Determination of the Ratio of B -Quark Fragmentation Fractions F{s} / f{d} in pp Collisions at √s̅ =7 TeV with the ATLAS Detector

With an integrated luminosity of 2.47 fb⁻¹ recorded by the ATLAS experiment at the LHC, the exclusive decays B_s^0 → J/ψϕ and B_d^0 → J/ψK^{*0} of B mesons produced in pp collisions at √s̅ = 7 TeV are used to determine the ratio of fragmentation fractions f_s / f_d. From the observed B_s^0 → J/ψϕ and B_d^0 → J/ψK^{*0} yields, the quantity (f_s ± 0.017(th). This result is based on a new approach that provides a significant improvement of the world average / f_d) [ℬ(B_s^0 → J/ψϕ) /ℬ(B_d^0 → J/ψK^{*0})] is measured to be 0.199 ± 0.004 (stat) ± 0.008(syst). Using a recent theory prediction for [ℬ(B_s^0 → J/ψϕ) / ℬ(B_d^0 → J/ψK^{*0})] yields (f_s / f_d)=0.240 ± 0.004(stat) ± 0.010(syst).