6533b823fe1ef96bd127ec5a

RESEARCH PRODUCT

Measurement of theCP-violating phaseβsJ/ψϕinBs0→J/ψϕdecays with the CDF II detector

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We present a measurement of the \CP-violating parameter \betas using approximately 6500 $$\BsJpsiPhi$$ decays reconstructed with the CDF\,II detector in a sample of $$p\bar p$$ collisions at $$\sqrt{s}=1.96$$ TeV corresponding to 5.2 fb$$^{-1}$$ integrated luminosity produced by the Tevatron Collider at Fermilab. We find the \CP-violating phase to be within the range $$\betas \in [0.02, 0.52] \cup [1.08, 1.55]$$ at 68% confidence level where the coverage property of the quoted interval is guaranteed using a frequentist statistical analysis. This result is in agreement with the standard model expectation at the level of about one Gaussian standard deviation. We consider the inclusion of a potential $S$-wave contribution to the $$\Bs\to J/\psi K^+K^-$$ final state which is found to be negligible over the mass interval $$1.009 < m(K^+K^-)<1.028 \gevcc$$. Assuming the standard model prediction for the \CP-violating phase \betas, we find the \Bs decay width difference to be $$\deltaG = 0.075 \pm 0.035\,\textrm{(stat)} \pm 0.006\,\textrm{(syst)} \ps$$. We also present the most precise measurements of the \Bs mean lifetime $$\tau(\Bs) = 1.529 \pm 0.025\,\textrm{(stat)} \pm 0.012\,\textrm{(syst)}$$ ps, the polarization fractions $$|A_0(0)|^2 = 0.524 \pm 0.013\,\textrm{(stat)} \pm 0.015\,\textrm{(syst)}$$ and $$|A_{\parallel}(0)|^2 = 0.231 \pm 0.014\,\textrm{(stat)} \pm 0.015\,\textrm{(syst)}$$, as well as the strong phase $$\delta_{\perp}= 2.95 \pm 0.64\,\textrm{(stat)} \pm 0.07\,\textrm{(syst)} \textrm{rad}$$. In addition, we report an alternative Bayesian analysis that gives results consistent with the frequentist approach.