Measurement of Non-prompt ${\mathrm{D}}^0$-meson Elliptic Flow in Pb-Pb Collisions at $\sqrt{s_{\mathrm{N}\mathrm{N}}}$ = 5.02 TeV

The elliptic flow ($v_2$) of ${\mathrm{D}}^0$ mesons from beauty-hadron decays (non-prompt ${\mathrm{D}}^0$) was measured in midcentral (30-50%) Pb-Pb collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{\mathrm{N}\mathrm{N}}}$ = 5.02 TeV with the ALICE detector at the LHC. The ${\mathrm{D}}^0$ mesons were reconstructed at midrapidity ($\mathrm{\mid }y\mathrm{\mid }<0.8$) from their hadronic decay ${\mathrm{D}}^0\to {\mathrm{K}}^{-}{\pi }^{+}$, in the transverse momentum interval $2<p_{\mathrm{T}}<12$ GeV/$c$. The result indicates a positive $v_2$ for non-prompt ${\mathrm{D}}^0$ mesons with a significance of 2.7$\sigma$. The non-prompt ${\mathrm{D}}^0$-meson $v_2$ is lower than that of prompt non-strange D mesons with 3.2$\sigma$ significance in $2<p_{\mathrm{T}}<8$ GeV/$c$, and compatible with the $v_2$ of beauty-decay electrons. Theoretical calculations of beauty-quark transport in a hydrodynamically expanding medium describe the measurement within uncertainties.