Fundamental physics is described by the so-called Standard Model. It is one of the finest creations of humanity, allowing detailed predictions of particle physics and improving our understanding of the universe like never before. Despite all this, it is limited. We know that it doesn’t include gravity, for example. So while, on the one hand, it is one of physics' greatest tools, on the other researchers are trying to find ways to break it. And one group might have done just that.
In a paper uploaded on arXiv, Professor Derek Fox from Penn State University and colleagues described two anomalous observations from the Antarctic Impulsive Transient Antenna (ANITA) experiment. According to the paper, these signals could not have been made by any particle within the Standard Model.
ANITA studies ultra-high energy cosmic neutrinos. Neutrinos are particles with no electric charge and a tiny mass. They can easily move through a planet unscathed. If you hold up your thumb, about 100 billion neutrinos will pass through your thumbnail every second.
Neutrinos can interact with matter once in a while. The energies of these particular cosmic ones are so high that they can turn into massive particles. One particular change was expected for certain tau neutrinos (which is one of their types or “flavors”). They can turn into tau leptons, which is a heavy version of the standard electrons. The Standard Model has a very specific prediction for this change, but the recent observations don’t match. The angles of the particles detected by ANITA were much steeper than if it was a tau lepton. It must have been something else.
The team looked at other possible candidates and nothing we have ever encountered matched what they saw in the data. In the paper, they suggest this could be an example of a supersymmetric particle akin to the tau lepton. Supersymmetry is a yet-to-be-proven theory that assigns to every known particle a companion to explain some intrinsic differences we see in particle physics but are difficult to explain using the Big Bang Theory.
So is the Standard Model truly broken? We can’t be sure just yet. The paper has been submitted to the journal Physics Review D, and it will be certainly picked apart in the peer-review process by many other groups around the world.
Even if it doesn’t pan out, there are many other anomalies currently being investigated that points at physics beyond the Standard Model. The fundamental theory might survive this study, but the moment we truly break it is getting closer and closer every day.