Transverse momentum and process dependent azimuthal anisotropies in sNN=8.16 TeV p+Pb collisions with the ATLAS detector

Abstract

The azimuthal anisotropy of charged particles produced in sNN=8.16$$\sqrt{s_{\mathrm {NN}}}=8.16$$ TeV p+Pb collisions is measured with the ATLAS detector at the LHC. The data correspond to an integrated luminosity of 165 nb-1$$\mathrm {nb}^{-1}$$ that was collected in 2016. Azimuthal anisotropy coefficients, elliptic v2$$v_2$$ and triangular v3$$v_3$$, extracted using two-particle correlations with a non-flow template fit procedure, are presented as a function of particle transverse momentum (pT$$p_\mathrm {T}$$) between 0.5 and 50 GeV. The v2$$v_2$$ results are also reported as a function of centrality in three different particle pT$$p_\mathrm {T}$$ intervals. The results are reported from minimum-bias events and jet-triggered events, where two jet pT$$p_\mathrm {T}$$ thresholds are used. The anisotropies for particles with pT$$p_\mathrm {T}$$ less than about 2 GeV are consistent with hydrodynamic flow expectations, while the significant non-zero anisotropies for pT$$p_\mathrm {T}$$ in the range 9–50 GeV are not explained within current theoretical frameworks. In the pT$$p_\mathrm {T}$$ range 2–9 GeV, the anisotropies are larger in minimum-bias than in jet-triggered events. Possible origins of these effects, such as the changing admixture of particles from hard scattering and the underlying event, are discussed.