The symmetry between matter and antimatter
A survey that has used the data collected by the LAT aboard the Fermi space telescope NASA suggests the presence of traces of helical magnetic fields in space, the ‘signature’ of the violation of the symmetry between matter and antimatter, which occurred in the first few moments after Big Bang.
The universe is not large. We are created from energy and so are the planets and the galaxies that we see. Only 4-5 percent of the total mass and energy. Yet, we can consider ourselves lucky because, in the big bang theory, all the mass of ordinary matter created event horizon universe that would have to create the exact same amount of antimatter. This is kind of awkward because if a particle of matter interacts with a mirror of antimatter, what remains is only a flash of energy. Instead, from what we measure today antimatter would total just one tenth of ordinary matter. Evidently, in the first infinitesimal fraction of a second after the Big Bang must have occurred something that physicists call CP symmetry breaking, which led to this very clear imbalance.
To search for traces of this concrete phenomenon, researchers led by Wenlei Chen (University of Washington in the United States), used data from the gamma radiation collected by the LAT aboard NASA’s Fermi space observatory. The idea of exploiting this information from a theoretical work proposed in 2001 by Tanmay Vachaspati from Arizona State University that traces of CP symmetry breaking can be found in the configuration of helical magnetic fields that permeate the universe. Their predominant helicity, or the fact that “twisting” mainly in one direction between two possible (left or right) would be just the clue primordial imbalance between matter and antimatter.
The gamma rays that travel in the cosmos work like indirect indicators of these magnetic fields: when a photon of very high energy it strikes another of lower energy, such as those that constitute the cosmic microwave background radiation (CMB), produces a pair of particles: an electron and a positron, which are deflected by magnetic fields, cosmic. This deviation determines the re-emission of photons of lower energies. Analyzing the distribution of this radiation can, in principle, obtain information on the orientation of the dominant magnetic fields and their helicity.
Chen and his team, including Vachaspati, all researchers outside the Fermi-LAT collaboration, seem to have found just that trend analysis of gamma photons collected by Fermi and made public by NASA. The data would show the presence of magnetic fields helical, with an excess of left-handed ones. A finding that suggests the mechanisms that led to the almost total absence of antimatter. For example, some phenomena occurred billionths of a second after the Big Bang, when the Higgs field has given mass to all particles, predict the presence of left-handed fields present in the universe, and while phenomena that allegedly took place before suggesting the predominance of those right-handed.
“The technique proposed in this work is interesting and innovative, and it shows, as other published studies, the importance of gamma rays to also include key aspects of the cosmology of the universe,” says Luca Latronico, the National Institute of Nuclear Physics, member Fermi LAT team. “When the measured signal is very small and does not allow talking about discovery, but indicates a promising direction of study, with potential consequences on important and fundamental questions unresolved as the matter-antimatter asymmetry. It is important to note however that such sophisticated measures of quantity derived with complex mathematical calculations require checks of profound methods of data processing. The authors themselves point out in some inconsistencies of their results, as the difference in the results for the Northern and Southern hemispheres of the sky, most likely due to a contamination of the photons of our Galaxy in the data used. These can be explained only in part with reasonable assumptions, and require further checks to be able to say definitively that the proposed method is robust. Once established, however, it will be necessary to wait to collect many more data with the instrument LAT of Fermi satellite, to be able to say with certainty that it has detected the signal sought. “