Charged pions tagged with polarized photons probing strong CP violation in a chiral-imbalance medium
Charged pions tagged with polarized photons probing strong CP violation in a chiral-imbalance medium
复制标题
用偏振光子标记的带电π介子探测手性不平衡介质中的强CP破坏
DOI：
10.1103/physrevc.95.065204
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发表时间：
2017
影响因子：
3.1
通讯作者：
Ruiwen Ouyang
中科院分区：
文献类型：
--
作者：
Mamiya Kawaguchi;Shinya Matsuzaki;Masayasu Harada;Ruiwen Ouyang
预计在热QCD系统中，由于胶子拓扑组态(QCD球面)所携带的缠绕数不同而产生的非零手性会产生局域宇称奇域。这种局域被称为手性不平衡介质，其特征是手性化学势不为零，可以解释为强相的时间变化。我们发现，手性化学势在带电介子的电磁形状因子中产生宇称破缺项。重离子碰撞实验可以通过介子和光子在介质中的弹性散射来观察这种奇宇称形状因子的唯象结果。然后，我们通过测量与介子相关的光子的偏振来量化宇称破坏的不对称率，并讨论了如何在确定的实验室框架下测量它。我们粗略地估计了非对称性的典型大小，仅通过拾取pion共振过程就可以发现，该信号可以足够大到足够大，而不是来自宇称破缺的电弱过程可能的背景事件。我们的发现可能为对强违规的残留物进行明显检测提供了一种新的可能性。
It is expected that in a hot QCD system, a local parity-odd domain can be produced due to nonzero chirality, which is induced from the difference of winding numbers carried by the gluon topological configuration (QCD sphaleron). This local domain is called the chiral-imbalance medium, characterized by nonzero chiral chemical potential, which can be interpreted as the time variation of the strongphase. We find that the chiral chemical potential generates the parity breaking term in the electromagnetic form factor of charged pions. Heavy ion collision experiments could observe the phenomenological consequence of this parity-odd form factor through the elastic scattering of a pion and a photon in the medium. Then we quantify the asymmetry rate of the parity violation by measuring the polarization of the photon associated with the pion, and discuss how it could be measured in a definite laboratory frame. We roughly estimate the typical size of the asymmetry, just by picking up the pion resonant process, and find that the signal can be sufficiently larger than possible background events from parity-breaking electroweak process. Our findings might provide a novel possibility to make a manifest detection for the remnant of the strongviolation.