Dark matter in Hidden Valley models with stable and unstable light dark mesons

Abstract

It is a distinct possibility that a Hidden Valley sector would have a spectrum of light particles consisting of both stable and unstable dark mesons. The simultaneous presence of these two types of particles can lead to novel mechanisms for generating the correct dark matter relic abundance, which in turn can reflect themselves into new exotic signatures at colliders. We study the viability of such sectors for various Hidden Valley models and map the valid parameter space to possible collider signatures. Mediators studied include various scalar bifundamentals and a heavy Z . It is shown that in general bounds from direct and indirect detection can easily be avoided. In most of the allowed parameter space, the relic density is determined by stable mesons annihilating to unstable ones which in turn decay quickly to Standard Model particles. Dark mesons that decay mainly to heavier Standard Model fermions allow for more valid parameter space, though dark mesons are still allowed to decay exclusively to some of the lighter fermions. Possible exotic collider signatures include displaced vertices, emerging jets and semivisible jets.

Classification of dark pion multiplets as dark matter candidates and collider phenomenology

“…This discussion mirrors the previous work of Ref. [20]. Examples of the thermal evolution are shown in Fig.…”

“…In a lot of ways, this paper is a generalization of Ref. [20]. Previous work on combinations of stable and unstable dark mesons also include Refs.…”

“…Otherwise, bounds from direct detection would be difficult to satisfy (see Ref. [20]). Dark pions would also act mostly as standard WIMPs, which are already well studied.…”

“…If the pions interact with light particles, it should be sufficient for the two sectors to maintain kinematic equilibrium (see Ref. [20]), but could prove to be insufficient if the pions interact exclusively with heavy SM particles. One way or the other, this should not affect qualitatively any results.…”

“…Past this point is the so-called coupling-independent regime of Ref. [20], dubbed this way because further increasing the decay widths of the unstable pions does not affect the relic densities anymore. Effectively, the unstable pions become just another component of the plasma.…”