Abstract:
This paper describes the first measurement of b-quark fragmentation fractions into bottom hadrons in Run II of the Tevatron Collider at Fermilab. The result is based on a 360 pb-1 sample of data collected with the CDF II detector in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV. Semileptonic decays of [overline B]0, B-, and [overline B]s0 mesons, as well as Lambdab0 baryons, are reconstructed. For an effective bottom hadron pT threshold of 7 GeV/c, the fragmentation fractions are measured to be fu/fd=1.054\pm 0.018(stat)-0.045+0.025(sys)\pm 0.058([script B]), fs/(fu+fd)=0.160\pm 0.005(stat)-0.010+0.011(sys)-0.034+0.057([script B]), and fLambdab/(fu+fd)=0.281\pm 0.012(stat)-0.056+0.058(sys)-0.087+0.128([script B]), where the uncertainty [script B] is due to uncertainties on measured branching ratios. The value of fs/(fu+fd) agrees within one standard deviation with previous CDF measurements and the world average of this quantity, which is dominated by LEP measurements. However, the ratio fLambdab/(fu+fd) is approximately twice the value previously measured at LEP. The approximately 2sigma discrepancy is examined in terms of kinematic differences between the two production environments.
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