论文标题
在$ \ sqrt {s _ {_ {\ rm nn}}} $ = 200 GEV中,对在au+au碰撞中寻找手性磁效应时的质量不变质量隔离背景。
Pair invariant mass to isolate background in the search for the chiral magnetic effect in Au+Au collisions at $\sqrt{s_{_{\rm NN}}}$= 200 GeV
论文作者
论文摘要
夸克与拓扑gluon构型的相互作用会引起量子染色体动力学中局部手性失衡和均衡违规,这可能导致手性磁效应(CME) - 相对论重型离子碰撞中强磁场的电荷分离。 CME敏感的方位角相关器可观察的($Δγ$)受到背景污染,部分原因是共振衰减与椭圆性各向异性($ V_ {2} $)污染。我们在这里报告了相关器的差异测量值,该测量值是在20-50 \%centrality au+au collisions $ \ sqrt {s _ {_ {_ {_ {\ rm nn}} $ = 200 GEEV by star Rhic中的$ \ sqrt {s _ {_ {_ {_ {_ {_ {_ {_ {_ {_ {_ {_ {_ {_ {_ {观察到对$δγ$的强共振背景贡献。在很大的$ m _ {\ rm Inv} $下,此背景大大减少,$Δγ$值的值明显较小。部署了事件形状工程技术来确定$ V_ {2} $背景形状作为$ M _ {\ rm Inv} $的函数。我们提取$ v_2 $ - 独立和$ m _ {\ rm inv} $ - 平均信号$Δγ_{\ rm sig} $ =(0.03 $ \ pm $ 0.06 $ \ pm $ 0.08) $Δγ(m_{\rm inv}>0.4$ GeV/$c^2$)$ =(1.58 \pm 0.02 \pm 0.02) \times10^{-4}$, within pion $p_{T}$ = 0.2 - 0.8~\gevc and averaged over pseudorapidity ranges of $-1 < η< -0.05$ and $ 0.05 <η<1 $。这代表上限为$ 0.23 \ times10^{ - 4} $,或$ 15 \%$ $ 15 \%$,为$ 95 \%$ $置信度,$ m _ {\ rm inv} $ - 集成的CME贡献。
Quark interactions with topological gluon configurations can induce local chirality imbalance and parity violation in quantum chromodynamics, which can lead to the chiral magnetic effect (CME) -- an electric charge separation along the strong magnetic field in relativistic heavy-ion collisions. The CME-sensitive azimuthal correlator observable ($Δγ$) is contaminated by background arising, in part, from resonance decays coupled with elliptic anisotropy ($v_{2}$). We report here differential measurements of the correlator as a function of the pair invariant mass ($m_{\rm inv}$) in 20-50\% centrality Au+Au collisions at $\sqrt{s_{_{\rm NN}}}$= 200 GeV by the STAR experiment at RHIC. Strong resonance background contributions to $Δγ$ are observed. At large $m_{\rm inv}$ where this background is significantly reduced, the $Δγ$ value is found to be significantly smaller. An event-shape-engineering technique is deployed to determine the $v_{2}$ background shape as a function of $m_{\rm inv}$. We extract a $v_2$-independent and $m_{\rm inv}$-averaged signal $Δγ_{\rm sig}$ = (0.03 $\pm$ 0.06 $\pm$ 0.08) $\times10^{-4}$, or $(2\pm4\pm5)\%$ of the inclusive $Δγ(m_{\rm inv}>0.4$ GeV/$c^2$)$ =(1.58 \pm 0.02 \pm 0.02) \times10^{-4}$, within pion $p_{T}$ = 0.2 - 0.8~\gevc and averaged over pseudorapidity ranges of $-1 < η< -0.05$ and $0.05 < η< 1$. This represents an upper limit of $0.23\times10^{-4}$, or $15\%$ of the inclusive result, at $95\%$ confidence level for the $m_{\rm inv}$-integrated CME contribution.