Precise Relic WIMP Abundance and its Impact on Searches for Dark Matter Annihilation

By G. Steigman, B. Dasgupta, J. Beacom. 2012

637 citations recorded by the source corpus.

If dark matter (DM) is a weakly interacting massive particle (WIMP) that is a thermal relic of the early Universe, then its total self-annihilation cross section is revealed by its present-day mass density. The canonical thermally averaged cross section for a generic WIMP is usually stated as 3*10^-26 cm^3s^-1, with unspecified uncertainty, and taken to be independent of WIMP mass. Recent searches for annihilation products of DM annihilation have just reached the sensitivity to exclude this canonical cross section for 100% branching ratio to certain final states and small WIMP masses. The ultimate goal is to probe all kinematically allowed final states as a function of mass and, if all states are adequately excluded, set a lower limit to the WIMP mass. Probing the low-mass region is further motivated due to recent hints for a light WIMP in direct and indirect searches. We revisit the thermal relic abundance calculation for a generic WIMP and show that the required cross section can be calculated precisely. It varies significantly with mass at masses below 10 GeV, reaching a maximum of 5.2*10^-26 cm^3s^-1 at masses around 0.3 GeV, and is 2.2*10^-26 cm^3s^-1 with feeble mass-dependence for masses above 10 GeV. These results, which differ significantly from the canonical value and have not been taken into account in searches for annihilation products from generic WIMPs, have a noticeable impact on the interpretation of present limits from Fermi-LAT and WMAP+ACT.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/718647389ecab1039a1f35ab47f67694a8071ceb

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Citations in the corpus

Bound-state formation for thermal relic dark matter and unitarity (2014, background): “4 × 10−26 cm3 s−1, assuming non-self-conjugate DM with mass above 10 GeV [22].”
Galactic Searches for Dark Matter (2012, background): “e is related to its thermally-averaged annihilation cross section times relative velocity as h˙ annviˇ 3 10 27 cm3s 1 DMh2 (1) (Zeldovich, 1965; Chiu, 1966; Steigman, 1979; Scherrer and Turner, 1986; Steigman et al., 2012). Recent cosmological measurements nd that the fraction of non-baryonic dark m”
INTEGRAL constraints on primordial black holes and particle dark matter (2020, background): “3, along with the cross-section required to obtain the correct DM abundance as a thermal relic [78].”
Recommendations on presenting LHC searches for missing transverse energy signals using simplified s-channel models of dark matter (2016, background): “A standard reference providing the values of ⟨σvrel⟩ as a function of mDM is [62].”
Dark matter, millicharges, axion and scalar particles, gauge bosons, and other new physics with LDMX (2018, background): “[70] G.”
Neutrino decoupling beyond the Standard Model: CMB constraints on the Dark Matter mass with a fast and precise Neff evaluation (2018, background): “This is because δρχ/δt takes into account both scattering and annihilation interactions, but the condition of obtaining the correct relic abundance only fixes the annihilation rate to be 〈σv〉 ' 3×10−26 cm3/s [62, 63].”
WIMP dark matter candidates and searches—current status and future prospects (2017, background): “The canonical thermal annihilation rate [72] is shown as a gray dotted line and the current limits Figure 6.”
Sensitivity projections for dark matter searches with the Fermi large area telescope (2016, neutral): “0027 [12, 13], provided the annihilation cross section averaged over the velocity distribution is near 〈σv〉 ∼ 3× 10−26 cm(3) s−1 [18](1).”
A review of indirect searches for particle dark matter (2016, methodology): “Based on the measured abundance of dark matter, Equation (1) implies that a particle that constitutes all of the dark matter will have a total pair annihilation cross-section of 〈σAv〉 ∼ 3 × 10−26 cm3 s−1 (see also the more precise calculation of [20]); this value is often used as a benchmark and is ”
Gravitational probes of dark matter physics (2017, background): “A necessary component of this is a thermally averaged annihilation cross section in the early Universe of 〈σv〉 ≈ 3× 10−26 cm(3)/s [60].”