# Charm-Baryon Production in Proton-Proton Collisions

## TL;DR

This paper explains the unexpectedly high charm-baryon production in proton-proton collisions at the LHC by extending the statistical hadronization model with additional charm-baryon states, successfully matching experimental data.

## Contribution

The study introduces an augmented set of charm-baryon states guided by quark models and lattice QCD into the statistical hadronization model to explain charm-baryon yields.

## Key findings

- Enhanced feeddown from excited charm baryons explains the $ ext{Lambda}_c/ ext{D}^0$ ratio.
- The model reproduces the $p_T$ spectra of $D$-mesons and $ ext{Lambda}_c$ in proton-proton collisions.
- Low-$p_T$ enhancement in $ ext{Lambda}_c/ ext{D}^0$ ratio is due to missing charm-baryon states.

## Abstract

Recent measurements of charm-baryon production in proton-proton collisions at the LHC have found a surprisingly large yield relative to those of $D$-mesons. We propose that this observation can be explained by the statistical hadronization model (SHM), by employing a largely augmented set of charm-baryon states beyond the current listings of the particle data group. We estimate the additional states using guidance from the relativistic quark model and from lattice QCD. Using charm- and strange-quark fugacity factors to account for the well-known suppression of heavy flavor in elementary collisions, we compute the yields and spectra of $D$, $D_s$ and $\Lambda_c$ hadrons in proton-proton collisions at $\sqrt{s}=5$\,TeV. Our main finding is that the enhanced feeddown from excited charm baryons can account for the $\Lambda_c/D^0$ ratio measured by ALICE at midrapidity, with some caveat for the forward-rapidity LHCb data. Furthermore, assuming independent fragmentation of charm quarks but with the hadronic ratios fixed by the SHM, the measured transverse-momentum ($p_T$) spectra of $D$-mesons and $\Lambda_c$ can also be described; in particular, the low-$p_T$ enhancement in the observed $\Lambda_c/D^0$ ratio is attributed to the enhanced feeddown from "missing" charm-baryon states. We comment on the implications of these findings for measurements of $D_s$ and $\Lambda_c$ in heavy-ion collisions.