Measurement of Ratios of Fragmentation Fractions for Bottom Hadrons in p-pbar Collisions at sqrt{s}=1.96 TeV

TL;DR

This study measures the fragmentation fractions of b-quarks into various bottom hadrons in proton-antiproton collisions at 1.96 TeV, providing new insights into hadronization processes and comparing results with previous experiments.

Contribution

First measurement of b-quark fragmentation fractions into bottom hadrons in Run II of the Tevatron at Fermilab, using semileptonic decay reconstruction in p-pbar collisions.

Findings

Measured fragmentation ratios f_u/f_d, f_s/(f_u+f_d), and f_{Lambda_b}/(f_u+f_d).

Found f_s/(f_u+f_d) consistent with previous measurements and world average.

Observed f_{Lambda_b}/(f_u+f_d) approximately twice the LEP value, indicating possible kinematic differences.

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-pbar collisions at sqrt{s}=1.96 TeV. Semileptonic decays of B0, B+, and B_s mesons, as well as Lambda_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 (Br), f_s/(f_u+f_d)=0.160 +/- 0.005 (stat) +0.011-0.010 (sys) +0.057-0.034 (Br), and f_{Lambda_b}/(f_u+f_d)=0.281\pm0.012 (stat) +0.058-0.056 (sys) +0.128-0.086 (Br), where the uncertainty (Br) 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.