Effects of cold dark matter decoupling and pair annihilation on cosmological perturbations

Journal Article · Fri Sep 15 00:00:00 EDT 2006 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.74.063509· OSTI ID:20871183

Bertschinger, Edmund ^[1]

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1. Department of Physics, MIT Room 37-602A, 77 Massachusetts Ave., Cambridge, Massachusetts 02139 (United States)

Weakly interacting massive particles (WIMPs) are part of the lepton-photon plasma in the early universe until kinetic decoupling, after which time the particles behave like a collisionless gas with nonzero temperature. The Boltzmann equation for WIMP-lepton collisions is reduced to a Fokker-Planck equation for the evolution of the WIMP distribution including scalar density perturbations. This equation and the Einstein and fluid equations for the plasma are solved numerically including the acoustic oscillations of the plasma before and during kinetic decoupling, the frictional damping occurring during kinetic decoupling, and the free-streaming damping occurring afterwards and throughout the radiation-dominated era. An excellent approximation reduces the solution to quadratures for the cold dark matter density and velocity perturbations. The subsequent evolution is followed through electron pair annihilation and the radiation-matter transition; analytic solutions are provided for both large and small scales. For a 100 GeV WIMP with bino-type interactions, kinetic decoupling occurs at a temperature T{sub d}=23 MeV. The transfer function in the matter-dominated era leads to an abundance of small cold dark matter halos; with a smooth window function the Press-Schechter mass distribution is dn/dlnM{proportional_to}M{sup -1/3} for M<10{sup -4}(T{sub d}/10 MeV){sup -3}M{sub {center_dot}}.

• OSTI ID: 20871183
• Journal Information: Physical Review. D, Particles Fields, Vol. 74, Issue 6; Other Information: DOI: 10.1103/PhysRevD.74.063509; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ABUNDANCE
ANALYTICAL SOLUTION
ANNIHILATION
APPROXIMATIONS
BOLTZMANN EQUATION
DAMPING
DECOUPLING
DENSITY
DISTURBANCES
ELECTRON PAIRS
FOKKER-PLANCK EQUATION
GEV RANGE
LEPTONS
MASS DISTRIBUTION
MEV RANGE
NONLUMINOUS MATTER
OSCILLATIONS
PARTICLE IDENTIFICATION
PHOTONS
QUADRATURES
SCALARS
TRANSFER FUNCTIONS
UNIVERSE
WEAK INTERACTIONS