Evidence of different ${\Lambda }_{\mathrm{c}}$-baryon and D-meson elliptic flow in Pb$-$Pb collisions at $\sqrt{{\text{s}}_{\mathrm{NN}}}$ = 5.36 TeV with ALICE at the LHC

Abstract

The ALICE collaboration reports the azimuthal-anisotropy coefficient $v_2$ of prompt D${}^0$, D${}^{+}$, D${}_{\mathrm{s}}^{+}$ mesons and the first measurement of $v_2$ of prompt ${\Lambda }_{\mathrm{c}}$ baryons in semicentral Pb$-$Pb collisions at a center-of-mass energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}}=5.36$ TeV. The D mesons and ${\Lambda }_{\mathrm{c}}$ baryons are reconstructed in their hadronic decays at midrapidity ($|y|<0.8$) in the transverse-momentum interval $0.5<p_{\mathrm{T}}<24$ GeV/$c$. Similar $v_2$ values are measured for D${}^0$ and D${}^{+}$, while a hint of a difference ($2.6\sigma$) emerges between D${}^0$ and D${}_{\mathrm{s}}^{+}$ mesons in the $1<p_{\mathrm{T}}<5$ GeV/$c$ interval. A larger $v_2$ for ${\Lambda }_{\mathrm{c}}$ baryons with respect to D${}^0$ mesons is observed with $3.7\sigma$ significance for $4<p_{\mathrm{T}}<12$ GeV/$c$, providing evidence for the partonic origin of charm-hadron $v_2$ and hadron formation via quark coalescence. This interpretation is further supported by comparisons with theoretical calculations of charm-quark transport in a hydrodynamically expanding medium.

24 pages, 3 captioned figures, 1 table, authors from page 19, submitted to PRL, figures at http://alice-publications.web.cern.ch/node/13174