Forward-backward asymmetry induced $CP$ asymmetry of $B^{\pm}\rightarrow \pi^{\pm}\pi^{+}\pi^{-}$

Abstract

$CP$ violation of the decay $B^{\pm}\rightarrow \pi^{\pm}\pi^{+}\pi^{-}$ in the $f_{0}(500)-\rho(770)^{0}$ interfering region is analyzed. The forward-backward asymmetries (FBAs) and the corresponding $CP$ asymmetries FB-$CP$As are particularly investigated. To isolate the $CP$V caused by the interference of different partial wave more cleanly, we also introduce the direct-$CP$V-subtracted FB-$CP$A. Based on the LHCb data, we extract the FBAs, FB-$CP$As, direct-$CP$V-subtracted FB-$CP$A, as well as the regional $CP$As with invariant mass of the $\pi^{+}\pi^{-}$ pair in the range 0.2 GeV/$c^{2}<\sqrt{s_{\text{low}}}<1.8$ GeV/$c^{2}$. It is found that the (direct-$CP$V-subtracted) FB-$CP$As are quite large in the $f_{0}(500)-\rho(770)^{0}$ interfering region, which confirms that the interference of the intermediate resonances $f_{0}(500)$ and $\rho(770)^{0}$ plays an important role for the $CP$ violation of the three-body decay channel $B^{\pm}\rightarrow \pi^{\pm}\pi^{+}\pi^{-}$.