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Direct search for solar axions by using strong magnetic field and X-ray detectors

Shigetaka Moriyama, Makoto Minowa, Toshio Namba, Yoshizumi Inoue, Yuko Takasu, Akira Yamamoto

TL;DR

The paper reports a direct helioscope search for solar axions produced in the Sun via the Primakoff process and reconverted to X-rays in a strong magnetic field. A superconducting magnet (>3.9 T) and nine PIN photodiodes tracked the Sun for several days, detecting X-rays in the 2–20 keV range and employing extensive shielding to suppress backgrounds. By modeling the axion-to-photon conversion spectrum and subtracting backgrounds, the authors derive a 95% CL upper limit on the two-photon coupling, $g_{a\gamma\gamma} < 6.0\times10^{-10}$ GeV$^{-1}$ for $m_a < 0.03$ eV, improving previous bounds by roughly a factor of 4.5 and exceeding the solar-age bound. This work demonstrates the viability of direct axion searches with helioscope-like setups and tightens constraints on axion parameter space relevant to astrophysical limits.

Abstract

We have searched for axions which could be produced in the solar core by exploiting their conversion to X rays in a strong laboratory magnetic field. The signature of the solar axion is an increase in the rate of the X rays detected in a magnetic helioscope when the sun is within its acceptance. From the absence of such a signal we set a 95% confidence level limit on the axion coupling to two photons $g_{aγγ}\equiv 1/M < 6.0\times 10^{-10}$ GeV$^{-1}$, provided the axion mass $m_a<0.03$ eV. The limit on the coupling is factor 4.5 more stringent than the recent experimental result. This is the first experiment whose sensitivity to $g_{aγγ}$ is higher than the limit constrained by the solar age consideration.

Direct search for solar axions by using strong magnetic field and X-ray detectors

TL;DR

The paper reports a direct helioscope search for solar axions produced in the Sun via the Primakoff process and reconverted to X-rays in a strong magnetic field. A superconducting magnet (>3.9 T) and nine PIN photodiodes tracked the Sun for several days, detecting X-rays in the 2–20 keV range and employing extensive shielding to suppress backgrounds. By modeling the axion-to-photon conversion spectrum and subtracting backgrounds, the authors derive a 95% CL upper limit on the two-photon coupling, GeV for eV, improving previous bounds by roughly a factor of 4.5 and exceeding the solar-age bound. This work demonstrates the viability of direct axion searches with helioscope-like setups and tightens constraints on axion parameter space relevant to astrophysical limits.

Abstract

We have searched for axions which could be produced in the solar core by exploiting their conversion to X rays in a strong laboratory magnetic field. The signature of the solar axion is an increase in the rate of the X rays detected in a magnetic helioscope when the sun is within its acceptance. From the absence of such a signal we set a 95% confidence level limit on the axion coupling to two photons GeV, provided the axion mass eV. The limit on the coupling is factor 4.5 more stringent than the recent experimental result. This is the first experiment whose sensitivity to is higher than the limit constrained by the solar age consideration.

Paper Structure

This paper contains 4 sections, 2 equations, 4 figures.

Table of Contents

  1. Introduction
  2. Experimental Apparatus
  3. Measurements and Analysis
  4. Conclusion

Figures (4)

  • Figure 1: Schematic view of the apparatus
  • Figure 2: Energy spectrum of the source runs and the background runs. Each spectrum is obtained by summing up the data of nine PIN diodes.
  • Figure 3: Fitting of the axion spectrum with experimental data. $m_a=0.001$ eV is assumed.
  • Figure 4: The 95% CL upper limit for the two-photon coupling constant $g_{a\gamma\gamma}$. The result of Lazarus Lazarus is our calculation. He corrected his result privatecom. The recent result of Avignone III was obtained with a germanium detector Avignone.