Electron Spectra for $D$ and $B$ Meson Semi-leptonic Decays at RHIC from   PYTHIA with Modified Heavy Quark Fragmentation
  We present a study of charmed hadron transverse momentum distribution from p+p collisions at $\sqrt{s_{NN}}=200$ GeV using the PYTHIA Monte Carlo event generator. The PHENIX tuned PYTHIA parameter set based on electron measurements alone yields a $D$ meson $p_{T}$ distribution softer than the preliminary STAR experimental data from d+Au collisions scaled by the number of binary collisions. In order to match the STAR $p_{T}$ spectrum, the higher order QCD effects in PYTHIA have to be taken into account, and a fragmentation function of charm quarks much harder than the default Peterson function is needed. Electrons from beauty quark semi-leptonic decays are found significantly below the contribution from charm quark decays for the $p_{T}$ region up to 8 GeV/c in our modified fragmentation scheme, while in the default fragmentation scheme the B decay electrons dominate at $p_{T}$ above 4 GeV/c. We propose an experimental measurement of electron and charged hadron correlation to differentiate these scenarios. 
Xiaoyan Lin