Abstract
The azimuthal anisotropy of charged particles produced in 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 mathrm {nb}^{-1} that was collected in 2016. Azimuthal anisotropy coefficients, elliptic v_2 and triangular v_3, extracted using two-particle correlations with a non-flow template fit procedure, are presented as a function of particle transverse momentum (p_mathrm {T}) between 0.5 and 50 GeV. The v_2 results are also reported as a function of centrality in three different particle p_mathrm {T} intervals. The results are reported from minimum-bias events and jet-triggered events, where two jet p_mathrm {T} thresholds are used. The anisotropies for particles with p_mathrm {T} less than about 2 GeV are consistent with hydrodynamic flow expectations, while the significant non-zero anisotropies for p_mathrm {T} in the range 9–50 GeV are not explained within current theoretical frameworks. In the 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.
Highlights
This suppression is understood to result from high momentum transfer parton–parton interactions followed by the outgoing partons losing energy via radiative and collisional processes in the quark–gluon plasma (QGP) – processes referred to as jet quenching [4,5,6]
This paper presents a measurement of the azimuthal acnenistoratrloitpyyinof√unsNidNen=tifi8e.d16haTderVonsp+asPba function of pT collisions with and the ATLAS detector
This paper presents Fourier coefficients of the azimuthal dist√risbNuNtio=n of unidentified 8.16 TeV p+Pb charged particles from 165 nb−1 of collisions at the Large Hadron Collider (LHC) and measured with the ATLAS detector
Summary
The production of high transverse momentum hadrons ( pT 10 GeV) is highly suppressed relative to the yields expected from nuclear thickness scaling of proton– proton collision yields [3] This suppression is understood to result from high momentum transfer parton–parton interactions followed by the outgoing partons losing energy via radiative and collisional processes in the QGP – processes referred to as jet quenching [4,5,6]. These high- pT hadrons and associated jets are observed to have a non-zero azimuthal anisotropy [7,8,9], despite being well outside the nominal domain where the anisotropies are interpreted in terms of hydrodynamic flow. There are a number of proposed explanations for resolving this puzzle in heavy-ion collisions – see Refs. [12,13,14,15,16,17] for examples
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
