Vector dark matter from inflationary fluctuations

Abstract

We calculate the production of a massive vector boson by quantum fluctuations during inflation.This gives a novel dark-matter production mechanism quite distinct from misalignment or thermal production. While scalars and tensors are typically produced with a nearly scale-invariant spectrum, surprisingly the vector is produced with a power spectrum peaked at intermediate wavelengths. Thus dangerous, long-wavelength, isocurvature perturbations are suppressed. Further, at long wavelengths the vector inherits the usual adiabatic, nearly scale-invariant perturbations of the inflaton, allowing it to be a good dark matter candidate. The final abundance can be calculated precisely from the mass and the Hubble scale of inflation, HI . Saturating the dark matter abundance we find a prediction for the mass m ≈ 10 −5 eV×(10 14 GeV/HI ) 4 . High-scale inflation, potentially observable in the CMB, motivates an exciting mass range for recently proposed direct detection experiments for hidden photon dark matter. Such experiments may be able to reconstruct the distinctive, peaked power spectrum, verifying that the dark matter was produced by quantum fluctuations during inflation and providing a direct measurement of the scale of inflation. Thus a detection would not only be the discovery of dark matter, it would also provide an unexpected probe of inflation itself.

Atlas of solar hidden photon emission

“…Phenomenologically, they give rise to a number of puzzling (and yet unobserved) phenomena: distortions of the cosmic microwave background spectrum [7][8][9][10][11] and radio sources [12], deviations of the Coulomb law [13,14] and distortions of planetary magnetic fields, atomic level shifts [15] and light-shining through walls [16][17][18][19]. HPs can be also produced in the early universe contributing to the dark radiation [11,20] or dark matter (DM) of the universe [21][22][23][24][25][26][27][28], in which case they can be searched in dark matter direct detection experiments [29] or through a small relic background of photons, which they produce because they are (slowly) decaying dark matter [21,22]. When the HP mass is above twice the electron mass, their fast decay into two electrons precludes them from being -1 - Log 10 m eV Log 10 Χ Figure 1.…”

Searching for dark absorption with direct detection experiments

“…[29][30][31]. An intriguing possibility, however, is that the A itself is sufficiently stable to play the role of the DM particle [32][33][34]. In this case, relic A s may be absorbed by ordinary matter in direct-detection experiments, just like an ALP.…”

Recent Progress in Search for Dark Sector Signatures

“…The observed DM abundance and the spectrum of its density inhomogeneities could naturally be produced by inflation if the DM particle were to be an ultra-light vector boson [15]. This fundamental and widely expected connection between particle physics and cosmology is the driving motivation behind most DM searches.…”

“…Such light-field DM is generally produced nonthermally (unlike the WIMP), often by the misalignment mechanism [15], and is best described as a classical, background field oscillating with frequency roughly equal to its mass [59][60][61]. To search for this field-like behavior of DM candidates a new class of experiments has been proposed [63,66,68], a bit similar to those already used in the detection of the ultra high energy cosmic rays with the help of radio techniques [69].…”