First measurement of ${\mathrm{\Xi }}_{\mathrm{c}}^0$ production in $\mathbf{P}\mathbf{b}-\mathbf{P}\mathbf{b}$ collisions at $\sqrt{{\mathit{\text{s}}}_{\mathrm{N}\mathrm{N}}}$ = 5.02 TeV

The ALICE Collaboration reports the first measurement of the production of prompt ${\mathrm{\Xi }}_{\mathrm{c}}^0$ baryons in nucleus$-$nucleus collisions by analyzing data from $\mathrm{P}\mathrm{b}-\mathrm{P}\mathrm{b}$ collisions at $\sqrt{s_{\mathrm{N}\mathrm{N}}}=5.02\mathrm{T}\mathrm{e}\mathrm{V}$. The production and transverse-momentum ($p_{\mathrm{T}}$) differential spectra of ${\mathrm{\Xi }}_{\mathrm{c}}^0$ are particularly sensitive to the hadronization process and to strangeness production in the quark–gluon plasma formed in high-energy heavy-ion collisions. The ${\mathrm{\Xi }}_{\mathrm{c}}^0$ baryons are reconstructed at midrapidity ($\mathrm{\mid }y\mathrm{\mid }<0.5$) in the transverse-momentum intervals $3<p_{\mathrm{T}}<12\mathrm{G}\mathrm{e}\mathrm{V}\mathrm{/}c$ and $4<p_{\mathrm{T}}<12\mathrm{G}\mathrm{e}\mathrm{V}\mathrm{/}c$ in the 0$-$10% and 30$-$50% centrality intervals, respectively. The nuclear modification factor ($R_{\mathrm{A}\mathrm{A}}$) reaches values up to 3 in the interval $3<p_{\mathrm{T}}<4\mathrm{G}\mathrm{e}\mathrm{V}\mathrm{/}c$, which is the largest value measured so far for charm hadrons. Model predictions are compatible with the measured $R_{\mathrm{A}\mathrm{A}}$, while, in the measured $p_{\mathrm{T}}$ intervals, they underestimate the production yield as well as the measured ${\mathrm{\Xi }}_{\mathrm{c}}^0\mathrm{/}{\mathrm{D}}^0$, ${\mathrm{\Xi }}_{\mathrm{c}}^0\mathrm{/}{\mathrm{\Lambda }}_{\mathrm{c}}^{+}$, and ${\mathrm{\Xi }}_{\mathrm{c}}^0\mathrm{/}{\mathrm{D}}_{\mathrm{s}}^{+}$ yield ratios.