报告摘要：The dark matter (DM) detection is typically limitted by experimental thresholds, especially for light particle candidates. This applies not only for direct but also indirect detections. For direct detection, I will provide two possible ways of overcoming this issue, the cosmic ray boosted DM (CRDM) and the fermionic mass absorption DM. (1) For the former, the nonrelativistic DM is hit and boosted by the highly energetic cosmic rays to the relativistic regime to overcome the detection threshold. With both cosmic ray and halo DM mainly distributed around the Milky Way galaxy center, this acceleration prefers to happen there. However, the boosted CRDM from galaxy center needs to cross the rotating Earth and gets attenuated before arriving at detector. The periodic variation of trajectory length inside Earth causes diurnal modulation of the signal strength and recoil energy spectrum which is a unique feature of CRDM. As long as DM can be directly detected, CRDM and its modulation has to exist. (2) Another possibility is that the DM mass is fully absorpted and converted to recoil energies. For a fermionic DM, such process can happen if the DM particle becomes a massless neutrino when scattering with the detection target. Since the mass to energy conversion is very efficient according to the Einstein mass-energy relation, even sub-MeV DM can cause large enough recoil. (3) In addition to direct detection, the threshold issue also happens for the indirect one. One particular example is the DM scenario with forbidden annihilation channel. Such forbidden DM can annihilate in the early Universe, but not nowadays. We point out the possibility of reactivating the forbidden channel around a supermassive black hole and provide concrete models for illustration.
个人简介：
葛韶锋，2002-2006年清华物理系本科，毕业时获叶企孙奖；2006-2012年清华高能物理中心博士，2009年在美国德克萨斯州立大学奥斯汀分校联合培养。2012-2014年获得日本学术振兴会（JSPS）学者在日本高能加速器研究机构（KEK）、2014-2017年在德国海德堡马普所MPIK、2017-2019年由日本东京大学Kavli IPMU和美国加州大学伯克利分校联合聘请从事理论研究；2017年获美国费米加速器国家实验室（Fermilab）中微子中心（NPC）学者奖、并受邀于2018年夏天访问研究三个月。2019年加入上海交通大学李政道研究所，任李政道学者、副教授；IPMU连携研究员。主要研究领域为中微子和暗物质相关的粒子物理、天体物理和宇宙学理论与唯象研究。