论文标题
在200 GEV AU + AU碰撞中，沿着磁场的电荷分离的测量
Measurement of the charge separation along the magnetic field with Signed Balance Function in 200 GeV Au + Au collisions at STAR
论文作者
论文摘要
在重型离子碰撞中对手性磁效应（CME）的实验搜索已经进行了十年，到目前为止，还没有关于其存在的结论性证据。最近，已经提出了基于检查沿着平面外和非平面外向的电荷对的动量顺序的概念的签名平衡函数（SBF）。在这种方法中，调用了一对可观察到的物品：一个是$ r _ {\ mathrm {rest}} $，平面外与平面比为$ΔB$在PAIR的休息框架中测得的$ΔB$，其中$ΔB$是$ΔB$是签名平衡功能之间的差异；另一个是双比，$ r _ {\ mathrm {b}} = r _ {\ mathrm {rest}}}/r _ {\ mathrm {lab}} $，其中$ r _ {\ r _ {\ mathrm {lab}} $是$ r _}的$ r _ { 框架。与由共振流量和全局自旋对齐产生的背景相关性相比，这两个可观察结果对CME驱动的电荷分离产生了相反的响应。 $ r _ {\ mathrm {rest}} $和$ r _ {\ mathrm {b}} $比Unity大，可以被视为有利于CME存在的情况。通过实验发现，$ r _ {\ mathrm {rest}} $，$ r _ {\ mathrm {lab}} $和$ r _ {\ mathrm {b}} $在200 Gev中的AU+AU碰撞中的Unity大于200 GEV，而不是现实的模型计算。这些发现很难用仅背景场景来解释。
Experimental searches for Chiral Magnetic Effect (CME) in heavy-ion collisions have been going on for a decade, and so far there is no conclusive evidence for its existence. Recently, the Signed Balance Function (SBF), based on the idea of examining the momentum ordering of charged pairs along the in- and out-of-plane directions, has been proposed as a probe of CME. In this approach, a pair of observables is invoked: one is $r_{\mathrm{rest}}$, the out-of-plane to in-plane ratio of $ΔB$ measured in pair's rest frame, where $ΔB$ is the difference between signed balance functions; The other is a double ratio, $R_{\mathrm{B}} = r_{\mathrm{rest}}/r_{\mathrm{lab}}$, where $r_{\mathrm{lab}}$ is a measurement similar to $r_{\mathrm{rest}}$ but measured in the laboratory frame. These two observables give opposite responses to the CME-driven charge separation compared to the background correlations arising from resonance flow and global spin alignment. Both $r_{\mathrm{rest}}$ and $R_{\mathrm{B}}$ being larger than unity can be regarded as a case in favor of the existence of CME. It is found experimentally that $r_{\mathrm{rest}}$, $r_{\mathrm{lab}}$ and $R_{\mathrm{B}}$ are larger than unity in Au+Au collisions at 200 GeV, and larger than realistic model calculations with no CME implemented. These findings are difficult to be explained by a background-only scenario.
