Bottom Hadrochemistry in High-Energy Hadronic Collisions
M. He, Ralf Rapp
Abstract
The hadrochemistry of bottom quarks (b) produced in hadronic collisions encodes valuable information on the mechanism of color neutralization in these reactions. Since the b-quark mass is much larger than the typical hadronic scale of ∼1 GeV, bb[over ¯] pair production is expected to be well separated from subsequent hadronization processes. A significantly larger fraction of b baryons has been observed in proton-proton (pp) and proton-antiproton (pp[over ¯]) reactions relative to e^{+}e^{-} collisions, challenging theoretical descriptions. We address this problem by employing a statistical hadronization approach with an augmented set of b-hadron states beyond currently measured ones, guided by the relativistic quark model and lattice-QCD computations. Assuming relative chemical equilibrium between different b-hadron yields, thermal densities are used as fragmentation weights of b quarks into various hadron species. With quark model estimates of the decay patterns of excited states, the fragmentation fractions of weakly decaying b hadrons are computed and found to agree with measurements in pp[over ¯] collisions at the Tevatron. By combining transverse-momentum (p_{T}) distributions of b quarks from perturbative QCD with thermal weights and independent fragmentation toward high p_{T}, a fair description of the p_{T}-dependent B[over ¯]_{s}^{0}/B^{-} and Λ_{b}^{0}/B^{-} ratios measured in pp collisions at the LHC is obtained. The observed enhancement of Λ_{b}^{0} production is attributed to the feeddown from thus far unobserved excited b baryons. Finally, we implement the hadrochemistry into a strongly coupled transport approach for b quarks in heavy-ion collisions, utilizing previously determined b-quark transport coefficients in the quark-gluon plasma, to highlight the modifications of hadrochemistry and collective behavior of b hadrons in Pb-Pb collisions at the LHC.