Abstract
The CERN Axion Solar Telescope has finished its search for solar axions with (3)He buffer gas, covering the search range 0.64 eV ≲ ma ≲ 1.17 eV. This closes the gap to the cosmological hot dark matter limit and actually overlaps with it. From the absence of excess x rays when the magnet was pointing to the Sun we set a typical upper limit on the axion-photon coupling of gaγ ≲ 3.3 × 10(-10) GeV(-1) at 95% C.L., with the exact value depending on the pressure setting. Future direct solar axion searches will focus on increasing the sensitivity to smaller values of gaγ, for example by the currently discussed next generation helioscope International AXion Observatory.
Highlights
The CERN Axion Solar Telescope has finished its search for solar axions with 3He buffer gas, covering the search range 0.64 eV ≲ ma ≲ 1.17 eV
We show constraints from Sumico [9,10,11], horizontal branch (HB) stars [29], and the hot dark matter (HDM) bound [31]
For the analysis presented in this Letter, the density profiles derived from turbulent computational fluid dynamics (CFD) simulations made with the magnet horizontal and over the full range of Phase II density settings were subjected to a simple and conservative coherence criterion (Δρ < 0.001 kg m−3)
Summary
The CERN Axion Solar Telescope has finished its search for solar axions with 3He buffer gas, covering the search range 0.64 eV ≲ ma ≲ 1.17 eV. Search for Solar Axions by the CERN Axion Solar Telescope with 3He Buffer Gas: Closing the Hot Dark Matter Gap QCD axions with parameters in this range thermalize in the early Universe after the QCD phase transition by interactions with pions [34] and would exist with a present-day number density of around 50 cm−3, comparable to 0.5 neutrino species, and are susceptible to hot dark matter bounds [31,35,36].
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