It seems that another week has passed, and I find myself at my second conference of the summer. This is the Origins of Mass conference in Odense, hosted by CP3 Origins. This is my first time at this conference.
9:00 am: Present and Future of Axion Searches: The International Axion Observatory IAXO, Igor Irastorza
This talk is a review of past axion searches, particularly solar helioscopes, but most particularly a presentation about the near-future IAXO experiment.
We start, of course, with a standard overview of the need for axions and axion phenomenology, particularly the coupling to photons.
Axion DM talk later, but some details here. BICEP2 seems to disfavour classical window for axions, with Peccei-Quinn scale before inflation (though note that this result has come under heightened criticism in the last few days).
Standard experimental axion search: Axions produced in Sun (by Primakoff mechanism) followed by axion decay to two photons (outside the Sun). Look for photon line at very low energies. Also possible to look for these lines as part of standard DM search. Some other astrophysical hints from anomalous white dwarf cooling and anomalous universe transparency. Finally, terrestrial light-shining-through-walls searches. IAXO is first of these types.
Solar axion searches benefit from our understanding of solar physics; the axion spectrum is just that of photons from the sun, scaled by the conversion factor.
Current state of the art experiment, CAST, resuses old LHC test magnet! This kind of recycling always amuses me, for some reason. IAXO would use a purpose-built magnet, but otherwise seems to use standard technology; there are no radical/conceptual improvements in the design. But this still will allow an improvement in the sensitivity to the axion-photon coupling by better than an order of magnitude.
IAXO magnet uses technology developed for LHC, several Tesla field strength. Actually lower than CAST, but much larger cross sectional area compensates. Optics based on technology used already in NuSTAR experiment.
IAXO will probe region suggested by galactic transparency, as well as "high mass" region of QCD parameter space. Unfortunately, there will remain a lot of parameter space unconstrained.