Time-dependent angular analysis of the decay $ B_s^0\to {J \left/ {{\psi \phi }} \right.} $ and extraction of ΔΓ s and the CP-violating weak phase ϕ s by ATLAS

A bstract A measurement of $ B_s^0\to {J \left/ {{\psi \phi }} \right.} $ decay parameters, including the CP -violating weak phase ϕ s and the decay width difference ΔΓ s is reported, using 4 . 9 fb −1 of integrated luminosity collected in 2011 by the ATLAS detector from LHC pp collisions at a centre-of-mass energy $ \sqrt{s}=7 $ TeV. The mean decay width Γ s and the transversity amplitudes | A 0 (0)| 2 and | A ∥ (0)| 2 are also measured. The values reported for these parameters are: $ \begin{array}{*{20}{c}} {{\phi_s}=0.22 \pm 0.41\ \left( {\mathrm{s}\mathrm{tat}.} \right) \pm 0.10\ \left( {\mathrm{s}\mathrm{yst}.} \right)\ \mathrm{rad}} \\ {\varDelta {\varGamma_s}=0.053 \pm 0.021\ \left( {\mathrm{s}\mathrm{tat}.} \right) \pm 0.010\ \left( {\mathrm{s}\mathrm{yst}.} \right)\ \mathrm{p}{{\mathrm{s}}^{-1 }}} \\ {{\varGamma_s}=0.677 \pm 0.007\ \left( {\mathrm{s}\mathrm{tat}.} \right) \pm 0.004\ \left( {\mathrm{s}\mathrm{yst}.} \right)\ \mathrm{p}{{\mathrm{s}}^{-1 }}} \\ {|{A_0}(0){|^2} = 0.528 \pm 0.006\ \left( {\mathrm{s}\mathrm{tat}.} \right) \pm 0.009\ \left( {\mathrm{s}\mathrm{yst}.} \right)} \\ {|{A_{\parallel }}(0){|^2} = 0.220 \pm 0.008\ \left( {\mathrm{s}\mathrm{tat}.} \right) \pm 0.007\ \left( {\mathrm{s}\mathrm{yst}.} \right)} \\ \end{array} $ where the values quoted for ϕ s and ΔΓ s correspond to the solution compatible with the external measurements to which the strong phase δ ⊥ is constrained and where ΔΓ s is constrained to be positive. The fraction of S -wave KK or f 0 contamination through the decays $ B_s^0\to {J \left/ {{\psi {K^{+}}{K^{-}}\left( {{f_0}} \right)}} \right.} $ is measured as well and is found to be consistent with zero. Results for ϕ s and ΔΓ s are also presented as 68%, 90% and 95% likelihood contours, which show agreement with Standard Model expectations.

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