整体自旋取向矢量介子对重离子碰撞中手征磁效应研究的影响
Impact of globally spin-aligned vector mesons on the search for the chiral magnetic effect in heavy-ion collisions
摘要：
在高能重离子碰撞中，由于核介质中夸克的手征性不平衡与强磁场的相互作用，将产生手征磁效应（CME），导致电荷沿磁场方向分离.虽然在相对论重离子对撞机（RHIC）和大型强子对撞机（LHC）的实验中仍在寻找CME，但需要仔细检查CME敏感的观测数据，以排除非CME的贡献。在这项工作中，我们研究的影响，全球自旋对齐$ρ$介子的$γ_{112}$相关器，$R_{Ψ_2}(ΔS)$相关器，和有符号的平衡功能，通过一个玩具模型和多相输运模型（AMPT）。在重离子碰撞中，矢量介子的自旋整体排列可能起源于非CME机制，并由自旋密度矩阵$ρ_{00}$的00分量表征。我们发现CME观测值对$ρ_{00}$有相似的依赖性，并且当$ρ$介子的$ρ_{00}$大于（小于）1/3时，可以得到$ρ$衰变介子的正（负）贡献.由于π介子是这种碰撞中最丰富的粒子，$ρ$介子的$ρ_{00}$测量对于解释CME数据至关重要。
英文摘要：
In high-energy heavy-ion collisions, the chiral magnetic effect (CME) is predicted to arise from the interplay between the chirality imbalance of quarks in the nuclear medium and the intense magnetic field, and will cause a charge separation along the magnetic field direction. While the search for the CME is still ongoing in experiments at Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC), the CME-sensitive observables need to be scrutinized to exclude the non-CME contributions. In this work, we examine the influence of globally spin-aligned $ρ$ mesons on the $γ_{112}$ correlator, the $R_{Ψ_2}(ΔS)$ correlator, and the signed balance functions, via a toy model and a multiphase transport model (AMPT). The global spin alignment of vector mesons could originate from non-CME mechanisms in heavy-ion collisions, and is characterized by the 00-component of the spin density matrix, $ρ_{00}$. We find that the CME observables show similar dependence on $ρ_{00}$, and could receive a positive (negative) contribution from $ρ$-decay pions, if the $ρ_{00}$ of $ρ$ mesons is larger (smaller) than 1/3. Since pions are the most abundant particles in such collisions, the $ρ_{00}$ measurements for $ρ$ mesons become crucial to the interpretation of the CME data.
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