University of Colorado, Boulder, Colorado 80309, USA.
Phys Rev Lett. 2013 Nov 22;111(21):212301. doi: 10.1103/PhysRevLett.111.212301. Epub 2013 Nov 20.
The PHENIX collaboration at the Relativistic Heavy Ion Collider (RHIC) reports measurements of azimuthal dihadron correlations near midrapidity in d+Au collisions at √(s(NN))=200 GeV. These measurements complement recent analyses by experiments at the Large Hadron Collider (LHC) involving central p+Pb collisions at √(s(NN))=5.02 TeV, which have indicated strong anisotropic long-range correlations in angular distributions of hadron pairs. The origin of these anisotropies is currently unknown. Various competing explanations include parton saturation and hydrodynamic flow. We observe qualitatively similar, but larger, anisotropies in d+Au collisions at RHIC compared to those seen in p+Pb collisions at the LHC. The larger extracted v2 values in d+Au are consistent with expectations from hydrodynamic calculations owing to the larger expected initial-state eccentricity compared with that from p+Pb collisions. When both are divided by an estimate of the initial-state eccentricity the scaled anisotropies follow a common trend with multiplicity that may extend to heavy ion data at RHIC and the LHC, where the anisotropies are widely thought to arise from hydrodynamic flow.
重离子对撞机（RHIC）上的 PHENIX 合作组报道了在质心系能量为 √(s(NN))=200GeV 的 d+Au 碰撞中，近中心快度处双介子各向异性关联的测量结果。这些测量结果补充了近期大型强子对撞机（LHC）上涉及质心系能量为 √(s(NN))=5.02TeV 的中心 p+Pb 碰撞的实验分析，这些实验表明在介子对的角分布中存在强烈的各向异性长程关联。这些各向异性的起源目前尚不清楚。各种竞争的解释包括部分子饱和和流体力学流动。与 LHC 上的 p+Pb 碰撞相比，我们在 RHIC 上的 d+Au 碰撞中观察到定性上相似但更大的各向异性。由于与 p+Pb 碰撞相比，预期初始态的偏心度更大，因此在 d+Au 中提取的更大 v2 值与流体力学计算的预期相符。当两者都除以初始态偏心度的估计值时，标度各向异性与多重数遵循共同的趋势，这种趋势可能会扩展到 RHIC 和 LHC 的重离子数据，在那里，人们普遍认为各向异性是由流体力学流动引起的。
