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Register a new userMeasurement of CP violating asymmetries in B^0 -> K^+K^- K^0_S decays with a time-dependent Dalitz approach
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We report a measurement of $CP$ violating asymmetries in $B^0(overline{B}^0) to K^+ K^- K^0_S$ decays with a time-dependent Dalitz approach. This analysis is based on a data sample of $657times 10^6$ $Boverline{B}$ pairs accumulated at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. As the result of an unbinned maximum likelihood fit to the selected candidates, the mixing-induced and direct $CP$ violation parameters, $phi^{rm eff}_1$ and ${cal A}_{CP}$ are obtained for $B^0 to phi(1020) K^0_S$, $B^0 to f_0(980) K^0_S$ and other $B^0 to K^+ K^- K^0_S$ decays. We find four solutions that describe the data. There are {eqnarray*} phi_1^{rm eff}(B^0to phi(1020) K^0_S) & = & (32.2 pm 9.0 pm 2.6 pm 1.4)^{circ}; phi_1^{rm eff}(B^0to phi(1020) K^0_S) & = & (26.2 pm 8.8 pm 2.7 pm 1.2)^{circ}; phi_1^{rm eff}(B^0to phi(1020) K^0_S) & = & (27.3 pm 8.6 pm 2.8 pm 1.3)^{circ}; {rm and} phi_1^{rm eff}(B^0to phi(1020) K^0_S) & = & (24.3 pm 8.0 pm 2.9 pm 5.2)^{circ}.{eqnarray*} The values for the $CP$ violating phase in $B^0to phi(1020) K^0_S$ are similar but other properties of the Dalitz plot are quite different for the four solutions. These four solutions have consistent $phi^{rm eff}_1$ values for all three $B$ meson decay channels and none of them deviates significantly from the values measured in $B to (cbar{c}) K^0$ decays with the currently available statistics. In addition, we find no significant direct $CP$ violation.
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We report a measurement of time-dependent $CP$ violation in $B^0 to K^0_S pi^0 pi^0$ decays using a data sample of $772 times 10^6$ $Bbar{B}$ pairs collected by the Belle experiment runnin g at the $Upsilon (4S)$ resonance at the KEKB $e^+ e^-$ collider. This decay proceeds mainly via a $bto sdbar{d}$ penguin amplitude. The results are $sin 2phi^{rm eff}_1 = 0.92^{+0.27}_{-0.31}~$ (stat.) $pm 0.11$ (syst.) and $mathcal{A} = 0.28 pm 0.21$ (stat.) $pm 0.04$ (syst.), which are the most precise measurements of $CP$ violati on in this decay mode to date. The value for the $CP$-violating parameter $sin 2phi^{rm eff}_1$ is consistent with that obtained using decay modes proceeding via a $bto cbar{c}s$ tree amplitude.
The decay-time-dependent $CP$ asymmetry in $B^{0}_{s}to J/psi K^{+} K^{-}$ decays is measured using proton-proton collision data, corresponding to an integrated luminosity of $1.9,mathrm{fb^{-1}}$, collected with the LHCb detector at a centre-of-mass energy of $13,mathrm{TeV}$ in 2015 and 2016. Using a sample of approximately 117,000 signal decays with an invariant $K^{+} K^{-}$ mass in the vicinity of the $phi(1020)$ resonance, the $CP$-violating phase $phi_s$ is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the $B^{0}_{s}$-$bar{B}^{0}_{s}$ system, $DeltaGamma_s$. The difference of the average $B^{0}_{s}$ and $B^{0}$ meson decay widths, $Gamma_s-Gamma_d$, is determined using in addition a sample of $B^{0} to J/psi K^{+} pi^{-}$ decays. The values obtained are $phi_s = -0.083pm0.041pm0.006,mathrm{rad}$, $DeltaGamma_s = 0.077 pm 0.008 pm 0.003, mathrm{ps^{-1}}$ and $Gamma_s-Gamma_d = -0.0041 pm 0.0024 pm 0.0015,mathrm{ps^{-1}}$, where the first uncertainty is statistical and the second systematic. These are the most precise single measurements of these quantities to date and are consistent with expectations based on the Standard Model and with a previous LHCb analysis of this decay using data recorded at centre-of-mass energies 7 and 8 TeV. Finally, the results are combined with recent results from $B^{0}_{s}to J/psi pi^{+} pi^{-}$ decays obtained using the same dataset as this analysis, and with previous independent LHCb results.
The time-integrated $CP$ asymmetry in the decay $D^0 to K^0_S K^0_S$ is measured using $3 fb^{-1}$ of proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The flavour of the $D^0$ meson is determined by use of the decay $D^{*+} to D^0 pi^+$ and its charge conjugate mode. The result is [ {cal A}_{CP} = -0.029 pm 0.052 pm 0.022, ] where the first uncertainty is statistical and the second systematic. The result is consistent with Standard Model expectations and improves the uncertainty with respect to the only previous measurement of this quantity by more than a factor of three.
A measurement of the time-integrated $CP$ asymmetry in $D^0rightarrow K^0_S K^0_S$ decays is reported. The data correspond to an integrated luminosity of about $2$ fb$^{-1}$ collected in 2015-2016 by the LHCb collaboration in $pp$ collisions at a centre-of-mass energy of $13$ TeV. The $D^0$ candidate is required to originate from a $D^{ast +} rightarrow D^0 pi^+$ decay, allowing the determination of the flavour of the $D^0$ meson using the pion charge. The $D^0 rightarrow K^{+}K^{-}$ decay, which has a well measured $CP$ asymmetry, is used as a calibration channel. The $CP$ asymmetry for $D^0rightarrow K^0_S K^0_S$ is measured to be begin{equation*} mathcal{A}^{CP}(D^0rightarrow K^0_S K^0_S) = (4.3pm 3.4pm 1.0)%, end{equation*} where the first uncertainty is statistical and the second is systematic. This result is combined with the previous LHCb measurement at lower centre-of-mass energies to obtain begin{equation*} mathcal{A}^{CP}(D^0rightarrow K^0_S K^0_S) = (2.3pm 2.8pm 0.9)%. end{equation*}
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