Speaker
Description
In high-energy hadronic collisions, heavy quarks are produced predominantly in the initial hard scatterings. $B$-mesons, which are composed of a bottom antiquark and another type of a light quark can then undergo a variety of decays, and studying these decays provides valuable insights on QCD mediums produced by the collisions. In this talk, the PHENIX experiment presents first of all a new measurement of the beauty contribution to inclusive $J/\psi$ production in $p+p$ collisions. $J/\psi$ mesons from $B$-meson decays are statistically separated from prompt $J/\psi$ using displaced decay vertices. The fraction of $B$$\rightarrow$ $J/\psi$ is measured over wide transverse momentum and rapidity ranges and compared with results from other experiments and theoretical calculations based on FONLL combined with the color evaporation model. It should be pointed out that this result is the first to directly access the total bottom quark cross section in the mid-rapidity region at RHIC. Secondly, new measurement of $J/\psi$ production as a function of event multiplicity in p+p and p+Au collisions is presented. The charmonium yield and event activity are measured in different combinations of rapidity regions, reducing auto-correlation effects and enabling studies of nuclear medium effects on $J/\psi$ production and hadronization over different Bjorken-x regimes. Together, these two measurements establish a comprehensive framework for understanding heavy-quark production and hadronization in nuclear collisions at RHIC energies.
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