Standard modelCPviolation in polarizedb→dl+l−

Abstract

In the standard model, we study CP violating rate asymmetries in the decay $\stackrel{\ensuremath{\rightarrow}}{b}{\mathrm{dl}}^{+}{l}^{\ensuremath{-}}$ when one of the leptons is polarized. We find an asymmetry of (5--15)% in the polarized decay spectrum which is comparable to the known results for the unpolarized case. In the kinematic region separating the $\ensuremath{\rho}\ensuremath{-}\ensuremath{\omega}$ and $c\overline{c}$ resonances, which is also theoretically cleanest, the polarized contribution to the asymmetry is larger than the unpolarized results. In order to observe a $3\ensuremath{\sigma}$ signal for direct CP violation in the polarized spectrum, assuming 100% efficiency, about ${10}^{10}$ $B\overline{B}$ pairs are required at a B factory. Our results indicate an asymmetric contribution from the individual polarization states to the unpolarized CP asymmetry. Taking advantage of this, one can attribute any new physics to be most sensitive to a specific polarization state.