Abstract
The time-dependent $C\!P$ asymmetries in $B^0\to\pi^+\pi^-$ and $B_s^0\to K^+\!K^-$ decays are measured using a data sample of $pp$ collisions corresponding to an integrated luminosity of 3.0 fb$^{-1}$, collected with the LHCb detector at centre-of-mass energies of 7 and 8 TeV. The same data sample is used to measure the time-integrated $C\!P$ asymmetries in $B^0\to K^+\pi^-$ and $B_s^0\to\pi^+ K^-$ decays. The results are $C_{\pi^+\pi^-} = -0.34 \pm 0.06 \pm 0.01$, $S_{\pi^+\pi^-} = -0.63 \pm 0.05 \pm 0.01$, $C_{K^+\!K^-} = 0.20 \pm 0.06 \pm 0.02$, $S_{K^+\!K^-} = 0.18 \pm 0.06 \pm 0.02$, $C_{K^+\!K^-}^{\Delta\Gamma} = -0.79 \pm 0.07 \pm 0.10$, $A_{C\!P}^{B^0} = -0.084 \pm 0.004 \pm 0.003$, and $A_{C\!P}^{B_s^0} = 0.213 \pm 0.015 \pm 0.007$, where the first uncertainties are statistical and the second systematic. Evidence for $C\!P$ violation is found in the $B_s^0\to K^+\!K^-$ decay for the first time.
Highlights
The study of CP violation in charmless decays of B0ðsÞ mesons to charged two-body final states represents a powerful tool to test the Cabibbo-Kobayashi-Maskawa (CKM) picture [1,2] of the quark-flavor mixing in the Standard Model (SM) and to investigate the presence of physics lying beyond [3,4,5,6,7,8,9]
It has been proposed to combine the CP asymmetries of the B0 → πþπ− and B0s → KþK− decays with information provided by the semileptonic decays B0 → π−lþν and B0s → K−lþν, in order to achieve a substantial reduction of the theoretical uncertainty on the determination of −2βs [12,13]
Where AKD−πþ is the asymmetry between the efficiencies of the K−πþ and Kþπ− final states without the application of the particle identification (PID) requirements and AKPI−Dπþ is the asymmetry between the efficiencies of the PID requirements selecting the K−πþ and Kþπ− final states
Summary
The study of CP violation in charmless decays of B0ðsÞ mesons to charged two-body final states represents a powerful tool to test the Cabibbo-Kobayashi-Maskawa (CKM) picture [1,2] of the quark-flavor mixing in the Standard Model (SM) and to investigate the presence of physics lying beyond [3,4,5,6,7,8,9]. Measurements of the time-dependent CP asymmetries in B0 → πþπ− and B0s → KþK− decays and of the time-integrated CP asymmetries in B0 → Kþπ− and B0s → πþK− decays are presented. The current experimental knowledge on Cf and Sf for the B0 → πþπ− and B0s → KþK− decays, and on ACP for the B0 → Kþπ− (ABC0P) and B0s → πþK− (ABC0sP) decays, is summarized in Tables I and II, respectively. The interaction of the generated particles with the detector, and its response, are implemented using the GEANT4 toolkit [35] as described in Ref. [36]
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