) }$,
where s=q${}^{2}/{{\mathit m}^{2}}_{{{\mathit B}}}$, and $\theta $ is the angle of the ${{\mathit \ell}^{-}}$ (${{\mathit h}^{-}}$) with respect to the flight direction of the ${{\mathit B}}$ meson, measured in the dilepton (dihadron) rest frame. In addition, the fraction of longitudinal polarization F$_{L}$ of the ${{\mathit K}^{*}}$ and F$_{S}$, the relative contribution from scalar and pseudoscalar penguin amplitudes in ${{\mathit B}}$ $\rightarrow$ ${{\mathit K}}{{\mathit \ell}^{+}}{{\mathit \ell}^{-}}$, can be measured from the angular distribution of its decay products.

A$_{FB}({{\mathit B}}$ $\rightarrow$ ${{\mathit K}}{{\mathit \ell}^{+}}{{\mathit \ell}^{-}}$) (q${}^{2}$ $>$ 0.1 GeV${}^{2}$/c${}^{4}$)

INSPIRE   JSON  (beta) PDGID:
S049FB2
VALUE DOCUMENT ID TECN  COMMENT
$\bf{ 0.11 \pm0.12}$ OUR AVERAGE
$0.15$ ${}^{+0.21}_{-0.23}$ $\pm0.08$ 1
AUBERT,B
2006J
BABR ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \Upsilon}{(4S)}}$
$0.10$ $\pm0.14$ $\pm0.01$ 2
ISHIKAWA
2006
BELL ${{\mathit e}^{+}}$ ${{\mathit e}^{-}}$ $\rightarrow$ ${{\mathit \Upsilon}{(4S)}}$
1  Results with different q${}^{2}$ cuts are also reported.
2  Using an unbinned max. likelihood fits to the $\mathit M_{bc}$ distribution in five q${}^{2}$ bins for cos $~\theta >$0 and cos $~\theta <$0.
References