# First evidence of direct $C\!P$ violation in charmless two-body decays of $B^0_s$ mesons

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## Abstract

Using a data sample corresponding to an integrated luminosity of 0.35 $\mathrm{fb}^{-1}$ collected by LHCb in 2011, we report the first evidence of CP violation in the decays of $B^0_s$ mesons to $K^\pm \pi^\mp$ pairs, $A_{CP}(B^0_s \rightarrow K \pi)=0.27 \pm 0.08\,\mathrm{(stat)} \pm 0.02\,\mathrm{(syst)}$, with a significance of 3.3$\sigma$. Furthermore, we report the first observation of CP violation in $B^0$ decays at a hadron collider, $A_{CP}(B^0 \rightarrow K\pi)=-0.088 \pm 0.011\,\mathrm{(stat)} \pm 0.008\,\mathrm{(syst)}$, with a significance exceeding 6$\sigma$.

## Figures and captions

 Invariant $K\pi$ mass spectra obtained using the event selection adopted for the best sensitivity on (a, b) $A_{C\!P}(B^0 \rightarrow K\pi)$ and (c, d) $A_{C\!P}(B^0_s \rightarrow K\pi)$. Plots (a) and (c) represent the $K^+\pi^-$ invariant mass whereas plots (b) and (d) represent the $K^-\pi^+$ invariant mass. The results of the unbinned maximum likelihood fits are overlaid. The main components contributing to the fit model are also shown. ckpi_b[..].pdf [138 KiB] HiDef png [242 KiB] Thumbnail [83 KiB] *.C file cpik_b[..].pdf [170 KiB] HiDef png [299 KiB] Thumbnail [106 KiB] *.C file ckpi_b[..].pdf [136 KiB] HiDef png [254 KiB] Thumbnail [85 KiB] *.C file cpik_b[..].pdf [135 KiB] HiDef png [242 KiB] Thumbnail [84 KiB] *.C file Distributions of the invariant mass or invariant mass difference of (a) $D^{0}\rightarrow K^{-}\pi^{+}$, (b) $D^{*+}\rightarrow D^{0}(K^{-}\pi^{+})\pi^{+}$, (c) $D^{*+}\rightarrow D^{0}(K^{-}K^{+})\pi^{+}$ and (d) $B^{0}\rightarrow J/\psi(\mu^+\mu^-) K^{*0}(K^+\pi^-)$. The results of the maximum likelihood fits are overlaid. d02kpi.pdf [125 KiB] HiDef png [188 KiB] Thumbnail [69 KiB] *.C file dstard[..].pdf [122 KiB] HiDef png [183 KiB] Thumbnail [69 KiB] *.C file dstarD02kk.pdf [127 KiB] HiDef png [186 KiB] Thumbnail [71 KiB] *.C file B02jps[..].pdf [121 KiB] HiDef png [205 KiB] Thumbnail [75 KiB] *.C file Animated gif made out of all figures. PAPER-2011-029.gif Thumbnail

## Tables and captions

 Summary of selection criteria adopted for the measurement of $A_{C\!P}(B^0 \rightarrow K\pi)$ and $A_{C\!P}(B^0_s \rightarrow K \pi)$. Table_I.pdf [50 KiB] HiDef png [96 KiB] Thumbnail [16 KiB] tex code Summary of systematic uncertainties on $A_{C\!P}(B^0 \rightarrow K \pi)$ and $A_{C\!P}(B^0_s \rightarrow K\pi)$. The categories (a), (b) and (c) defined in the text are also indicated. The total systematic uncertainties given in the last row are obtained by summing the individual contributions in quadrature. Table_II.pdf [48 KiB] HiDef png [119 KiB] Thumbnail [14 KiB] tex code

Created on 02 March 2019.Citation count from INSPIRE on 20 March 2019.