RT Journal Article
T1 Exact theory of freeze-out
A1 Cannoni, Mirco
AB We show that the standard theory of thermal productionand chemical decoupling of WIMPs is incomplete.The hypothesis that WIMPs are produced and decouple froma thermal bath implies that the rate equation the bath particlesinteracting with the WIMPs is an algebraic equationthat constraints the actual WIMPs abundance to have a preciseanalytical form down to the temperature x∗ = m  /T∗.The point x∗, which coincides with the stationary point of theequation for the quantity  = Y −Y0, is where the maximumdeparture of theWIMPs abundance Y from the thermal valueY0 is reached. For each mass m  and total annihilation crosssection   annvr , the temperature x∗ and the actual WIMPsabundance Y (x∗) are exactly known. This value provides thetrue initial condition for the usual differential equation thathave to be integrated in the interval x ≥ x∗. The matchingof the two abundances at x∗ is continuous and differentiable.The dependence of the present relic abundance on the abundanceat an intermediate temperature is an exact result. Theexact theory suggests a new analytical approximation thatfurnishes the relic abundance accurate at the level of 1–2 %in the case of S-wave and P-wave scattering cross sections.We conclude the paper studying the evolution of the WIMPschemical potential and the entropy production using methodsof non-equilibrium thermodynamics.
PB SpringerOpen
SN 1434-6044
YR 2015
FD 2015-03
LK http://hdl.handle.net/10272/18371
UL http://hdl.handle.net/10272/18371
LA eng
NO Cannoni, M. (2015). Exact theory of freeze-out. The European Physical Journal C, 75(3). DOI:  https://doi.org/10.1140/epjc/s10052-015-3328-6
NO Funded by SCOAP3 / License Version CC BY 4.0.
DS Repositorio Institucional de la Universidad de Huelva
RD 1 jun 2026