Measurement of ratios of fragmentation fractions for bottom hadrons inpp¯collisions ats=1.96TeV

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 $360{\mathrm{pb}}^{-1}$ sample of data collected with the CDF II detector in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$. Semileptonic decays of ${\overline{B}}^0$, $B^{-}$, and ${\overline{B}}_s^0$ mesons, as well as ${\Lambda }_b^0$ baryons, are reconstructed. For an effective bottom hadron $p_T$ threshold of $7\mathrm{GeV}/c$, the fragmentation fractions are measured to be $f_u/f_d=1.054\pm 0.018(\mathrm{stat}{)}_{-0.045}^{+0.025}(\mathrm{sys})\pm 0.058(\mathcal{B})$, $f_s/(f_u+f_d)=0.160\pm 0.005(\mathrm{stat}{)}_{-0.010}^{+0.011}(\mathrm{sys}{)}_{-0.034}^{+0.057}(\mathcal{B})$, and $f_{{\Lambda }_b}/(f_u+f_d)=0.281\pm 0.012(\mathrm{stat}{)}_{-0.056}^{+0.058}(\mathrm{sys}{)}_{-0.087}^{+0.128}(\mathcal{B})$, where the uncertainty $\mathcal{B}$ is due to uncertainties on measured branching ratios. The value of $f_s/(f_u+f_d)$ 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 $f_{{\Lambda }_b}/(f_u+f_d)$ is approximately twice the value previously measured at LEP. The approximately $2\sigma$ discrepancy is examined in terms of kinematic differences between the two production environments.