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首页> 外文期刊>Physical review, D >Polarization difference between hyperons and antihyperons induced by an external magnetic field
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Polarization difference between hyperons and antihyperons induced by an external magnetic field

机译：外磁场引起的超子和反超子之间的极化差异

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We investigate the quantum correlated Λ Λ ˉ production in the reaction e + e ? → J / ψ → Λ Λ ˉ . Since the Λ or Λ ˉ has a nonzero magnetic moment, its spin will undergo a Larmor precession in the magnetic field of the detector, such as the BESIII experiment. Because of the spin precession, the angular distribution of the Λ and Λ ˉ is slightly modified. Therefore, we obtain the corresponding term of the modified angular distribution due to the effect of the Larmor precession. We also estimate its potential effect on the measurements of C P violation, as well as the decay asymmetry parameter and polarization of Λ . The polarization of the Λ or Λ ˉ at the production vertex will rotate around the B -field axis, over an angle depending on the flight length, but it still could be measured by fit to the corrected angular distribution. Of important note, we conclude that a nonzero C P asymmetry of order 10 ? 4 will be caused once neglecting spin precession of the Λ and Λ ˉ in the e + e ? → J / ψ → Λ Λ ˉ process. The size of this C P asymmetry is several times that of predicted within Standard Model in the hyperon decay. Although this effect is small, it will play an important role in future high precision experiments, such as the super-tau-charm factory.
机译：我们研究了反应e + e中与量子有关的ΛΛˉ产生。 →J /ψ→ΛΛˉ。由于or或ˉ的磁矩非零，因此其自旋将在探测器的磁场中经历拉莫尔进动，例如BESIII实验。由于自旋进动，对and和ˉ的角度分布进行了轻微修改。因此，由于拉莫尔进动的影响，我们获得了修正角度分布的相应项。我们还估计了其对C P违规的测量以及衰减不对称参数和Λ极化的潜在影响。生产顶点处的or或ˉ极化将围绕B场轴旋转，其角度取决于飞行长度，但仍可以通过拟合校正后的角度分布进行测量。重要的是，我们得出结论：10阶的非零C P不对称性。一旦忽略e + e中Λ和的自旋进动，将导致4。 →J /ψ→ΛΛˉ过程。这种C P不对称的大小是Hyperon衰变中标准模型中预测的大小的几倍。尽管这种影响很小，但它将在未来的高精度实验中发挥重要作用，例如超级tau-charm工厂。

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