Transverse momentum and multiplicity dependence of $\Lambda_{c}^{+}/D^{0}$ ratio in $pp$ collisions at $\sqrt{s}=13$ TeV

We apply an equal-velocity quark combination model to study the $\Lambda_{c}^{+}/D^{0}$ ratio in the range $p_{T}\lesssim10$ GeV/c in $pp$ collisions at $\sqrt{s}=13$ TeV. We decompose the ratio into four parts which are related to quark numbers, light-flavor quark $p_{T}$ spectrum, charm quark $p_{T}$ spectrum, momentum correlation between light and charm quarks, respectively. Their influence on $\Lambda_{c}^{+}/D^{0}$ ratio are individually studied. The curvature property of light-flavor quark $p_{T}$ spectrum is found to be the main reason of the non-monotonic $p_{T}$ dependence of $\Lambda_{c}^{+}/D^{0}$ ratio exhibited in high multiplicity events. Moreover, the multiplicity dependence of $\Lambda_{c}^{+}/D^{0}$ ratio as the function of $p_{T}$ is mainly because of the multiplicity dependence of light-flavor quark $p_{T}$ spectrum. Using the light-flavor quark $p_{T}$ spectrum obtained from experimental data of light-flavor hadrons and charm quark $p_{T}$ spectrum obtained from FONLL and/or PYTHIA calculations, the $p_{T}$ dependence of experimental data of $\Lambda_{c}^{+}/D^{0}$ ratio in high multiplicity events and that in low multiplicity events in $pp$ collisions at $\sqrt{s}=13$ TeV are reasonably understood.