Search for solar axions produced in the p(d,3He)A reaction with Borexino detector

Search for solar axions produced in the p(d,3He)A reaction with Borexino detector
G. Bellini et al. (Borexino collaboration)
Phys. Rev. D 85, 092003
Published 4 May 2012
doi:10.1103/PhysRevD.85.092003 (preprint on arXiv)

Abstract

A search for 5.5 MeV solar axions produced in the $p+d\to 3\mathrm{He}+A$ (5.5 MeV) reaction was performed using the Borexino detector.  The Compton conversion of axions to photons, $A+e\to e+\gamma$; the axioelectric effect, $A+e+Z\to e+Z$; the decay of axions into two photons, $A\to 2\gamma$; and inverse Primakoff conversion on nuclei, $A+Z\to \gamma +Z$, are considered. Model-independent limits on axion-electron ($g_{Ae}$), axion-photon ($g_{A\gamma }$), and isovector axion-nucleon ($g_{3AN}$) couplings are obtained: $|g_{Ae}\times g_{3AN}|\le 5.5\times {10}^{-13}$ and $|g_{A\gamma }\times g_{3AN}|\le 4.6\times {10}^{-11}{\mathrm{GeV}}^{-1}$ at $m_A<1\mathrm{MeV}$ (90% confidence level).  These limits are 2–4 orders of magnitude stronger than those obtained in previous laboratory-based experiments using nuclear reactors and accelerators.