arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2006.00973hep-ph
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解开$Z$衰变中暗玻色子的自旋

Untangling the spin of a dark boson in $Z$ decays

A. Comelato, E. Gabrielli

摘要:

我们分析了$Z$ -玻色子衰变$Z\to γ\, X$为光子($γ$)加上属于黑暗或僻静区域的假设轻玻色子($X$)。由于它与标准模型场的相互作用很弱,这个暗玻色子在探测器中表现为丢失的能量。我们考虑了$X$中自旋为1(无质量暗光子)、自旋为0(类轴子)和自旋为2(类引力子)的粒子,并探讨了解开其自旋起源的方法。所有这些情况都预示了这种衰变的普遍特征,其特征是在$Z$质心有一个单色光子,其能量约为$Z$质量的一半,加上与$X$玻色子相关的中微子样的丢失能量。我们表明,如果$Z\to γ\, X$信号应在$e^+e^-$对撞机上发现,在$e^+e^-\to Z\to γ\, X$的单色光子的角分布可以提供一个干净的探针,以区分$J=1$和替代$J=0/2$自旋性质的$X$暗玻色子。

英文摘要:

We analyze the $Z$-boson decay $Z\to γ\, X$ into a photon ($γ$) plus a hypothetical light boson ($X$) belonging to a dark or secluded sector. Due to its feeble interactions with Standard Model fields, this dark boson is behaving as missing energy in the detector. We consider for $X$ the cases of spin-1 (massless dark-photon), spin-0 (axion-like), and spin-2 (graviton-like) particles and explore the way to untangle its spin origin. All these scenarios predict a universal signature for this decay, characterized by a single mono-chromatic photon in the $Z$ center of mass, with energy about half of the $Z$ mass, plus a neutrino-like missing energy associated to the $X$ boson. We show that if the $Z\to γ\, X$ signal should be discovered at $e^+e^-$ colliders, the angular distribution of the mono-chromatic photon in $e^+e^-\to Z\to γ\, X$ can provide a clean probe to discriminate between the $J=1$ and alternative $J=0/2$ spin nature of the $X$ dark boson.

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