The first spectrum of anti-hydrogen has just been obtained by CERN’s ALPHA team and studies are on-going to find differences between its spectrum and that of ordinary hydrogen. Hanging in the balance are answers to crucial questions on the nature of anti-matter and why matter supersedes anti-matter in the visible Universe.
Mysteries of the Universe
The fundamental mystery is this: why is there more matter than anti-matter in the Universe, even though all equations of physics predict that the two are exactly the same. If we lived in a Universe made up of anti-matter particles, we wouldn’t know the difference. Or would we? A hypothesis, involving two discrete symmetries of nature – Charge (you reverse the charge on a particle), denoted by C and Parity (you take the mirror image of a particle), denoted by P – taken together and called CP symmetry, could be broken giving rise to more matter particles than anti-matter particles. However, this still doesn’t violate another symmetry called CPT symmetry, in which Charge and Parity are joined by Time reversal symmetry.
The object of study is this: There is an anti-proton about which a positron (anti-electron) orbits. As is well known, such a system will have energy levels like those of the hydrogen atom, composed of a proton orbited by an electron. The question is how similar are the two systems. How much is CP symmetry violated? What about CPT symmetry?
How is the study done?
The study, published in Nature, describes the very first attempts at studying resonances in this bound system. They attempted to flip the magnetic moment of the atoms using a microwave laser radiation. This is basically flipping the poles of a tiny atomic magnet. Now, the trapping of the anti-atoms, perfected by the same team at ALPHA, CERN, depends on the magnetic moment. If that is flipped, the anti-atoms leave the trap, escape and get annihilated. This happens at a particular energy. If the laser is tuned to this energy, most of the laser energy will be absorbed. This signifies a resonance.
This is just the first among, surely, several tests that will be performed on anti-hydrogen, now that it can be produced and trapped easily.