Kavli Affiliate: Jia Liu
| First 5 Authors: Jinhui Guo, Jinhui Guo, , ,
| Summary:
We propose and study a purely inelastic scalar dark matter model, where two
real scalars-dark matter $phi_1$ and its excited partner $phi_2$ interact
with the Standard Model via a Higgs portal. After mass diagonalization, only
inelastic couplings remain, allowing the model to evade stringent bounds from
direct detection. We show that thermal (co-)annihilation between $phi_1$ and
$phi_2$ naturally yields the observed dark matter relic abundance. The same
interaction structure can induce a strongly first-order phase transition in the
early universe, generating detectable gravitational waves in upcoming
experiments. Meanwhile, the slight mass splitting between $phi_1$ and
$phi_2$, along with the heavy off-shell mediator SM Higgs, leads to long-lived
particle signatures of $phi_2$ at the HL-LHC via the displaced muon-jets
technique. We pinpoint a feasible parameter space where the correct relic
abundance, observable gravitational waves, and collider signals can all be
achieved concurrently, presenting a valuable chance to validate this scenario
through a comprehensive examination encompassing cosmological, astrophysical,
and collider investigations.
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