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Register a new userFirst measurement of time-dependent CP violation in Bs -> K+K- decays
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Direct and mixing-induced CP-violating asymmetries in Bs -> K+K- decays are measured for the first time using a data sample of pp collisions, corresponding to an integrated luminosity of 1.0 fb^{-1}, collected with the LHCb detector at a centre-of-mass energy of 7 TeV. The results are C_{KK} = 0.14 pm 0.11 pm 0.03 and S_{KK} = 0.30 pm 0.12 pm 0.04, where the first uncertainties are statistical and the second systematic. The corresponding quantities are also determined for B0 -> pi+pi- decays to be C_{pipi} = -0.38 pm 0.15 pm 0.02 and S_{pipi} = -0.71 pm 0.13 pm 0.02, in good agreement with existing measurements.
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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.
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.
The time-dependent $CP$ asymmetry in $B_s^0 to J/psi K^+K^-$ decays is measured using $pp$ collision data, 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. In a sample of 96 000 $B_s^0 to J/psi K^+K^-$ decays, the $CP$-violating phase $phi_s$ is measured, as well as the decay widths $Gamma_{L}$ and $Gamma_{H}$ of the light and heavy mass eigenstates of the $B_s^0-bar{B}_s^0$ system. The values obtained are $phi_s = -0.058 pm 0.049 pm 0.006$ rad, $Gamma_s equiv (Gamma_{L}+Gamma_{H})/2 = 0.6603 pm 0.0027 pm 0.0015$ps$^{-1}$, and$DeltaGamma_s equiv Gamma_{L} - Gamma_{H} = 0.0805 pm 0.0091 pm 0.0032$ps$^{-1}$, where the first uncertainty is statistical and the second systematic. These are the most precise single measurements of those quantities to date. A combined analysis with $B_s^{0} to J/psi pi^+pi^-$ decays gives $phi_s = -0.010 pm 0.039 $rad. All measurements are in agreement with the Standard Model predictions. For the first time the phase $phi_s$ is measured independently for each polarisation state of the $K^+K^- $ system and shows no evidence for polarisation dependence.
An analysis of B0->D K*0 decays is presented, where D represents an admixture of D0 and D0b mesons reconstructed in four separate final states: K-pi+, pi-K+, K+K- and pi+pi-. The data sample corresponds to 3.0fb-1 of proton-proton collision, collected by the LHCb experiment. Measurements of several observables are performed, including CP asymmetries. The most precise determination is presented of rB(DK*0), the magnitude of the ratio of the amplitudes of the decay B0->D K+ pi- with a b->u or a b->c transition, in a K pi mass region of +/-50 MeV/c2 around the K*(892) mass and for an absolute value of the cosine of the K*0 helicity angle larger than 0.4.
Using pp collision data, corresponding to an integrated luminosity of $1.0 mathrm{fb}^{-1}$, collected by LHCb in 2011 at a center-of-mass energy of 7 TeV, we report the measurement of direct CP violation in $B^0_s to K^-pi^+$ decays, $A_{C/!P}(B^0_s rightarrow K^- pi^+)=0.27 pm 0.04,mathrm{(stat)} pm 0.01,mathrm{(syst)}$, with significance exceeding five standard deviations. This is the first observation of CP violation in the decays of $B^0_s$ mesons. Furthermore, we provide an improved determination of direct CP violation in $B^0 to K^+pi^-$ decays, $A_{C/!P}(B^0rightarrow K^+ pi^-)=-0.080 pm 0.007,mathrm{(stat)} pm 0.003,mathrm{(syst)}$, which is the most precise measurement of this quantity to date.
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