Measurement of beauty-strange meson production in Pb–Pb collisions at s_NN=5.02TeV via non-prompt D_s⁺ mesons

The production yields of non-prompt D_s⁺ mesons, namely D_s⁺ mesons from beauty-hadron decays, were measured for the first time as a function of the transverse momentum (p_T) at midrapidity (|y|<0.5) in central and semi-central Pb–Pb collisions at a centre-of-mass energy per nucleon pair s_NN=5.02TeV with the ALICE experiment at the LHC. The D_s⁺ mesons and their charge conjugates were reconstructed from the hadronic decay channel D_s⁺→ϕπ⁺, with ϕ→K⁻K⁺, in the 4<p_T<36GeV/c and 2<p_T<24GeV/c intervals for the 0–10% and 30–50% centrality classes, respectively. The measured yields of non-prompt D_s⁺ mesons are compared to those of prompt D_s⁺ and non-prompt D⁰ mesons by calculating the ratios of the production yields in Pb–Pb collisions and the nuclear modification factor R_AA. The ratio between the R_AA of non-prompt D_s⁺ and prompt D_s⁺ mesons, and that between the R_AA of non-prompt D_s⁺ and non-prompt D⁰ mesons in central Pb–Pb collisions are found to be on average higher than unity in the 4<p_T<12GeV/c interval with a statistical significance of about 1.6σ and 1.7σ, respectively. The measured R_AA ratios are compared with the predictions of theoretical models of heavy-quark transport in a hydrodynamically expanding QGP that incorporate hadronisation via quark recombination.