On ultraviolet freeze-in dark matter during reheating

Abstract

The absence of any confirmative signals from extensive DM searching motivates\nus to go beyond the conventional WIMPs scenario. The feebly interacting massive\nparticles (FIMPs) paradigm provides a good alternative which, despite of its\nfeebly interaction with the thermal particles, still could correctly produce\nrelic abundance without conventional DM signals. The Infrared-FIMP based on the\nrenormalizable operators is usually suffering the very tiny coupling drawback,\nwhich can be overcome in the UltraViolet-FIMP scenario based on high\ndimensional effective operators. However, it is sensitive to the history of the\nvery early Universe. The previous works terminates this sensitivity at the\nreheating temperature $T_{RH}$. We, motivated by its UV-sensitivity,\ninvestigate the effects from the even earlier Universe, reheating era. We find\nthat in the usual case with $T_{RH}\\gg m_{\\rm DM}$, the production rate during\nreheating is very small as long as the effective operators dimension $d \\leq\n8$. Besides, we consider the contribution from the mediator, which may be\nproduced during reheating. Moreover, we study the situation when $T_{RH}$ is\neven lower than $m_{\\rm DM}$ and DM can be directly produced during reheating\nif its mass does not exceed $T_{MAX}$.\n