Evaporation of dark matter from celestial bodies. (arXiv:2104.12757v3 [hep-ph] UPDATED)
<a href="http://arxiv.org/find/hep-ph/1/au:+Garani_R/0/1/0/all/0/1">Raghuveer Garani</a> (INFN, Florence), <a href="http://arxiv.org/find/hep-ph/1/au:+Palomares_Ruiz_S/0/1/0/all/0/1">Sergio Palomares-Ruiz</a> (IFIC, Valencia U. – CSIC)
Scatterings of galactic dark matter (DM) particles with the constituents of
celestial bodies could result in their accumulation within these objects.
Nevertheless, the finite temperature of the medium sets a minimum mass, the
evaporation mass, that DM particles must have in order to remain trapped. DM
particles below this mass are very likely to scatter to speeds higher than the
escape velocity, so they would be kicked out of the capturing object and
escape. Here, we compute the DM evaporation mass for all spherical celestial
bodies in hydrostatic equilibrium, spanning the mass range $[10^{-10} –
10^2]~M_odot$, for constant scattering cross sections and $s$-wave
annihilations. We illustrate the critical importance of the exponential tail of
the evaporation rate, which has not always been appreciated in recent
literature, and obtain a robust result: for the geometric value of the
scattering cross section and for interactions with nucleons, at the local
galactic position, the DM evaporation mass for all spherical celestial bodies
in hydrostatic equilibrium is approximately given by $E_c/T_chi sim 30$,
where $E_c$ is the escape energy of DM particles at the core of the object and
$T_chi$ is their temperature. In that case, the minimum value of the DM
evaporation mass is obtained for super-Jupiters and brown dwarfs, $m_{rm evap}
simeq 0.7$ GeV. For other values of the scattering cross section, the DM
evaporation mass only varies by a factor smaller than three within the range
$10^{-41}~textrm{cm}^2 leq sigma_p leq 10^{-31}~textrm{cm}^2$, where
$sigma_p$ is the spin-independent DM-nucleon scattering cross section. Its
dependence on parameters such as the galactic DM density and velocity, or the
scattering and annihilation cross sections is only logarithmic, and details on
the density and temperature profiles of celestial bodies have also a small
impact.
Scatterings of galactic dark matter (DM) particles with the constituents of
celestial bodies could result in their accumulation within these objects.
Nevertheless, the finite temperature of the medium sets a minimum mass, the
evaporation mass, that DM particles must have in order to remain trapped. DM
particles below this mass are very likely to scatter to speeds higher than the
escape velocity, so they would be kicked out of the capturing object and
escape. Here, we compute the DM evaporation mass for all spherical celestial
bodies in hydrostatic equilibrium, spanning the mass range $[10^{-10} –
10^2]~M_odot$, for constant scattering cross sections and $s$-wave
annihilations. We illustrate the critical importance of the exponential tail of
the evaporation rate, which has not always been appreciated in recent
literature, and obtain a robust result: for the geometric value of the
scattering cross section and for interactions with nucleons, at the local
galactic position, the DM evaporation mass for all spherical celestial bodies
in hydrostatic equilibrium is approximately given by $E_c/T_chi sim 30$,
where $E_c$ is the escape energy of DM particles at the core of the object and
$T_chi$ is their temperature. In that case, the minimum value of the DM
evaporation mass is obtained for super-Jupiters and brown dwarfs, $m_{rm evap}
simeq 0.7$ GeV. For other values of the scattering cross section, the DM
evaporation mass only varies by a factor smaller than three within the range
$10^{-41}~textrm{cm}^2 leq sigma_p leq 10^{-31}~textrm{cm}^2$, where
$sigma_p$ is the spin-independent DM-nucleon scattering cross section. Its
dependence on parameters such as the galactic DM density and velocity, or the
scattering and annihilation cross sections is only logarithmic, and details on
the density and temperature profiles of celestial bodies have also a small
impact.
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