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Results for “invisible decays”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1987

Early-universe thermal production of not-so-invisible axions

It is found that, for Peccei-Quinn symmetry-breaking scales of less than about 4 x 10 to the 8th GeV (corresponding to axion masses of greater than about 0.03 eV) thermal production of axions in the early universe (via the Primakoff and photoproduction processes) dominates coherent production by a factor of about 1200/m sub a/(1 eV)/ exp 2.175. The photon luminosity from the decays of these relic axions leads to an upper limit to the axion mass of order 2-5 eV. If the axion mass saturates this bound, relic axion decays may well be detectable.

Turner, Michael S.↗
NASA NTRS1992

Constraints on dark matter from intergalactic radiation

Several of the dark matter candidates that have been proposed are believed to be unstable to decay, which would contribute photons to the radiation field between galaxies. The main candidates of this type are light neutrinos and axions, primordial mini-black holes, and a nonzero 'vacuum' energy. All of these can be constrained in nature by observational data on the extragalactic background light and the microwave background radiation. Black holes and the vacuum can be ruled out as significant contributors to the 'missing mass'. Light axions are also unlikely candidates; however, those with extremely small rest energies (the so-called 'invisible' axions) remain feasible. Light neutrinos, like those proposed by Sciama, are marginally viable. In general, we believe that the intergalactic radiation field is an important way of constraining all types of dark matter.

Overduin, J. M.↗