Taking a closer look at LHC

In the late 1920's Paul Dirac applied to quantum mechanics the ideas of Einstein's special theory of relativity. It followed from Dirac's equations that there must be states of negative energy.
Dirac suggested that a deficiency of an electron in one of these states would be equivalent to ashort-lived positively charged particle, or a positron with the same mass as the electron, but intrinsically opposite in terms of electrical charge. In ordinary matter, a positron would rapidly encounter an electron and annihilate, resulting in a very short lifetime for it, but in a perfect vacuum a positron can live forever.

Actually, for every matter particle there corresponds an anti-matter particle. Anti-matter particles can correspond to matter particles in every respect except that any kind of charge (or quantum characteristic) is opposite.

When a particle and an anti-particle meet,they annihilate into pure energy and may give rise to energetic neutral force-carrier particles, such as gluons, photons or Z-bosons. Conversely, energetic force-carrier particles can give rise to matter particle/anti-particle pairs (pair production).

An unsolved mystery of cosmology is why the universe is dominated by matter rather than anti-matterThat's just what the LHCb experimentsee violation CP).aims to find out (


The experimental High Energy Physics Group at the University of Santiago de Compostela (SPAIN) focuses its research activity in quark physics, trying to probe the limits of the Standard Model. The main current project is Flavour Physics and CP-violation at the LHCb experiment at CERN


The first ever creation of atoms of antimatter at CERN has opened the door to the systematic exploration of the anti world. The recipe for anti-hydrogen is very simple - take one antiproton, bring up one anti-electron, and put the latter into orbit around the former - but it is very difficult to carry out as antiparticles do not naturally exist on earth. They can only be created in the laboratory. In even rarer cases, the positron's velocity was sufficiently close to the velocity of the antiproton for the two particles to join - creating an atom of anti-hydrogen


Three quarters of our universe is hydrogen and much of what we have learned about it has been found by studying ordinary hydrogen. If the behaviour of anti-hydrogen differed even in the tiniest detail from that of ordinary hydrogen, physicists would have to rethink or abandon many of the established ideas on the symmetry between matter and antimatter. It is believed that antimatter "works" under gravity in the same way as matter, but if nature has chosen otherwise, we must find out how and why.  

The next step is to check whether anti-hydrogen does indeed "work" just as well as ordinary hydrogen. Comparisons can be made with tremendous accuracy, as high as one part in a million trillion, and even an asymmetry on this tiny scale would have enormous consequences for our understanding of the universe. To check for such an asymmetry would mean holding the anti-atoms still, for seconds, minutes, days or weeks. The techniques needed to store antimatter are under intense development at CERN.


Can we hope to use antimatter as a source of energy? Could antimatter power vehicles in the future, or would it just be used for major power sources? See ...


Xabier Cid Vidal, PhD in experimental Particle Physics for Santiago University (USC). Research Fellow in experimental Particle Physics at CERN from January 2013 to Decembre 2015. Currently, he is in USC Particle Physics Department (Spanish Postdoctoral Junior Grants Programme).

Ramon Cid Manzano, secondary school Physics Teacher at IES de SAR (Santiago - Spain), and part-time Lecturer (Profesor Asociado) in Faculty of Education at the University of Santiago (Spain). He has a Degree in Physics and in Chemistry, and is PhD for Santiago University (USC).



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 For the bibliography used when writing this Section please go to the References Section

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