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Catching chameleons in the Sun

Monumental space “parade” with the participation of the Sun and the black hole may help in the search of the particles that comprise dark matter.

The parade of planets is a relatively rare phenomenon, the essence of which is that several planets lined up in a straight line. But there is in the Universe and more ambitious “parades” like the one that happened on December 18 when Earth, Sun and black hole at the center of the milky Way lined up. Although directly observe such an event is difficult, astrophysicists have been able to accomplish during it interesting measurement, directly addressing issues of dark matter and energy.


Standing between Earth and the black hole, the Sun can amplify the flow of particles of which presumably is the dark matter (Photo by NASA Goddard Space Flight Center / Flickr.com.)

The telescope is made of CAST dipolog magnet for the LHC and moves on special rails to track the movement of the Sun throughout the day (Photo: Maximilien Brice/ CERN .)”

Our universe consists mainly of matter. However, during the Big Bang was supposed to occur the same amount of matter and antimatter. The so-called CP-invariant was proposed by Lev Landau as the fundamental symmetry between matter and antimatter: they turn to each other in mirror reflection with simultaneous replacement of particles on antiparticles, and physical laws must obey the invariant without exception. However, CP-invariant was violated, and the matter was more than antimatter. The exact mechanism of why this happened, is unclear, and this is one of the most important unsolved problems of physics.

Today we have experimental evidence that the CP-invariant is violated for the weak interaction responsible for the process of nuclear decay. But though it is unclear whether one such violation of the invariant, to explain the imbalance between matter and antimatter.

At the same time, the preservation of CP-invariant in the strong interaction which holds the nucleus together is an important task of quantum chromodynamics – section of theoretical physics that describes the strong interaction. The equation which describes the strong interaction, provides a setting, when very small value of the CP-symmetry is preserved. But why, of all possible values it accepts this value? In the late 70-ies, Roberto Peccei and Helen Quinn proposed an elegant solution to the problem. They suggested that the equation should include not an external parameter, and the hypothetical neutral particle with very low mass, which is called the axion.

The axion was a great future. The fact that another fundamental mystery, which is trying to solve modern physics is the question of the nature of dark matter and dark energy. They are called dark because it does not interact with light and cannot be observed directly. However, they help to explain the expansion rate of the Universe; moreover, the calculations show that the amount of dark matter and energy in the Universe is much more than material “tangible”.

There are several theories that describe the possible device of dark matter, most of which agree that dark matter consists of electrically neutral particles with very tiny mass, is kept to a virtual minimum their interaction with ordinary matter. Thus, the axion may well be one of the “bricks” of dark matter. Presumably, being in a strong magnetic field, the axion has to turn into a photon from the x-ray spectrum. If so, then it can be detected experimentally.

Chameleon is an even more exotic particle, which is also considered a “member” of dark matter. The effective mass of the chameleon depends on the energy density of the environment, and if in the intergalactic space, the mass of the chameleon is very small, then, for example, on Earth, it should be significantly more. Chameleons and axions, should turn into photons in a strong magnetic field, therefore the two particles can be searched using the same experimental setup.

European organization for nuclear research, or CERN (CERN), in addition to its main activities, they have taken a large number of “child” research. Some of them are performed on Axion Solar Telescope at CERN (CAST – CERN Axion Solar Telescope), which combines astronomy with developments in the field of accelerators, x-ray detectors, magnets and cryogenics. Experiments on CAST’e focused on the search for axions and chameleons. If axions exist, they must exist in the center of the Sun. In that moment, when the Sun and the Earth are on the same line with the black hole, physics can use the Sun as part of your equipment: its gravitational field should slow focus or axions chameleons emitted by the black hole. The experiment on 18 December was the first attempt of the telescope to detect the exotic particles emitted by the black hole.

“Usually we try to find the Sunny exotic particles, but in such a special day (when there is a “parade” with a black hole – approx. ed.) we are able to look beyond the Sun and see whether there will be anything else. The center of the galaxy can emit particles that we could detect. This would give us a lot of new information about “dark universe,” because the Sun needs to strengthen a weak stream of particles a billion times at the moment when it is between a black hole and our planet,” explained Konstantin Zioutas, representative of a research group, carrying out the experiment.

Based CAST’a – dipole magnet; of these magnets is composed of the Large hadron Collider. A longitudinal hole inside the magnet (initially provided for the acceleration of elementary particles in the Collider) in this case is used as a “spyglass”. The system of focusing mirrors for x-rays borrowed from the German space program. Actually, the “eye” of the telescope is an x-ray detector, and the principle of operation of the device in General is that a strong magnetic field serves as an effective “catalyst” for the transformation of axions into x-rays, which captures a special detector.

To measure the chameleons interaction with matter, physicists need to “see” like chameleons “bounce” off the atoms, and this requires equipment with extreme sensitivity. For this purpose, physicists have built an additional “trap” – KWISP, or Thin kinetic detector of weakly interacting particles. KWISP is equipped with a special membrane force sensor, which vibrates with a certain frequency, when it come chameleons.

Now physics processes the received data, but preliminary results are no new particles were found. Next year the “parade” will include and the moon, which may increase the probability of detecting exotic axions and chameleons.

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