Search for direct $CP$ violation in charged charmless $B\to PV$ decays

Measurements of $CP$ asymmetry in charmless $B\to PV$ decays are presented, where $P$ and $V$ denote a pseudoscalar and a vector meson, respectively. Five different $B\to PV$ decays from four final states, $B^{\pm }\to {\pi }^{\pm }{\pi }^{+}{\pi }^{-}$, $B^{\pm }\to K^{\pm }{\pi }^{+}{\pi }^{-}$, $B^{\pm }\to K^{\pm }{K}^{+}{K}^{-}$ and $B^{\pm }\to {\pi }^{\pm }{K}^{+}{K}^{-}$ are analyzed. The measurements are based on a method that does not require full amplitude analyses, and are performed using proton-proton collision data at a center-of-mass energy of 13 TeV collected by LHCb between 2015 and 2018, corresponding to an integrated luminosity of $5.9{\mathrm{fb}}^{-1}$. In the ${\pi }^{+}{\pi }^{-}$ $P$-wave, in the region dominated by the $B^{\pm }\to \rho (770{)}^0{K}^{\pm }$ decay, a $CP$ asymmetry of $A_{CP}=+0.150\pm 0.019\pm 0.011$ is measured, where the first uncertainty is statistical and the second is systematic. This is the first observation of $CP$ violation in this process. For the other four decay channels, in regions dominated by the $B^{\pm }\to \rho (770{)}^0{\pi }^{\pm }$, $B^{\pm }\to \stackrel{(¯)}{K}{}^{*}(892{)}^0{\pi }^{\pm }$, $B^{\pm }\to \stackrel{(¯)}{K}{}^{*}(892{)}^0{K}^{\pm }$ and $B^{\pm }\to \varphi (1020)K^{\pm }$ decays, $CP$ asymmetries in the $P$-wave compatible with zero are measured.

Figure 1

Distribution of $s_{\perp }$ for $B^{+}$ and $B^{-}$ candidates and the corresponding quadratic fits for (a) $\rho (770{)}^0$ in $B^{\pm }\to {\pi }^{\pm }{\pi }^{+}{\pi }^{-}$, (b) $\rho (770{)}^0$ in $B^{\pm }\to K^{\pm }{\pi }^{+}{\pi }^{-}$, (c) $\stackrel{(¯)}{K}{}^{*}(892{)}^0$ in $B^{\pm }\to K^{\pm }{\pi }^{+}{\pi }^{-}$, (d) $\stackrel{(¯)}{K}{}^{*}(892{)}^0$ in $B^{\pm }\to {\pi }^{\pm }{K}^{+}{K}^{-}$, and (e) $\varphi (1020)$ in $B^{\pm }\to K^{\pm }{K}^{+}{K}^{-}$. In the symmetric channels, the phase space distribution and its projections are presented with the two axes being the squares of the low-mass $m_{\mathrm{low}}$ and high-mass $m_{\mathrm{high}}$ combinations of the opposite-sign particle pairs, for visualization purposes.