${\mathrm{\Lambda }}_{\mathrm{c}}^{+}$ production and baryon-to-meson ratios in pp and p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV at the LHC

Abstract

The prompt production of the charm baryon ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}$ and the ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}/{\mathrm{D}}^0$ production ratios were measured at midrapidity with the ALICE detector in pp and p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$TeV. These new measurements show a clear decrease of the ${\mathrm{\Lambda }}_{\mathrm{c}}^{+}/{\mathrm{D}}^0$ ratio with increasing transverse momentum ($p_{\mathrm{T}}$) in both collision systems in the range $2<p_{\mathrm{T}}<12$ GeV/$c$, exhibiting similarities with the light-flavour baryon-to-meson ratios $\mathrm{p}/\pi$ and $\Lambda /{\mathrm{K}}_{\mathrm{S}}^0$. At low $p_{\mathrm{T}}$, predictions that include additional colour-reconnection mechanisms beyond the leading-colour approximation; assume the existence of additional higher-mass charm-baryon states; or include hadronisation via coalescence can describe the data, while predictions driven by charm-quark fragmentation processes measured in ${\mathrm{e}}^{+}{\mathrm{e}}^{-}$ and ${\mathrm{e}}^{-}\mathrm{p}$ 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.

arXiv comment20 pages, 2 captioned figures, authors from page 14, published version, figures at http://alice-publications.web.cern.ch/node/6702

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