Measurement of beauty-strange meson production in Pb$-$Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV via non-prompt $\mathrm{D_s}^{+}$ mesons

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

 

Submitted to: PLB
e-Print: arXiv:2204.10386 | PDF | inSPIRE
CERN-EP-2022-065
Figure group

Figure 1

Invariant mass distribution of non-prompt $\Ds$ candidates and their charge conjugates in the $4

Figure 2

Acceptance-times-efficiency factors for prompt and non-prompt $\Ds$ mesons as a function of $\pt$ in the 0--10\% and 30--50\% centrality intervals, together with their ratios (bottom panel).

Figure 3

Fraction of non-prompt $\Ds$ mesons in the extracted raw yield as a function of $\pt$ in the 0--10\% and 30--50\% centrality intervals. The vertical bars (boxes) report the statistical (systematic) uncertainties.

Figure 4

Prompt and non-prompt $\Ds$ meson production yield in central and semicentral Pb--Pb collisions at $\sqrtsNN = 5.02~\TeV$. The prompt $\Ds$ results are taken from Ref.~ and scaled by a factor 10 for visibility. The vertical bars (boxes) report the statistical (systematic) uncertainties.

Figure 5

The $\pt$-differential production yield of non-prompt $\Ds$ mesons divided by those of prompt $\Ds$ mesons (left panel) and non-prompt $\Dzero$ mesons (right panel) for the 0--10\% and 30--50\% centrality intervals in Pb--Pb collisions at $\sqrtsNN=5.02~\TeV$ from Refs.~ compared with those in pp collisions at the same centre-of-mass energy from Ref.~.

Figure 6

Left panels: prompt (Ref.~) and non-prompt $\Ds$-meson $\RAA$ in central (top) and semicentral (bottom) Pb--Pb collisions at $\sqrtsNN = 5.02$ TeV. Right panels: non-prompt $\Ds$- and $\Dzero$-meson (Ref.~) $\RAA$ in central (top) and semicentral (bottom) Pb--Pb collisions at $\sqrtsNN = 5.02$ TeV. The experimental results are compared with the predictions of the TAMU model~. Statistical (bars), systematic (boxes), and normalisation (shaded box around unity) uncertainties are shown.

Figure 7

The $\RAA$ of non-prompt $\Ds$ mesons divided by the one of prompt $\Ds$ mesons~ (left panel) and non-prompt $\Dzero$ mesons~ (right panel) for the 0--10\% and 30--50\% centrality intervals in Pb--Pb collisions at $\sqrtsNN=5.02~\TeV$. The measurements are compared with TAMU model predictions~. Statistical (bars) and systematic (boxes) uncertainties are shown.