Dark matter bound states via emission of scalar mediators

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It has been recently demonstrated that the 125 GeV Higgs boson can mediate a long-range force between TeV-scale particles, that can impact considerably their annihilation due to the Sommerfeld effect, and hence the density of thermal relic dark matter. In the presence of long-range interactions, the formation and decay of particle-antiparticle bound states can also deplete dark matter significantly. We consider the Higgs boson as mediator in the formation of bound states, and compute the effect on the dark matter abundance. To this end, we consider a simplified model in which dark matter co-annihilates with coloured particles that have a sizeable coupling to the Higgs. The Higgs-mediated force affects the dark matter depletion via bound state formation in several ways. It enhances the capture cross-sections due to the attraction it mediates between the incoming particles, it increases the binding energy of the bound states, hence rendering their ionisation inefficient sooner in the early universe, and for large enough couplings, it can overcome the gluon repulsion of certain colour representations and give rise to additional bound states. Because it alters the momentum exchange in the bound states, the Higgs-mediated force also affects the gluon-mediated potential via the running of the strong coupling. We comment on the experimental implications and conclude that the Higgs-mediated potential must be taken into account when circumscribing the viable parameter space of related models.

Section: Bound-state Formation Ionisation and Decaymentioning

confidence: 99%

Higgs-mediated bound states in dark-matter models

Harz

Petraki

2019

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“…[4,10], this is the overlap integral I k,n m (b), evaluated at b = 0 and up to the overall constant κ 3/2 B , here introduced to make R k,n m dimensionless. 5 For fermionic DM, we find that the (PΦ · r) 0 contributions would survive for + s + 1 = even, with s =0 or 1 being the total spin. However, the XX wavefunctions contain only S + s + 1 = odd modes.…”

Section: Amplitudementioning

confidence: 80%

Dark matter bound state formation via emission of a charged scalar

Oncala

Petraki

2020

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The formation of stable or meta-stable bound states can dramatically affect the phenomenology of dark matter (DM). Although the capture into bound states via emission of a vector is known to be significant, the capture via scalar emission suffers from cancellations that render it important only within narrow parameter space. While this is true for neutral scalar mediators, here we show that bound-state formation via emission of a charged scalar can be extremely significant. To this end, we consider DM charged under a dark U (1) force and coupled also to a light complex scalar that is charged under the same gauge symmetry. We compute the cross-sections for bound-state formation via emission of the charged scalar, and show that they can exceed those for capture via vector emission, as well as annihilation, by orders of magnitude. This holds even for very small values of the DM coupling to the charged scalar, and remains true in the limit of global symmetry. We then compute the DM thermal freeze-out, and find that the capture into meta-stable bound states via emission of a charged scalar can cause a late period of significant DM depletion. Our results include analytical expressions in the Coulomb limit, and are readily generalisable to non-Abelian interactions. We expect them to have implications for Higgs-portal scenarios of multi-TeV WIMP DM, as well as scenarios that feature dark Higgses or (darkly-)charged inert scalars, including models of self-interacting DM.

“…It is well known that light mediators can affect DM annihilations cross section through an enhancement factor (Sommerfeld enhancement) and bound state formation [4,5]. The Sp DM model includes two kinds of light mediators: a scalar particle (the scalon) and massless gauge bosons, which arise from the spontaneous symmetry breaking of the gauge group.…”

Section: Jhep06(2020)167mentioning

confidence: 99%

“…There is a second phenomenon, which is related to Sommerfeld enhancement, can affect both the relic abundance and the indirect detection cross section: two scattering particles can form bound states through the exchange of a light mediator [4,5,[15][16][17][18][19][20][21]. In particular, the interesting process is the formation of bound states via emission of the corresponding mediator (if the mediator is too heavy one can consider processes with emission of lighter particles, such as light glueballs).…”

Section: Jhep06(2020)167mentioning

confidence: 99%

“…The physics is very different for massive or massless mediators: if the mediator is massive, which is the case for the scalon exchange (with mass M s ) among W, X , and Z that we mentioned above, bound states can exist only if they satisfy the condition α eff M > κM s (for the ground state; for excited states the condition is even stronger) [4,5], where α eff = g 2 /16π and M = {M W , M X } is the mass of the particles involved in the scattering. However, this condition is never satisfied in our model, so there will be no bound states generated by potential (16).…”

Section: Jhep06(2020)167mentioning

confidence: 99%

See 1 more Smart Citation

Dark Matter in scalar Sp($$ \mathcal{N} $$) gauge dynamics

Landini

Wang

2020

We consider a model with Sp dark gauge group and a scalar field in the fundamental representation, which leads to two co-stable DM candidates at the perturbative level thanks to a global U(1) accidental symmetry. After gauge confinement at low energy scale, only one of the two candidates is still stable. We compute the DM relic abundance by solving the Boltzmann equations numerically. The presence of light dark glueballs gives extra cosmological effects and can affect Higgs physics. We study the DM phenomenology, providing the predictions for direct and indirect detection (including the Sommerfeld enhancement). We show that the model predicts a slightly suppressed indirect detection cross section in comparison to the usual WIMPs paradigm.