Paper detail

The effects of a family non-universal Z-prime boson on B--->pipi decays

Motivated by the measured large branching ratio of $\bar{B}^{0}\toπ^0π^0$ (the so-called "$ππ$" puzzle), we investigate the effects of a family non-universal $Z^{\prime}$ model on the tree-dominated $B\toππ$ decays. We find that the $Z^{\prime}$ coupling parameter $ζ_{d}^{LR}\sim0.05$ with a nontrivial new weak phase $ϕ_d^L\sim-50^{\circ}$, which is relevant to the $Z^{\prime}$ contributions to the QCD penguin sector $\triangle C_5$, is needed to reconcile the observed discrepancy. Combined with the recent fitting results from $B\toπK$, $πK^{\ast}$ and $ρK$ decays, the $Z^{\prime}$ parameter spaces are severely reduced but still not excluded entirely, implying that both the "$ππ$" and "$πK$" puzzles could be accommodated simultaneously within such a family non-universal $Z^{\prime}$ model.