Determination of the ratio of b-quark fragmentation fractions fs/fd in pp collisions at vs = 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 0s?J/?? and B0d?J/?K*0 of B mesons produced in pp collisions at vs=7??TeV are used to determine the ratio of fragmentation fractions fs/fd. From the observed B0s?J/?? and B0d?J/?K*0 yields, the quantity (fs/fd)[B(B0s?J/??)/B(B 0d?J/?K*0)] is measured to be 0.199±0.004(stat)±0.008(syst). Using a recent theory prediction for [B(B0s?J/??)/B(B0d?J/?K*0)] yields (fs/fd)=0.240±0.004(stat)±0.010(syst)±0.017(th). This result is based on a new approach that provides a significant improvement of the world average.