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Measurements of azimuthal anisotropies at forward and backward rapidity with muons in high-multiplicity p–Pb collisions at TeV

2023    CERN İşbirliği

The study of the azimuthal anisotropy of inclusive muons produced in p–Pb collisions at $\sqrt{{s}_{\mathrm{NN}}}=8.16$ TeV, using the ALICE detector at the LHC is reported. The measurement of the second-order Fourier coefficient of the particle azimuthal distribution, ${v}_{2}$, is performed as a function of transverse momentum ${p}_{T}$ in the 0–20% high-multiplicity interval at both forward ($2.03<{y}_{\mathrm{CMS}}<3.53$) and backward ($-4.46<{y}_{\mathrm{CMS}}<-2.96$) rapidities over a wide ${p}_{T}$ range, $0.5<{p}_{T}<10$ GeV/c, in which a dominant contribution of muons from heavy-flavour hadron decays is expected at ${p}_{T}>2$ GeV/c. The ${v}_{2}$ coefficient of inclusive muons is extracted using two different techniques, namely two-particle cumulants, used for the first time for heavy-flavour measurements, and forward–central two-particle correlations. Both techniques give compatible results. A positive ${v}_{2}$ is measured at both forward and backward rapidities with a significance larger than 4.7σ and 7.6σ, respectively, in the interval $2<{p}_{T}<6$ GeV/c. Comparisons with previous measurements in p–Pb collisions at $\sqrt{{s}_{\mathrm{NN}}}\phantom{\rule{0.25em}{0ex}}=\phantom{\rule{0.25em}{0ex}}5.02$ TeV, and with AMPT and CGC-based theoretical calculations are discussed. The findings impose new constraints on the theoretical interpretations of the origin of the collective behaviour in small collision systems.