Speaker
Description
Charged particles in small collision systems such as $pp$ and $p$+Pb have been observed to have significant azimuthal modulations of their momenta, commonly interpreted as flow, up to a transverse momentum of $p_{T} \approx 10$~GeV. In large collision systems such as Pb+Pb, lower but non-zero flow coefficients at higher $p_{T}$ ($> 10$~GeV) are usually understood to reflect jet quenching, and specifically the path-length differential energy loss in elliptical events. Extending these measurements in small systems to high-$p_{T}$ particles, which are predominantly produced in jets, can thus provide crucial information on the origin of these collective phenomena. This talk presents a new measurement by ATLAS of two-particle angular correlations in 8.16 TeV $p$+Pb events with a jet trigger. An additional restriction on the associated particle positions is used to suppress the large non-flow contributions in the jet events. Measurements of the resulting single-particle second- and third-order flow coefficients are presented for charged-hadrons from $p_{T}$ = 0.5 to 50 GeV, in selections of $p$+Pb event activity. The $p_{T}$-dependent results are compared to those from minimum-bias $p$+Pb events, and the differences between the two event samples are analyzed in terms of the different origin of particles in these events, such as the different fraction of particles that arise from the jet fragmentation process.
