论文标题
在$ e^+e^ - $ colliders寻找深色矢量玻色子的两极分化效果
Polarization effects in the search for dark vector boson at $e^+e^-$ colliders
论文作者
论文摘要
我们认为，通过$ e^+e^ - \ toz_dγ$搜索黑暗向量玻色子可以确定$ z_dl^+l^ - $耦合的Lorentz结构，并检测Leptonic衰减$ z_d \ to l^+l^ - $。我们假设一个一般框架，即通过向量和轴向向量耦合，暗矢量玻色子与普通费米相互作用。由于Ward-Takahashi身份，$ z_d $在限制$ m_ {z_d} \ ll \ sqrt {s} $中横向两极化。另一方面，对于$ m_ {z_d} $，与$ \ sqrt {s} $相当的纵向$ z_d $的分数是不可忽略的。可以通过$ z_d $衰减的最终状态粒子的角度分布来分析这种极化效应。采用$ l^{\ pm} \equivμ^{\ pm} $，我们研究$ z_d $角度相对于$ e^ - $ e^ - $ e^ - $ e^ - $ e^+e^ - $ e^ - $ cm框架和$ cm框架和$μ^ - $角度相对于$ z_d $在$ z_d $ REST框架中的$ z_d $的相对于$ z_d $的增强方向。该相关性显示可用于探测$ z_dl^+l^ - $耦合的Lorentz结构。我们讨论了Belle II探测器中这种相关性的测量，并考虑了检测器的接受和能量分辨率。
We argue that the search for dark vector boson through $e^+e^-\to Z_dγ$ can determine the Lorentz structure of $Z_dl^+l^-$ couplings with the detection of leptonic decays $Z_d\to l^+l^-$. We assume a general framework that the dark vector boson interacts with ordinary fermions through vector and axial-vector couplings. As a consequence of Ward-Takahashi identity, $Z_d$ is transversely polarized in the limit $m_{Z_d}\ll \sqrt{s}$. On the other hand, the fraction of longitudinal $Z_d$ is non-negligible for $m_{Z_d}$ comparable to $\sqrt{s}$. Such polarization effects can be analyzed through angular distributions of final-state particles in $Z_d$ decays. Taking $l^{\pm}\equiv μ^{\pm}$, we study the correlation between $Z_d$ angle relative to $e^-$ beam direction in $e^+e^-$ CM frame and $μ^-$ angle relative to the boost direction of $Z_d$ in $Z_d$ rest frame. This correlation is shown to be useful for probing the Lorentz structure of $Z_dl^+l^-$ couplings. We discuss the measurement of such correlation in Belle II detector, taking into account the detector acceptance and energy resolution.
