I am attending the International Conference on High Energy Physics in Melbourne and for the last two days, it seems the main theme has been reviewing the many unsuccessful attempts at breaking the Standard Model of particle physics. But why would physicists try to do that? Can’t we just be happy about having found what could be the Higgs boson, the last major missing piece of an extremely successful theory?
Of course, we are still extremely proud of this achievement but finding the secret passage to the next layer of the theory, which every theorist believes exists, is the next step on our agenda. Any deviation from a prediction of the Standard Model would open the door to new discoveries. So every experiment is scrutinizing the model to the minutest detail, trying to find the slightest flaw.
The LHCb experiment at CERN’s Large Hadron Collider (LHC) showed two interesting results today. First they presented a measurement that is different from one reported by D0 from Fermilab two years ago, which showed a deviation from what the Standard Model predits. The LHCb result is consistent with the Standard Model prediction and does not confirm the deviation reported by the D0 experiment.
The second LHCb result established for the first time that there is a slight asymmetry in some specific decays of B mesons. B mesons are composite particles made of a u quark and an anti-b quark. They observed that more B mesons than their antimatter counterparts, anti-B mesons, decay into one kaon and two pions, or into three kaons.
Such asymmetries are studied in the hope of explaining why the universe apparently evolved to be made entirely of matter. When matter is created out of pure energy (like at the time of the Big Bang or out of the energy released in proton collisions in the LHC), matter and antimatter are created in equal amounts. Why did the universe evolve into a place where matter clearly dominates? This is one of the key questions the LHCb collaboration is trying to answer and every small asymmetry, such as the one reported today, sheds a bit of light on this question.
In parallel, both CMS and ATLAS, two multi-purpose experiments operating also at the LHC, showed an impressive number of searches for new phenomena going beyond the Standard Model, something that would reveal the existence of what is referred to as “New Physics”.
Either way will take us ahead: directly, by finding new particles not postulated by the current theory or indirectly, by discovering a flaw in the Standard Model. So far, nothing has emerged. Just as with the quest for the Higgs boson, we have to be patient as many theorists have reminded us already. In the mean time, every new limit, every new measurement steers us in the right direction. As my mother liked to say: “Go over your work a hundred times until it is perfect”. With enough perseverance, by eliminating one by one all the wrong models, we will eventually find the right one.
Pauline Gagnon
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