Precise WIMP Dark Matter Abundance and Standard Model Thermodynamics

Abstract

A weakly interacting massive particle (WIMP) is a leading candidate of the dark matter. The WIMP dark matter abundance is determined by the freeze-out mechanism. Once we know the property of the WIMP particle such as the mass and interaction, we can predict the dark matter abundance. There are, however, several uncertainties in the estimation of the WIMP dark matter abundance. In this work, we focus on the effect from Standard Model thermodynamics. We revisit the estimation of the WIMP dark matter abundance and its uncertainty due to the equation of state (EOS) in the Standard Model. We adopt the up-todate estimate of the EOS of the Standard Model in the early Universe and find nearly 10% difference in the 1-1000 GeV dark matter abundance, compared to the conventional estimate of the EOS.

The Bactrian Effect: Multiple Resonances and Light Dirac Dark Matter

“…While such theories remain very interesting, the lack of any observational signatures at the LHC or in either direct or indirect detection searches [7][8][9][10] has resulted in a slowly shrinking allowed parameter space for these models. This has led to the construction of a plethora of new DM scenarios based on the introduction of non-SM interactions to reproduce the observed relic abundance [11,12] with very wide ranges in both the possible DM masses and coupling strengths [13][14][15]. Many of these potential new interactions can be described via a set of 'portals' which link DM, and possibly other 'dark' sector fields, with those of the SM, only a few of which can result from renormalizable, dimension-4 terms in the Lagrangian.…”

“…The proximity of these two masses can occur naturally in several setups: for example, if a common dark Higgs vev generates both the DM mass and is simultaneously responsible for the breaking of U (1) D or in KM models with extra dimensions where the compactification radius sets the common scale for particle masses [24][25][26][27]. In this low mass regime, there are several constraints on the model parameters: first, there is the required annihilation cross section necessary to obtain the observed relic density during freeze out, e.g., < σv rel > F O 4.5 × 10 −26 cm 3 s −1 for an s-wave annihilating Dirac fermion DM [11,12], which is the case that we will consider below. For such a light mass, we will assume in what follows that pair annihilation of DM via virtual spin-1 exchanges is responsible for this and that it results in a SM final state consisting of pairs of electrons, muons, or light charged hadrons.…”

Dark Moments for the Standard Model ?

“…Recent analyses [50,51] of this constraint informs us that this bound lies roughly at the level of ∼ 5 × 10 −29 (m DM /100 MeV) cm 3 s −1 , noting that it depends approximately linearly on the DM mass. This is, in any case, roughly three orders of magnitude below that needed at freeze out to recover the observed relic density [14,15] of ∼ 4 − 8 × 10 −26 cm 3 s −1 , with a more specific value depending upon the detailed nature of the DM. For example, if the DM is a complex scalar, as we will assume below, then for the range of masses of interest to us the target annihilation cross section is then 7.5σ 0 [15] where σ 0 is defined as σ 0 = 10 −26 cm 3 s −1 , the typical scale required for the thermal freeze-out mechanism.…”

“…This is, in any case, roughly three orders of magnitude below that needed at freeze out to recover the observed relic density [14,15] of ∼ 4 − 8 × 10 −26 cm 3 s −1 , with a more specific value depending upon the detailed nature of the DM. For example, if the DM is a complex scalar, as we will assume below, then for the range of masses of interest to us the target annihilation cross section is then 7.5σ 0 [15] where σ 0 is defined as σ 0 = 10 −26 cm 3 s −1 , the typical scale required for the thermal freeze-out mechanism. We also note in passing that there are additional constraints of a very similar magnitude for this range of DM masses from a completely different source which arise from Voyager 2 data [52,53].…”

“…Traditional DM matter candidates, such as Weakly Interacting Massive Particles(WIMPs) [2,3] and axions [4][5][6], though far from being excluded, continue to have their parameter spaces slowly eroded by the lack of any signals in direct or indirect detection experiments or at the LHC [7][8][9][10] and this has opened the door to an ever widening array of possible DM models covering huge ranges in both DM masses and interaction coupling strengths [11][12][13]. These new models also can involve new DM production/annihilation mechanisms in order to reproduce the observed relic abundance besides that of the familiar thermal relic [14,15]. A large class of these new interactions can be described as being through either renormalizable (dim=4) or non-renormalizable (dim > 4) 'portals' via which the DM interacts with the SM via the existence of a new set of intermediary particles with a wide range of possible masses.…”