University of Colorado, Boulder, Colorado 80309, USA.
Phys Rev Lett. 2010 Jun 25;104(25):252301. doi: 10.1103/PhysRevLett.104.252301. Epub 2010 Jun 21.
Hard-scattered parton probes produced in collisions of large nuclei indicate large partonic energy loss, possibly with collective produced-medium response to the lost energy. We present measurements of π^{0} trigger particles at transverse momenta p{T}{t}=4-12 GeV/c and associated charged hadrons (p{T}{a}=0.5-7 GeV/c) vs relative azimuthal angle Δϕ in Au+Au and p+p collisions at sqrt[s{NN}]=200 GeV. The Au+Au distribution at low p{T}{a}, whose shape has been interpreted as a medium effect, is modified for p{T}{t}<7 GeV/c. At higher p{T}{t}, the data are consistent with unmodified or very weakly modified shapes, even for the lowest measured p{T}{a}, which quantitatively challenges some medium response models. The associated yield of hadrons opposing the trigger particle in Au+Au relative to p+p (I{AA}) is suppressed at high p{T} (I{AA}≈0.35-0.5), but less than for inclusive suppression (R{AA}≈0.2).
在大原子核碰撞中产生的硬散射部分子探针表明部分子能量大量损失，可能伴随着集体产生的介质对损失能量的响应。我们展示了在 sqrt[s{NN}]=200 GeV 下 Au+Au 和 p+p 碰撞中，横动量 p{T}{t}=4-12 GeV/c 的 π^{0}触发粒子和关联带电强子（p{T}{a}=0.5-7 GeV/c）相对于相对方位角 Δϕ 的测量结果。在低 p{T}{a}下的 Au+Au 分布，其形状被解释为介质效应，在 p{T}{t}<7 GeV/c 时被修改。在更高的 p{T}{t}下，数据与未修改或修改很弱的形状一致，即使是测量到的最低 p{T}{a}，这定量上挑战了一些介质响应模型。相对于 p+p，Au+Au 中与触发粒子相对的强子的关联产额（I{AA}）在高 p{T}（I{AA}≈0.35-0.5）时被抑制，但比包容性抑制（R{AA}≈0.2）要小。
