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SUMMARY:Seminar - Prof. Eung Jin Chun (KIAS)\,
DTSTART:20260921T070000Z
DTEND:20260921T080000Z
DTSTAMP:20261017T113200Z
UID:indico-event-13@ihepco.yonsei.ac.kr
DESCRIPTION:Title :  Self-Interacting Sterile Neutrino Cold Dark Matter: 
 Resonant Production Mechanism in the Early Universe\nAbstract:\n\nSterile 
 neutrinos are well-motivated dark matter candidates\, but their con- venti
 onal production through active–sterile mixing is tightly constrained by 
 X-ray searches and structure-formation observations. We propose a distinct
  production mechanism oper- ating entirely within a sterile sector: two st
 erile neutrinos\, N1 and N2\, coupled to a singlet scalar ϕ\, with N1 the
  dark matter candidate and N2 held in equilibrium through frequent scatter
 ing induced by its scalar interaction. Thermal self-energies induced by th
 e N2 and ϕ backgrounds generate both a temperature-dependent mass splitti
 ng and an off-diagonal mixing between N1 and N2. As the Universe cools\, t
 he in-medium levels can undergo a level crossing\, leading to resonantly e
 nhanced conversion of the thermal N2 population into N1. We formulate the 
 conversion using a density-matrix kinetic equation that consistently incor
 porates coherent N1–N2 conversion\, collisional decoherence\, and therma
 l repopulation of N2. For a narrow resonance\, the integrated conversion p
 robability admits a simple ana- lytic form that coincides with the Landau
 –Zener result\, despite the underlying collisionally damped dynamics. In
  the weak-conversion regime relevant for freeze-in\, this correspon- dence
  provides a robust analytic description of the resonant production. We der
 ive the resulting dark matter abundance and identify the conditions for co
 smological stability of N1 and for resonant conversion to dominate over di
 rect scattering and decay production. The resulting relic abundance scales
  as Y1 ∝g2 12g22MPl/m1\, making the dark matter en- ergy density approxi
 mately independent of m1. This mechanism provides a new route to sterile-n
 eutrino dark matter that does not require appreciable active–sterile mix
 ing.\n\n \nPaper : https://arxiv.org/pdf/2609.04650\n\nhttps://ihepco.yon
 sei.ac.kr/event/13/
LOCATION:Yonsei University (S327)
URL:https://ihepco.yonsei.ac.kr/event/13/
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