Multiplicity dependence of ${\Xi }_c^{+}$ and ${\Xi }_c^0$ production in pp collisions at $\sqrt{s}=13$ TeV

Abstract

The first measurement at midrapidity ($|y|<0.5$) of the production yield of the strange-charm baryons ${\Xi }_c^{+}$ and ${\Xi }_c^0$ as a function of transverse momentum ($p_{\mathrm{T}}$) in different charged-particle multiplicity classes in proton-proton collisions at $\sqrt{s}=13$ TeV with the ALICE experiment at the LHC is reported. The ${\Xi }_c^{+}$ baryon is reconstructed via the ${\Xi }_c^{+}\to {\Xi }^{-}{\pi }^{+}{\pi }^{+}$ decay channel in the range $4<p_{\mathrm{T}}<12$ GeV/$c$, while the ${\Xi }_c^0$ baryon is reconstructed via both the ${\Xi }_c^0\to {\Xi }^{-}{\pi }^{+}$ and ${\Xi }_c^0\to {\Xi }^{-}{e}^{+}{\nu }_e$ decay channels in the range $2<p_{\mathrm{T}}<12$ GeV/$c$. The baryon-to-meson (${\Xi }_c^{0,+}/{\mathrm{D}}^0$) and the baryon-to-baryon (${\Xi }_c^{0,+}/{\Lambda }_{\mathrm{c}}^{+}$) production yield ratios show no significant dependence on multiplicity. In addition, the observed yield ratios are not described by theoretical predictions that model charm-quark fragmentation based on measurements at $e^{+}{e}^{-}$ and $e^{-}$p colliders, indicating differences in the charm-baryon production mechanism in pp collisions. A comparison with different event generators and tunings, including different modelling of the hadronisation process, is also discussed. Moreover, the branching-fraction ratio of BR(${\Xi }_c^0\to {\Xi }^{-}{e}^{+}{\nu }_e$)/BR(${\Xi }_c^0\to {\Xi }^{-}{\pi }^{+}$) is measured as 0.825 $\pm$ 0.094 (stat.) $\pm$ 0.081 (syst.). This value supersedes the previous ALICE measurement, improving the statistical precision by a factor of 1.6.

27 pages, 6 captioned figures, 6 tables, authors from page 22, figures at http://alice-publications.web.cern.ch/node/12747

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