暗物质的直接探测通过观测暗物质与靶核的散射信号来寻找暗物质，这对质量为数十乃至数百个GeV的WIMP型暗物质来说是有效的，然而至今并未观测到确切的信号。如果暗物质的质量为几个GeV或更轻，因散射的能量很小，很难通过靶核散射的方式观测到。这里关注的就是此类暗物质。. 在重味粒子的一些FCNC衰变过程中，标准模型的贡献被压得很低，新物理的贡献可能超过标准模型的贡献，同时新的相互作用可能与暗物质区有关联。如t->c，b->s等过程中的不可见衰变产物，除中微子外，衰变到暗物质也会贡献很大的能量丢失。.研究中，我们将构造一个存在FCNC的作用形式，并分析t,b夸克的FCNC衰变过程的不可见末态的产生情况，进而对GeV和sub-GeV暗物质进行唯象研究。同时,来自对撞机实验及暗物质遗迹丰度对相应参数的限制也将被考虑。

The dark matter-target nucleus scattering signals are searched in direct detection of dark matter, and this is effective for WIMPs with mass of tens and hundreds GeV. However, no confident event was observed by now. If the mass of dark matter is a few GeV or lighter, with small scattering energy target nucleus obtained, it is very difficult to be observed via the target scattering. This type dark matter is of our concern. .In some FCNC processes of heavy flavor decays, the contributions from the standard model are deeply suppressed, and the new physics's effort would be predominant. Moreover, the new interaction may be related with dark sector. For example, the unobservable products in the process t->c,b->s, besides neutrinos, dark matter decay channel may contribute mostly to the missing energy.. We will discuss a lagrange with FCNC interacting form, and discuss the invisible decay prodcts in the FCNC decays of top and bottom quarks. With this method, we phenomenologically study the GeV and sub-GeV dark matter. The constraints of the parameters from the dark matter relic desity and collider are also considered.