Asymmetric Dark Matter: Theories, signatures, and constraints

Abstract

We review theories of Asymmetric Dark Matter (ADM), their cosmological implications and detection. While there are many models of ADM in the literature, our review of existing models will center on highlighting the few common features and important mechanisms for generation and transfer of the matter-anti-matter asymmetry between dark and visible sectors. We also survey ADM hidden sectors, the calculation of the relic abundance for ADM, and how the DM asymmetry may be erased at late times through oscillations. We consider cosmological constraints on ADM from the cosmic microwave background, neutron stars, the Sun, and brown and white dwarves. Lastly, we review indirect and direct detection methods for ADM, collider signatures, and constraints.

Cosmic microwave background limits on accreting primordial black holes

“…First and foremost, we compute the radiative efficiency ≡ L/Ṁ c 2 from first principles, generalizing Shapiro's classic calculation for spherical ac- 7 The astute reader may wonder why even given several probed PBH masses, some best-fitf pbh do not deviate by more than one standard deviation from 0; the reason is that the effect of PBHs of different masses on the CMB is very similar, hence the best-fit values are expected to be correlated. 8 Strictly speaking, given the prior f pbh ≥ 0, defining the 68%-confidence interval is a bit more subtle; given the large uncertainties of the calculation, we shall not delve into such technical details here.…”

“…We show σ f pbh in Fig. 14, as a simple proxy for the upper limit on this parameter 8 . We see that in the collisional ionization limit, CMB anisotropy measurements by Planck exclude PBHs with masses M 10 2 M as the dominant component of the dark matter.…”

“…Chapline was the first to suggest that PBHs could make the dark matter (DM) [3]. Though this class of DM candidate has taken a back seat to the notion that DM is a new elementary particle [4][5][6][7][8], the idea of PBH dark matter was recently rekindled [9,10], following the first detection of two merging ∼ 30 M black holes by LIGO [11]. Given the increasingly constraining null searches for particle DM, PBHs and their observational consequences are worth reconsidering [12,13].…”

Calibration, event reconstruction, data analysis, and limit calculation for the LUX dark matter experiment

“…The identity of the CDM is unknown, but a number of theoretical models predict that dark-matter particles interact very weakly with ordinary matter. Such models include weakly interacting massive particles (WIMPs) [4,5] and asymmetric dark matter [6,7] and in both cases predict that the dark-matter particles can elastically scatter with nuclei, producing nuclear recoils with energies of order 1-100 keV. Such elastic scattering events could be detectable using sufficiently sensitive instruments.…”

Annihilation signals from asymmetric dark matter

“…In such models the DM, which we denote here B , has an (approximately) conserved quantum number (which we also call B ). The relic density is determined by a particle-antiparticle asymmetry between B and B , in direct analogy to baryons [1][2][3]. If the DM has a similar mass to the proton m B ∼ m p and the hidden and visible sectors are connected via portal operators which violate B, L and B , but conserve some linear combination, then this can explain the cosmological coincidence Ω DM ∼ 5Ω B .…”