The prompt production of the charm baryon ${\mathrm{\Lambda }}_c^{+}$ and the ${\mathrm{\Lambda }}_c^{+}/D^0$ production ratios were measured at midrapidity with the ALICE detector in $pp$ and $p$-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$. These new measurements show a clear decrease of the ${\mathrm{\Lambda }}_c^{+}/D^0$ ratio with increasing transverse momentum ($p_T$) in both collision systems in the range $2<p_T<12\mathrm{GeV}/c$, exhibiting similarities with the light-flavor baryon-to-meson ratios $p/\pi$ and $\mathrm{\Lambda }/K_S^0$. At low $p_T$, predictions that include additional color-reconnection mechanisms beyond the leading-color approximation, assume the existence of additional higher-mass charm-baryon states, or include hadronization via coalescence can describe the data, while predictions driven by charm-quark fragmentation processes measured in $e^{+}{e}^{-}$ and $e^{-}p$ collisions significantly underestimate the data. The results presented in this Letter provide significant evidence that the established assumption of universality (colliding-system independence) of parton-to-hadron fragmentation is not sufficient to describe charm-baryon production in hadronic collisions at LHC energies.

• Received 22 December 2020
• Revised 27 May 2021
• Accepted 10 August 2021

DOI:https://doi.org/10.1103/PhysRevLett.127.202301

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