Title: Can a millicharged dark matter particle emit an observable gamma-ray line? Show Chinese title

Title: 一个具有微电荷的暗物质粒子能否发射可观察的伽马射线谱线？

Abstract: If a gamma-ray line is observed in the near future, it will be important to determine what kind of dark matter (DM) particle could be at its origin. We investigate the possibility that the gamma-ray line would be induced by a slow DM particle decay associated to the fact that the DM particle would not be absolutely neutral. A "millicharge" for the DM particle can be induced in various ways, in particular from a kinetic mixing interaction or through the Stueckelberg mechanism. We show that such a scenario could lead in specific cases to an observable gamma-ray line. This possibility can be considered in a systematic model-independent way, by writing down the corresponding effective theory. This allows for a multi-channel analysis, giving in particular upper bounds on the intensity of the associated gamma-ray line from cosmic rays emission. Our analysis includes the possibility that in the two-body decay the photon is accompanied with a neutrino. We show that, given the stringent constraints which hold on the millicharge of the neutrinos, this is not an option, except if the DM particle mass lies in the very light KeV-MeV range, allowing for a possibility of explanation of the recently claimed, yet to be confirmed, ~3.5KeV X-ray line. Show Chinese abstract

Abstract: 如果在未来不久观测到伽马射线谱线，确定哪种暗物质（DM）粒子可能与其起源有关将非常重要。 我们研究了伽马射线谱线可能是由一种缓慢的DM粒子衰变引起的可能性，这与DM粒子并非绝对中性这一事实有关。 DM粒子可以以多种方式产生“毫电荷”，特别是通过动能混合相互作用或通过Stueckelberg机制。 我们表明，在特定情况下，这种情景可能导致可观测的伽马射线谱线。 可以通过写出相应的有效理论，以系统且模型无关的方式考虑这种可能性。 这允许进行多通道分析，特别是从宇宙射线辐射中给出相关伽马射线谱线强度的上限。 我们的分析包括在双体衰变中光子伴随中微子的可能性。 我们表明，鉴于对中微子毫电荷的严格限制，除非DM粒子质量位于非常轻的KeV-MeV范围内，否则这不是一个可行的选择，这使得解释最近声称但尚未确认的~3.5KeV X射线谱线成为可能。