Limits on the abundance and coupling of cosmic axions at 4.5<ma<5.0 μeV

Abstract

We report preliminary results from a search for galactic axions in the frequency range 1.09 < f a < 1.22 GHz. For an axion linewidth V a < 200 Hz we obtain the experimental limit (g arr /m a ) 2 pa <1.4xl0" 41 . The theoretical prediction is (g ar y/m a ) 2 p a = 3.9x 10 ~4 4 with p a =300 MeV/cm 3 . We have also searched for the presence of a continuous spectrum of light pseudoscalar particles; if we assume that the above p a is contained between the upper and lower frequencies of our search, then we find thatg flyr <2xl0-30 MeV ,/2 cm 3/2^1 0" 11 GeV" 1 .PACS numbers: 98.60. Df, 14.80.Gt, 98.80.Es On the basis of rotation curves of galaxies and galactic clusters, it is widely believed today that the total mass in the Universe greatly exceeds the observable luminous matter. Also, arguments concerning primordial nucleosynthesis of the light elements limit the total baryonic matter to less than 0.2 times the critical density required to close the Universe. Little is known about the missing or "dark" matter but many candidate constituent particles have been proposed, some of them exotic.* A leading candidate is a very light pseudoscalar particle, the so-called "invisible axion." 2In 1977 Peccei and Quinn 3 (PQ) introduced a new global symmetry which is spontaneously broken in such a way as to cancel the CP-nonconserving terms that are present in the QCD Lagrangean but not observed. Weinberg 4 and Wilczek 4 pointed out that the breaking of the PQ symmetry must give rise to a pseudoscalar Goldstone boson named the axion. Accelerator searches 5 have failed to detect axions with mass greater than 200 keV, but models with light, weakly interacting axions have been proposed. 2 In these models, the mass of the axion and its coupling to fermions are inversely proportional to the vacuum expectation energy f a at which the PQ symmetry is broken. Specifically,where f n = 93 MeV and m^ = 135 MeV. While m a is not predicted by theory, observations on the cooling rate of ordinary stars 6 imply that m a < 1 eV, while neutron stars 7 imply that m a <4xl0 -2 eV; the best upper limit of m a < 1 x 10 ~2 eV comes from redgiant evolution. 8 At the same time cosmological considerations 9 place a lower limit of m a > 10 ~5 eV. In this window m a~~\ 0~s eV is preferred if the axions are to close the Universe. Axions should have been produced in the early stages of the Universe and later condensed into the galaxies with their present velocity being equal to the virial galactic velocity. Turner has calculated the expected axion density near the Earth on the assumption that galactic halos are due primarily to the presence of axions. 10 He finds that <p fl >=5xl0~2 5 g/cm 3^3 00 MeV/cm 3 .The axion couples to fermions and, through a triangle graph, to two photons [see Fig. 1(a)]. Sikivie 11 proposed that, in spite of the extremely weak coupling, axions could be converted to photons in the presence of an intense electromagnetic field via the PrimakofT effect 12 [ Fig. 1(b)]. The interaction Lagrangean is given by Lint = ~~ (#a yy /4;r)E-B(p...

First axion dark matter search with toroidal geometry

“…On top of a T p,cavity of 0.1 K, quantum-noise-limited superconducting amplifiers were employed as the 1st amplifiers whose noise temperatures are proportional to not only the frequencies (T n,amp ∼ hν/k B ln 2) [28] but also the ambient temperatures (T p,cavity in axion haloscopes) to achieve fast DFSZ scanning rates from the small AC-TION experiment. Figure 5 shows the exclusion limits expected from the large and small ACTION experiments, and therein the exclusion limits from RBF [12], UF [13], ADMX [14,15], HAYSTAC [16], and CAST [22] are also shown.…”

“…Assuming the axions have an isothermal distribution, the signal power given in Eq. (1) would then distribute over a Maxwellian shape with an axion rms speed of about 270 km/s in our galaxy [11], which is the basic model considered in this paper.Most of the axion haloscope searches to date [12][13][14][15][16] have employed a cylindrical resonator without an open resonator [17]. In this paper, we report the first axion haloscope search with toroidal geometry.…”

“…Most of the axion haloscope searches to date [12][13][14][15][16] have employed a cylindrical resonator without an open resonator [17]. In this paper, we report the first axion haloscope search with toroidal geometry.…”

Axion detection by ring lasers

“…Sikivie [3] suggested that relic axions could be detected through their conversion to photons in a resonant cavity bathed in a strong magnetic field. Experiments of this sort, which rely on the assumption that axions form a significant component of the galactic halo, have yet to confirm the presence of axions [4]. Attempts to produce axions and detect their * hep-ph/9502256, submitted to Phys.…”

Electromagnetic detection of axions

“…He suggested that this method can be used to detect the hypothetical galactic axion flux that would exist if axions were the dark matter of the Universe. Various terrestrial experiments to detect invisible axions by making use of their coupling to photons have been proposed [6,7,8], and the first result of such experiments appeared recently [9].…”