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−−−√=8.16sNN=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−1nb−1 that was collected in 2016. Azimuthal anisotropy coefficients, elliptic v2v2 and triangular v3v3, extracted using two-particle correlations with a non-flow template fit procedure, are presented as a function of particle transverse momentum (pTpT) between 0.5 and 50 GeV. The v2v2 results are also reported as a function of centrality in three different particle pTpT intervals. The results are reported from minimum-bias events and jet-triggered events, where two jet pTpT thresholds are used. The anisotropies for particles with pTpT less than about 2 GeV are consistent with hydrodynamic flow expectations, while the significant non-zero anisotropies for pTpT in the range 9–50 GeV are not explained within current theoretical frameworks. In the pTpT 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.