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 anti-p collisions at s**(1/2)
= 1.96 TeV. Semileptonic decays of B-bar0, B-, and B-bar0_s mesons, as
well as Lambda0(b) baryons, are reconstructed. For an effective bottom
hadron p(t) threshold of 7 GeV/c, the fragmentation fractions are measured
to be f_u/f_d = 1.054 +/- 0.018 (stat)+0.025_-0.045 (sys) +/- 0.058 (B),
f_s/(f_u + f_d) = 0.160 +/- 0.005 (stat)+0.011_-0.010 (sys)+0.057_-0.034
(B), and f_Lambda_b/(f_u + f_d) = 0.281 +/- 0.012 (stat)+0.058_-0.056
(sys)+0.128_-0.086 (B), where the uncertainty 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.
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Updated: Friday, 2008 April 25 11:03:15 CDT automatically from input from carol picciolo