Measurement of non-prompt D -meson elliptic flow in Pb–Pb collisions at √sNN=5.02 TeV

The elliptic flow (v₂) of D mesons from beauty-hadron decays (non-prompt D) was measured in midcentral (30–50%) Pb–Pb collisions at a centre-of-mass energy per nucleon pair sNN=5.02 TeV with the ALICE detector at the LHC. The D mesons were reconstructed at midrapidity (| y| < 0.8) from their hadronic decay D → K ^-π ⁺ , in the transverse momentum interval 2 < p_T< 12 GeV/c. The result indicates a positive v₂ for non-prompt D mesons with a significance of 2.7 σ . The non-prompt D -meson v₂ is lower than that of prompt non-strange D mesons with 3.2 σ significance in 2<pT<8GeV/c , and compatible with the v₂ of beauty-decay electrons. Theoretical calculations of beauty-quark transport in a hydrodynamically expanding medium describe the measurement within uncertainties.