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Register a new userMeasurement of Branching Fraction and Search for $CP$ Violation in $Bto phi phi K$
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We report the measurement of branching fractions and $CP$-violation asymmetries in $Bto phi phi K$ decays based on a $711,{rm fb}^{-1}$ data sample containing $772times 10^6$ $Bbar{B}$ events. The data were recorded at the $Upsilon (4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. For $B^+ to phi phi K^+$, the branching fraction and $CP$-violation asymmetry measured below the $eta_{c}$ threshold ($m_{phiphi}<2.85,{rm GeV}/c^2$) are $[3.43^{,+,0.48}_{,-,0.46}({rm stat})pm 0.22({rm syst})] times10^{-6}$ and $-0.02pm0.11({rm stat})pm0.01({rm syst})$, respectively. Similarly, the branching fraction obtained for $B^0 tophiphi K^0$ below the $eta_{c}$ threshold is $[3.02^{,+,0.75}_{,-,0.66} ({rm stat})pm ,0.20({rm syst})]times10^{-6}$. We also measure the $CP$-violation asymmetry for $B^+ tophiphi K^+$ within the $eta_{c}$ region ($m_{phiphi}in [2.94,3.02],{rm GeV}/c^2$) to be $+0.12pm0.12({rm stat})pm0.01({rm syst})$.
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Using a dataset corresponding to an integrated luminosity of 3.0 fb$^{-1}$ collected in $pp$ collisions at centre-of-mass energies of 7 and 8 TeV, the $B_s^0 to phi phi$ branching fraction is measured to be [ mathcal{B}(B_s^0 to phi phi) = ( 1.84 pm 0.05 (text{stat}) pm 0.07 (text{syst}) pm 0.11 (f_s/f_d) pm 0.12 (text{norm}) ) times 10^{-5}, ] where $f_s/f_d$ represents the ratio of the $B_s^0$ to $B^0$ production cross-sections, and the $B^0 to phi K^*(892)^0$ decay mode is used for normalization. This is the most precise measurement of this branching fraction to date, representing a factor five reduction in the statistical uncertainty compared with the previous best measurement. A search for the decay $B^0 to phi phi$ is also made. No signal is observed, and an upper limit on the branching fraction is set as [ mathcal{B}(B^0 to phi phi) < 2.8 times 10^{-8} ] at 90% confidence level. This is a factor of seven improvement compared to the previous best limit.
A measurement of the decay time dependent CP-violating asymmetry in $B_s^0 to phiphi$ decays is presented, along with measurements of the $T$-odd triple-product asymmetries. In this decay channel, the CP-violating weak phase arises from the interference between $B_s^0$-$bar{B}_s^0$ mixing and the loop-induced decay amplitude. Using a sample of proton-proton collision data corresponding to an integrated luminosity of $3.0, fb^{-1}$ collected with the LHCb detector, a signal yield of approximately 4000 $B_s^0 to phiphi$ decays is obtained. The CP-violating phase is measured to be ${phi_s =-0.17pm0.15mathrm{,(stat)}pm0.03mathrm{,(syst)}}$ rad. The triple-product asymmetries are measured to be ${A_U=-0.003pm0.017mathrm{,(stat)}pm0.006mathrm{,(syst)}}$ and ${A_V=-0.017pm0.017mathrm{,(stat)}pm0.006mathrm{,(syst)}}$. Results are consistent with the hypothesis of CP conservation.
Study of CP violation in the decay channel Bs->J/psi phi is essential to exploring and constraining physics beyond the Standard Model in the quark flavour sector. The experimental progress in this area of activity at the LHC and Tevatron is discussed.
We report a study of the decay $D^0 to K^0_S K^0_S$ using 921~fb$^{-1}$ of data collected at or near the $Upsilon(4S)$ and $Upsilon(5S)$ resonances with the Belle detector at the KEKB asymmetric energy $e^+e^-$ collider. The measured time-integrated $CP$ asymmetry is $ A_{CP}(D^0 to K^0_S K^0_S) = (-0.02 pm 1.53 pm 0.02 pm 0.17) %$, and the branching fraction is $mathcal{B} (D^{0}rightarrow K_{S}^{0}K_{S}^{0})$ = (1.321 $pm$ 0.023 $pm$ 0.036 $pm$ 0.044) $times$ 10$^{-4}$, where the first uncertainty is statistical, the second is systematic, and the third is due to the normalization mode ($D^0 to K_S^0 pi^0$). These results are significantly more precise than previous measurements available for this mode. The $A_{CP}$ measurement is consistent with the standard model expectation.
We briefly discuss measurements of CP violation in Bs --> J/psi phi decay. Both the phenomenology of Bs mixing and the importance of the measurement to searches for new physics, as well as technical details and issues with the analysis are included. While current results are consistent with the standard model, even large contributions from new physics cannot be excluded.
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