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arXiv 1611.03367hep-ph
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亲顶$Z^\prime$玻色子与核子相互作用的注记

Remarks on Top-philic $Z^\prime$ Boson Interactions with Nucleons

Frederick S. Sage, Jason N. E. Ho, T. G. Steele, Rainer Dick

摘要:

为了计算矢量门暗物质核反冲截面,本文计算了核子与优先与顶夸克或第三代费米子耦合的$Z^\prime$玻色子之间的有效顶点函数.考虑了新规范群$U(1)^\prime$和标准模型超荷群$U(1)_Y$之间的混合效应。利用重夸克展开式定量计算了重夸克对$U(1)^\prime$核子流的贡献。还考虑了单圈$Z^\prime$ -胶子相互作用的贡献和核子中轻夸克的混合诱导贡献。我们发现,对于合理的值的$U(1)^\prime$规范参数,来自轻夸克的贡献占主导地位,尽管被混合抑制。它表明,这适用于大多数模型,即使混合效应不出现在树级。来自重夸克和胶子的贡献被$1/m_Q^2$抑制,也可能被与暗物质直接探测相关的低动量转移极限中的动量抑制。我们讨论在何种条件下,从属条款成为相关的。

英文摘要:

This article provides the calculation of an effective vertex function between a nucleon and a $Z^\prime$ boson that couples preferentially to either the top quark or the third generation of fermions, for the purpose of calculating vector-portal dark matter nuclear recoil cross sections. Mixing effects between the new gauge group $U(1)^\prime$ and the Standard Model hypercharge group $U(1)_Y$ are taken into account. Contributions to the $U(1)^\prime$ nucleon current from heavy quarks are quantified using the heavy quark expansion. Also taken into account are contributions from the 1-loop $Z^\prime$-gluon interactions and mixing-induced contributions from the light quarks in the nucleon. We find that, for reasonable values of the $U(1)^\prime$ gauge parameter, contributions from the light quarks dominate despite being mixing-suppressed. It is shown that this holds for most models even if mixing effects do not appear at tree level. Contributions from the heavy quarks and gluons are suppressed by $1/m_Q^2$ and possibly also by momentum in the low momentum transfer limits relevant for dark matter direct detection. We discuss under which conditions the subdominant terms become relevant.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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