Measurements of azimuthal anisotropy and charged-particle multiplicity in
+ Au collisions at
= 200, 62.4, 39, and 19.6 GeV
=200, 62.4, 39, and 19.6GeVでの![$$d$$](/search/images/ERSCI.gif)
Au衝突における方位角異方性と荷電粒子多重度の測定
Aidala, C.*; 長谷川 勝一
; 佐甲 博之
; 佐藤 進
; 谷田 聖
; PHENIX Collaboration*; 他246名*
Aidala, C.*; Hasegawa, Shoichi; Sako, Hiroyuki; Sato, Susumu; Tanida, Kiyoshi; PHENIX Collaboration*; 246 of others*
We present measurements of the elliptic flow,
, as a function of transverse momentum (
), pseudorapidity (
), and centrality in ![$$d$$](/search/images/ERSCI.gif)
Au collisions at
200, 62.4, 39, and 19.6 GeV. The beam-energy scan of ![$$d$$](/search/images/ERSCI.gif)
Au collisions provides a testing ground for the onset of flow signatures in small collision systems. We measure a nonzero
signal at all four collision energies, which, at midrapidity and low
, is consistent with predictions from viscous hydrodynamic models. Comparisons with calculations from parton transport models (based on the
Monte Carlo generator) show good agreement with the data at midrapidity to forward (
-going) rapidities and low
. At backward (Au-going) rapidities and
GeV/
, the data diverges from
calculations of
relative to the initial geometry, indicating the possible dominance of nongeometry related correlations, referred to as nonflow. We also present measurements of the charged-particle multiplicity (
) as a function of
in central ![$$d$$](/search/images/ERSCI.gif)
Au collisions at the same energies. We find that in ![$$d$$](/search/images/ERSCI.gif)
Au collisions at
200 GeV the
scales with
over all
in the PHENIX acceptance. At
62.4, and 39 GeV,
scales with
at midrapidity and forward rapidity, but falls off at backward rapidity. This departure from the
scaling may be a further indication of nonflow effects dominating at backward rapidity.