Speaker:	Ayuki Kamada (U Warsaw)
Title:	Perturbative Unitarity of dark pion dark matter
Date (JST):	Tue, Aug 02, 2022, 16:00 - 17:30
Place:	Seminar Room A
Abstract:	Strongly interacting massive particles (SIMPs) are an intriguing sub-GeV dark matter candidate. They naturally evade the conventional searches for weakly interacting massive particles (WIMPs), while can be probed in newly proposed experiments. The correct relic abundance through a 3->2 process and the upper bound on the self-scattering cross section require SIMP self-couplings to be large. With a large coupling even below a naive perturbativity bound, perturbatively computed scattering amplitudes of semi-relativisitc particles may violate the partial-wave Unitarity bound (perturbative Unitarity). By taking a dark pion SIMP model as an example, we demonstrate that perturbative Unitarity bound is actually violated in the relevant parameter region. We propose improved amplitudes, which automatically satisfy the Unitarity bound, but still can be computed perturbatively, and re-compute the relic abundance and self scattering cross section of dark pions. We find that the required self-coupling gets 10% larger around the naive perturbativity bound and quickly increases above it, leading to the upper bound on the viable dark pion mass.

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