$β$ -衰变微分谱中Fierz项的运动敏感性
Kinematic sensitivity to the Fierz term of $β$-decay differential spectra
摘要：
从Fierz干涉项出发，得到了目前对中子和核$β$衰变中涉及左手中微子的奇异标量或张量耦合的最严格约束.相关系数中对该项的敏感性通常由能量平均运动学因子驱动，该因子朝向$β$端点能量的较小值单调增加。我们在这里首先指出，这种性质不适用于某些直接敏感于Fierz项的微分观测量，如$β$或反冲能谱。这一观察结果是相关的选择敏感的过渡，通过光谱形状测量寻找异国情调的耦合。然后，我们指出以前的错误，在利用测量的$β-ν$角相关系数，并讨论其影响的提取约束奇异耦合。
英文摘要：
The current most stringent constraints on exotic scalar or tensor couplings in neutron and nuclear $β$ decay, involving left-handed neutrinos, are obtained from the Fierz interference term. The sensitivity to this term in a correlation coefficient is usually driven by an energy-averaged kinematic factor that increases monotonically toward smaller values of the $β$ endpoint energies. We first point out here that this property does not hold for certain differential observables that are directly sensitive to the Fierz term, such as the $β$ or the recoil energy spectrum. This observation is relevant for the selection of sensitive transitions in searches for exotic couplings through spectrum shape measurements. We then point out previous errors in the exploitation of measurements of the $β-ν$ angular correlation coefficient and discuss their impact on the extraction of constraints on exotic couplings.
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