Title: keV Photon Emission from Light Nonthermal Dark Matter Show Chinese title

Title: 千电子伏特光子从轻非热暗物质发射

Abstract: We propose a possible explanation for the recent claim of an excess at 3.5 keV in the X-ray spectrum within a minimal extension of the standard model that explains dark matter and baryon abundance of the universe. The dark matter mass in this model is ${\cal O}({\rm GeV})$ and its relic density has a non-thermal origin. The model includes two colored scalars of ${\cal O}({\rm TeV})$ mass ($X_{1,2}$), and two singlet fermions that are almost degenerate in mass with the proton ($N_{1,2}$). The heavier fermion $N_2$ undergoes radiative decay to the lighter one $N_1$ that is absolutely stable. Radiative decay with a life time $\sim 10^{23}$ seconds can account for the claimed 3.5 keV line, which requires couplings $\sim 10^{-3}-10^{-1}$ between $X_{1,2}, ~ N_{1,2}$ and the up-type quarks. The model also gives rise to potentially detectable monojet, dijet, and monotop signals at the LHC. Show Chinese abstract

Abstract: 我们提出一种可能的解释，针对近期在X射线谱中3.5 keV处出现的过量现象，在标准模型的一个最小扩展中解释暗物质和宇宙重子丰度。 该模型中的暗物质质量为${\cal O}({\rm GeV})$，其残留密度具有非热起源。 该模型包括两个颜色标量，质量为${\cal O}({\rm TeV})$（$X_{1,2}$），以及两个几乎与质子质量简并的单态费米子（$N_{1,2}$）。 较重的费米子$N_2$会通过辐射衰变到较轻的费米子$N_1$，后者是绝对稳定的。 辐射衰变的寿命为$\sim 10^{23}$秒可以解释所谓的3.5 keV线，这需要$\sim 10^{-3}-10^{-1}$的耦合在$X_{1,2}, ~ N_{1,2}$和上型夸克之间。 该模型还在大型强子对撞机上产生了可能被探测到的单喷注、双喷注和单顶信号。