Abstract
A finite axion–nucleon coupling, nearly unavoidable for QCD axions, leads to the production of axions via the thermal excitation and subsequent de-excitation of ^{57}Fe isotopes in the sun. We revise the solar bound on this flux adopting the up to date emission rate, and investigate the sensitivity of the proposed International Axion Observatory IAXO and its intermediate stage BabyIAXO to detect these axions. We compare different realistic experimental options and discuss the model dependence of the signal. Already BabyIAXO has sensitivity far beyond previous solar axion searches via the nucleon coupling and IAXO can improve on this by more than an order of magnitude.
Highlights
The axion phenomenology and experimental landscape are discussed in several recent reviews [13–17]
Our analysis shows the potential of BabyIAXO to study areas of the parameter space, well beyond the solar bound and the region probed by CERN Axion Solar Telescope (CAST)
We have presented the first dedicated investigation of the BabyIAXO and International Axion Observatory (IAXO) potential to detect 14.4 keV
Summary
The axion phenomenology and experimental landscape are discussed in several recent reviews [13–17]. In this sense, measuring the axion– nucleon coupling would be a good indication of the QCD axion nature Such a detection by a helioscope would likely be accompanied by a signal from Primakoff (and possibly Compton/Bremsstrahlung) axions. Other nuclear transitions turn out to generate a substantially smaller axion flux (see Appendix 1) The search for these 57Fe axions has a long history. The currently most powerful helioscope, the CERN Axion Solar Telescope (CAST) [39], as well as CUORE [40] and, more recently, XENON1T [41], have searched for axions produced in this transition and provided constraints on the axion– nucleon coupling. 2, we revisit the problem of the solar axion production in nuclear transitions, provide an updated expression for the flux from 57Fe and discuss its dependence on the specific axion model; in Sect.
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