Will the sun reveal its dark side? Print E-mail

ImageWill we be able to detect some of the dark matter and dark energy content of the sun? This is the question addressed by the CAST experiment at CERN, looking for axions and chameleons, particles never detected up to now.



Chameleon particles
This idea has been already tested in past years but now there is a new promising proposal to exploit this possibility. The most ambitious but feasible plan is to improve the sensitivity by a factor of 10, in which case the prospect of a discovery is greatly enhanced. In addition to improving on the axion detection capability there is now a new very interesting parallel road for CAST. It could also become a powerful dark energy detector searching for chameleons! 
Even hunting for chameleons?

Chameleons are very special scalar fields, the mass of which changes according to the local mass density of their environment – a weird chameleonic property. These fields fill the space with “dark energy” or more precisely they serve as the means which causes the accelerating expansion of the universe by creating a negative pressure. According to the theory, in analogy to axions, since these particles couple to photons, they can also be produced in the magnetized inner sun, with the best place localised so far being the so called “tachocline”, a thin layer at some 200 000 km below the solar surface, where there is general consensus that the macroscopic magnetic fields there should reach 50-100 Tesla; the few kGauss fields we observe in sunspots are supposed to have their roots there. Then, the so created chameleons can escape outwards as axions or neutrinos do. Moreover they can interact with the virtual photons of a magnetic field and produce low energy X-rays, which can be spotted by the CAST detectors.
An argument in support of the creation of chameleons inside the sun is that a small part of them may well be back converted to X-rays in the sun’s photosphere and modify the X rays of the observed solar photon spectrum, which cannot be explained with conventional mechanisms of photon production by such a relatively “cool” object like our sun.  

The assumed parameters for the solar chameleons suggest that not only a next generation CAST experiment but even CAST with its current configuration, but with improved detector performance, should be able to detect chameleons from the sun!

In addition, CAST considers the prospects of becoming also a state-of-the-art paraphoton helioscope, CAST results having put the best limits for low mass paraphotons. CAST has a brilliant past and looks into a promising future.
Submitted by Georgios Fanourakis & Theodoros Geralis (Demokritos - Greece)


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