Constraints on the axion-electron coupling for solar axions produced by a Compton process and bremsstrahlung

Abstract

The search for solar axions produced by Compton ( þ e À ! e À þ A) and bremsstrahlunglike (e À þ Z ! Z þ e À þ A) processes has been performed. The axion flux in both cases depends on the axionelectron coupling constant. The resonant excitation of the low-lying nuclear level of 169 Tm was looked for: A þ 169 Tm ! 169 Tm à ! 169 Tm þ (8.41 keV). The Si(Li) detector and 169 Tm target installed inside the low-background setup were used to detect 8.41 keV rays. As a result, a new model-independent restriction on the axion-electron and the axion-nucleon couplings was obtained: g Ae  jg 0 AN þ g 3 AN j 2:1  10 À14 . In the model of the hadronic axion this restriction corresponds to the upper limit on the axion-electron coupling and on the axion mass g Ae  m A 3:1  10 À7 eV (90% C.L.). The limits on the axion mass are m A 105 eV and m A 1:3 keV for the Dine-Fischler-Srednicki-Zhitnitskii-and Kim-Shifman-Vainstein-Zakharov-axion models, correspondingly (90% C.L.).

Constraints on the axion-electron coupling constant for solar axions appearing owing to bremsstrahlung and the compton process

“…6). [35,36], (4) decay of orthop ositronium [37], (5) CoGeNT [38], (6) CDMS [39], (7) bound for the axion luminosity of the Sun [22], (8) red giants [40], and (9) experiment with 169 Tm [26]. The regions of excluded values lie above the corresponding lines.…”

“…We used silicon and germanium detectors designed for seeking dark g Ae 4 g Ae matter [38,39]. Solar axions having a continuous energy spectrum should lead to the resonant excitation of low lying nuclear levels [26].…”

“…The calculation procedures were described in detail in [26], where simple parameterizations describing the spectra with an accuracy of 1% in the range of 1-10 keV were presented.…”

On the detectability of57Fe axion-photon mode conversion in the Sun

“…Compton scattering and electron-nucleus bremsstrahlung can also produce DFSZ axions. The Primakoff process alone produces around 10−100 times more axions (Andriamonje et al 2009) than the 57 Fe decay, while the other two process increase the axion flux by approximately 10 3 (Moriyama 1995;Derbin et al 2011). The count rate so produced according to axion models would be ∼10 −8 s −1 at a mass of 10 −2 eV, still too low for observational feasibility, but possibly adequate to detect the arion.…”

“…The count rate so produced according to axion models would be ∼10 −8 s −1 at a mass of 10 −2 eV, still too low for observational feasibility, but possibly adequate to detect the arion. However these axions, and consequently the photons produced by their mode conversion, dominantly have energies in the 1−3 keV range (Derbin et al 2011). At these energies, the dominant opacity is photoelectric absorption rather than Compton scattering, and the depth of solar atmosphere from which mode converted photons may be detected is smaller.…”